All-offspring dispersal in a tropical mammal with resource defense polygyny

In polygynous mammals, males are usually responsible for gene flow while females are predominantly philopatric. However, there is evidence that in a few mammalian species female offspring may disperse to avoid breeding with their father when male tenure exceeds female age at maturity. We investigated offspring dispersal and local population structure in the Neotropical bat Lophostoma silvicolum. The mating system of this species is resource defense polygyny, with the resource being active termite nests, excavated by single males, which are then joined by females. We combined field observations of 14 harems during 3 years and data about the genetic structure within and between these groups, calculated with one mitochondrial locus and nine nuclear microsatellite loci. The results show that both male and female offspring disperse before maturity. In addition, we estimated life span of excavated termite nests and the duration they were occupied by the same male. Our findings suggest that long male tenure of up to 30 months is indeed a likely cause for the observed dispersal by female offspring that can reach maturity at a low age of 6 months. We suggest that dispersal by offspring of both sexes may occur quite frequently in polygynous tropical bats and thus generally may be more common in mammals than previously assumed.

Related papers:

title: Mating systems, philopatry and dispersal in birds and mammals
abstract: Many species of birds and mammals are faithful to their natal and breeding site or group. In most of them one sex is more philopatric than the other. In birds it is usually females which disperse more than males; in mammals it is usually males which disperse more than females. Reproductive enhancement through increased access to mates or resources and the avoidance of inbreeding are important in promoting sex differences in dispersal. It is argued that the direction of the sex bias is a consequence of the type of mating system. Philopatry will favour the evolution of cooperative traits between members of the sedentary sex. Disruptive acts will be a feature of dispersers.

title: Competition for mates and predominant juvenile male dispersal in mammals
abstract: Competition among males for mates may partially explain the predominant dispersal of juvenile male California ground squirrels (Spermophilus beecheyi). I tested the generality of this hypo- thesis by comparing dispersal patterns in many species of mammals. In most polygynous and promiscu- ous species of mammals, juvenile males are the predominant dispersers. In most monogamous species of mammals, juvenile males and juvenile females are predominant dispersers with little distinction as to sex. While many factors may influence dispersal, achieving outcrossing and advantages in competition for mates are most likely to explain predominant dispersal by juvenile males in many mammal species. On the average, juvenile survival might be greatest in the natal area, especially if dispersal is risky. Juveniles that remain in the natal area, however, may be likely to compete for resources (and eventually mates) with related individuals. Thus there may be evolutionary incentives for some juveniles to disperse, and compete (and mate) with unrelated individuals. Which juveniles disperse may depend on the particular benefits of dispersal. Natural selection might favour dispersal by juvenile California ground squirrels, Spermo- philus beecheyi, if they gain some advantage in competition for environmental resources, in achieving outcrossing, or in competition for mates (Dobson 1979). In juvenile California ground squirrels nearly all males, but few females, disperse from the natal area (Fitch 1948). Juvenile male ground squirrels may dis- perse primarily in order to outcross (Dobson 1979). Dispersers that successfully outcross might avoid inbreeding depression (e.g. Packer 1979; Pusey 1980), or find mates with especially com- patible genotypes. The promotion ofoutcrossing, however, could be accomplished equally well if juvenile females dispersed and juvenile males remained sedentary. Why do males, rather than females disperse? I will attempt to anwer this question by re-examining hypotheses that might explain the evolved tendency for juvenile male dispersal.

title: Dispersal and Inbreeding Avoidance
abstract: Using a game‐theoretical approach, we investigate the dispersal patterns expected if inbreeding avoidance were the only reason for dispersal. The evolutionary outcome is always complete philopatry by one sex. The rate of dispersal by the other sex depends on patch size and mating system, as well as inbreeding and dispersal costs. If such costs are sex independent, then two stable equilibria coexist (male or female philopatry), with symmetric domains of attraction. Which sex disperses is determined entirely by history, genetic drift, and gene flow. An asymmetry in costs makes one domain of attraction extend at the expense of the other. In such a case, the dispersing sex might also be, paradoxically, the one that incurs the higher dispersal costs. As asymmetry increases, one equilibrium eventually disappears, which may result in a sudden evolutionary shift in the identity of the dispersing sex. Our results underline the necessity to control for phylogenetic relationships (e.g., through the use of independent‐comparisons methods) when investigating empirical trends in dispersal. Our model also makes quantitative predictions on the rate of dispersal by the dispersing sex and suggests that inbreeding avoidance may only rarely be the sole reason for dispersal.

title: Mammalian mating systems.
abstract: Male mammals show a diverse array of mating bonds, including obligate monogamy, unimale and group polygyny and promiscuity. These are associated with a wide variety of different forms of mate guarding, including the defence of feeding and mating territories, the defence of female groups and the defence of individual receptive females. Female mating bonds include long-term monogamy, serial monogamy, polyandry and promiscuity. Both male and female mating behaviour varies widely within species. Variation in male mating behaviour is related to the effect of male assistance in rearing young and to the defensibility of females by males. The latter is, in turn, related to female ranging behaviour and to the size and stability of female groups. Much of the variation in mammalian mating bonds and systems of mate guarding can be attributed to differences in these three variables.

title: Mating Systems and Strategies
abstract: This book presents the first unified conceptual and statistical framework for understanding the evolution of reproductive strategies. Using the concept of the opportunity for sexual selection, the authors illustrate how and why sexual selection, though restricted to one sex and opposed in the other, is one of the strongest and fastest of all evolutionary forces. They offer a statistical framework for studying mating system evolution and apply it to patterns of alternative mating strategies. In doing so, they provide a method for quantifying how the strength of sexual selection is affected by the ecological and life history processes that influence females' spatial and temporal clustering and reproductive schedules. Directly challenging verbal evolutionary models that attempt to explain reproductive behavior without quantitative reference to evolutionary genetics, this book establishes a more solid theoretical foundation for the field. Among the weaknesses the authors find in the existing data is the apparent ubiquity of condition-dependent mating tactics. They identify factors likely to contribute to the evolution of alternative mating strategies--which they argue are more common than generally believed--and illustrate how to measure the strength of selection acting on them. Lastly, they offer predictions on the covariation of mating systems and strategies, consider the underlying developmental biology behind male polyphenism, and propose directions for future research. Informed by genetics, this is a comprehensive and rigorous new approach to explaining mating systems and strategies that will influence a wide swath of evolutionary biology.

title: Female transfer and inbreeding avoidance in social mammals
abstract: In most social mammals, males leave their natal group to breed in other groups whereas females commonly remain in the same group throughout their lives1. In a few species however, females usually transfer between groups during adolescence1. The functional significance of sex differences in dispersal and their connection, if any, to the avoidance of inbreeding is disputed2–7. Here I show that in polygynous mammals where females commonly remain to breed in their natal group, thdr average age at first conception typically exceeds the average period of residence of adult males in breeding groups. In contrast, where females usually transfer to breed in other groups, the average residence of breeding males or of resident male kin groups typically exceeds the average age of females at first conception. These results support the suggestion that female mammals commonly transfer to avoid inbreeding with their father or other close relatives, although female dispersal may also occur for other reasons8,9.

title: Male-biased dispersal, female philopatry, and routes to fitness in a social corvid
abstract: 1 
Dispersal in many species is sex-biased. Greenwood (1980, Animal Behaviour, 28, 1140–1162) hypothesized that the direction of sex bias was dependent on the mating system, and suggested that female-biased dispersal in birds is associated with monogamy and resource defence by males, while mammalian male-biased dispersal is associated with polygyny and male defence of mates. 
 
