bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cannibalizing Harmonia axyridis (Coleoptera: Coccinellidae) larvae use endogenous cues to avoid eating relatives
Authors: Joseph  , Snyder  , Moore  
Published: March 2003

Abstract
Cannibalism is widespread among many different organisms, and can have both negative and positive fitness consequences. Avoiding eating relatives can minimize negative fitness consequences of cannibalism. Such avoidance requires kin discrimination, but evidence for this ability among cannibals is limited with little data that address the cues used in such discrimination. We examined whether larvae of the ladybird beetle Harmonia axyridis avoid eating their relatives. We further manipulated environmental factors to create individuals that had similar or dissimilar rearing environments to begin to test for endogenous versus exogenous recognition cues. In our experiments, third-instar larvae were much less likely to cannibalize if they were interacting with a relative. Larvae that did cannibalize kin required more encounters, and significantly delayed cannibalism, compared to larvae cannibalizing unrelated individuals. Acquired cues were less important. Even though the different rearing environment resulted in significantly different phenotypic effects, similarity or dissimilarity of rearing environment had no effect on cannibalism, and there was no interaction between environments and relatedness in cannibalism. We suggest that H. axyridis has a well-developed kin discrimination system, and that kin recognition in this ladybird beetle is based on endogenous rather than exogenous cues. We also argue that these cues reflect either direct or indirect genetic effects on larval phenotypes.
Evolution of kleptoparasitism as a war of attrition
Authors: Ruxton  , Broom  
Published: March 2003

Abstract
Previous models of kleptoparasitism (resource stealing) assume that contests over resource items are of fixed duration. Here we suggest that such contests will often be well represented as a war of attrition, with the winner being the individual who is prepared to contest for the longer time. Given that time spent in contests cannot be used to search for other resource items, we provide an analytical expression for the evolutionarily stable distribution of contest times. This can be used to investigate the circumstances under which we would expect kleptoparasitism to evolve. In particular, we focus on situations where searching for conspecifics to kleptoparasitize can only be achieved at a cost of reduced resource discovery by other means; under such circumstances we show that kleptoparasitism is not evolutionarily stable.
Variation of plastic responses to oxygen availability within the hybridogenetic Rana esculenta complex
Authors: Plénet  , Pagano  , Joly  , Fouillet  
Published: March 2003

Abstract
The hypothesis of superiority of hybrid phenotype to explain the maintenance of hybridogenesis (exclusion of one parental genome in the germline before meiosis) was investigated in the Rana esculenta complex. Survival and growth of progenies from each parental and hybrid lineages were compared across contrasted conditions of oxygen availability (this factor is suspected to influence habitat utilization of each form of the complex). Whereas growth and development were strongly affected by constant hypoxic conditions in the R. ridibunda lineage, they were not altered in the R. lessonae lineage. Because the performance of the hybrid (R. esculenta) lineage proved to be intermediate between the parental species, no heterosis effect was detected. These results supported the intermediate niche hypothesis as an alternative to the heterotic hybrid superiority hypothesis. The ecological and evolutionary implications are then discussed.
Local population success in heterogeneous habitats: reciprocal transplant experiments completed on a desert spider
Authors: Riechert  , Hall  
Published: March 2003

Abstract
Reciprocal transplant experiments were completed to test for selection against the mixing of behavioural phenotypes in a desert spider. Most Agelenopsis aperta populations experience low prey abundances and competition for web-sites that provide shelter from thermal extremes. These conditions favour aggressiveness towards both prey and conspecifics (an ‘arid-land behavioural phenotype’). The spider also occupies narrow stretches of riparian habitat bordering spring-fed streams and rivers. Here it is released from competition for prey and foraging sites, but is subject to predation by birds. A less aggressive/more fearful behaviour is selected for in these riparian habitats (a ‘riparian behavioural phenotype’). Previous work with this spider indicates that there is genetic differentiation between arid-land and riparian populations. However, the degree to which genetic differentiation is achieved may be limited by gene flow. Reciprocal sets of enclosures were established in: (1) a dry evergreen woodland site (arid-land phenotype) and (2) a neighbouring riparian site (riparian phenotype) in south-eastern Arizona. Equal numbers of field collected, early instar A. aperta were introduced into native and transplant enclosures in each habitat. After 6 months of site-imposed selection, survivorship was determined and growth estimates and behavioural trials completed on spiders remaining in the different enclosures. The same behavioural test was subsequently applied to lab-reared offspring of the spiders surviving the respective selection regimes.
Riparian transplants showed both poor survival and retarded growth in the dry woodland habitat when compared with both arid-land and riparian natives. Arid-land transplants that survived, however, grew equally well in riparian habitat as did dry woodland and riparian natives. Behavioural assays conducted on test subjects after selection and on their offspring reared in a controlled laboratory environment indicate that phenotypes that were inappropriate to the respective habitats were selected against in the transplant experiments. The frequency distribution of transplant spider behaviour on a continuum from fearful to aggressive was intermediate between that exhibited by respective native riparian and dry woodland spiders. It is concluded that while arid-land and riparian behavioural ecotypes do exist, directional gene flow of arid-land phenotypes into riparian habitat limits population subdivision.
Genetic consequences of the metapopulation biology of a facultatively sexual freshwater invertebrate
Authors: Freeland  , Noble  , Okamura  
Published: March 2003

