Variation In Mating Behaviour Research Articles

Persistence of a population of palmate newts Lissotriton helveticus in a saline environment on the west coast of Scotland

A six year survey of a palmate newt (Lissotriton helveticus) population in rock pools on the west coast of Scotland indicates that this species has some tolerance of saline conditions. The newts were living with a mean salinity (conductivity) of 382 ppm (range 30.7 ppm to >4995 ppm). Other interesting observations include a variation in mating behaviour, in which normal open water behaviour is confined to crevices, and the occurrence of ‘pelvic bumps’ in some individuals that may indicate reduced body condition.

Roads, forest cover, and topography as factors affecting the occurrence of large carnivores: The case of the Andean bear (Tremarctos ornatus)

Global declines in large-bodied terrestrial vertebrates are widely linked to human disturbance and habitat loss. Identifying remaining opportunities to conserve areas wherein such species may persist or might be reintroduced has thus become a key challenge in biodiversity conservation globally. We used multi-year camera trap data and spatial capture-recapture models to test how individually-identified Andean bears (Tremarctos ornatus) responded to roads and a suite of forest cover and topographic variables that may be indicative of food resources in critically-threatened, equatorial dry forest habitats of northern Peru. Bear density averaged 4 individuals per 100 km2 in our 668 km2 study area, but proximity to roads significantly reduced density, possibly because they are avoided and/or facilitate demographic sinks or human hunting. In contrast, the effects of forest cover and topographic variables on bear density varied seasonally, reflecting documented variation in mating behavior that may result from seasonal food resources. Despite large uncertainties in model predictions on the occurrence of bear habitat outside our study area, extrapolating our results suggests that a substantial area of high-quality habitat for Andean bears exists outside the recognized IUCN range, including equatorial dry forest habitats known to harbor many threatened species. Because Andean bears are vulnerable to extinction and are an established flagship species in much of South America, the expanded range and potential habitats that we identify here require urgent validation for possible inclusion in landscape-level plans to conserve equatorial dry forests of the Andes.

Understanding variation in women's sexual attitudes and behavior across sexual orientations: Evaluating three hypotheses

Although evolutionary logic has provided abundant insight into how differential biological costs, mating opportunities, and exposures to psychosocial stressors shape functional variation in mating behavior among heterosexual men and women, it is less clear how such factors influence behavior among those who do not identify as heterosexual. Here, we evaluate three evolutionarily-informed hypotheses proposed to explain variation in women's sexual attitudes and behavior across sexual orientations. A sample of 328 women (111 heterosexual, 75 lesbian, and 142 bisexual; ages 18–36) completed questionnaires assessing their current sexual permissiveness, past sexual behavior, and past alcohol use. Lesbian and bisexual women reported more risky sexual (and non-sexual) attitudes/intentions and behaviors than did heterosexual women. The observed differences were best explained by increased psychosocial stress experienced by sexual minority (versus heterosexual) women.

ASSESSING THE EFFECTS OF GENETIC DIVERGENCE AND MORPHOLOGY ON ANOLIS LIZARD MATING

The brown anole (Anolis sagrei) is a widespread neotropical lizard found on many islands in the West Indies as well as the coast of Central America. Across their range, brown anole populations show extensive ecomorphological trait variation and substantial genetic divergence. It is unclear, however, whether this genetic and morphological divergence is indicative of reproductive isolation between populations. We investigated variation in mating behavior across populations by analyzing 4 h of video for each of 234 captive male-female pairs encompassing all 36 possible pairings from six sampled islands. For each pair of individuals, we tested for an association between the occurrence of mating, morphological traits, and genetic relatedness of their populations. We found no support for the hypotheses of ecological divergence, nonecological divergence, or both ecological and nonecological divergence driving premating reproductive isolation in A. sagrei. We did find that males with relatively short heads tend to mate more quickly and hypothesize potential explanations that warrant future investigation.

Mate fidelity improves survival and breeding propensity of a long-lived bird.

