Variation In Mating Strategies Research Articles

Extrapair paternity in two populations of the socially monogamous Thorn-tailed Rayadito Aphrastura spinicauda (Passeriformes: Furnariidae).

Studies on extrapair paternity (EPP) are key to understanding the ecological and evolutionary drivers of variation in avian mating strategies, but information is currently lacking for most tropical and subtropical taxa. We describe the occurrence of EPP in two populations of a South American socially monogamous bird, the Thorn‐tailed Rayadito, based on data from 266 broods and 895 offspring that were sampled during six breeding seasons in north‐central and southern Chile. In the northern population, 21% of the broods contained at least one extrapair young and 14% of all offspring were sired by an extrapair male, while in the southern population, we detected extrapair offspring (EPO) in 14% of the broods, and 6% of all offspring were EPO. Variation in the frequency of EPP could stem from population differences in the duration of the breeding season or the density of breeding individuals. Other factors such as differences in breeding synchrony and variation in food availability need to be evaluated. More reports on EPP rates are necessary to determine the patterns of taxonomic and geographic variation in mating strategies in Neotropical birds, and to better understand the differences in ecological dynamics between northern and southern hemisphere populations.

Female dispersion and sex ratios interact in the evolution of mating behavior: a computational model

The evolution of mating strategies is not well understood. Several hypotheses have been proposed to explain the variation in mating strategies, with varying levels of support. Specifically, female dispersion, adult sex ratio and mate guarding have been proposed as drivers of the evolution of monogamous strategies. In this study, we used an agent-based model (ABM) to examine how different mating behaviors evolve in a population under different conditions related to these putative drivers, looking to understand the interaction between them. We found an interaction among different factors in the evolution of social monogamy, and their impact is in this order: adult sex ratio (ASR), female dispersion and extra-pair copulation. Thus, when the adult sex ratio is male-biased, monogamous strategies are strongly favored. However, this is only the case if mate guarding is fully efficient, i.e., if there is no extra-pair copulation. On the other hand, in scenarios where the population is female-biased, or mate guarding is not efficient, we find that polygamous strategies are favored but proportionally to the dispersion of females. These results confirm previous findings regarding mate guarding and sex ratios, while also showing how female dispersion enters the dynamics.

Intraseasonal temporal variation of reproductive effort for male grey seals

Reproductive skew in polygynous mating systems leads to variation in mating strategies, or the tactics within strategies, adopted by individual males. For example, variation in the timing of reproductive effort might reflect trade-offs between maximizing access to receptive females and minimizing interactions with competitors. For capital breeding grey seals, Halichoerus grypus, male mating success has been positively linked to total duration of tenure, but without differentiation of intraseasonal changes in reproductive effort. The aims of this study were to identify tactics within the tenured male strategy based on the timing of social dominance as a metric of reproductive effort, and to compare mating success across identified tactics. Our results confirm that duration of stay on the colony explained the most variation in mating success, but effect strength was reduced for tenures longer than 10 days. Additionally, there was evidence that timing of reproductive effort within a breeding season also contributed to observed variation in mating success. Males that maximized their dominance score at or after the peak in female attendance achieved greater mating success, relative to those who were dominant earlier in the breeding season. Males who timed their reproductive effort earlier in the season still achieved some mating success, but it was reduced. Individuals' tactics were flexible across years, and we found no evidence to support the hypotheses that timing of reproductive effort before or after the peak in female attendance was used by smaller tenured males, or to avoid conflict. These results highlight that understanding temporal scheduling of individual reproductive effort within a breeding season, relative to the availability of resources, constraints of fasting and intermale competition, is a key aspect to consider when differentiating individual tactics in long-lived, capital polygynous breeders.

Human mating strategies: from past causes to present consequences.

In both humans and nonhuman animals, mating strategies represent a set of evolutionary adaptations aimed at promoting individual fitness by means of reproduction with the best possible partners. Given this critical role, mating strategies influence numerous aspects of human life. In particular, between-sex divergence in the intensity of intrasexual competition could account for robust cross-cultural sex differences in psychology and behavior (e.g., personality, psychiatric disorders, social behavior, violence). Several other factors (including individual differences, relationship type and environment) affect-in an evolutionarily consistent manner-variation in mating strategy that individuals pursue (as one example, awareness of one's own attractiveness impinges on mating standards). Here we provide an overview of relevant theoretical frameworks and empirical evidence on variation in mating strategies. Given its multifaceted nature and intense research interest over several decades, this is a challenging task, and we highlight areas where further investigation is warranted in order to achieve a clearer picture and resolve apparent inconsistencies. However, we suggest that addressing outstanding questions using a variety of different methodological approaches, a deeper understanding of the cognitive representations involved in mating strategies is within reach. WIREs Cogn Sci 2018, 9:e1456. doi: 10.1002/wcs.1456 This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition Neuroscience > Behavior Neuroscience > Cognition.