Abstract
Theoretical models of the impact of a metapopulation structure on the genetics of a species have resulted in multiple predictions that have seldom been empirically evaluated. Here we present microsatellite data from 14 populations of a freshwater bryozoan, Cristatella mucedo, collected along a waterfowl migratory route in north-western Europe. C. mucedo is facultatively sexual and has the unusual tactic of dispersing via asexually generated propagules. These propagules are likely to be dispersed by waterfowl and therefore the populations that we sampled were expected to maintain some degree of connectivity. Our data illustrate a metapopulation comprising well-differentiated populations connected by low levels of ongoing gene flow, patterns that agree with predictions based on theoretical work. However, contrary to expectations of a metapopulation, particularly one in which asexual reproduction predominates, genetic variation within populations was often high. This diversity seems to be at least partially attributable to the gene flow that results from ongoing dispersal.
Cryptic speciation among intestinal parasites (Trematoda: Digenea) infecting sympatric host fishes (Sparidae)
Authors: Jousson  , Bartoli  , Pawlowski  
Published: March 2003

Abstract
In the north-western (NW) Mediterranean, the teleosts Diplodus sargus, D. vulgaris and D. annularis coexist in infralittoral habitats. These fishes are infected by two species of the Digenea (Platyhelminthes, Trematoda): Macvicaria crassigula (Opecoelidae) and Monorchis parvus (Monorchiidae) for which we obtained Internal Transcribed Spacer rDNA sequences. Each parasite species represents a complex of two cryptic species, one restricted to D. annularis, and the other shared by D. sargus and D. vulgaris. Cytochrome b mtDNA sequences were used to infer host phylogenetic relationships which showed that the distribution of parasites in Diplodus hosts is not a consequence of coevolutionary interactions. We used diet analyses available for the fish hosts to assess the degree of overlap in the use of food among the three species. The feeding overlap was significant only between D. sargus and D. vulgaris, but not for the other fish pairs. The possible mechanisms involved in the speciation of the digenean fauna of Diplodus fishes are discussed.
Genetic variation and asexual reproduction in the facultatively parthenogenetic cockroach Nauphoeta cinerea: implications for the evolution of sex
Authors: Corley L. S. , Blankenship J. R. , Moore A. J. 
Published: March 2003

Abstract
Asexual reproduction could offer up to a two-fold fitness advantage over sexual reproduction, yet higher organisms usually reproduce sexually. Even in facultatively parthenogenetic species, where both sexual and asexual reproduction is sometimes possible, asexual reproduction is rare. Thus, the debate over the evolution of sex has focused on ecological and mutation-elimination advantages of sex. An alternative explanation for the predominance of sex is that it is difficult for an organism to accomplish asexual reproduction once sexual reproduction has evolved. Difficulty in returning to asexuality could reflect developmental or genetic constraints. Here, we investigate the role of genetic factors in limiting asexual reproduction in Nauphoeta cinerea, an African cockroach with facultative parthenogenesis that nearly always reproduces sexually. We show that when N. cinerea females do reproduce asexually, offspring are genetically identical to their mothers. However, asexual reproduction is limited to a nonrandom subset of the genotypes in the population. Only females that have a high level of heterozygosity are capable of parthenogenetic reproduction and there is a strong familial influence on the ability to reproduce parthenogenetically. Although the mechanism by which genetic variation facilitates asexual reproduction is unknown, we suggest that heterosis may facilitate the switch from producing haploid meiotic eggs to diploid, essentially mitotic, eggs.
Phylogeography of Caribbean lizard malaria: tracing the history of vector-borne parasites
Authors: Perkins S. L. 
Published: March 2003