2 
Cooperatively breeding brown jays Cyanocorax morio live in large territorial groups and are one of the few bird species known to exhibit male-biased dispersal. Survivorship of adults is high, and both males and females delay breeding for many years. 
 
3 
In this study, dispersers almost always moved to neighbouring social groups, rarely in response to a known breeding vacancy, and both sexes dispersed into groups with fewer members of the same sex than their origin group. 
 
4 
Dispersal and extra-group forays were strongly male biased. Forays were more common during nest building and egg laying, suggesting that males were monitoring mating opportunities, and many males later dispersed into the groups they visited. Genetic parentage analyses indicated that males mainly obtain paternity outside their natal groups through extra-group forays and dispersal. 
 
5 
The major routes to breeding status for females are inheritance of breeding positions on their natal territories and/or breeding there concurrently with an established breeder. Females usually dispersed on their own into groups where reproductive success had previously been poor. 
 
6 
Kin facilitation appears to affect male dispersal options: related males formed coalitions and tended to disperse to groups where male relatives were already established. 
 
7 
Male dispersal, female philopatry, and a matrilineal society correspond to three of Greenwood's seven predictions for a ‘mate-defence’ system, but overt mate defence itself is absent, territorial defence is communal, and genetic polyandry is common. Social behaviour appears to affect a reversal in sex-specific costs and benefits of dispersal, so that females benefit from philopatry and matrilineal inheritance, while males benefit from expanded dispersal options in part through kin facilitation, but without effective mate defence or clear cut sex-specific resource defence.

title: Bat Mating Systems
abstract: Publisher Summary This chapter describes the mating systems of bats, emphasizing research from the last 20 years. For completeness, the chapter lists all species where mating systems are defined, but it discusses only those where there is new information or where additional interpretations are possible. In total, it includes information on the mating systems of 66 species of bats in 10 families. Bats from the largest families (Vespertilionidae, Pteropodidae, Phyllostomidae) are best represented in this literature. In proportion to their species diversity, bats in the Rhinolophidae and Molossidae have received the least attention. Bats from the zoogeographic regions with the greatest numbers of species (Ethiopian, Neotropical, Oriental) also have received the most study. In proportion to regional species richness, mating systems have been least studied in bats from the Australian and Oriental regions. Combined with detailed field studies, the immediate future is likely to see an increasing emphasis on the use of these new molecular methods to resolve the big issues in bat mating systems. It is anticipated that these issues are the questions of apparent monogamy, the significance of multiple mating by females, and the roles of female choice and sperm competition.

title: Social structure of a polygynous tent-making bat, Cynopterus sphinx (Megachiroptera)
abstract: The social structure of an Old World tent-making bat Cynopterus sphinx (Megachiroptera), was investigated in western India. A combination of census and mark–recapture data over 2 years (1996–98) was used to infer the form of the mating system, compositional stability of social groups and mode of new social group formation. The breeding population of C. sphinx was subdivided into diurnal roosting colonies, each of which contained one to five discrete roosting groups and often one or more solitary bats in adjacent roosts. Bats most frequently roosted in stem tents constructed in the flower/fruit clusters of the kitul palm Caryota urens. Temporal variation in social structure was assessed using visual census data for a subset of the study population over 3 years (1995–98) spanning six consecutive reproductive periods. The sex and age composition of diurnal roosting groups indicated a polygynous harem-forming mode of social organization, as groups invariably contained a single adult male, 1–37 reproductive females and their dependent young (n= 33 harems). Harem size averaged 6.1 adults in the wet season (n= 19, sd= 3.5) and 13.6 adults in the dry season (n= 14, sd= 8.5). The same harem social configuration was maintained year-round, despite a high degree of synchrony and seasonality in the timing of reproduction. Juveniles of both sexes dispersed after weaning and sexually immature bats were never present in harems at the time of parturition. Adult females often remained associated as roostmates from one parturition period to the next, and group cohesion was unaffected by turnover of harem males. Adult females frequently transferred among roosts within the same colony, and harems underwent periodic fissions and fusions. The founding of new harems most often resulted from the fissioning of previously cohesive harems within the same colony. However, some harems contained disproportionate numbers of yearling females, indicating that new groups are also founded by nulliparous females of the same age cohort. A significant degree of heterogeneity in age composition among harems was revealed in the 1998 dry season, but was unrelated to age-stratification of tent roosts. Although formation of new harems may be non-random with respect to age composition of the founders, founding events are not restricted to newly created tents and often involve recolonization of previously occupied roosts.

title: Mating system of a Neotropical roost-making bat: the white-throated, round-eared bat, Lophostoma silvicolum (Chiroptera: Phyllostomidae)
abstract: The vast majority of bats strongly depend on, but do not make, shelters or roosts. We investigated Lophostoma silvicolum, which roosts in active termite nests excavated by the bats themselves, to study the relationship between roost choice and mating systems. Due to the hardness of the termite nests, roost-making is probably costly in terms of time and energy for these bats. Video-observations and capture data showed that single males excavate nests. Only males in good physical condition attracted females to the resulting roosts. Almost all groups captured from excavated nests were single male-multifemale associations, suggesting a harem structure. Paternity assignments based on ten polymorphic microsatellites, revealed a high reproductive success of 46% by nest-holding males. We suggest that the mating system of L. silvicolum is based on a resource-defense polygyny. The temperatures in the excavated nests are warm and stable, and might provide a suitable shelter for reproductive females. Reproductive success achieved by harem males appears to justify the time and effort required to excavate the nests. Reproductive success may thus have selected on an external male phenotype, the excavated nests, and have contributed to the evolution of an otherwise rare behavior in bats.

title: SEXUAL SEGREGATION IN UNGULATES: A NEW APPROACH
abstract: Inmany mammals,males and females live solitarilyor inseparate groups outside the breeding season. Sexual segregation is wide-spread in ungulates, but also occurs in whales, seals, monkeys, macropods, elephants, e sh and bird species. What causes segregation by sex is still poorly understood, despite intense research done mainly on different ungulate species. In most species studied, males were clearly larger than females. The evolution of sexual dimorphism in body size has largely been attributed to sexual selection and mating strategies. While the consequences of body-size differences on energy requirements and metabolic rates received most attention, studies on consequences of sexual body-size differences on behavior are lacking. This review emphasizes the importance to study a wide range of social mammals with a different or no degree of sexual segregation and sexual dimorphism in body size; something which has not been done and has greatly limited our ability to test alternative hypotheses. More emphasis has to be put on the study of activity budgets, sociality and habitat choice of non-dimorphic species to explain the evolution of permanent territoriality, of long-term bonds of male-female pairs and of the occurrence of mixed-sex groups (adults), as well as its absence in dimorphic species. We review eve hypotheses proposed to explain sexual segregation, discuss alternative outcomes and predictions for each hypothesis, suggest alternative explanations for the evolution of sexual segregation and mating systems, and indicate new and important directions for research. We conclude that a phylogenetic comparison of behavior of a wide range of ungulates and other mammals will be needed to solve the enigma of sexual segregation.