Genome-wide SNP analysis reveals a genetic basis for sea-age variation in a wild population of Atlantic salmon (Salmo salar).

Delaying sexual maturation can lead to larger body size and higher reproductive success, but carries an increased risk of death before reproducing. Classical life history theory predicts that trade-offs between reproductive success and survival should lead to the evolution of an optimal strategy in a given population. However, variation in mating strategies generally persists, and in general, there remains a poor understanding of genetic and physiological mechanisms underlying this variation. One extreme case of this is in the Atlantic salmon (Salmo salar), which can show variation in the age at which they return from their marine migration to spawn (i.e. their 'sea age'). This results in large size differences between strategies, with direct implications for individual fitness. Here, we used an Illumina Infinium SNP array to identify regions of the genome associated with variation in sea age in a large population of Atlantic salmon in Northern Europe, implementing individual-based genome-wide association studies (GWAS) and population-based FST outlier analyses. We identified several regions of the genome which vary in association with phenotype and/or selection between sea ages, with nearby genes having functions related to muscle development, metabolism, immune response and mate choice. In addition, we found that individuals of different sea ages belong to different, yet sympatric populations in this system, indicating that reproductive isolation may be driven by divergence between stable strategies. Overall, this study demonstrates how genome-wide methodologies can be integrated with samples collected from wild, structured populations to understand their ecology and evolution in a natural context.

Variable mode of estrus affects female decision for multiple mating

Investigating patterns of variation in mating strategies may shed light on their evolutionary importance as well as their impact on the strength and shape of sexual selection. Multimale mating (polyandry) and mate choice are intensely studied subjects in the area of sexual selection, but little is known about intraspecific patterns of variation that may respond to dynamic cost-benefit balances. In a laboratory study, we investigated the mating behavior of female bank voles (Myodes glareolus) with distinctly different time and energy budgets: They were either in cycling estrus (CE) or postpartum estrus (PPE) shortly after delivery. Postpartum mating is highly constrained by time and energy due to maternal commitments to the newborn litter. All females had a free and simultaneous choice among 4 males that differed in scent-marking frequency (indicator of dominance) and body mass. We show that females in CE engaged significantly more often in multimale mating than females in PPE. Additionally, PPE females mated with males that scent marked more, whereas CE females seemingly mated indiscriminately. We discuss our findings in light of time and energy budgets of females and also consider alternative explanations such as pup protection against infanticidal males or physiological constraints to estrus modes.

Genetic monogamy across variable demographic landscapes in cooperatively breeding Florida scrub-jays

Variation in ecological and demographic characteristics may alter the value of extrapair paternity (EPP) for socially monogamous species, thereby leading to variation in mating strategies among conspecific populations. Environmental factors influencing the need for parental care, and demographic factors influencing relatedness of social pairs or availability of unrelated extrapair partners, are both predicted to influence the direct and indirect benefits of EPP in cooperatively breeding birds. We examined genetic mating strategies in 3 long-term study populations of cooperatively breeding Florida scrub-jays (FSJs; Aphelocoma coerulescens) in which the value of EPP—or opportunities for it—was likely to vary: a fragmented site with a high frequency of inbreeding (potentially elevating the value of EPP as a means of increasing offspring heterozygosity); a suburban population with high rates of brood reduction (potentially elevating the value of shared parental investment); and a wildland site with a high frequency of unrelated breeders and opposite-sex auxiliaries (potentially elevating the opportunity for shared within-group parentage). Despite these differences, genetic monogamy dominated at all sites: 100% of the offspring sampled from the suburban site (144 offspring) and fragmented site (258 offspring), and 99.5% of offspring from the wildland site (367 of 369 offspring) were produced monogamously. Rare exceptions in our study populations demonstrate that, even in the FSJ, genetic monogamy is a plastic trait. The near ubiquity of genetic monogamy across 3 ecologically different study sites, however, suggests that this tendency toward monogamy is impervious to the population-level environmental and social variation that we documented. Key words: Aphelocoma coerulescens, extrapair paternity, Florida scrub-jay, genetic monogamy. [Behav Ecol]

Evidence for small scale variation in the vertebrate brain: mating strategy and sex affect brain size and structure in wild brown trout (Salmo trutta)

