Level Of Theory Research Articles

Links between personality, reproductive success and re‐pairing patterns in a long‐lived seabird

AbstractIn long‐lived monogamous species, the trigger of costly re‐pairing is not always clear. Limited research suggests that within‐pair behavioural compatibility may be an important driver of partnership success, as cooperation should be enhanced when pair members' decisions complement one another. Animals' decision‐making processes are influenced by personality traits – defined as individual differences in behaviour that are stable in time. Despite the potential for the personality trait ‘boldness’ to (a) directly impact individual willingness to re‐pair and (b) indirectly impact re‐pairing choices via reproductive success, there is currently little work exploring how re‐pairing decisions might be impacted by the pair members' personalities. Using a 13‐year dataset, we investigated whether within‐pair boldness and its relationship with breeding success explained re‐pairing patterns of black‐legged kittiwakes (Rissa tridactyla), breeding in two Arctic colonies. We found that pairs with dissimilar boldness levels were more likely to experience breeding failure and that failed pairs were more likely to re‐pair the following year. Despite this, only one colony displayed evidence of assortative mating by boldness, and there was no indication that re‐pairing impacted reproductive success the following season. Neither individual nor pair boldness directly influenced re‐pairing probability; however, in both colonies, re‐pairing birds chose partners that were slightly more similar to themselves in boldness than their previous mates. These results imply an indirect pathway by which poorer behavioural compatibility within pairs may lead to breeding failure and ultimately re‐pairing. Our findings highlight the importance of behavioural compatibility, and possibly personality, in mitigating sexual conflict and its population‐specific drivers.

Assortative mating and earnings inequality in South Korea

Assortative mating and earnings inequality in South Korea

Telomere length links with physiological phenotype and breeding patterns in a long-lived seabird

Abstract Telomere length (TL) is known to covary with a suite of physiological traits involved in energy balances that may influence breeding success. Thus, TL may be an indicator of individual quality, influencing mate choice and breeding strategies. In the Brown Booby (Sula leucogaster), a long-lived seabird, we investigated in a total of 72 pairs whether TL may indicate the individual physiological phenotype by examining how it relates to mitochondrial DNA copy number (mtDNAcn) and corticosterone (CORT) levels. Then, we tested if TL is associated with mating patterns by looking for covariation with skin coloration (a condition-dependent sexual trait), whether there is assortative mating by TL, and if the degree of TL similarity between partners influences an individual’s likelihood of changing mates between reproductive seasons. Because environmental conditions can have important effects on the condition and reproductive strategies of individuals, the study was performed in 2 colonies with contrasting breeding conditions. We found that TL was positively related to mtDNAcn (but not CORT levels), suggesting that individuals with shorter telomeres may have a reduced mitochondrial density. TL was reflected in sexual coloration, but only in the colony with good breeding conditions. There was positive assortative mating by TL; however, the degree of assortative mating was unrelated to the probability of mate change, which greatly varied between the 2 colonies. Our results suggest that TL is associated with the physiological phenotype of individuals and their breeding patterns. Importantly, contrasting environmental conditions influenced the link between TL and sexual coloration and the propensity of individuals to change mate, highlighting the importance of environmental variation on mating patterns.

Demographic imbalance in the hybrid zone led to asymmetric gene flow between two closely related geckos, Gekko hokouensis and Gekko yakuensis (Squamata: Gekkonidae)

Abstract Introgressive hybridization caused by invasive species may lead to the extinction of pure native species, but a theoretical model of the invasion process with hybridization (the neutral demographic model) suggests that introgression occurs mainly from native to invasive species. Clarifying the direction of introgression is important to evaluate the impact of hybridization on native species. In southern Japan, a widely disseminated gecko, Gekko hokouensis, and a local gecko, Gekko yakuensis, have formed mosaic hybrid zones. Given the presumed invasiveness of Gekko hokouensis, the neutral demographic model predicts that introgression would mainly occur in the direction to Gekko hokouensis, whereas possible asymmetric assortative mating suggested by a previous study predicts the opposite direction of introgression. Our investigations using microsatellite markers and mitochondrial DNA for the gecko assemblages in 12 localities and comparisons with allozyme data collected 18 years ago indicated that Gekko hokouensis expanded its range and tended to have replaced hybrids and Gekko yakuensis. Introgression was skewed towards Gekko hokouensis, but interspecific mating between the parental species was reciprocal. These results suggest that their hybridization progress follows the neutral demographic model and that the higher population growth rate of Gekko hokouensis is the major cause of species replacement, although we cannot rule out the possibility that asymmetric assortative mating also influences the later stages of species replacement.