title: Parentage, reproductive success and breeding behaviour in the greater horseshoe bat (Rhinolophus ferrumequinum)
abstract: Female greater horseshoe bats form maternity colonies each summer in order to give birth and raise young. During the mating period, females visit males occupying territorial sites, copulation takes place and sperm are stored until ovulation occurs, normally in April. Using microsatellite markers and a likelihood method of parentage analysis, we studied breeding behaviour and male reproductive success over a five–year period in a population of bats in south–west Britain. Paternity was assigned with 80% confidence to 44% of young born in five successive cohorts. While a small annual skew in male reproductive success was detected, the variance increased over five years due to the repeated success of a few individuals. Mating was polygynous, although some females gave birth to offspring sired by the same male in separate years. Such repeated partnerships probably result from fidelity for either mating sites or individuals or from sperm competition. Females mated with males born both within and outside their own natal colony; however, relatedness between parents was no less than the average recorded for male–female pairs. Gene flow between colonies is likely to be primarily mediated by both female and male dispersal during the mating period rather than more permanent movements.

title: Behavioural and Genetic Data Suggest that Bechstein's Bats Predominantly Mate Outside the Breeding Habitat
abstract: Investigating mating systems of species with a cryptic lifestyle often requires a combination of behavioural and genetic data. We used such a combined approach to investigate the mating system of the communal breeding Bechstein's bat (Myotis bechsteinii). Although females of this species are philopatric, gene flow among colonies is high. Gene flow occurs if dispersing males mate within the colony to which they moved. Males could gain local matings by defending resources or females in their breeding habitat. Alternatively, mating may take place at swarming sites, apart from the breeding habitat of the females, where males and females of several colonies meet. Whether or not males defend resources or females in the breeding habitat is of importance for understanding the mating system. Detailed observations of individual foraging and roosting behaviour over 4 yr suggest that males do not defend resources or females to gain matings. Moreover, paternity assignment based on microsatellite data of four complete juvenile cohorts showed that local males fathered less than 25% of the juveniles born in the colony where they settled. Even more striking, none of the males that had immigrated into our study area reproduced with the local females.

title: Mate fidelity and intra-lineage polygyny in greater horseshoe bats
abstract: Mating strategies that lead to increased kinship within socially cooperative groups may offer inclusive fitness benefits to individuals, but can also result in higher levels of inbreeding. Here we show in a sexually segregated bat species that females avoid this conflict through two mating behaviours. First, most females revisit and breed with specific, individual males across years, so that their single offspring born in different years are full siblings. Second, relatives in the maternal line, including mothers and daughters, share breeding partners (intra-lineage polygyny) more often than expected by chance. Although these behaviours increased levels of co-ancestry among colony members, there was no concomitant rise in inbreeding. We suggest that when females engage in mate fidelity and intra-lineage polygyny, kin ties among female roost mates will be strengthened, thereby potentially contributing to social group cohesiveness. Our findings reveal the hidden complexity that can underlie polygynous breeding, and highlight a new potential route by which female mate choice could influence social evolution.

title: Genetic variation and population structure in the endangered greater horseshoe bat Rhinolophus ferrumequinum
abstract: Following a dramatic decline last century, the British population of the endangered greater horseshoe bat Rhinolophus ferrumequinum is highly fragmented. To examine the consequences of fragmentation and limited dispersal on patterns of genetic structure and variation, we used microsatellite markers to screen bats from around 50% of the known maternity colonies in Britain, and two areas from continental Europe. Analyses revealed that Welsh and English colonies were genetically isolated. This, and lower variability in Britain than north France, may result from either genetic drift, or the species’ colonization history. Gene flow among most neighbouring colonies was not generally restricted, with one exception. These findings have important implications for the ongoing conservation management of this species.

title: Seeing in the dark: molecular approaches to the study of bat populations
abstract: Whilst the use of molecular genetic techniques is widespread in the fields of population and evolutionary biology, their application within the mammalian order Chiroptera neither reflects the species richness nor the ecological and behavioural diversity of the order. This is despite the fact that the Chiroptera are problematic to study using more direct observational techniques. Here, we standardize and synthesise the current data, assess the contribution of molecular research to the study of bat species and highlight the importance of its continued and expanded use. At an inter‐population level, molecular studies have demonstrated a great diversity of population genetic structure within the order. Among populations of migratory species, genetic structure appears universally low, and hence seasonal movement is likely to be the prevailing influence. However, for sedentary species an array of factors including dispersal ability, extrinsic barriers to gene flow and historical events may determine the extent of genetic partitioning among populations. Intrinsic factors such as wing morphology or roost requirements may also influence population genetic structure in sedentary bat species, a proposal which requires further research. Molecular studies have also made important contributions towards an understanding of social organisation in bats. Evidence indicates that in many polygynous species male mating success does not translate directly into reproductive success, perhaps as a result of multiple mating by females. Estimates of relatedness within and genetic structure among colonies are, in general, very low; a finding which has important implications regarding theories concerning the formation and persistence of bat social groups. Molecular studies have provided new and important insights into the ecology of bats, and have opened up exciting and previously unexplored avenues of research. The data from these studies suggest not only a predictive framework for future studies, but also the use of genetic data in the management and conservation of bat species.

title: SEX‐BIASED DISPERSAL IN A MIGRATORY BAT: A CHARACTERIZATION USING SEX‐SPECIFIC DEMOGRAPHIC PARAMETERS
abstract: We studied the noctule bat (Nyctalus noctula), in which the mitochondrial FST is about 10 times that revealed by nuclear markers, to address two questions. We first verified whether random dispersal of one sex is compatible with highly contrasted mitochondrial and nuclear population structures. Using computer simulations, we then assessed the power of multilocus population differentiation tests when the expected population structure departs only slightly from panmixia. Using an island model with sex‐specific demographic parameters, we found that random male dispersal is consistent with the population structure observed in the noctule. However, other parameter combinations are also compatible with the data. We computed the minimum sex bias in dispersal (at least 69% of the dispersing individuals are males), a result that would not be available if we had used more classical population genetic models. The power of multilocus population differentiation tests was unexpectedly high, the tests being significant in almost 100% of the replicates, although the observed population structure infered from nuclear markers was extremely low (FST= 0.6%).

title: Extreme sex‐biased dispersal in the communally breeding, nonmigratory Bechstein's bat (Myotis bechsteinii)
abstract: Maternity colonies of the communally breeding, nonmigratory Bechstein's bat consist of closely related females that live together with unrelated females, and average colony relatedness is low despite the absence of immigration. We compared the genetic structure of both nuclear and mitochondrial microsatellites in order to quantify sex‐specific dispersal rates. More specifically, we aimed at testing whether male dispersal is able to balance the genetic effect of strong (absolute) female philopatry. Absolute female philopatry, indicated by an extreme mitochondrial DNA population differentiation of 96%, was indeed opposed by strong (possibly complete) male dispersal. Based on our knowledge of the biology of Myotis bechsteinii, we conclude that inbreeding avoidance is likely to be the crucial factor driving male dispersal in this species.

