bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reconciling gene trees with organism history: the mtDNA phylogeography of three Nesotes species (Coleoptera: Tenebrionidae) on the western Canary Islands
Authors: Rees D. J. , Emerson B. C. , Oromí P. , Hewitt G. M. 
Published: March 2003

Abstract
The processes of island colonization and speciation are investigated through mtDNA studies on Canary Island beetles. The genus Nesotes (Coleoptera: Tenebrionidae) is represented by 19 endemic species on the Canary Islands, the majority of which are single island endemics. Nesotes conformis is the most widespread, occurring on Gran Canaria, Tenerife, La Palma and El Hierro. Nesotes conformis forms a paraphyletic assemblage, with a split between Gran Canaria and the other three islands. Nesotes conformis of the western Canary Islands cluster with Nesotes altivagans and Nesotes elliptipennis from Tenerife. Fifty-two individuals from this western islands species complex have been sequenced for 675 base pairs of the mtDNA cytochrome oxidase II gene, representing Tenerife, La Palma and El Hierro. A neighbour joining analysis of maximum likelihood distances resulted in three distinct mtDNA lineages for N. conformis, two of which also include mitotypes of N. altivagans and N. elliptipennis. Through application of parametric bootstrap tests, we are able to reject hypotheses of monophyly for both N. conformis and N. altivagans. Nesotes altivagans and N. elliptipennis are poorly separated morphologically and mtDNA sequence data adds support to this being one species with a highly variable morphology. We propose that N. altivagans/N. elliptipennis is recently derived from two ancestral mtDNA lineages within N. conformis from the Teno region of Tenerife. We further propose colonization of the younger islands of La Palma and El Hierro by N. conformis from a mitochondrial lineage within the Teno massif (colonization; diversification; mitochondrial DNA; Canary Islands; Coleoptera).
Analysis of asymmetries in the African fruit bats Eidolon helvum and Rousettus egyptiacus (Mammalia: Megachiroptera) from the islands of the Gulf of Guinea. II. Integration and levels of multivariate fluctuating asymmetry across a geographical range
Authors: Juste J. , López-González C. , Strauss R. E. 
Published: March 2003

Abstract
Using a set of cranial morphometric characters, trends of variation in multivariate fluctuating asymmetry were evaluated and compared in populations of African fruit bats Rousettus egyptiacus and Eidolon helvum from the Gulf of Guinea islands, and the adjacent mainland. Levels of asymmetry were compared across populations and species, and significant differences were found in both comparisons. Differences coincided with species-specific patterns of morphological and genetic differentiation. Concordance of correlation matrices of asymmetry was also compared. Results were significant; concordance is hypothesized to be a by-product of developmental processes that produce the ‘fox-like’ morphology shared by these species. Consistency of asymmetry patterns suggests that the developmental pathway producing it is highly canalized. A prediction of the above hypothesis is that a radical change in the ‘fox-like’ structural pattern would result in breakage of the asymmetry parameter associated with it.
Heterozygous fitness effects of clonally transmitted genomes in waterfrogs
Authors: Vorburger C. 
Published: March 2003

Abstract
The European waterfrog Rana esculenta (RL-genotype) is a natural hybrid between R. ridibunda (RR) and R. lessonae (LL) and reproduces by hybridogenesis, i.e. it eliminates the L-genome from the germline and produces gametes only containing the clonally transmitted R-genome. Because of the lack of recombination, R-genomes are prone to accumulate spontaneous deleterious mutations. The homozygous effects of such mutations become evident in matings between hybrids: their offspring possess two clonal R-genomes and are generally inviable. However, the evolutionary fate of R. esculenta mainly depends on the heterozygous effects of mutations on the R-genome. These effects may be hidden in the hybrid R. esculenta because it has been shown to benefit from spontaneous heterosis. To uncouple clonal inheritance from hybridity, I crossed R. esculenta with R. ridibunda to produce nonhybrid offspring with one clonal and one sexual R-genome, and compared their survival and larval performance with normal, sexually produced R. ridibunda tadpoles. Because environmental stress can enhance the negative effects of mutation accumulation, I measured the performance at high and low food levels. There was no indication that tadpoles with a clonal genome performed worse at either food level, suggesting that at least in the larval stage, R. esculenta benefits from heterosis without incurring any costs because of heterozygous effects of deleterious mutations on the clonally transmitted R-genome.
Collective action in an RNA virus
Authors: Brown S. P. 
Published: March 2003

