Diurnal changes and frequency dependence in male mating preference for female morphs in the damselfly Ischnura senegalensis (Rambur) (Odonata: Coenagrionidae)

Ischnura senegalensis females exhibit color dimorphism, consisting of an andromorph and a gynomorph, which might be maintained under a frequency-dependent process of mating harassment by mate-searching males. Males change their mating preference for female morph depending on prior copulation experience. Binary choice experiments between two female morphs were carried out in four local populations in the early morning (07.00–09.00 hours) and the afternoon (12.00–14.00 hours), times which mark the onset and the end of diurnal mating activity, respectively. According to the line census along the water's edge, the proportion of andromorphs in the female population varied from 21 to 67% throughout the survey period for four local populations. Males showed non-biased preference for female morphs in the early morning in each local population, while they chose the common morph in the afternoon. Male mating preference for female morphs was positively correlated to the proportion of female morphs in the population. If the selective mating attacks on the common female morphs inhibit their foraging and/or oviposition behavior, frequency-dependent male mating attacks might provide a selective force for maintaining the female color dimorphism in I. senegalensis .     

Facultative pupal mating in Heliconius erato: Implications for mate choice,female preference,and speciation

Mating systems have broad impacts on how sexual selection and mate choice operate within a species, but studies of mating behavior in the laboratory may not reflect how these processes occur in the wild. Here, we examined the mating behavior of the neotropical butterfly Heliconius erato in the field by releasing larvae and virgin females and observing how they mated. H. erato is considered a pupal‐mating species (i.e., males mate with females as they emerge from the pupal case). However, we observed only two teneral mating events, and experimentally released virgins were almost all mated upon recapture. Our study confirms the presence of some pupal‐mating behavior in H. erato, but suggests that adult mating is likely the prevalent mating strategy in this species. These findings have important implications for the role of color pattern and female mate choice in the generation of reproductive isolation in this diverse genus.     

Conflict between direct and indirect benefits of female choice in desert Drosophila

Identifying the factors that contribute to the adaptive significance of mating preferences is one major goal of evolutionary research and is largely unresolved. Both direct and indirect benefits can contribute to mate choice evolution. Failure to consider the interaction between individual consequences of mate choice may obscure the opposing effects of individual costs and benefits. We investigate direct and indirect fitness effects of female choice in a desert fly (Drosophila mojavensis), a species where mating confers resistance to desiccation stress. Females prefer males that provide a direct benefit: greater resistance to desiccation stress. Mating preferences also appear to have indirect consequences: daughters of preferred males have lower reproductive success than daughters of unpreferred males, although additional experimentation will be needed to determine if the indirect consequences of female preferences actually arise from 'sexually antagonistic' variation. Nevertheless, the results are intriguing and are consistent with the hypothesis that an interaction between direct and indirect benefits maintains sexually antagonistic variation in these desert flies: increased desiccation resistance conferred by mating might offset the cost of producing low-fecundity daughters.     

Experimental evidence for female choice and energetic costs of male tail elongation in red-collared widowbirds

The black nuptial plumage of the highly polygynous male red‐collared widowbird (Euplectes ardens) comprises a red carotenoid‐based collar patch and a long graduated tail (c. 22 cm). Tail length was the strongest predictor of male mating success in a previous selection analysis, motivating this experimental test of the relative importance of tail plumes in male contest competition and female choice. Males were assigned to either a short (12.5 cm) or control (20 cm) tail manipulation prior to territory establishment. Male contest competition was unaffected by the tail treatments as the shortened‐ and control‐tailed males were equally successful in acquiring territories of similar size and quality. In contrast, however, although the longer‐tailed control males spent less time in flight and courtship displays, they attracted significantly more prospecting and nearly three times as many nesting females to their territories compared to the short‐tailed males. In further support of tail length as the primary mate choice cue, none of the other measured and potential female cues (e.g. body size, collar colorimetrics, territorial behaviours or territory quality) influenced male reproductive success. In addition to potentially increasing detectability (‘signal efficacy’), the long tail is also a likely indicator of male quality (‘signal content’). Despite the higher activities of short‐tailed males, control‐tailed males showed a steeper decline in condition (relative body mass) during the breeding season. Furthermore, both short‐ and control‐tailed residents lost more condition than did the short‐ and control‐treated floaters (males not establishing territories), suggesting an interaction between tail length and the costs of territory acquisition, defence and courtship displays. These results confirm the role of mate choice and honest quality advertising as the main selection pressures behind elongated tails in widowbirds. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 35–43.     

