Patricia Adair Gowaty

Free female mate choice in house mice affects reproductive success and offspring viability and performance

We tested a critical assumption of sexual dialectics theory (Gowaty 1997, Feminism and Evolutionary Biology, Chapman & Hall) using house mice, Mus musculus. We asked if female house mice accrue viability benefits for their offspring when they mate with males they prefer versus with males they do not prefer. Our experiment was designed to eliminate or control other mechanisms of reproductive competition besides female mate choice. After allowing females to discriminate behaviourally between two males, which were at random with respect to phenotypic variation discriminating females were paired with preferred (P) or nonpreferred (NP) males. We then tested whether females mating with males they preferred had offspring of higher viability than females mating with nonpreferred males. In pairwise comparisons, we tested for differences in offspring performance in dominance contests and in nest-building skill. At weaning, we exposed half of the pups to cold stress. We tested progeny performance and viability in the laboratory or in outdoor field enclosures. In comparison to P females, NP females produced significantly fewer litters. Sons from P matings were socially dominant to sons from NP matings. Adult offspring from P matings built better nests than those from NP matings. In field enclosures significantly fewer NP than P offspring survived to 60 days after introduction. Male and female progeny from P matings established larger home ranges and constructed better nests than progeny from NP matings. This is the first demonstration of progeny viability differences for females allowed to express mate preferences between males presented to them at random. Copyright 2000 The Association for the Study of Animal Behaviour.

Male house mice produce fewer offspring with lower viability and poorer performance when mated with females they do not prefer

We report experimental results consistent with the hypothesis that constraints on the expression of male mating preferences affect breeder fitness, offspring viability and performance. If constraints on the expression of mating preferences are common, tests of fitness variation associated with mate preferences must eliminate as many constraints on mate preferences as possible. We tested whether male mate preferences influenced breeder fitness, offspring performance and viability in typically polygynous house mice, Mus domesticus, from a feral source population. Our ‘free mate choice’ trials not only eliminated female preferences, male–male and female–female competition, but also our best guesses of the traits mediating choosers preferences. Males mated with their preferred (P) females sired more litters than males mated with their nonpreferred (NP) females. Offspring viability was significantly lower when males reproduced with females they did not prefer compared with females they did prefer. Adult sons of males that mated with their P females were socially dominant to sons of males that mated with their NP females. Adult offspring from P pairings built better nests than offspring from NP pairings. The slope of the survivorship curve for P offspring was significantly higher than for NP offspring. These results showed (1) males mate preferences affected their fitness, (2) males that mated with females they preferred produced more litters than males that mated with females they did not prefer, and (3) their offspring were significantly more viable and performed significantly better on standardized performance tests. This is the first demonstration of fitness benefits of male choice behaviour in a mammal species with typical paternal investment. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Field Studies of Parental Care in Birds: New Data Focus Questions on Variation among Females1

Publisher Summary This chapter reviews the present studies of data, questions, and theories about natural selection and parental care in birds. Biparental care is the most common pattern in birds. These field studies include: (1) descriptive studies of what parental care is and how it varies, though most of these seem to be attempts to explain variation in males rather than females; (2) experimental studies about the advantage of male parental care for females fitness, usually done in an effort to understand the selective forces favoring social monogamy in birds; (3) descriptive studies evaluating the extent of uncertain maternity and paternity, which document the frequency of conspecific brood parasitism and extra-pair paternity using molecular genetic markers; and (4) correlative studies that attempt to evaluate the relationship between paternal care and genetic paternity. Some studies focus more attention on females and include studies about conflicts of interest between females and males cooperating in parental care and the resultant allocations of parental effort. Even newer studies focus uniquely on females maternal behavior as a function of the quality of their mates. The chapter discusses how attention to variation among females and the environments females are in may change future empirical studies.