title: High gene diversity at swarming sites suggest hot spots for gene flow in the endangered Bechstein's bat
abstract: Our study shows that endangered Bechstein'sbats utilise distinct habitats at differentstages of their reproductive cycle, a findingthat has implications how habitat should beselected for preservation. Using nuclear andmitochondrial microsatellite DNA markers wecompared gene diversity of Bechstein's batswithin breeding colonies and at potentialmating sites. Bechstein's bat is one of themost threatened European bat species. Duringsummer it depends largely on mature deciduousforests. Females exhibit strict natalphilopatry. They form demographicallyindependent breeding colonies comprisingmaternally closely related bats. Males aresolitary. Like other temperate bats,Bechstein's bats swarm at the end of summer infront of caves. Because the sexes meet there,such swarming sites are potentially importantfor gene flow. Our genetic analyses reveal thatswarming sites have greater mitochondrial DNAgene diversity than colonies. Furthermore,field data on the phenology and reproductivestatus of several hundred individuals suggestthat Bechstein's bats mate during swarming. Incombination our field and genetic data showthat swarming sites provide the opportunity forgene flow among bats originating from differentcolonies. Therefore, we suggest that swarmingsites should be strictly protected to maintainthe observed high levels of gene flow amongcolonies.

title: Contrasted patterns of mitochondrial and nuclear structure among nursery colonies of the bat Myotis myotis
abstract: Thirteen nursery colonies of Myotis myotis were sampled in central Europe to investigate the dispersal behaviour of this bat species. Mitochondrial DNA sequences of 260 bats reveal the occurrence of three evolutionary lineages that have probably originated in distinct glacial refugia and meet in a contact zone near the Alps. Moreover, the strong haplotypic segregation (ΦST=0.540) suggests that breeding females are philopatric. Contrastingly, the low population structure at 15 microsatellite loci (FST=0.022), suggests the homogenizing effect of nuclear gene flow. The different perspectives given by these two markers are consistent with strong male‐biased dispersal. As a result of female philopatry, the local haplotypic variability seems to be largely influenced by historical processes of colonization. Conversely, the homogeneity of nuclear variability within roosts that are located north of the Alps seems to mainly reflect contemporary gene flow. Finally, despite the fact that females are faithful to their natal colony, movements of both males and females occur outside the breeding period. Mitochondrial survey of individuals sampled exclusively in nurseries may thus poorly reflect the metapopulation dynamics of this species.

title: Mean colony relatedness is a poor predictor of colony structure and female philopatry in the communally breeding Bechstein's bat (Myotis bechsteinii)
abstract: In order to understand why animals are social and how group members interact with each other it is important to know their relatedness. However, few studies have investigated the genealogy in complete social groups of free-living animals with low reproductive skew. This holds particularly true for bats. Although almost all bat species are social, their sociobiology is not well understood. Because they are volant, nocturnal and have a rather cryptic life-style, bats are difficult to observe in the wild. Furthermore females are generally gregarious making genetic parent-offspring assignment a challenging task. We used genetic markers in combination with knowledge about age and colony membership of individually marked bats to construct pedigrees in completely sampled maternity colonies of Bechstein's bats (Myotis bechsteinii). Despite considerable fluctuations in population size, no immigration occurred over 5 years in four colonies living in close proximity. Additionally, confrontation tests showed that females of one maternity colony were able to detect and attempted to prevent the intrusion of foreign females into a roost they occupy. Although colonies were absolutely closed, and 75% of the colony members lived together with close relatives (r≥=0.25), mean colony relatedness was nearly zero (0.02). Average relatedness therefore is a poor estimator for the potential of kin selection in Bechstein's bat colonies and may be misleading when attempting to understand the social structure of animals living in groups where many members breed. Based on our results we discuss the potential adaptive value of living in closed societies with low reproductive skew.

title: Population genetic structure and gene flow in a gleaning bat, Plecotus auritus
abstract: During summer the brown long–eared bat Plecotus auritus (Vespertilionidae) forms stable colonies, comprised of both adult females and males and young of the year. A long–term ringing study conducted in north–east Scotland has established that little movement occurs among colonies and that both sexes are recruited into their natal colony. The aim of the present study was to investigate, using microsatellite DNA markers, if genetic structure within the population reflects the spatial structure indicated by ringing. Inter–colony FST estimates obtained for all colony members, and for females and males separately, were low (0.019, 0.026 and 0.011, respectively), but all values differed significantly from zero. These data indicate high gene flow between colonies, although some coancestry among colony members is evident in both sexes. On combining the ringing and genetic data, it is concluded that gene flow occurs via extra–colony copulation, rather than natal dispersal, and that each colony behaves as a distinct subpopulation. Microgeographical genetic isolation by distance was demonstrated for, to our knowledge, the first time in a bat species, and found to be apparent both across the entire study area and along one river valley. The results suggest that extensive macrogeographical population genetic structure may be evident across the species'range.

title: Mitochondrial DNA (mtDNA) reveals that female Bechstein’s bats live in closed societies
abstract: We present a microgeographic analysis of mitochondrial DNA (mtDNA) in Bechstein’s bats using three sources of control region sequence variability, including a novel mtDNA microsatellite, to assess individual relatedness both within and among 10 maternity colonies. Comparison of marker variability among 268 adult females revealed little genetic variability within each colony. However, most colonies were clearly distinguished by colony‐specific mitochondrial haplotypes (total n = 28). Low intracolony variability and strong haplotype segregation among colonies, was reflected by an extraordinary high FST of 0.68, indicating a very low intercolony dispersal rate of approximately one female in five generations. Haplotype distribution among 18 solitary males showed that males frequently disperse between colony locations, indicating the absence of dispersal barriers. Bechstein’s bat maternity colonies are thus closed groups that comprise 20–40 females probably belonging to only one or, at most, two matrilines. The genetic population structure of Bechstein’s bats is in agreement with the hypothesis that females seek familiar and, at least, partially related cooperation partners for raising their young. Alternatively strong philopatry might reflect the importance of profound roost or habitat knowledge for successful reproduction in female Bechstein’s bats.

title: Relatedness structure and kin-biased foraging in the greater horseshoe bat (Rhinolophus ferrumequinum)
abstract: Female greater horseshoe bats (Rhinolophus ferrumequinum) exhibit strong natal philopatry to their maternity roost over many years, leading to the aggregation of matrilineal kin. Maternity colonies may, therefore, be expected to comprise highly related individuals, and, as such, provide conditions suitable for the evolution of kin-selected behaviours. To test these predictions, we examined relatedness and behaviour among matrilineal kin within a colony in south-west Britain. Genetic analysis of 15 matrilines, identified from microsatellite genotyping and long-term ringing surveys, revealed average relatedness levels of 0.17 to 0.64. In contrast, background relatedness among colony females approximated to zero (0.03). These results suggest that inclusive fitness benefits may only be accrued through discriminate cooperation within matrilines, and not at the wider colony level. To examine whether the potential for such benefits is realised through kin- biased cooperation during foraging, females from two matrilines were radio-tracked simultaneously over 3 years. Pairwise home-range overlap correlated significantly with Hamilton's relatedness coefficient. The greatest spatial associations were observed between females and their adult daughters, which shared both foraging grounds and night roosts, sometimes over several years. Tagged females, however, generally foraged and roosted alone, suggesting that kin-biased spatial association probably does not result from either information-transfer or cooperative territorial defence. Such patterns may instead result from a mechanism of maternal inheritance of preferred foraging and roosting sites.