RBahadur: efficient simulation of structured high-dimensional genotype data with applications to assortative mating

Existing methods for generating synthetic genotype data are ill-suited for replicating the effects of assortative mating (AM). We propose rb_dplr, a novel and computationally efficient algorithm for generating high-dimensional binary random variates that effectively recapitulates AM-induced genetic architectures using the Bahadur order-2 approximation of the multivariate Bernoulli distribution. The rBahadur R library is available through the Comprehensive R Archive Network at https://CRAN.R-project.org/package=rBahadur.

Both reduced ovarian reserve and severe semen alterations are overrepresented in couples seeking assisted reproductive technology treatment for the first time: a cross-sectional study

BackgroundOnce a mate choice decision has been made, couples that fail to reach a live birth in natural and/or intrauterine insemination (IUI) cycles will likely visit fertility clinics seeking assisted reproductive technology (ART) treatment. During the more or less prolonged period of infertility experienced, those couples with mild/moderate reproductive anomalies would have advantage over couples displaying more severe reproductive alterations in achieving a natural or IUI conception. Thus, we can expect to find a progressive increase in the proportion of couples with more severe reproductive anomalies as duration of infertility rises. In this study, we aim to ascertain whether there is an association between male and female infertility diagnoses and duration of infertility in couples seeking ART treatment for the first time.MethodsA cross-sectional analysis of 1383 infertile couples that sought ART treatment for the first time. Forward-stepwise binary logistic regression analyses were applied to calculate exponentiated regression coefficients.ResultsMen suffering from any combination of oligo-, astheno-, and teratozoospermia (ACOAT) exhibited higher odds of having a duration of infertility > 2 years compared with non-ACOAT men [odds ratio (95% confidence interval): 1.340 (1.030–1.744)]. Women from ACOAT couples displaying a duration of infertility > 2 years presented shorter menstrual cycles (P ≤ 0.047) and lower antral follicular count (AFC) values (P ≤ 0.008) and serum anti-Müllerian hormone (AMH) levels (P ≤ 0.007) than women from non-ACOAT couples exhibiting > 2 years of infertility. Likewise, AFC values (P ≤ 0.013) and serum AMH levels (P ≤ 0.001) were decreased when compared with women from ACOAT couples displaying ≤ 2 years of infertility. A relative low but significant percentage of ACOAT couples displaying > 2 years of infertility stood out for their smoking habits.ConclusionsCouples consisting of ACOAT men and women with a relative low ovarian reserve are overrepresented in couples seeking ART treatment for the first time after experiencing > 2 years of infertility. This outcome leads us to develop a general hypothesis proposing that the origin of couple’s infertility is a consequence of a process of positive assortative mating shaped by sexual selection forces.

Marital sorting, family output, and wealth inequality

Abstract In this article, we analytically model marital sorting, intergenerational transfers, and inequality in a household optimization model with uncertainty. We modify and apply a ‘sorting, reverse sorting’ numerical approach by Demirtas in the context of marriage market mating, illustrating the robustness of our analytical results. We show that the parameters of the family production function play an important role in driving the path of an economy’s inequality. One finding is that, under assortative mating, factor shares in the family production function positively affect inequality, while under disassortative mating, the relationship between the factor shares and inequality is U-shaped. This and other results that we obtain can stimulate further empirical research, holding potentially important policy implications.

An economic model and evidence of the evolution of human intelligence in the Middle Pleistocene: Climate change and assortative mating.

A main objective of this paper is to provide the first model of how climate change, working through sexual selection, could have led to dramatic increases in hominin brain size, and presumably intelligence, in the Middle Pleistocene. The model is built using core elements from the field of family economics, including assortative mating and specialization and complementarities between mates. The main assumptions are that family public goods (e.g., conversation, shelter, fire) were particularly cognitively intensive to produce and became increasingly important for child survival during glacial phases. Intermediate climates (e.g., not the depths of severe glacial phases) create the largest gains from specialization, encouraging negative assortative mating. In contrast, severe glacial phases encourage positive assortative mating because of the rising importance of family public goods. One testable hypothesis is that absence of severe glacial phases should have led to stasis in brain size. Two other testable hypotheses are that severe glacial phases should have led to speciation events, as well as increases in brain size. The evidence shows that there was a million-year stasis in cranial size prior to the start of the severe glacial phases. This stasis is broken by a speciation event (Homo heidelbergensis), with the oldest fossil evidence dated near the close of the first severe glacial phase. In the next 300 kyr, there are two additional severe glacial phases, accompanied by considerable increases in cranial capacity. The last speciation event is Homo sapiens, with the earliest fossils dated near the end of the last of these two glacial phases.