Abstract
The Anolis lizards of the eastern Caribbean islands are parasitized by several species of malaria parasites (Plasmodium). Here I focus on two species of Plasmodium, using molecular data (mitochondrial cytochrome b sequences) to recover the phylogeography of the parasites throughout the Lesser Antilles and Puerto Rico. The two parasites were originally described as a single species, P. azurophilum, which infects both red and white blood cells. Here the two species are termed P. azurophilum Red and P. azurophilum White based on their host cell type. Six haplotypes were found in 100 infections sequenced of P. azurophilum Red and six in 45 infections of P. azurophilum White. Nested clade analysis revealed a significant association of geographical location and clades as well as a pattern of past fragmentation of parasite populations. This is consistent with the hypothesis that vector-borne parasites such as malaria may be subject to frequent local extinctions and recolonizations. Comparison of the phylogeography of the lizard and parasites shows only weak concordance; that is, the parasites colonized the lizards in the islands, but dispersal events between islands via vectors or failed lizard colonizations were present. The two parasites had different histories, P. azurophilum Red colonized the islands from both the north and south, and P. azurophilum White originated in the central Lesser Antilles, probably from P. azurophilum Red, then moved to both north and south. This is the first study to examine the biogeography of a pair of sibling species of vector-borne parasites within an island archipelago system.
Mate-choice copying by females: the advantages of a prudent strategy
Authors: Sirot E. 
Published: March 2003

Abstract
Mate choice by females may be influenced by both advertizing traits of males, and behaviour of other females. Here, a simple genetic and behavioural model studies the advantages of mate-choice copying. From a genetic point of view, a female preferring to copy others’ mate choice adopts a prudent strategy, because her offspring will inherit the same alleles from their father as the other young in the population. The model predicts that a female should copy others’ mate-choice, unless she encounters a relatively more attractive male than the one she has observed mating, and the attractiveness of the male reflects his genotype. For low or moderate reliability of male signalling, mate-copying is always predicted, even if the newcoming male is more attractive than the first male. This effect is attenuated, however, when the number of females that have already chosen the first male increases.
Quantitative genetics of immune function and body size in the house cricket, Acheta domesticus
Authors: Ryder J. J. , Siva-Jothy M. T. 
Published: March 2003

Abstract
Female house crickets are attracted to male calling song containing a relatively high number of syllables per ‘chirp’, which tends to be produced by large males. In a previous study, we showed that this song characteristic is also positively and independently correlated with haemocyte load, an important determinant of the ability to produce an encapsulation response in insects. Females will therefore tend to select males with high encapsulation ability (and large body size) as mates. The present study demonstrates that variation in haemocyte load and body size, together with a second parameter of immune function (the ability to encapsulate a synthetic substrate), is heritable in the same population. Moreover, all three traits are shown to be positively genetically correlated. In favouring males that produce calling song with the preferred characteristics, females should therefore also tend to produce larger offspring with a greater ability to produce an encapsulation response.
Kin recognition and cannibalism in a subsocial spider
Authors: Bilde T. , Lubin Y. 
Published: March 2003

Abstract
Evolution of cooperation and group living in spiders from subsocial family groups may be constrained by their cannibalistic nature. A tendency to avoid cannibalizing kin may facilitate tolerance among spiders and implies the ability to identify relatives. We investigated whether the subsocial spider Stegodyphus lineatus discriminates kin by recording cannibalism among juveniles in experiments during which amount of food and size difference among spiders in groups were varied. We hypothesized that family groups should be less cannibalistic than groups of mixed-parental origin. Further, we tested whether food-stress would influence cannibalism rates differently in kin and nonkin groups and the effect of relatedness on cannibalism within groups of spiders of variable size compared with those of homogenous size. In groups of six spiders, more spiders were cannibalized in nonsib groups than in sib groups under low food conditions. A tendency for nonkin biased cannibalism in starved spider pairs supported that kin recognition in S. lineatus is expressed when food is limited. Size variance of individuals within well-fed groups of siblings and unrelated spiders had no influence on cannibalism rates. Apparently, both hunger and high density are important promoters of cannibalism. In addition to inclusive fitness benefits, we suggest that an ability to avoid cannibalizing kin will favour the evolution of cooperation and group living in phylogenetically pre-adapted solitary species.
Comparing molecular measures for detecting inbreeding depression
Authors: Slate J. , Pemberton J. M. 
Published: March 2003

Abstract
Correlations between heterozygosity and components of fitness have been investigated in natural populations for over 20 years. Positive correlations between a trait of interest and heterozygosity (usually measured at allozyme loci) are generally recognized as evidence of inbreeding depression. More recently, molecular markers such as microsatellites have been employed for the same purpose. A typical study might use around five to ten markers. In this paper we use a panel of 71 microsatellite loci to: (1) Compare the efficacy of heterozygosity and a related microsatellite-specific variable, mean d2, in detecting inbreeding depression; (2) Examine the statistical power of heterozygosity to detect such associations. We performed our analyses in a wild population of red deer (Cervus elaphus) in which inbreeding depression in juvenile traits had previously been detected using a panel of nine markers. We conclude that heterozygosity-based measures outperform mean d2-based measures, but that power to detect heterozygosity-fitness associations is nonetheless low when ten or fewer markers are typed.
Evolution of syncarpy in angiosperms: theoretical and phylogenetic analyses of the effects of carpel fusion on offspring quantity and quality
Authors: Armbruster W. S. , Debevec E. M. , Willson M. F. 
Published: March 2003