title: Social organization and kinship in the polygynous bat Phyllostomus hastatus
abstract: Summary1.Social behavior in the bat Phyllostomus hastatus was examined in Trinidad, W.I. over a 26-month period. The studies included (a) long-term observations on marked individuals, (b) the use of allozyme polymorphisms to estimate paternity and the genetic relationships among individuals in social groups, and (c) the investigation of foraging behavior by radio-tracking.2.Day-roosting cave colonies of this bat are subdivided into highly stable, compact clusters of adult females (mean cluster size=17.9±5.1 females) and less stable bachelor groups. Female clusters are always tended by a single adult male and genetic tests demonstrated that these harem males father most or all of the babies born to the females in clusters. Harem males actively defend female clusters from other males in the roost.3.Membership in female clusters is extremely stable and the same individuals roost together for years at a time. Harem male tenure can also be very long and several males retained residence in harems through a minimum of three annual reproductive periods. However, harem male turnovers were also frequently observed and in no instance did a change in males result in disruption of the female roosting cluster. Experimentally disrupted harems reconstituted their original memberships even in the absence of males.4.These stable female clusters are not matrilineal kin groups. Juveniles of both sexes disperse and are not recruited into parental social units. New stable female clusters were formed as cohorts of yearling females drawn from different harems and cave colonies. This was corroborated by independent studies on the age structure of harems. Genetic tests showed that the females comprising any cluster were a genetically random sample of the total adult population.5.Radio-tracking revealed that each individual has its own foraging area that it utilizes throughout the year. The foraging areas of females belonging to the same cluster were adjacent to one another and apparently segregated into larger cluster-specific areas. Females occasionally foraged within the areas of other females in their roosting cluster, but females from different clusters did not forage near one another. Harem males did not defend female foraging areas and in fact foraged in areas well apart from their harem females.6.These compact and stable female roosting clusters are the fundamental unit of P. hastatus' social organization, and apparently they facilitate a male strategy of female-defense polygamy. We hypothesize that these stable clusters arise from active cooperative interactions among females on the foraging grounds. The most likely form of cooperation is the sharing of unpredictable food sources among cluster members. In P. hastatus, such behavior has not evolved through nepotism or processes of group selection that require high group stability. All of our observations and the basic biology of this bat suggest that reciprocity is the most likely means by which the system operates. Mutualism and weak altruism may play secondary roles but cannot be evaluated without additional field study.7.Bachelor groups appear to be much less structured than female clusters, and the possibility of cooperation among bachelors is still open to study.

title: GENETIC CONSEQUENCES OF POLYGYNY AND SOCIAL STRUCTURE IN AN INDIAN FRUIT BAT, CYNOPTERUS SPHINX. I. INBREEDING, OUTBREEDING, AND POPULATION SUBDIVISION
abstract: Population subdivision into behaviorally cohesive kin groups influences rates of inbreeding and genetic drift and has important implications for the evolution of social behavior. Here we report the results of a study designed to test the hypothesis that harem social structure promotes inbreeding and genetic subdivision in a population with overlapping generations. Genetic consequences of harem social structure were investigated in a natural population of a highly polygynous fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae), in western India. The partitioning of genetic variance within and among breeding groups was assessed using 10‐locus microsatellite genotypes for 431 individually marked bats. Genetic analysis of the C. sphinx study population was integrated with field data on demography and social structure to determine the specific ways in which mating, dispersal, and new social group formation influenced population genetic structure. Microsatellite data revealed striking contrasts in genetic structure between consecutive offspring cohorts and between generations. Relative to the 1998 (dry‐season) offspring cohort, the 1997 (wet‐season) cohort was characterized by a more extensive degree of within‐group heterozygote excess (FIS=−0.164 vs. −0.050), a greater degree of among‐group subdivision (FST= 0.123 vs. 0.008), and higher average within‐group relatedness (r= 0.251 vs. 0.017). Differences in genetic structure between the two offspring cohorts were attributable to seasonal differences in the number and proportional representation of male parents. Relative to adult age‐classes, offspring cohorts were characterized by more extensive departures from allelic and genotypic equilibria and a greater degree of genetic subdivision. Generational differences in F‐statistics indicated that genetic structuring of offspring cohorts was randomized by natal dispersal prior to recruitment into the breeding population. Low relatedness among harem females (r= 0.002–0.005) was primarily attributable to high rates of natal dispersal and low rates of juvenile survivorship. Kin selection is therefore an unlikely explanation for the formation and maintenance of behaviorally cohesive breeding groups in this highly social mammal.

title: Genetic mating system and the significance of harem associations in the bat Saccopteryx bilineata
abstract: We analysed the polygynous mating system of the bat Saccopteryx bilineata using behaviour observations and genetic data on 11 microsatellite DNA loci. Basic social units in S. bilineata are harem groups that consist of single males and up to eight females. Colonies comprise several harem groups, and the composition of colonies and harems is often stable over several reproductive seasons. The combination of parentage exclusion and likelihood‐based parentage assignment in this study produced detailed parentage information for a large colony of S. bilineata. Reproduction occurred mostly within the colony (17% extra‐colony paternity), but social associations in harems within the colony did not represent reproductive units (70% extra‐harem paternity). The latter finding was consistent over three reproductive seasons. Spatial association of the roosting sites of males and females could not explain parentage patterns in the colony. Even though intra‐harem paternity was less frequent than expected, it contributed significantly to reproduction of harem males. On average, the number of offspring sired by a male with females in his harem territory increased significantly with harem size, which corresponds to the higher energetic investment that is related to the maintenance of large harems. However, extra‐harem paternity was not correlated with a male's harem size or intra‐harem reproductive success. This suggests that individual preferences of females rather than male traits associated with the ability to defend large harems are most likely to cause the detected differences between social association and genetic mating system.

title: Ecology of an exceptional roost: Energetic benefits could explain why the bat Lophostoma silvicolum roosts in active termite nests
abstract: The ability to create shelters that provide protection from the environment is widespread among animals. However, in spite of the central role roosts play in the life of bats (Chiroptera), only a few species have developed the ability to make their own refuges, one of them being the Neotropical Lophostoma silvicolum. This bat creates and inhabits cavities in active arboreal nests of the termite Nasutitermes corniger. We measured temperature in cavities inside active and dead termite nests, and in tree holes occupied by closely related bats, to determine whether energetic benefits compensate for the cost of excavating the hard nests. The inside temperatures of active termite nests were very stable and 2.1–2.8 °C warmer than those of the other two potential roost types. The observed temperature difference is estimated to allow euthermic 
L. silvicolum to save about 5% of their daily energy expenditure when roosting in active 
termite nests instead of dead nests or tree holes. Suitable roosting conditions result from the presence of termites and are independent of nest architecture. Our results indicate that the benefits of higher temperatures may be one of the driving forces promoting the evolution of active roost making in bats.

title: Roosting and Foraging Behavior of Two Neotropical Gleaning Bats, Tonatia silvicola and Trachops cirrhosus (Phyllostomidae)1
abstract: We studied roosting and foraging behavior of two Neotropical gleaning bats, ďOrbigny's round-eared bat, Tonatia silvicola, and the fringe-lipped bat, Trachops cirrhosus (Phyllostomidae). Techniques included radio-tracking in a tropical lowland forest in Panama and analysis of data from long-term studies in Panama and Venezuela. Day roosts of T. silvicola were in arboreal termite nests. T. cirrhosus roosted in a hollow tree. T. silvicola emerged late (ca 60 min after sunset), and foraged close to the roosts (maximum distance 200–500 m). T. cirrhosus emerged early (ca 30 min after local sunset), and foraged farther from its roost (>1.5 km). Both bats used small foraging areas (3–12 ha) in tall, open forest. They foraged in continuous flight (maximum 27–36 min) or in short sally flights (<1 minute) from perches (“hang-and-wait” strategy). The small foraging areas of these bats and their sedentary foraging mode most likely make them vulnerable to habitat fragmentation.