Abstract
A recent empirical study by Turner and Chao on the evolution of competitive interactions among phage virus strains revealed that a strain grown at high rates of co-infection evolved towards lowered fitness relative to an ancestral strain. The authors went on to show that the fitness pay-off matrix between the evolved and ancestral strain conforms to the prisoners’ dilemma. In this paper, I use Turner and Chao’s data to parameterize a simple model of parasite collective action. The prisoners’ dilemma is based on pairwise interactions of a discrete cooperate/defect nature. In contrast, the collective action model explicitly deals with individual–group interactions where the extent of cooperation is a continuous variable. I argue here that the ‘collective action’ modelling approach is more appropriate than the prisoners’ dilemma for the biology of virus evolution, and hence better able to form a predictive framework for further work on related strains of virus, linking mixing ecology, cooperative phenotype and fitness. Furthermore, the collective action model is used to motivate discussion on the evolutionary ecology of viruses, with a focus on the ‘levels of selection’ debate and the evolution of virulence.
Evidence for an even sex allocation in haplodiploid cyclical parthenogens
Authors: Aparici E. , Carmona M. J. , Serra M. 
Published: March 2003

Abstract
Recent theoretical work has shown that haplodiploid cyclical parthenogens, such as rotifers, are expected to have an equal frequency of male-producing and resting-egg producing females during their sexual phase. We tested this prediction by following sexual reproduction dynamics in two laboratory populations and one field population of the rotifer Brachionus plicatilis through two growing seasons. We recorded population density, proportion of sexual females, and sex allocation (the proportion of male-producing sexual females as a fraction of total sexual females). We found this sex allocation ratio to vary from 0.3 to 1.0 in single sampling events. However, when we computed sex allocation by using the integrated densities of both male-producing sexual females and resting-egg producing sexual females over time, the two laboratory populations and one of the two field growing seasons showed sex allocation ratios that did not significantly differ from the expected value of 0.5.
Inversion and allozyme polymorphism show contrasting patterns of microgeographical population structure in a natural population of Drosophila buzzatii from Argentina
Authors: Fernández Iriarte P. J. , Rodríguez C. , Hasson E. 
Published: March 2003

Abstract
Second chromosome inversions and genotypic frequencies at seven allozyme loci were determined in a natural population of the cactophilic species Drosophila buzzatii that uses as breeding sites the necrotic cladodes of the prickly pear Opuntia quimilo and the rotting stems of cardón, Trichocereus terschekii. Different processes govern the evolutionary fate of inversion and allozyme polymorphisms. A pattern of heterotic balance for inversions seems to be acting uniformly in each breeding site and could depend on different regimes of density-dependent selection within cactus hosts. Patterns of variation of allozymes revealed significant heterogeneity in allele frequencies for Esterase-1 (Est-1) among O. quimilo rots and Aldehyde oxidase (Aldox) and Xanthine dehydrogenase (Xdh) among T. terschekii substrates and showed gene-cactus effects only for Esterase-2 (Est-2). Consistent and significant excesses of homozygotes were detected at both the within-rot and in the total population levels that could be accounted for by diversifying selection among individual breeding sites.
No reduction of female sexual receptivity following mating in a stalk-eyed fly, Cyrtodiopsis dalmanni (Diptera: Diopsidae)
Authors: Grant C. A. , Fowler K. , Chapman T. 
Published: March 2003

Abstract
The level of female sexual receptivity is an important component of male and female reproductive success. In many insects, mating itself causes a sharp decline in female receptivity. This can be a direct result of the physical act of mating, or because of actions of sperm or seminal fluid proteins. The degree to which males can decrease female receptivity will directly affect their reproductive success, by altering the chance that their sperm will be used in fertilizations in the interval before the female mates again. In this study, we investigated the effect of mating on female receptivity in the sexually dimorphic stalk-eyed fly, Cyrtodiopsis dalmanni. Our results showed no evidence for mating-induced reductions in female receptivity. In addition, we found that matings with males that differed in eyespan did not cause differences in the level of female receptivity. There was also no evidence that females remated sooner when presented with large eyespan males. These results are surprising, given the indirect benefits that females gain from matings with large eyespan males. Finally we demonstrate that males do not appear to discriminate between females on the basis of female mating status.
Can indirect selection and genetic context contribute to trait diversification? A transition-probability study of blossom-colour evolution in two genera
Authors: Armbruster W. S. 
Published: March 2003