The basis for our knowledge of brain evolution in vertebrates rests heavily on empirical evidence from comparative studies at the species level. However, little is still known about the natural levels of variation and the evolutionary causes of differences in brain size and brain structure within-species, even though selection at this level is an important initial generator of macroevolutionary patterns across species. Here, we examine how early life-history decisions and sex are related to brain size and brain structure in wild populations using the existing natural variation in mating strategies among wild brown trout (Salmo trutta). By comparing the brains of precocious fish that remain in the river and sexually mature at a small size with those of migratory fish that migrate to the sea and sexually mature at a much larger size, we show, for the first time in any vertebrate, strong differences in relative brain size and brain structure across mating strategies. Precocious fish have larger brain size (when controlling for body size) but migratory fish have a larger cerebellum, the structure in charge of motor coordination. Moreover, we demonstrate sex-specific differences in brain structure as female precocious fish have a larger brain than male precocious fish while males of both strategies have a larger telencephalon, the cognitive control centre, than females. The differences in brain size and structure across mating strategies and sexes thus suggest the possibility for fine scale adaptive evolution of the vertebrate brain in relation to different life histories.

Correlated evolution of mating behaviour and morphology in large carpenter bees (Xylocopa)

Carpenter bees (Xylocopa) display variation in mating strategies. In several subgenera males defend territories that contain resources for females. In other subgenera males defend a small non-resource territory. Here, we investigate the correlation between three morphological traits and mating strategy. We found associations between mating strategy and male eye size, size of the mesosomal gland and sexual colour dimorphism, as well as correlative evolution between the morphological characters. Analysis of the evolutionary pathways shows that resource defence, small glands and monomorphic sexes are ancestral states. Increases in gland size seem to precede or coincide with changes in mating behaviour, but changes towards sexual dimorphism follow changes in mating behaviour. Once a non-resource defence strategy with correlated morphology has evolved there are no reversals to the ancestral states. We discuss the types of selection that may have caused these correlative changes.

Geographical variability, pheromones

The worldwide variation in mating strategies can be explained by differential paternal investment theory, which traces the differences back to the climates where the various peoples (races) evolved. Male provisioning is necessary for women and children to survive cold winters, which is less essential for tropical women. Androstenone may be the substance that makes symmetrical men smell better to fertile females.

Different reproductive tactics in male collared flycatchers signalled by size of secondary sexual character

Most studies of variation in male reproductive tactics have focused on conspicuous categorical differences in mating behaviour (i.e. variation in mating strategies). However, in the presence of trade–offs between investment in competition over matings, parental care and survival, a male's optimal allocation rule might vary according to his physiological condition and social or ecological environment. Thus, there may also be more subtle variation in male reproductive tactics. Here, I show that the reproductive effort (estimated as residual change in condition) of male collared flycatchers was affected by the size of their forehead patch (a secondary sexual character), age and date of arrival at the breeding grounds. Among early males (i.e. males with a high likelihood of both attracting more than one female and obtaining extra-pair copulations), large–patched males made a relatively large reproductive effort and as a result were in worse condition at the time of feeding offspring as compared to small–patched males. Furthermore, among early breeders, young males and males with experimentally increased forehead patch size made a relatively high effort. By contrast, regardless of age and badge size, there were no such patterns observed among late breeders. These results suggest that collared flycatchers use different reproductive tactics depending on both internal and external factors, and that the size of a secondary sexual trait may not only indicate variation in individual condition but also predict how resources will be allocated between pre– and post–mating reproductive activities.

Ecological and behavioural variables affecting the fallow deer mating system in Doñana

The rutting behaviour of fallow deer (Dama dama) at Doñana National Park (SW Spain) was studied in order to test the ecological and behavioural factors affecting variation in fallow deer mating strategies. Rutting area attendance was an important determinant of male reproductive success. An increase in population density during the study period did not seem to affect the variables related to the males' reproductive success, although a reduction in the size of area occupied by the males, and in the amount of their overlap between neighbours was detected. Despite this result, non-territorial strategies were perceived, and “dominance-groups” was the most successful mating strategy. In the past territorial strategies such as “rutting stands” have been described in the study area, but leks were never observed. It would appear, then, that in Doñana shifts in density do not fit the pattern which foresees that an increase in density contributes to continuous increases in territorial behaviour, reaching extremes such us multiple stands and lekking. Our study reveals that increases in density did not result in a change from non-territorial strategies. Our hypothesis is that when environmental conditions are unpredictable and/or the main mortality factors are predation and chaotic events, such as drought in the case of Doñana, environmental stress plays a more relevant role than social stress and density-dependent factors have a secondary influence on the variation in mating strategies.