title: Length and sequence variation in evening bat D-loop mtDNA.
abstract: Length variation in D-loop mitochondrial DNA was observed after amplification with the polymerase chain reaction (PCR) in 28% of 195 evening bats, Nycticeius humeralis, from seven colonies. Nucleotide sequences of PCR products show that this heteroplasmy is characterized by an 81-bp region which is tandemly repeated five to eight times. Southern blots using PCR products as probes on HaeIII genomic digests confirm the presence of heteroplasmy. Furthermore, densitometry of electrophoresed PCR products from 109 mother-offspring pairs indicate that heteroplasmy is stably transmitted from mother to offspring with one exception: a heteroplasmic offspring had a homoplastic mother and sib. Nucleotide sequences from this family reveal that a repeat duplication and deletion occurred. The observed mutation rate per generation, mu, for length polymorphism is comparable to an independent estimate, mu = 10(-2), based on hierarchical diversity statistics. With the exception of the repeat nearest the proline tRNA gene, sequence similarities between repeats within bats are consistent with a model of concerted evolution due to unidirectional replication slippage. Selection is inferred to act on the first repeat because in comparison to other repeats it has the least sequence divergence among bats, the fewest transversions, and the lowest minimum free energy associated with folding.

title: Evolution of repeated sequence arrays in the D-loop region of bat mitochondrial DNA.
abstract: Analysis of mitochondrial DNA control region sequences from 41 species of bats representing 11 families revealed that repeated sequence arrays near the tRNA-Pro gene are present in all vespertilionine bats. Across 18 species tandem repeats varied in size from 78 to 85 bp and contained two to nine repeats. Heteroplasmy ranged from 15% to 63%. Fewer repeats among heteroplasmic than homoplasmic individuals in a species with up to nine repeats indicates selection may act against long arrays. A lower limit of two repeats and more repeats among heteroplasmic than homoplasmic individuals in two species with few repeats suggests length mutations are biased. Significant regressions of heteroplasmy, theta and pi, on repeat number further suggest that repeat duplication rate increases with repeat number. Comparison of vespertilionine bat consensus repeats to mammal control region sequences revealed that tandem repeats of similar size, sequence and number also occur in shrews, cats and bighorn sheep. The presence of two conserved protein-binding sequences in all repeat units indicates that convergent evolution has occurred by duplication of functional units. We speculate that D-loop region tandem repeats may provide signal redundancy and a primitive repair mechanism in the event of somatic mutations to these binding sites.

title: ESTIMATING F‐STATISTICS FOR THE ANALYSIS OF POPULATION STRUCTURE
abstract: This journal frequently contains papers that report values of F-statistics estimated from genetic data collected from several populations. These parameters, FST, FIT, and FIS, were introduced by Wright (1951), and offer a convenient means of summarizing population structure. While there is some disagreement about the interpretation of the quantities, there is considerably more disagreement on the method of evaluating them. Different authors make different assumptions about sample sizes or numbers of populations and handle the difficulties of multiple alleles and unequal sample sizes in different ways. Wright himself, for example, did not consider the effects of finite sample size. The purpose of this discussion is to offer some unity to various estimation formulae and to point out that correlations of genes in structured populations, with which F-statistics are concerned, are expressed very conveniently with a set of parameters treated by Cockerham (1 969, 1973). We start with the parameters and construct appropriate estimators for them, rather than beginning the discussion with various data functions. The extension of Cockerham's work to multiple alleles and loci will be made explicit, and the use of jackknife procedures for estimating variances will be advocated. All of this may be regarded as an extension of a recent treatment of estimating the coancestry coefficient to serve as a mea-

title: Testing differentiation in diploid populations.
abstract: We examine the power of different exact tests of differentiation for diploid populations. Since there is not necessarily random mating within populations, the appropriate hypothesis to construct exact tests is that of independent sampling of genotypes. There are two categories of tests, FST-estimator tests and goodness of fit tests. In this latter category, we distinguish "allelic statistics", which account for the nature of alleles within genotypes, from "genotypic statistics" that do not. We show that the power of FST-estimator tests and of allelic goodness of fit tests are similar when sampling is balanced, and higher than the power of genotypic goodness of fit tests. When sampling is unbalanced, the most powerful tests are shown to belong to the allelic goodness of fit group.

title: ESTIMATING RELATEDNESS USING GENETIC MARKERS
abstract: A new method is described for estimating genetic relatedness from genetic markers such as protein polymorphisms. It is based on Grafen's (1985) relatedness coefficient and is most easily interpreted in terms of identity by descent rather than as a genetic regression. It has several advantages over methods currently in use: it eliminates a downward bias for small sample sizes; it improves estimation of relatedness for subsets of population samples; and it allows estimation of relatedness for a single group or for a single pair of individuals. Individual estimates of relatedness tend to be highly variable but, in aggregate, can still be very useful as data for nonparametric tests. Such tests allow testing for differences in relatedness between two samples or for correlating individual relatedness values with another variable.

title: Statistical confidence for likelihood‐based paternity inference in natural populations
abstract: Paternity inference using highly polymorphic codominant markers is becoming common in the study of natural populations. However, multiple males are often found to be genetically compatible with each offspring tested, even when the probability of excluding an unrelated male is high. While various methods exist for evaluating the likelihood of paternity of each nonexcluded male, interpreting these likelihoods has hitherto been difficult, and no method takes account of the incomplete sampling and error‐prone genetic data typical of large‐scale studies of natural systems. We derive likelihood ratios for paternity inference with codominant markers taking account of typing error, and define a statistic Δ for resolving paternity. Using allele frequencies from the study population in question, a simulation program generates criteria for Δ that permit assignment of paternity to the most likely male with a known level of statistical confidence. The simulation takes account of the number of candidate males, the proportion of males that are sampled and gaps and errors in genetic data. We explore the potentially confounding effect of relatives and show that the method is robust to their presence under commonly encountered conditions. The method is demonstrated using genetic data from the intensively studied red deer (Cervus elaphus) population on the island of Rum, Scotland. The Windows‐based computer program, CERVUS , described in this study is available from the authors. CERVUS can be used to calculate allele frequencies, run simulations and perform parentage analysis using data from all types of codominant markers.

title: Roost structure, modification, and availability in the white-throated, round-eared bat, Lophostoma silvicolum (Phyllostomidae) living in active termite nests
abstract: We studied roost structure, modification, and availability in Lophostoma silvicolum (Phyllostomidae), an insectivorous gleaning bat, on Barro Colorado Island (BCI),Panama. Collection of nest material beneath termitaria and infrared video filming indicated that males of L. silvicolum excavate and maintain cavities inside active
termite nests. A binary logistic regression analysis showed that to be suitable as roosts, termite nests have to be larger than 30 cm in diameter and taller than 30 cm,
well shaded, with few transecting branches, and freely accessible from below. Use of active termite nests as roosts may provide several benefits to L. silvicolum, including
reduction of competition for roost sites with sympatric bat species, reduced parasite load and a suitable microclimate. A comparison of number of all termite nests in selected forest plots with number of termite nests that are potentially suited as bat roosts and number of termite nests that are actually used by bats suggests that L. silvicolum may not be roost-limited on BCI in spite of its highly specialized roost choice.