Paternity data reveal high MHC diversity among sires in a polygynandrous, egalitarian primate.

Evidence from human and nonhuman primates suggests that females avoid breeding with close kin and may choose mates based on MHC diversity, which can improve offspring survival. In despotic societies, female mate choice may be hindered by male sexual coercion, but in egalitarian societies, females may be less constrained. Among northern muriquis-an egalitarian, polygynandrous primate with male philopatry-analyses of new data on paternity and variation at microsatellite and MHC loci, combined with behavioural and life-history data, revealed that sires showed higher MHC diversity than expected by chance and were never close kin of dams, consistent with predictions of female mate choice and close inbreeding avoidance. However, females did not differentially reproduce with males who were more distantly related to them or more dissimilar at the MHC than expected by chance, nor with those who had more MHC alleles distinct from their own. The lack of male dominance may permit females to identify and reproduce preferentially with non-offspring males and with males who are more diverse at the MHC. Nonetheless, the absence of disassortative mating at the MHC and neutral loci suggests that female mate choice may be limited by other factors impacting male fertilization success.

Sexual signal evolution and patterns of assortative mating across an intraspecific contact zone.

Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red-eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A. callidryas differ in a number of traits, several of which are known sexual signals that mediate premating reproductive isolation in allopatric populations. Along the Caribbean coast of Costa Rica, a ~100 km contact zone, situated between two phenotypically and genetically divergent parent populations, contains multiple colour pattern phenotypes and late-generation hybrids. This contact zone provides the opportunity to examine processes that are important in the earliest stages of lineage divergence. We performed analyses of colour pattern variation in five contact zone sites and six parental sites and found complex, continuous colour variation along the contact zone. We found discordance between the geographic distribution of colour pattern and previously described genomic population structure. We then used a parental site and contact zone site to measure assortative mating and directional selection from naturally-occurring amplectant mating pairs. We found assortative mating in a parental population, but no assortative mating in the contact zone. Furthermore, we uncovered evidence of directional preference towards the adjacent parental phenotype in the contact zone population, but no directional preference in the parent population. Combined, these data provide insights into potential dynamics at the contact zone borders and indicate that incipient speciation between parent populations will be slowed.

What causes concordance of hypertension between spouses in India? Identifying a critical knowledge gap from a nationally representative cross-sectional sample of 63,020 couples aged 15 + years

BackgroundHypertension, a critical risk factor for cardiovascular diseases, is found to cluster between spouses due to within-couple aggregation of antecedent environmental risk factors, either through assortative mating or cohabitation. However, majority of the evidence of spousal concordance of hypertension is from Caucasoid couples from western societies, whereas marriage, partner selection, and post-marital roles of husband and wives are very different in Indian society. Therefore, we aimed to comprehensively examine the phenomenon of spousal concordance of hypertension in Indian couples.MethodCouples from Longitudinal Ageing Study in India Wave 1 (n = 10,994) and National Family Health Survey Round 5 (n = 52,026) represented 15 years + Indian spouses. Hypertension was defined when systolic and/or diastolic blood pressure was > 139 and > 89 mmHg respectively, and/or if the individual was previously diagnosed or on anti-hypertensive medication. Odds Ratios (OR) estimated the within-couple concordance of hypertension while adjusting for five environmental risk factors of hypertension: individual-level body mass index, education and caste, and household-level wealth and place of residence.ResultOR marginally attenuated from 1.84 (95% Confidence Interval: 1.77, 1.92) to 1.75 (1.68, 1.83) after adjustment, signifying negligible explanation by environmental risk factors, and plausibility of “novel” risk factors. Concordance continued to weaken with age (OR: 2.25 (2.02, 2.52) in < 30 versus 1.36 (1.20, 1.53) in ≥ 60 years).ConclusionOur study underscores two critical knowledge gaps: first, the identity of “novel” risk factors of hypertension and second, the mechanism behind weakening of concordance with age. Future research should explore these novel risk factors rigorously and try to modify them. Also, primary healthcare policy of the country should focus on couples in addition to individuals for hypertension and cardiovascular disease screening and management.