Evolutionary and behavioural ecologists have long been interested in factors shaping the variation in mating behaviour observed in nature. Although much of the research on this topic has focused on the consequences of mate choice and mate change on annual reproductive success, studies of a potential positive link between mate fidelity and adult demographic rates have been comparatively rare. This is particularly true for long-lived birds with multi-year, socially monogamous pair bonds. We used a 26-year capture-mark-recapture dataset of 3,330 black brent Branta bernicla nigricans to test whether breeding with a familiar mate improved future breeding propensity and survival. We predicted that experienced breeders nesting with a new partner would have rates of survival similar to familiar pairs because long-lived species avoid jeopardizing survival since their lifetime fitness is sensitive to this vital rate. In contrast, we expected that any costs of breeding with a new partner would be paid through skipping the subsequent breeding attempt. We found that unfamiliar pairs had lower subsequent breeding propensity than faithful partners. However, contrary to our expectations, individuals breeding with a new mate also suffered reduced survival. These results add to a small number of studies indicating that a positive relationship between mate retention and adult demographic rates may exist in a diverse array of avian species. Given these results, researchers should consider costs of mate change that extend beyond within-season reproductive success to fully understand the potential adaptive basis for perennial social monogamy. We caution that if mate retention enhances survival prospects, improvements in annual reproductive success with pair-bond length could be a secondary factor favouring perennial social monogamy, particularly in species with slower life-history strategies. Furthermore, some cases where annual reproductive success does not improve with pair-bond duration, yet multi-year pair bonds are common, could be explained by benefits afforded by mate fidelity to adult vital rates.

Condition-Dependent Mutual Mate Preference and Intersexual Genetic Correlations for Mating Activity.

Although mating represents a mutual interaction, the study of mate preferences has long focused on choice in one sex and preferred traits in the other. This has certainly been the case in the study of the costs and condition-dependent expression of mating preferences, with the majority of studies concerning female preference. The condition dependence and genetic architecture of mutual mate preferences remain largely unstudied, despite their likely relevance for the evolution of preferences and of mating behavior more generally. Here we measured (a) male and female mate preferences and (b) intersexual genetic correlations for the mating activity in pedigreed populations of southern field crickets (Gryllus bimaculatus) raised on a favorable (free-choice) or a stressful (protein-deprived) diet. In the favorable dietary environment, mutual mate preferences were strong, and the intersexual genetic covariance for mating activity was not different from one. However, in the stressful dietary environment, mutual mate preferences were weak, and the intersexual genetic covariance for mating activity was significantly smaller than one. Altogether, our results show that diet environments affect the expression of genetic variation in mating behaviors: when the environment is stressful, both (a) the strength of mutual mate preference and (b) intersexual genetic covariance for mating activity tend to be weaker. This implies that mating dynamics strongly vary across environments.

The Genetics of Mating Song Evolution Underlying Rapid Speciation: Linking Quantitative Variation to Candidate Genes for Behavioral Isolation.

Differences in mating behaviors evolve early during speciation, eventually contributing to reproductive barriers between species. Knowledge of the genetic and genomic basis of these behaviors is therefore integral to a causal understanding of speciation. Acoustic behaviors are often part of the mating ritual in animal species. The temporal rhythms of mating songs are notably species-specific in many vertebrates and arthropods and often underlie assortative mating. Despite discoveries of mutations that disrupt the temporal rhythm of these songs, we know surprisingly little about genes affecting naturally occurring variation in the temporal pattern of singing behavior. In the rapidly speciating Hawaiian cricket genus Laupala, the striking species variation in song rhythms constitutes a behavioral barrier to reproduction between species. Here, we mapped the largest-effect locus underlying interspecific variation in song rhythm between two Laupala species to a narrow genomic region, wherein we find no known candidate genes affecting song temporal rhythm in Drosophila Whole-genome sequencing, gene prediction, and functional annotation of this region reveal an exciting and promising candidate gene, the putative cyclic nucleotide-gated ion channel-like gene, for natural variation in mating behavior. Identification and molecular characterization of the candidate gene reveals a nonsynonymous mutation in a conserved binding domain, suggesting that ion channels are important targets of selection on rhythmic signaling during establishment of behavioral isolation and rapid speciation.