Abstract
Darwin recognized that biological diversity has accumulated as a result of both adaptive and nonadaptive processes. Very few studies, however, have addressed explicitly the contribution of nonadaptive processes to evolutionary diversification, and no general procedures have been established for distinguishing between adaptive and nonadaptive processes as sources of trait diversity. I use the diversification of flower colour as a model system for attempting to identify adaptive and nonadaptive causes of trait diversification. It is widely accepted that variation in flower colour reflects direct, adaptive response to divergent selective pressures generated by different pollinators. However, diversification of flower colour may also result from the effects of nonadaptive, pleiotropic relationships with vegetative traits. Floral pigments that have pleiotropic relationships to vegetative pigments may evolve and diversify in at least two nonadaptive ways. (1) Indirect response to selection on the pleiotropically related nonfloral traits may occur (indirect selection). (2) Divergent evolution in response to parallel selective pressures (e.g. selection by pollinators for visually obvious flowers) may occur because populations are at different genetic starting points, and each population follows its own genetic `line of least resistance.' A survey of literature suggests that pleiotropic relationships between flower colour and vegetative traits are common. Phylogenetically informed analyses of comparative data from Dalechampia (Euphorbiaceae) and Acer (Aceraceae), based on trait-transition probabilities and maximum likelihood, indicated that floral and vegetative pigments are probably pleiotropically related in these genera, and this relationship better explains the diversification of floral colour than does direct selection by pollinators. In Dalechampia pink/purple floral bract colour may have originated by indirect response to selection on stem and leaf pigments. In Acer selection by pollinators for visually obvious flowers may to have led to the evolution of red or purple flowers in lineages synthesizing and deploying red anthocyanins in leaves, and pale-green or yellow flowers in species not deploying red anthocyanins in vegetative structures. This study illustrates the broader potential of indirect selection and parallel selection on different genetic starting points to contribute to biological diversity, and the value of testing directly for the operation of these nonadaptive diversifying processes.
Sperm competition selects for increased testes mass in Australian frogs
Authors: Byrne P. G. , Roberts J. D. , Simmons L. W. 
Published: March 2003

Abstract
Game theory predicts that investment in spermatogenesis will increase with the risk and intensity of sperm competition. Widespread support for this prediction has come from comparative studies of internal fertilizing species reporting positive associations between testes mass and the probability that females mate with more than one male. Data for external fertilizers have generated conflicting results. We investigated how risk of sperm competition affects testes size in two families of Australian frogs: the Myobatrachidae and the Hylidae. We also examined effects of clutch size, egg size and oviposition location as alternative factors that might influence sperm production. Species were ranked according to probability of group spawning, and hence risk of sperm competition. Controlling for body size and phylogenetic relationships, we demonstrated that within the Myobatrachidae, the risk of sperm competition explained a significant amount of variation in testes mass. Oviposition location had a weak influence, with species ovipositing into foam having smaller testes. No significant effects of clutch size or egg size were detected. In hylids, the relationship between testes mass and risk of sperm competition was positive but not significant, again with no predictable effects related to egg size or number. These data provide an important test of sperm competition theory for externally fertilizing taxa.
Oviposition tests of ant preference in a myrmecophilous butterfly
Authors: Fraser A. M. , Tregenza T. , Wedell N. , Elgar M. A. , Pierce N. E. 
Published: March 2003

Abstract
Butterflies in the family Lycaenidae that have obligate associations with ants frequently exhibit ant-dependent egg laying behaviour. In a series of field and laboratory choice tests, we assessed oviposition preference of the Australian lycaenid Jalmenus evagoras in response to different species and populations of ants. Females discriminated between attendant and nonattendant ant species, between attendant ant species, and to some extent, between populations of a single ant species. When preferences were found, ovipositing butterflies preferred their locally predominant attendant ant species and geographically proximate attendant ant populations. A reciprocal choice test using adults from a generation of butterflies reared in the absence of ants indicated a genetic component to oviposition preference. Individual females were flexible with respect to oviposition site choice, often ovipositing on more than one treatment during a trial. Preferences arose from a hierarchical ranking of ant treatments. These results are discussed in terms of local adaptation and its possible significance in the diversification of ant-associated lycaenids.
Mating system variation along a successional gradient in the allogamous and colonizing plant Crepis sancta (Asteraceae)
Authors: Cheptou P.-O. , Lepart J. , Escarre J. 
Published: March 2003

Abstract
We analysed mating system in an annual and colonizing plant, Crepis sancta, that occupies different successional stages in the French Mediterranean region. Based on a previous experiment, we hypothesized that low inbreeding depression measured in young successional stages should select for selfing whereas higher inbreeding depression in old stages should select for outcrossing. Nine populations of C. sancta (Asteraceae) from contrasting successional stages were used to analyse (1) Seed set after autonomous and enforced selfing in controlled conditions and (2) outcrossing rates in natural conditions using allozymes (progeny array analysis). We found that C. sancta possesses a pseudo-self-incompatibility system and that mating system varies among populations. Allozymes revealed that the population multilocus outcrossing rates vary from 0.77 to 0.99. The lowest outcrossing rates occur in the youngest successional stages and complete outcrossing is found in old stages. The data partially agree with the predictions we made and the results are more generally discussed in the light of factors changing during succession. We did not find any evidence of reproductive assurance in the nine populations, contrary to what is often assumed as a major factor governing mating system evolution in colonizing species. We propose that mating system variation can be interpreted as the result of the balance between the cost of outcrossing and inbreeding depression in a metapopulation context.
Genetic structure of lions (Panthera leo L.) in the Selous Game Reserve: implications for the evolution of sociality
Authors: Spong G. , Stone J. , Creel S. , Björklund M. 
Published: March 2003