title: Detectability, philopatry, and the distribution of dispersal distances in vertebrates.
abstract: Dispersal is of central importance to population biology, behavioral ecology and conservation. However, because field studies are based on finite study areas, nearly all dispersal distributions for vertebrates currently available are biased, often highly so. The inadequacy of dispersal data obtained directly by traditional methods using population studies of marked individuals is highlighted by comparing the resulting distributions with dispersal estimates obtained by radio-tracking and by using genetic estimates of gene flow.

title: Female-biased dispersal in the monogamous mammal Crocidura russula: evidence from field data and microsatellite patterns.
abstract: We investigated dispersal patterns in the monogamous Crocidura russula, based both on direct field observations (mark-recapture data) and on genetic analyses (microsatellite loci). Natal dispersal was found to be low. Most juveniles settled within their natal territory or one immediately adjacent. Migration rate was estimated to two individuals per year and per population. The correlation between genetic and geographical distances over a 16 km transect implies that migration occurs over short ranges. Natal dispersal was restricted to first-litter juveniles weaned in early May; this result suggests a direct dependence of dispersal on reproductive opportunities. Natal dispersal was highly female biased, a pattern unusual among mammals. Its association with monogamy provides support for the resource-competition model of dispersal. Our results demonstrate that a state-biased dispersal can be directly inferred from microsatellite genotype distributions, which opens new perspectives for empirical studies in this area.

title: Genetic evidence for a higher female migration rate in humans
abstract: Mitochondrial DNA and the Y chromosome have been used extensively in the study of modern human origins and other phylogenetic questions, but not in the context of their sex-specific modes of transmission. mtDNA is transmitted exclusively by females, whereas the Y chromosome is passed only among males. As a result, differences in the reproductive output or migration rate of males and females will influence the geographic patterns and relative level of genetic diversity on the Y chromosome, autosomes and mtDNA (ref. 1). We have found that Y chromosome variants tend to be more localized geographically than those of mtDNA and the autosomes. The fraction of variation within human populations for Y chromosome single nucleotide polymorphisms (SNPs) is 35.5%, versus 80–85% for the autosomes and mtDNA (refs 6, 7, 8). A higher female than male migration rate (via patrilocality, the tendency for a wife to move into her husband's natal household) explains most of this discrepancy, because diverse Y chromosomes would enter a population at a lower rate than mtDNA or the autosomes. Polygyny may also contribute, but the reduction of variation within populations that we measure for the Y chromosome, relative to the autosomes and mitochondrial DNA, is of such magnitude that differences in the effective population sizes of the sexes alone are insufficient to produce the observation.

title: Female dispersal and relatedness structure in common wombats (Vombatus ursinus)
abstract: Dispersal patterns were investigated in the common wombat Vombatus ursinus using microsatellite genetic data collected from three study sites. Two of these were within large, high-density populations in Victoria, south-eastern Australia, while the third was a small, isolated population in South Australia. Genetic assignment tests revealed that in the continuous populations, females were more likely to be immigrants into the sampling areas than were males, who were more likely to have been born locally. No such difference between the sexes was detected for the isolated population. At all three sites, pairwise relatedness estimates for males were negatively correlated with geographic distance, suggesting related males were clustered. This pattern was not observed among females, other than in the isolated population, where pairs of females showed a weak decline of relatedness with increasing geographic distance over a large spatial scale. Taken together, these data provide strong evidence that dispersal is predominantly by females. Furthermore, the observed spatial structure of relatedness suggests female breeding dispersal, a rare finding among mammalian species. Genetic variation within the isolated population was significantly reduced compared to the sites in Victoria. Our data are not sufficient to distinguish between two possible causes for this: (1) long-term small size and isolation of populations at the edge of the species' range where resources may be more patchily distributed; (2) a genetic bottleneck effect of recent isolation resulting from agricultural development.

title: Dispersed Male Networks in Western Gorillas
abstract: Although kin-selection theory has been widely used to explain the tendency of individuals to bias beneficial behaviors towards relatives living within the same social group, less attention has focused on kin-biased interactions between groups. For animal societies in which females emigrate, as is the case for mountain gorillas (Gorilla beringei beringei), encounters between males in different groups often involve aggressive displays that can escalate to physical violence and fatal injuries. However, recent findings on the little-studied western gorilla (Gorilla gorilla) indicate that interactions between social groups occur more frequently than they do in mountain gorillas and are often, although not always, surprisingly nonaggressive. We investigated the pattern of genetic relationships between individuals of different groups and found evidence suggesting a previously unrecognized "dispersed male network" social structure in western gorillas in which the single males leading social groups were usually related to one or more nearby males. We propose that this provides a basis for extra-group, kin-biased behaviors and may explain the reported peaceful intergroup interactions. Furthermore, these results suggest that a patrilocal social structure, in which males remain in their natal region and potentially benefit from kin associations, is a feature unifying African apes and humans.

title: Are dispersal and inbreeding avoidance related?
abstract: Sex differences in dispersal and inter-group transfer by birds and mammals are often con- sidered to be evolved responses to the phenomenon of inbreeding depression. This belief is derived from 'natural selection logic', which holds that (1) because inbreeding depression is demonstrably costly, selection must have acted to minimize its occurrence, and (2) as sex differences in dispersal often appear to be the only thing preventing inbreeding, these sex differences must be the expected adaptations for avoiding inbreeding depression. However, although the sex differences in median dispersal distance observed among many small mammals and birds may reduce average levels of inbreeding within a population, they nevertheless leave the majority of individuals 'at risk' for inbreeding; such differences can be responses to inbreeding depression only in a group selection model. Furthermore, natal dispersal by both sexes occurs in many group-living species. In these species, emigration by individuals of one sex cannot easily be attributed to avoiding inbreeding because opposite-sex relatives also emigrate. Though most authors acknowledge that sexual dispersal patterns may be epiphenomenal consequences of other factors (e.g. intrasexual aggression), this point is rarely considered further. In this paper we critically review several frequently cited examples of differential dispersal, and conclude that 'other factors', such as intrasexual competition and territory choice, explain these observations more com- pletely and consistently than does the inbreeding avoidance hypothesis. Observed dispersal patterns simply reflect sex differences in the balance between the advantages of philopatry and the costs of intrasexual competition.

title: Male dominance, paternity, and relatedness in the Jamaican fruit‐eating bat (Artibeus jamaicensis)
abstract: We analysed variation at 14 nuclear microsatellite loci to assess the genetic structure, relatedness, and paternity of polygynous Jamaican fruit‐eating bats. A total of 84 adults captured in two caves exhibited little genetic differentiation between caves (FST = 0.008). Average relatedness among adult females in 10 harem groups was very low (R = 0.014 ± 0.011), providing no evidence of harem structure. Dominant and subordinate males shared paternity in large groups, while dominant and satellite males shared paternity in smaller groups. However, our results suggest that male rank influences paternity. Dominant males fathered 69% of 40 offspring, followed by satellite (22%) and subordinate males (9%). Overall adult male bats are not closely related, however, in large harem groups we found that subordinate and dominant males exhibited relatedness values consistent with a father‐offspring relationship. Because dominant and subordinate males also sired all the pups in large groups, we propose that their association provides inclusive fitness to them.