Qualitative and quantitative comparisons of mating behaviour across multiple populations and six species of leiobunine harvestmen (Arachnida: Opiliones)

Abstract Mating behaviour is highly diverse in animals both among and within species. We examine variation in mating behaviour in leiobunine harvestmen, which show high diversity in genitalic traits that are predicted to correspond to patterns of behavioural diversity. We ran mating trials for six species of leiobunine from four locations, and measured body size for a subset of individuals. We described mating behaviour in detail—providing the first formal description for most species—and examined variation inter- and intraspecific in body size and behaviour. Individuals were smaller in northern populations. Furthermore, we found species- and population-specific behaviours, high variation in the timing and success of different stages of mating, and high remating rates. However, we found no correlation between behavioural and morphological variation. Leiobunine harvestmen offer an excellent system for understanding multiple mechanisms of sexual selection and geographic diversification of mating behaviour.

Demography and selection shape transcriptomic divergence in field crickets.

Gene flow, demography, and selection can result in similar patterns of genomic variation and disentangling their effects is key to understanding speciation. Here, we assess transcriptomic variation to unravel the evolutionary history of Gryllus rubens and Gryllus texensis, cryptic field cricket species with highly divergent mating behavior. We infer their demographic history and screen their transcriptomes for footprints of selection in the context of the inferred demography. We find strong support for a long history of bidirectional gene flow, which ceased during the late Pleistocene, and a bottleneck in G. rubens consistent with a peripatric origin of this species. Importantly, the demographic history has likely strongly shaped patterns of genetic differentiation (empirical FST distribution). Concordantly, FST -based selection detection uncovers a large number of outliers, likely comprising many false positives, echoing recent theoretical insights. Alternative genetic signatures of positive selection, informed by the demographic history of the sibling species, highlighted a smaller set of loci; many of these are candidates for controlling variation in mating behavior. Our results underscore the importance of demography in shaping overall patterns of genetic divergence and highlight that examining both demography and selection facilitates a more complete understanding of genetic divergence during speciation.

Polygyny does not explain the superior competitive ability of dominant ant associates in the African ant-plant, Acacia (Vachellia) drepanolobium.

The Acacia drepanolobium (also known as Vachellia drepanolobium) ant‐plant symbiosis is considered a classic case of species coexistence, in which four species of tree‐defending ants compete for nesting space in a single host tree species. Coexistence in this system has been explained by trade‐offs in the ability of the ant associates to compete with each other for occupied trees versus the ability to colonize unoccupied trees. We seek to understand the proximal reasons for how and why the ant species vary in competitive or colonizing abilities, which are largely unknown. In this study, we use RADseq‐derived SNPs to identify relatedness of workers in colonies to test the hypothesis that competitively dominant ants reach large colony sizes due to polygyny, that is, the presence of multiple egg‐laying queens in a single colony. We find that variation in polygyny is not associated with competitive ability; in fact, the most dominant species, unexpectedly, showed little evidence of polygyny. We also use these markers to investigate variation in mating behavior among the ant species and find that different species vary in the number of males fathering the offspring of each colony. Finally, we show that the nature of polygyny varies between the two commonly polygynous species, Crematogaster mimosae and Tetraponera penzigi: in C. mimosae, queens in the same colony are often related, while this is not the case for T. penzigi. These results shed light on factors influencing the evolution of species coexistence in an ant‐plant mutualism, as well as demonstrating the effectiveness of RADseq‐derived SNPs for parentage analysis.

The impact of mating systems and dispersal on fine-scale genetic structure at maternally, paternally and biparentally inherited markers.