Abstract
We use 14 microsatellites to examine the genetic structure of a lion (Panthera leo L.) population in southern Tanzania. Heterozygosity levels were high (0.75 ± 0.08). Relatedness estimates showed that prides often had close relatives in neighbouring prides, whereas few relatives were found in prides not sharing a border. The drop-off in relatedness with distance was highly significant. Female pridemates exhibited a higher mean relatedness (0.26 ± 0.07) to one another than did pride males (0.11 ± 0.07). Mean relatedness among females was significantly higher in small prides than in large ones. Prides exhibited significant inbreeding avoidance (FIL: −0.11). Mating did not detectably differ from random across prides (FIT: −0.02 ns). In addition to being recognizable behavioural and demographic units, prides were statistically distinct genetic units (FLT: 0.07). Some neighbouring prides grouped together both geographically and genetically, forming ‘superprides’ in the population (FZT = 0.05). Thus, although individual prides were genetically distinct, there was an important genetic structure above the level of social groups.
Gradual and quantum genome size shifts in the hystricognath rodents
Authors: Gallardo M. H. , Bickham J. W. , Kausel G. , Köhler N. , Honeycutt R. L. 
Published: March 2003

Abstract
We assessed genome size variation by flow cytometry within and among 31 species of nine families of African and South American hystricognath rodents. Interspecific variation was extensive and genome size was relatively high among the South American radiation whereas only moderate variation and smaller estimates of genome size were observed in the African counterparts. The largest genome size, indicating tetraploidy was recorded in the South American octodontid, Tympanoctomys barrerae (16.8 pg DNA). This quantum shift in DNA content represents a novel mechanism of genome evolution in mammals. As expected in polyploid organisms, varying nucleotypic effects were observed in the dimensions of the sperm cells and lymphocytes of T. barrerae. The role of control mechanisms that influence cell dimensions in polyploid organisms is discussed.
Multiple parasites are driving major histocompatibility complex polymorphism in the wild
Authors: Wegner K. M. , Reusch T. B. H. , Kalbe M. 
Published: March 2003

Abstract
Parasite mediated selection may result in arms races between host defence and parasite virulence. In particular, simultaneous infections from multiple parasite species should cause diversification (i.e. balancing selection) in resistance genes both at the population and the individual level. Here, we tested these ideas in highly polymorphic major histocompatibility complex (MHC) genes from three-spined sticklebacks (Gasterosteus aculeatus L.). In eight natural populations, parasite diversity (15 different species), and MHC class IIB diversity varied strongly between habitat types (lakes vs. rivers vs. estuaries) with lowest values in rivers. Partial correlation analysis revealed an influence of parasite diversity on MHC class IIB variation whereas general genetic diversity assessed at seven microsatellite loci was not significantly correlated with parasite diversity. Within individual fish, intermediate, rather than maximal allele numbers were associated with minimal parasite load, supporting theoretical models of self-reactive T-cell elimination. The optimal individual diversity matched those values female fish try to achieve in their offspring by mate choice. We thus present correlative evidence supporting the ‘allele counting’ strategy for optimizing the immunocompetence in stickleback offspring.
A direct experimental test of founder-flush effects on the evolutionary potential for assortative mating
Authors: Regan J. L. , Meffert L. M. , Bryant E. H. 
Published: March 2003

Abstract
Founder-flush speciation models propose that population bottlenecks can enhance evolutionary potential for reproductive isolation. To test this prediction, we subjected bottlenecked (three-pair founder-flush) and nonbottlenecked populations of the housefly to 18 generations of selection for assortative mating. After the selection regime, we analysed videotaped courtship bouts in these lines to identify correlated responses to the selection protocol. The realized heritabilities for assortative mating for both the bottlenecked and nonbottlenecked treatments were very low, but still significant. The founder-flush populations had thus responded to selection as well as the nonbottlenecked populations, although not significantly greater (i.e. total increases in assortative mating were 9.6 and 8.6%, respectively). Multivariate analyses on the courtship repertoires found that, although both bottlenecked and nonbottlenecked treatments attained similar levels of assortative mating, the treatments exhibited different evolutionary solutions in their correlated responses. Specifically, the bottlenecked lines demonstrated a significantly more diverse set of evolutionary trajectories (i.e. significant shifts along the second principal component for courtship). This suggests that the bottlenecked lines had greater potential for the evolution of novel phenotypes as predicted by founder-induced speciation models. Our results, however, cannot distinguish whether the more variable evolutionary responses resulted from increased heritabilities in courtship components, reduced potential to follow the convergent evolutionary trajectories noted for the nonbottlenecked lines, or some combination of both general processes in determining the resultant multivariate phenotype.