Overcoming attenuation bias in regressions using polygenic indices

Measurement error in polygenic indices (PGIs) attenuates the estimation of their effects in regression models. We analyze and compare two approaches addressing this attenuation bias: Obviously Related Instrumental Variables (ORIV) and the PGI Repository Correction (PGI-RC). Through simulations, we show that the PGI-RC performs slightly better than ORIV, unless the prediction sample is very small (N < 1000) or when there is considerable assortative mating. Within families, ORIV is the best choice since the PGI-RC correction factor is generally not available. We verify the empirical validity of the simulations by predicting educational attainment and height in a sample of siblings from the UK Biobank. We show that applying ORIV between families increases the standardized effect of the PGI by 12% (height) and by 22% (educational attainment) compared to a meta-analysis-based PGI, yet estimates remain slightly below the PGI-RC estimates. Furthermore, within-family ORIV regression provides the tightest lower bound for the direct genetic effect, increasing the lower bound for the standardized direct genetic effect on educational attainment from 0.14 to 0.18 (+29%), and for height from 0.54 to 0.61 (+13%) compared to a meta-analysis-based PGI.

Assortative mating in Gastropoda: A meta-analysis

The term ‘assortative mating’ denotes situations when the choice of a mating partner is nonrandom and the phenotypes across mate pairs are correlated, either positively or negatively. Assortative mating has been registered as a particular type of behaviour in many taxa of animals, including various vertebrate and invertebrate species. The aim of this study is to conduct a meta-analysis of published data concerning assortative mating in various taxa of Gastropoda. In total, we found 36 published peer-reviewed papers that consider the size-assortative mating in Gastropoda. 32 species belonging to different taxonomic groups of this class were studied, which provided 58 cases for further analysis. The range of estimates of the strength of assortment between individuals for species included into our meta-analysis (46 cases) is very wide: from –0.155 (Brephulopsis cylindrica) to +0.966 (Veronicella sloanii). Integrally, for the studied species of Gastropoda, the average weighted estimate of the strength of assortment between the sizes of copulating individuals was 0.381 ± 0.014. It revealed that virtually all the points representing individual studies form a funnel-shaped dispersion on a scatterplot that lies along the line representing the estimate of the generalized mean rgen = 0.343 and uniformly fill the funnel-shaped space between the lines of 95% confidence interval of the correlation coefficient for a given sample size adjusted for the overall mean. The distribution of the estimates of the correlation coefficient between copulating individuals among the various gastropod species has a shape close to the normal distribution (Kolmogorov-Smirnov's d = 0.061; P &gt; 0.20). Moreover, most estimates are concentrated within a range from 0.2 to 0.6. We found that the probability of obtaining reliable estimates of the correlation coefficient between the sizes of copulating individuals is dependent upon the number of pairs used in the analysis (binary logistic regression: χ2 = 8.92; df = 1; P = 0.0028). It can be argued that the existence of the negative size-assortative mating in Gastropoda has not yet been proved. On the other hand, if only statistically significant cases of size-assortative mating are considered (37 cases out of 58, or 63.7%), the average weighted estimate of the strength of assortment between sizes of copulating mollusks is 0.439 ± 0.015 (95% confidence interval: 0.409–0.468). If we consider the mating system and the environment simultaneously, the positive size-assortativity is most pronounced among the gonochoristic snails living in the aquatic environment (0.448 ± 0.021) while among the aquatic hermaphroditic species it is the weakest (0.315 ± 0.028). Terrestrial hermaphrodites (land snails and slugs) take the middle position. The numerous examples of the assortative mating with respect to different morphological traits, either quantitative or qualitative, have been described in various species of aquatic and land snails.

Conventional twin studies overestimate the environmental differences between families relevant to educational attainment

Estimates of shared environmental influence on educational attainment (EA) using the Classical Twin Design (CTD) have been enlisted as genetically sensitive measures of unequal opportunity. However, key assumptions of the CTD appear violated for EA. In this study we compared CTD estimates of shared environmental influence on EA with estimates from a Nuclear Twin and Family Design (NTFD) in the same 982 German families. Our CTD model estimated shared environmental influence at 43%. After accounting for assortative mating, our best fitting NTFD model estimated shared environmental influence at 26%, disaggregating this into twin-specific shared environments (16%) and environmental influences shared by all siblings (10%). Only the sibling shared environment captures environmental influences that reliably differ between families, suggesting the CTD substantially overestimates between-family differences in educational opportunity. Moreover, parental education was found to have no environmental effect on offspring education once genetic influences were accounted for.