For decades, studies have focused on how dispersal and mating systems influence genetic structure across populations or social groups. However, we still lack a thorough understanding of how these processes and their interaction shape spatial genetic patterns over a finer scale (tens-hundreds of metres). Using uniparentally inherited markers may help answer these questions, yet their potential has not been fully explored. Here, we use individual-level simulations to investigate the effects of dispersal and mating system on fine-scale genetic structure at autosomal, mitochondrial and Y chromosome markers. Using genetic spatial autocorrelation analysis, we found that dispersal was the major driver of fine-scale genetic structure across maternally, paternally and biparentally inherited markers. However, when dispersal was restricted (mean distance=100m), variation in mating behaviour created strong differences in the comparative level of structure detected at maternally and paternally inherited markers. Promiscuity reduced spatial genetic structure at Y chromosome loci (relative to monogamy), whereas structure increased under polygyny. In contrast, mitochondrial and autosomal markers were robust to differences in the specific mating system, although genetic structure increased across all markers when reproductive success was skewed towards fewer individuals. Comparing males and females at Y chromosome vs. mitochondrial markers, respectively, revealed that some mating systems can generate similar patterns to those expected under sex-biased dispersal. This demonstrates the need for caution when inferring ecological and behavioural processes from genetic results. Comparing patterns between the sexes, across a range of marker types, may help us tease apart the processes shaping fine-scale genetic structure.

Mating strategy flexibility in the laboratory: Preferences for long- and short-term mating change in response to evolutionarily relevant variables

Abstract One of the great challenges for evolutionary psychology has been to explain within-sex individual variation in mating behaviour. Several lines of evidence suggest that some of this variation stems from an adaptation for facultatively increasing or decreasing long- and short-term mating inclinations in response to circumstances. It remains unclear, however, how rapidly such changes can occur, and what stimuli might initiate them. This paper presents three experiments that investigate mating strategy change following exposure to the evolutionarily-relevant stimuli of parental care, resource-abundance, and danger. In each experiment, participants indicated their preferred relationship type (long-term, short-term, or none) for each of fifty other-sex individuals, both before and after priming. Relative to a control group, relationship preferences changed in all three experiments, in directions generally consistent with evolutionary psychological predictions. Moreover, short- and long-term relationship preferences were found to shift independently, such that a change in long-term preference was not accompanied by an opposite change in short-term, or vice versa. Together, these experiments represent the first direct test of the claim that brief interventions can shift the relative strength of people's preferences for long-term and short-term relationships.

Behavioural mechanisms of reproductive isolation between two hybridizing dung fly species

Characterization of the phenotypic differentiation and genetic basis of traits that can contribute to reproductive isolation is an important avenue to understand the mechanisms of speciation. We quantified the degree of prezygotic isolation and geographical variation in mating behaviour among four populations of Sepsis neocynipsea that occur in allopatry, parapatry or sympatry with four populations of its sister species Sepsis cynipsea. To obtain insights into the quantitative genetic basis and the role of selection against hybrid phenotypes we also investigated mating behaviour of F1 hybrid offspring and corresponding backcrosses with the parental populations. Our study documents successful hybridization under laboratory conditions, with low copulation frequencies in heterospecific pairings but higher frequencies in pairings of F1 hybrids signifying hybrid vigour. Analyses of F1 offspring and their parental backcrosses provided little evidence for sexual selection against hybrids. Longer copulation latencies in heterospecific pairings indicate species recognition, probably due to surface or volatile chemicals. The frequency of male mating attempts did not differ greatly between species or hybrid pairings, suggesting no male discrimination of mating partners. Female shaking duration, signifying female choice and/or reluctance to mate, differed strongly between the species and appears to contribute to avoiding heterospecific males; this trait is partially maternal inherited. Importantly, females of both species discriminated more strongly against males in areas of sympatry than allopatry indicating reinforcement. Shorter copulations in heterospecific parental pairings and longer copulations in F1 hybrids suggest mechanistic difficulties with sperm transfer. Overall, our study highlights an important role of character displacement affecting mating behaviour of hybridizing sepsid species in geographical areas of coexistence.