Chance, Time Allocation, and The Evolution of Adaptively Flexible Sex Role Behavior

Abstract An alternative to classic sexual selection hypotheses for sex differentiated pre-mating behavior is that time available for mating—as individuals experience it—along with fitness differences among alternative potential mates, induces choosy versus indiscriminate mating behavior. This alternative hypothesis says that selection has acted so that all individuals flexibly express fitness-enhancing choosy, indiscriminate, and competitive mating behavior, induced by time-varying life histories, environmental and social cues. Key predictions of DYNAMATE, the formal model of adaptively flexible sex role behavior of individuals of both sexes within dynamically changing populations, include: (1) All individuals regardless of sex assess likely fitness outcomes from mating with alternative potential mates before expressing choosy or indiscriminate behavior. (2) Males and females express adaptively flexible, choosy and indiscriminate behavior so that individuals may change their behavior—from moment to moment—to fit dynamically changing circumstances. (3) Indiscriminate behavior of males and (4) choosy behavior of females would often be maladaptive even in species with greater female than male parental investment, when females have longer latencies to receptivity to re-mating than males, and when the relative reproductive rate of males is greater than in females. (5) Whether or not females show choosy behavior will not affect whether or not males exhibit choosy or indiscriminate behavior, and vice versa. (6) When other model parameters are equal, the proportion of individuals of a given sex expressing choosy or indiscriminate mating behavior is a function of the distribution of fitness ratios (a distribution of all fitness differences that would be conferred on an individual by mating with any two sequentially or simultaneously encountered alternative potential mates). (7) Whether same-sex individuals behaviorally compete is a function of the fitness that would be conferred if the strategist won access to a potential mate, but not a function of relative reproductive rate or its proxy, the operational sex ratio. We call for re-evaluation of sex differences in choosy, indiscriminate, and competitive behavior under strong experimental controls that level the ecological playing fields of males and females, i.e., under experimental conditions informing the mechanisms of phenotypic expression. We end with comments on the classic question of questions: why are the sexes as they are?

Reproductive compensation for offspring viability deficits by female mallards, Anas platyrhynchos

The compensation hypothesis (CH) says that when impediments to the expression of mate preferences occur so that reproduction is with nonpreferred (NP) partners, mothers with NP mates compensate for lower-viability offspring through enhanced investment. Previously, we tested an assumption of the CH and showed that offspring viability was significantly lower when mothers reproduced with NP mates. Here we report tests of the CH. Egg mass differed significantly by mother agemate category. Second-year mothers in NP pairings laid significantly heavier eggs than second-years mothers in preferred (P) pairings; mean egg mass of first-year mothers with NP or P mates did not differ. However, mean egg mass per mother and mean number of eggs per mother were positively and significantly related. Thus, there was no trade-off between egg size and egg number for any category of mother. By fledging age, duckling performance, quality and condition were significantly lower for first-year mothers with NP mates compared with those for mothers in the other categories. Second-year, but not first-year mothers, successfully compensated for predictable deficits in offspring viability from reproduction with NP males. This is the first study showing that mothers compensate for viability deficits in offspring resulting from reproduction with NP partners.

INDISCRIMINATE FEMALES AND CHOOSY MALES: WITHIN‐ AND BETWEEN‐SPECIES VARIATION IN DROSOPHILA

Abstract The classic view of choosy, passive females and indiscriminate, competitive males gained theoretical foundations with parental investment theory. When females invest more in offspring than males, parental investment theory says that selection operates so that females discriminate among males for mates (i.e., females are choosy and passive) and males are indiscriminate (i.e., males are profligate and competitive). Here we report tests of predictions using Drosophila pseudoobscura and D. melanogaster, with typical asymmetry in gamete sizes (females > males), and in D. hydei with far less asymmetry in gamete size. Experimental observations revealed that the labels “choosy, passive females” and “profligate, indiscriminate males” did not capture the variation within and between species in premating behavior. In each of the species some females were as active in approaching males (or more so) than males in approaching females, and some males were as discriminating (or more so) than females. In pairs focal males and females responded differently to opposite‐sex than to same‐sex conspecifics. Drosophila hydei were less sex‐role stereotyped than the other two species consistent with parental investment theory. However, D. pseudoobscura females approached males more often than did D. melanogaster females, and male D. hydei approached females as often as males of the other two species, both results inconsistent with parental investment theory. Male D. pseudoobscura and D. hydei were more likely to approach males in same‐sex pairs than male D. melanogaster, inconsistent with parental investment theory.