Abstract
The repeated evolution of fused carpels (syncarpy) is one of the dominant features of angiosperm macroevolution. We present results of new phylogenetic and theoretical analyses to assess the frequency and nature of transitions to syncarpy, and the possible advantages of syncarpy over apocarpy under a variety of ecological conditions. Using a recent molecular estimate of angiosperm phylogeny, we ascertained that a minimum of 17 independent evolutionary transitions from apocarpy to syncarpy have occurred; about three-quarters of these transitions allowed pollen tubes to cross between carpels and fertilize ovules that would otherwise be left unfertilized. Most of these transitions also intensified competition between pollen, potentially enhancing offspring fitness. The high proportion of evolutionary transitions promoting pollen competition and pollen-tube access to all carpels supports the hypothesis that the main advantage of syncarpy is in increasing offspring quality and quantity. The potential advantages of syncarpy were more thoroughly evaluated by analytical and simulation studies. These showed that the advantage of syncarpy over apocarpy involving increased offspring-quantity held under conditions of marginal pollination and declined with increasing pollination. The offspring-quality advantage persisted over a wider range of conditions, including under quite high pollination rates.
The continuity of microevolution and macroevolution
Authors: Simons Andrew M. 
Published: March 2003

Abstract
A persistent debate in evolutionary biology is one over the continuity of microevolution and macroevolution – whether macroevolutionary trends are governed by the principles of microevolution. The opposition of evolutionary trends over different time scales is taken as evidence that selection is uncoupled over these scales. I argue that the paradox inferred by trend opposition is eliminated by a hierarchical application of the ‘geometric-mean fitness’ principle, a principle that has been invoked only within the limited context of microevolution in response to environmental variance. This principle implies the elimination of well adapted genotypes – even those with the highest arithmetic mean fitness over a shorter time scale. Contingent on premises concerning the temporal structure of environmental variance, selectivity of extinction, and clade-level heritability, the evolutionary outcome of major environmental change may be viewed as identical in principle to the outcome of minor environmental fluctuations over the short-term. Trend reversals are thus recognized as a fundamental property of selection operating at any phylogenetic level that occur in response to event severities of any magnitude over all time scales. This ‘bet-hedging’ perspective differs from others in that a specified, single hierarchical selective process is proposed to explain observed hierarchical patterns of extinction.
Mechanistic and experimental analysis of condition and reproduction in a polymorphic lizard
Authors: Svensson E.I. , Sinervo B. , Comendant T. 
Published: March 2003

Abstract
The importance of genetic and environmental variation in condition in shaping evolutionary trade-offs have recently been subject to much theoretical discussion, but is very difficult to investigate empirically in most field-based systems. We present the results from mechanistic experimental manipulations of reproductive investment and condition in two female colour morphs (‘orange’ and ‘yellow’) of side-blotched lizards (Uta stansburiana). We investigated the interactions between throat colour morphs, condition, local social environment and female survival using path-analysis. Using follice-ablation experiments, we show that large clutch size has a negative effect on field survival among yellow females, and that this effect is partly mediated by immunosuppressive effects of large clutches. In orange females these effects were less pronounced, and there was a negative survival effect of strong antibody responses. Hence, we experimentally confirmed our previous findings of correlational selection between female morphotype and immunocompetence, an important condition trait. Manipulation of corticosterone revealed multiple (‘pleiotropic’) direct and indirect effects of this hormone on both condition and reproductive traits. We argue that interaction effects (e.g. between local environments and genotypes) could explain a substantial fraction of variation in condition and reproduction in natural populations. Increased attention to such interaction effects and their fitness consequences will provide novel insights in field studies of selection and reproductive allocation.
Suboptimal timing of reproduction in Lobelia inflata may be a conservative bet-hedging strategy
Authors: Simons A. M. , Johnston M. O. 
Published: March 2003

Abstract
Age and size at reproduction are important components of fitness, and are variable both within and among angiosperm species. The fitness consequences of such life-history variation are most readily studied in organisms that reproduce only once in their lifetime. The timing of the onset of reproduction (bolting) in the monocarpic perennial, Lobelia inflata, occurs over a range of dates within a season, and may be postponed to a later year. Empirical relationships among life-history traits, derived from over 950 wild-growing and experimentally manipulated plants in the field, are used to model an optimal changing size threshold (norm of reaction) for bolting over the growing season. Comparisons are made between observed and expected norms of reaction governing bolting. An apparently suboptimal bolting schedule that precludes bolting beyond an early (conservative) date is observed, and is found to be qualitatively consistent with conservative bet hedging under unpredictable season lengths. On this basis we propose the schedule of bolting as a plausible example of a conservative bet-hedging strategy. The results underscore the critical need for long-term studies of fluctuating selection to distinguish suboptimality from bet hedging.