title: The social organization of the common vampire bat
abstract: SummaryVariability at seven polymorphic allozyme loci and observations of dispersal and mating provide evidence for nonrandom genetic structure among adult female groups of the highly social bat, Desmodus rotundus. The average degree of relatedness, estimated by allelic correlations at each locus, within three and six groups of females is 0.018 (SE=0.013) and 0.032 (SE=0.023), respectively. Even though these estimates do not differ significantly from zero, a multivariate analysis of variance of individual allele frequencies reveals that three of six pairwise comparisons of groups reach significance. This genetic heterogeneity within a population does not lead to increased genetic subdivision between populations. Mean classificatory ability of the discriminant functions drops from 84% for assignment to group to 56% for assignment to population. This pattern of genetic variability is due to recruitment of female offspring into their natal groups and forced male dispersal. Occasional movements of unrelated females between groups lead to the formation of multiple matrilines within groups. Although males fight viciously for access to the top of preferred female roosting sites and top males mate preferentially with females in that roost, mean maximum paternity for top males is only 46%. Consequently, male mating success is sufficiently random to maintain gametic equilibria among all pairs of loci. Given an infant mortality of 54%, mean male tenure of 17 months, and a birth interval of 10 months, females are unlikely to be related through common male ancestors. In one group, the average degree of relatedness, derived from matrilineal pedigrees, is 0.11 (SD=0.17). Computer simulations of the growth of a group of female D. routundus show that the low level of relatedness within groups is expected even if the proportion of unrelated females allowed into a group decreases. This pattern holds for any animal which recruits one sex into its social group and has relatively high juvenile mortality followed by low adult mortality.

title: FISSION, FUSION AND NONRANDOM ASSOCIATIONS IN FEMALE BECHSTEIN'S BATS (MYOTIS BECHSTEINII)
abstract: Maternity colonies of the Bechstein's bat (Myotis bechsteinii) are socially closed units that frequently split into subgroups which occupy different roosts. We analysed the social structure of one colony over three years in the field and quantified associations among pairs of females by using three association indices. Colony members exhibited marked mixing, although individual composition of subgroups was not completely random. Females associated according to the reproductive status, with lactating females preferentially roosting together. Relatedness, determined from 5 nuclear and 1 mitochondrial microsatellite, had no consistent influence on the degree of association. In combination, the indices allowed for the interpretation that nonrandom associations occur even in the absence of shared roost and group size preferences. High individual associations among reproducing female Bechstein's bats might reflect the importance of cooperation in maternity colonies. The frequent fission and fusion of subgroups suggests a flexible reaction of Bechstein's bats according to enviromental conditions.

title: Roost selection by the long-tailed bat, Chalinolobus tuberculatus, in temperate New Zealand rainforest and its implications for the conservation of bats in managed forests
abstract: Roost selection by the threatened New Zealand long-tailed bat (Chalinolobus tuberculatus) was examined in temperate beech (Nothofagus) rainforest in New Zealand. Seventy-three bats were radio-tracked during the summers of 1993–1997 to 304 roost cavities in 291 different trees. Roost tree and site characteristics were compared with those of 593 randomly selected trees. Bats selected roosts on the basis of topography, forest composition and tree characteristics. Ninety-five percent of roost trees were in mature, open-structured lowland forest on the relatively flat valley floor within 500 m of the forest edge. Four tree species (including dead trees) were used as day roosts. C. tuberculatus did not discriminate between tree species per se, but selected roost trees on the basis of functional characteristics associated with these trees. Bats actively selected taller trees which had relatively low canopy closure, larger stem diameters, larger trunk surface areas and greater numbers of cavities than random trees. Red beech (Nothofagus fusca) and dead trees were most likely to provide these preferred characteristics. Seventy-four percent of roost trees were c. 100–>600 years of age. Such trees are targeted for removal under most forest management practices. Selection of specialised roosts, high roost lability and low levels of roost re-use indicate that C. tuberculatus need large areas of mature forest. We predict that outside protected areas, the low availability of suitable roost trees may limit bat populations.

title: Analysis of Spix's disc-winged bat association patterns and roosting home ranges reveal a novel social structure among bats
abstract: Spix's disc-winged bats, Thyroptera tricolor , roost in young, rolled leaves of Heliconia or Calathea plants. In this paper, we examined how the combination of high habitat availability, low occupancy rate and short longevity of those roosts may affect the pattern of interactions among individuals in the population. We regularly censused a 5.69-ha study area in northeastern Costa Rica and examined patterns of association using mark–recapture data. Thyroptera tricolor formed behaviourally cohesive social groups of mixed sex, ranging in size from four to 14 individuals. Approximately 85% of dyads maintained associations over time periods of up to 100 days, and 40% of dyads maintained longer-term associations of at least 420 days across sex classes. Individuals within social groups did not always roost together, but they shared a small common roosting home range, which averaged just 0.19 ha. Members of different social groups rarely associated, although limited associations between members of select social groups in one subunit were observed. However, roosting home ranges of adjacent social groups often overlapped (up to 39% of home ranges, and up to 92% of the area of the smaller home range), and home range centres were situated less than 100 m apart. Thus, social groups rarely interacted but overlapped in space. The features of this social system are unique among bats and mammals in general, and point to groupings based on kinship or cooperation.

title: Mitochondrial DNA phylogeography of western lowland gorillas (Gorilla gorilla gorilla)
abstract: The geographical distribution of genetic variation within western lowland gorillas (Gorilla gorilla gorilla) was examined to clarify the population genetic structure and recent evolutionary history of this group. DNA was amplified from shed hair collected from sites across the range of the three traditionally recognized gorilla subspecies: western lowland (G. g. gorilla), eastern lowland (G. g. graueri) and mountain (G. g. beringei) gorillas. Nucleotide sequence variation was examined in the first hypervariable domain of the mitochondrial control region and was much higher in western lowland gorillas than in either of the other two subspecies. In addition to recapitulating the major evolutionary split between eastern and western lowland gorillas, phylogenetic analysis indicates a phylogeographical division within western lowland gorillas, one haplogroup comprising gorilla populations from eastern Nigeria through to southeast Cameroon and a second comprising all other western lowland gorillas. Within this second haplogroup, haplotypes appear to be partitioned geographically into three subgroups: (i) Equatorial Guinea, (ii) Central African Republic, and (iii) Gabon and adjacent Congo. There is also evidence of limited haplotype admixture in northeastern Gabon and southeast Cameroon. The phylogeographical patterns are broadly consistent with those predicted by current Pleistocene refuge hypotheses for the region and suggest that historical events have played an important role in shaping the population structure of this subspecies.

title: Activity levels of bats and katydids in relation to the lunar cycle
abstract: Animals are exposed to many conflicting ecological pressures, and the effect of one may often obscure that of another. A likely example of this is the so-called “lunar phobia” or reduced activity of bats during full moon. The main reason for lunar phobia was thought to be that bats adjust their activity to avoid predators. However, bats can be prey, but many are carnivorous and therefore predators themselves. Thus, they are likely to be influenced by prey availability as well as predation risk. We investigated the activity patterns of the perch-hunting Lophostoma silvicolum and one of its main types of prey, katydids, to assess the influence of the former during different phases of the lunar cycle on a gleaning insectivorous bat. To avoid sampling bias, we used sound recordings and two different capture methods for the katydids, as well as video monitoring and radio-telemetry for the bats. Both, bats and katydids were significantly more active during the dark periods associated with new moon compared to bright periods around the full moon. We conclude that foraging activity of L. silvicolum is probably influenced by prey availability to a large extent and argue that generally the causes of lunar phobia are species-specific.