MUTUAL INTEREST BETWEEN THE SEXES AND REPRODUCTIVE SUCCESS IN DROSOPHILA PSEUDOOBSCURA

Abstract.— The pre‐mating behavior of female Drosophila pseudoobscura has been considered passive and “coy” relative to more active, “ardent,” and indiscriminate male behavior. To test whether this long‐held view–the “received wisdom” about mating behavior in Drosophila–is really true we carried out observations on how often D. pseudoobscura females approached males prior to courtship and copulation. By including only virgin females and males in the experiments, we eliminated the possibility that males are “coy” due to sperm limitation and females flexibly “coy” due to male manipulations that may affect the duration of remating inhibition. We observed the movements of females and males in vials during the first five minutes of exposure to one another. Video records revealed females went toward males as frequently as males toward females; we inferred that females were as interested in males as males in females. The total number of offspring emerging as adults correlated significantly with mutual, precourtship interest of both males and females in their vial‐mates and latency to copulation. Thus, we hypothesize that females in nature approach males, perhaps actively soliciting male courtship simply by remaining close to them.

Patterns of natal dispersal, turnover and dispersal costs in eastern bluebirds

Abstract Most hypotheses explain dispersal patterns in vertebrate populations based upon an assumption that individuals incur costs when moving away from their natal territories. The geometric distribution of dispersal distances that typically reflects observed dispersal, however, may also be modelled from the basic structure and demographic parameters of the resident population, independent of costs to dispersers. For example, sex-biased natal dispersal might then be explained by differential turnover rates of adult males and females. Patterns of natal dispersal were determined for a South Carolina population of eastern bluebirds, Sialia sialis , from 1985 to 1991 and relationships between different measures of dispersal and initial reproductive success, survival of parents and availability of nest sites were subsequently examined. Females settled significantly further from the natal territory than did males and were more likely to emigrate from the local population. In addition, immigrant females outnumbered immigrant males within local populations. The initial reproductive success of philopatric and dispersing second-year males and females did not differ, but the possibility of high dispersal costs associated with mortality alone could not be excluded. Adult turnover rates did not affect dispersal of individual offspring or general philopatry rates within local populations (as a factor determining overall territory availability). Therefore, alternative factors, such as competitive interactions or intrinsic mechanisms, may be more likely proximate causes of natal dispersal patterns than adult survivorship.

Isolation and characterization of microsatellite loci from blue-footed boobies (Sula nebouxii)

Blue-footed boobies (Sula nebouxii) are socially monogamous, colonial seabirds exhibiting intra-specific nest parasitism and extra-pair copulations. Prior DNA fingerprinting assays failed to detect extra-pair offspring in the nests of congeners, and the rate of intra-specific nest parasitism has not been estimated using molecular techniques. We describe the development and characterization of 11 microsatellite DNA loci, tested using 31 individuals collected on Isla Isabel, Nayarit, México. The number of alleles per locus ranged from three to 22, averaging seven; total exclusionary power of the microsatellite panel was 0.99; no loci deviated from Hardy-Weinberg equilibrium; and we did not detect linkage disequilibrium following Bonferroni correction. This microsatellite panel will facilitate future studies of nest parasitism and extra-pair paternity in blue-footed boobies.

Eighteen microsatellite loci developed from western burrowing owls (Athene cunicularia hypugaea)

Western burrowing owls (Athene cunicularia hypugaea) are ground-dwelling owls distributed throughout western North America. Because of population declines, this species is considered endangered in Canada, and burrowing owls are listed as a species of conservation concern in states of the western USA. Korfanta et al. (2002) previously presented primers for seven microsatellite loci in burrowing owls. Parentage and relatedness studies require a larger number of markers for accuracy and precision. Here, we developed and characterized 18 additional microsatellite DNA loci, and we tested these loci in 23 individuals. The number of alleles per locus ranged from 2 to 11; two loci deviated from Hardy–Weinberg equilibrium following Bonferroni correction; we did not detect linkage disequilibrium following Bonferroni correction; and the probability of exclusion for parent pairs using all loci was >0.9999. We envision these loci will facilitate detailed analyses of the genetic mating system of burrowing owls, which is poorly understood.