Circulating white blood cell counts in captive and wild rodents are influenced by body mass rather than testes mass, a correlate of mating promiscuity

Summary Comparative studies of captive primates and carnivores have shown a positive correlation between total white blood cell (WBC) counts and the level of inferred mating promiscuity (e.g. using testes mass). This correlation has been interpreted to support the ‘sexually transmitted diseases (STDs)’ hypothesis, which states that differential spread of STDs is caused by variation in mating behaviour which shapes baseline aspects of the immune system in mammals. In the present study, we tested the STDs hypothesis in rodents using 28 species from free‐ranging and 9 species from captive populations. We compiled data set for the 9 studies of captive rodent populations from the International Species Information System (ISIS) and gathered 136 studies of wild populations from the literature. Using phylogenetic generalized least‐squares statistical models considering non‐independence resulting from shared ancestry, we confirmed that species with greater adult body mass averaged across sexes had elevated total WBC and differential WBC (neutrophils and lymphocytes) counts and that captive animals presented higher lymphocyte counts than free‐ranging ones. However, we found that the total and differential WBC counts did not covary with the residual testes mass – a correlate of mating promiscuity. The results suggest that selection pressures caused by STDs may strongly vary among taxonomic groups. In order to determine the drivers of immunological variation among mammals, further comparative immunological studies including a wide range of taxonomic groups and socio‐ecological variables should be performed and we recommend doing so by primarily focusing on free‐ranging animals.

Geographic variation in polyandry of the Eastern Honey Bee, Apis cerana, in Thailand.

The repeated evolution of extreme polyandry in advanced social insects is exceptional and its explanation has attracted significant attention. However, most reported estimates of the number of matings are derived from limited sampling. Temporal and geographic variation in mating behavior of social insects has not been sufficiently studied. Worker offspring of 18 Eastern Honey Bee (Apis cerana Fabr.) queens from three populations across Thailand were genotyped at five microsatellite markers to test for population differences of mating behavior across three different ecosystems. The number of matings decreased from a northern, more seasonal environment to a southern tropical population and was lowest in a tropical island population. Our study confirms earlier findings that social insect mating behavior shows biogeographic variation and highlights that data from several populations are needed for reliable species-specific estimates of the number of matings. Detailed studies of populations that show significant differentiation in the number of matings may be able to discriminate effectively among the different hypotheses that have been proposed to explain the evolution of polyandry in honey bees and other advanced social insects.

Intra-population variation in behavior modification by the acanthocephalan Acanthocephalus dirus: are differences mediated by host condition?

The acanthocephalan parasite Acanthocephalus dirus infects the freshwater isopod Caecidotea intermedius as an intermediate host before completing its life cycle in a fish. Male C. intermedius infected by A. dirus parasites are less likely to engage in mating behavior than uninfected males but there is a significant intra-population variation in the occurrence of this behavioral change. Previous studies on uninfected isopods have shown that glycogen content is a predictor of male mating behavior and we examined whether the intra-population variation in the mating behavior of infected male C. intermedius could be explained by this relationship. A field-based behavioral experiment was used to quantify intra-population variation in male mating behavior, which showed that 50% of infected males were responsive to females and 50% were not responsive. Biochemical analysis of responsive and non-responsive males revealed that glycogen content was a predictor of the mating behavior for uninfected males but was not a predictor of mating behavior for infected males. For infected males, parasite intensity was a predictor of mating behavior. Males that contained more A. dirus parasites were less likely to undergo modification of mating behavior. We propose that the intra-population variation in the mating behavior of infected C. intermedius identified in nature was not mediated by host condition.