Zoo-bred female birds prefer songs of zoo-bred males: Implications for adaptive management of reintroduction programs

Understanding the factors affecting the success of animal reintroductions is crucial for facilitating endangered species recovery. Cultural differences between individuals from different animal populations can lead to assortative mating, whereby individuals prefer to breed within their own familiar cultural cohort. Assortative mating can hinder the assimilation of zoo-bred individuals into wild populations, so quantifying this risk becomes important for informing adaptive management strategies in conservation. We conducted mate choice experiments on zoo-bred female regent honeyeaters (Anthochaera phrygia) to assess whether they showed stronger behavioural responses to the familiar but abnormal songs of zoo-bred male regent honeyeaters than those of their wild counterparts or an interspecific control song. Female regent honeyeaters were no more likely to enter the playback aviary in response to the songs of zoo-bred males than those of wild males or a different species. However, females that did enter the playback aviary were significantly more likely to respond quickly, approach the speaker closely and remain in the playback aviary for longer in response to the songs of zoo-bred males than wild songs or control songs. Our study is the first to show experimentally that zoo-bred females prefer familiar, but abnormal, zoo-bred songs over unfamiliar wild-type songs. We suggest that assortative mating amongst released birds is a risk in reintroduced regent honeyeaters, given recent evidence that the breeding success of reintroduced pairs is low. Our study demonstrates how small-scale experiments conducted within applied zoo-breeding settings can yield useful information to refine husbandry techniques and reduce cultural divides between wild and reintroduced populations.

Subtle Introgression Footprints at the End of the Speciation Continuum in a Clade of Heliconius Butterflies.

Quantifying gene flow between lineages at different stages of the speciation continuum is central to understanding speciation. Heliconius butterflies have undergone an adaptive radiation in wing color patterns driven partly by natural selection for local mimicry. Color patterns are also known to be used as assortative mating cues. Therefore, wing pattern divergence is considered to play a role in speciation. A corollary is that mimicry between closely related species may be associated with hybridization and interfere with reproductive isolation. Here, we take a multifaceted approach to explore speciation history, species boundaries, and traits involved in species differentiation between the two closely related species, Heliconius hecale and Heliconius ismenius. We focus on geographic regions where the two species mimic each other and contrast this with geographic regions where they do not mimic each other. To examine population history and patterns of gene flow, we tested and compared a four-population model accounting for linked selection. This model suggests that the two species have remained isolated for a large part of their history, yet with a small amount of gene exchange. Accordingly, signatures of genomic introgression were small except at a major wing pattern allele and chemosensing genes and stronger in the mimetic populations compared with nonmimetic populations. Behavioral assays confirm that visual confusion exists but that short-range cues determine strong sexual isolation. Tests for chemical differentiation between species identified major differences in putative pheromones which likely mediate mate choice and the maintenance of species differences.

Lack of genetic differentiation between two sympatric lacustrine morpho-species within the Astyanax (Characidae: Teleostei) genus, Mexico

We analyzed two morpho-species, Astyanax aeneus and Astyanax caballeroi, coexisting in Lake Catemaco, with ecological differences previously associated with different trophic niches. While A. aeneus is a widely distributed species, A. caballeroi is endemic to Lake Catemaco. Due to the contrasting morphology between these two sympatric species, they were originally assigned to different genera, but little is known about their genetic differentiation. We hypothesized that these two species, which present differentiation in morphology and in trophic niches, co-occur in concomitance with assortative mating and form distinct genetic clusters. We tested this prediction by typing a set of 12 microsatellites in 348 individuals of the two morpho-species, comparing their genetic structure patterns with that of an allopatric population of A. aeneus (i.e., the Maquinas population). Genetic structure analysis, assignment analyses, and estimation of gene flow between the sympatric morpho-species were carried out. Contrary to expectations, there is a lack of genetic differentiation between the A. aeneus and A. caballeroi morpho-species. However, there was a genetic differentiation between Lake Catemaco and Río Maquinas populations of A. aeneus. In addition, we found an asymmetric gene flow pattern, with a larger migration rate from A. aeneus to A. caballeroi than in the other direction. Finally, the allopatric population of A. aeneus showed lower levels of genetic diversity than those reported for both morpho-species in the lacustrine system. Consequently, our results support the notion that these morpho-species are either in an early phase of speciation or represent a single polymorphic species. This model provides relevant information to understanding the presence of polymorphisms under gene flow and their potential impact on the speciation process.