Rates of Evolution of Hominoid Seminal Proteins are Correlated with Function and Expression, Rather than Mating System

In species where females mate with multiple males during a single ovulatory cycle, sperm competition is hypothesized to increase the rate of adaptive evolution of proteins expressed in male reproductive tissues through recurrent selective sweeps (positive selection). The hominoids, comprising apes and humans, are a group of closely related primates with extensive variation in mating behaviors and predicted levels of sperm competition. Since previous studies of individual male reproductive genes have shown evidence of positive selection, we estimated rates of evolution of a comprehensive set of proteins expressed in ejaculated semen. Our results show that these proteins in hominoids do not have elevated rates of nonsynonymous substitutions (Ka) compared with a control dataset of nonreproductive genes. Species with greater sperm competition do not have faster rates of seminal protein evolution. Although at these broad levels our hypotheses were not confirmed, further analyses indicate specific patterns of molecular evolution. Namely, the Ka of seminal genes is more strongly correlated with measures of tissue specificity than nonreproductive genes, suggesting that the former may more readily adapt to tissue-specific functions. Proteins expressed from the seminal vesicles evolve more rapidly than those from other male reproductive tissues. Also, several gene ontology categories show elevated rates of protein evolution, not seen in the control data set. While the generalization that male reproductive genes evolve rapidly in hominoids is an oversimplification, a subset of proteins can be identified that are likely targets for adaptive evolution driven by sexual selection.

Divergence in genital morphology may contribute to mechanical reproductive isolation in a millipede

Genitalia appear to evolve rapidly and divergently in taxa with internal fertilization. The current consensus is that intense directional sexual selection drives the rapid evolution of genitalia. Recent research on the millipede Antichiropus variabilis suggests that the male genitalia are currently experiencing stabilizing selection – a pattern of selection expected for lock-and-key structures that enforce mate recognition and reproductive isolation. Here, we investigate how divergence in genital morphology affects reproductive compatibility among isolated populations of A. variabilis. Females from a focal population were mated first to a male from their own population and, second, to a male from one of two populations with divergent genital morphology. We observed variation in mating behavior that might indicate the emergence of precopulatory reproductive barriers: males from one divergent population took significantly longer to recognize females and exhibited mechanical difficulty in genital insertion. Moreover, we observed very low paternity success for extra-population males who were successful in copulating. Our data suggest that divergence in genital shape may be contributing to reproductive isolation, and incipient speciation among isolated populations of A. variabilis.

Variation in male and female mating behaviour among different populations of the two-spot ladybird, Adalia bipunctata (Coleoptera: Coccinellidae)

Investigating the function of both male and female mating behaviours is essential in our attempts to understand the evolution of mating systems. Variation in mating behaviours among different populations within a species provides a useful opportunity to explore how behaviours may co-vary, although comparative studies are still rather few in number. Population variation in mating behaviour may also have important implications in terms of the evolution of reproductive isolation, the distribution of genetic diversity within and between populations, and the associated ability of those populations to adapt. Here we consider male and female mating behaviour in two populations of the two-spot ladybird, Adalia bipunctata, from the UK and Russia. We find that male and female mating behaviours differ between the populations in terms of the length of female rejection behaviour and the duration of mating, and that this variation is independent of which population an individual's mating partner is from. Our data confirm that patterns of sexual selection and reproductive behaviour are likely to vary across populations in the two-spot ladybird. The extent to which this variation is due to current ecological factors or population history remains to be verified for this species, as for many others.

Spatial variation in food supply, mating behavior, and sexually transmitted disease epidemics

Mating behavior helps to shape the epidemiology of sexually transmitted infections (STIs) by determining the rate at which infectious and susceptible individuals make contact. To the extent that mating behavior shows spatial variation, it is expected that STI epidemics will also show spatial heterogeneity (provided that dispersal is limited). However, empirical data are lacking for natural systems. Here, therefore, we investigate the association between local mating behavior and STI epidemiology in natural populations of the two-spot ladybird, Adalia bipunctata, and dissect the causes of this variation. Variation in mating behavior was observed over local and regional spatial scales and high mating rate led to stronger local epidemics of the STI. Initial ecological observations suggested that reduced mating rate was associated largely with low food supply (and possibly to a lesser extent with local population density) and not with differences in thermal environment. We tested the potential role of food supply in fuelling STI epidemics in laboratory populations and confirmed that high food provision led to greater STI transmission. We conclude that food supply is strongly associated with mating rate in the field and that this produces heterogeneity in STI epidemiology. A consequence is that STI-induced sterility will reduce reproduction in habitat patches of high food quality.