Multiple traits predict reproductive success and assortative mating in mutually ornamented Campo flickers (Colaptes campestris campestris)

Multiple traits predict reproductive success and assortative mating in mutually ornamented Campo flickers (Colaptes campestris campestris)

Gas Phase Reaction of Ketene with H2S in Troposphere: Catalytic Effects of Water and Ammonia

Background: Additions of water monomer (H2O) to simplest ketene, i.e., H2C=C=O (mentioned as ketene, henceforth) in the Earth's atmosphere results in the formation of acetic acid. However, this reaction is not feasible under tropospheric conditions due to the high reaction barrier amounting to nearly 40 kcal mol-1. A Significant reduction of the barrier height (below 20 kcal mol-1) is achieved upon addition of another H2O molecule as a catalyst. It is worth mentioning that like H2O and ammonia (NH3), H2S could also play an important role in the “loss mechanism” of various atmospherically important species such as ketones and aldehydes. Aims: This study aims to get insight into the energetics and kinetics of a reaction between ketene and H2S in the troposphere which has not been done before. Objective: Due to close similarity of H2O and H2S, studying the sulfolysis reaction between ketene and H2S could provide some interesting insights into the nature of various hydrogen bonded complexes of ketene as well as the impact on the products formed under the atmospheric conditions. Methods: The water and ammonia catalyzed gas-phase addition reactions of ketene with H2S has been investigated using CCSD(T)-F12a/cc-pVTZ-F12a//M06-2X/6-311++G** level of theory. In this study, rate constants for all possible reaction channels are calculated using transition state theory. Results: It is found that, under tropospheric conditions at 298 K and 1 atm, the rates via catalyzed reaction channels are significantly faster than those via uncatalyzed reactions. Between the two catalysts, ammonia acts as far better catalyst than water for this reaction. However, since the concentration of water is significantly larger than ammonia, the effective rate of water catalyzed reaction becomes higher than that of ammonia catalyzed reaction. Combustion is a major source of ketene in atmosphere. Under combustion conditions such as in the presence of air and at or above ignition temperature, the ammonia catalyzed channel is faster below 1500 K, while the uncatalyzed reaction channel becomes faster above that temperature. Conclusion: Results from the present study show that the barrier for thioacetic acid formation through uncatalyzed sulfolysis of ketene via faster C=O addition pathway is substantially high as 40.6 kcal mol-1. The barrier height of the two transition states TS1 and TS2 are 19.7 and 13.8 kcal mol-1 for water catalyzed reaction and 14.4 and 7.2 kcal mol-1 for ammonia catalyzed reaction. Thus, ammonia has appreciably lowered the barrier height compared to water as catalyst. It has been observed that the hydrolysis reaction is more probable than the sulfolysis reaction under atmospheric conditions in the troposphere, but the ammonia catalysed sulfolysis is the fastest one at 298 K. The effective rate constant of the water catalysed hydrolysis reaction is found to be more than the ammonia catalysed reaction due to the higher monomer concentration of water than ammonia. Ammonia catalyzed reaction rate increases monotonously with increasing temperature. Further rate coefficient for uncatalyzed reaction is found to be dominant under combustion conditions, i.e., above 1500 K.

Genotype and growth rate influence female mate preference in Xiphophorus multilineatus: Potential selection to optimize mortality-growth rate tradeoff.

The extent to which mate preferences are adaptive requires a better understanding of the factors that influence variation in mate preferences. Xiphophorus multilineatus is a live-bearing fish with males that exhibit alternative reproductive tactics (courter/sneaker). We examined the influence of a female's genotype (courter vs sneaker lineage), growth rate, and social experience on mate preference for courter as compared to sneaker males. We found that females with a sneaker genotype and slower growth rates had stronger mate preferences for the faster growing courter males than females with a courter genotype, regardless of mating experience with one or both types of males. In addition, the relationship between strength of preference and growth rate depended on a females' genotype; females with sneaker genotypes decreased their preference as their growth rates increased, a pattern that trended in the opposite direction for females from the courter genotypes. Disassortative mating preferences are predicted to evolve when heterozygous offspring benefit from increased fitness. Given male tactical dimorphism in growth rates and a mortality-growth rate tradeoff previously detected in this species, the variation in mating preferences for the male tactics we detected may be under selection to optimize the mortality-growth rate tradeoff for offspring.