Male choice generates stabilizing sexual selection on a female fecundity correlate

We know very little about male mating preferences and how they influence the evolution of female traits. Theory predicts that males may benefit from choosing females on the basis of traits that indicate their fecundity. Here, we explore sexual selection generated by male choice on two components of female body size (wing length and body mass) in Drosophila serrata. Using a dietary manipulation to alter female size and 828 male mate choice trials, we analysed linear and nonlinear sexual selection gradients on female mass and wing length. In contrast to theoretical expectations and prevailing empirical data, males exerted stabilizing rather than directional sexual selection on female body mass, a correlate of fecundity. Sexual selection was detected only among females with access to standard resource levels as an adult, with no evidence for sexual selection among resource-depleted females. Thus the mating success of females with the same body mass differed depending upon their access to resources as an adult. This suggests that males in this species may rely on signal traits to assess body mass rather than assessing it directly. Stabilizing rather than directional sexual selection on body mass together with recent evidence for stabilizing sexual selection on candidate signal traits in this species suggests that females may trade-off resources allocated to reproduction and sexual signalling.     

Age at mating and male quality influence female patterns of reproductive investment and survival

The trade‐off between the allocation of resources toward somatic maintenance or reproduction is one of the fundamentals of life history theory and predicts that females invest in offspring at the expense of their longevity or vice versa. Mate quality may also affect life history trade‐offs through mechanisms of sexual conflict; however, few studies have examined the interaction between mate quality and age at first mating in reproductive decisions. Using house crickets (Acheta domesticus), this study examines how survival and reproductive trade‐offs change based on females’ age at first reproduction and exposure to males of varying size. Females were exposed to either a large (presumably high‐quality) or small male at an early (young), middle (intermediate), or advanced (old) age, and longevity and reproductive investment were subsequently tracked. Females mated at a young age had the largest number of eggs but the shortest total lifespans while females mated at older ages produced fewer eggs but had longer total lifespans. The trade‐off between age at first mating and eggs laid appears to be mediated through higher egg‐laying rates and shorter postmating lifespans in females mated later in life. Exposure to small males resulted in shorter lifespans and higher egg‐laying rates for all females indicating that male manipulation of females, presumably through spermatophore contents, varies with male size in this species. Together, these data strongly support a trade‐off between age at first reproduction and lifespan and support the role of sexual conflict in shaping patterns of reproduction.     

The distribution patterns of dragonflies (Insecta: Odonata) along the Kiewa River,Australia, and their relevance in conservation assessment

Sampling of larval and adult Odonata from 16 sites along the Kiewa River, Victoria, yielded 34 species: 10 Zygoptera, 24 Anisoptera. Patterns of larval and adult incidence were appraised, and showed that most species were restricted in incidence to several consecutive sites along the river, and that there is clear distinction also between the faunas of the potamon, rhithron and eucrenon regions. Different species of some genera of Anisoptera displayed different zonational distributions, and patterns of incidence and relative abundance of larvae and adults confirmed zonational occupancy. For larvae, these distribution patterns transcended the mode of collection, although many species were found most abundantly in one microhabitat or by one of several sampling methods employed at each site. Sampling of the two stages separately showed considerable concurrence of distributional patterns, so that either stage alone may provide data of value in faunal and conservation assessment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mate sampling and the sexual conflict over mating in seaweed flies

The order in which females encounter, or sample, males in apopulation may have important consequences for mate choice,with the information gathered about males influencing boththe preference function and degree of choosiness of females.Sexual selection may be affected as a result. Sampling of particularsubsets of males may be a crucial component of individual variation in mate preferences within populations. However, the sequencein which males are sampled may also be important in specieswithout traditional, active mate choice, such as when sexualselection involves sexual conflict over mating. This wouldoccur if the likelihood of a female mating with a male of acertain phenotype changes as a result of previous encounters.We examined the effects of encountering males differing inbody size, a sexually selected phenotype, in the seaweed flyCoelopa frigida. Sexual selection occurs in this species asa result of a sexual conflict over mating. We show that theoutcome of the sexual conflict is independent of the orderin which males are encountered by female seaweed flies, withthe overall mating advantage to large males being unaffected.In addition, we explored female preference functions and evaluatethe heterogeneity in female willingness to mate. We suggestthat consideration of mate sampling theory is valuable whenexamining mate choice in species in which sexual selectionis driven by sexual conflict.     

Female mate choice across mating stages and between sequential mates in flour beetles

Few studies have examined how female premating choice correlates with the outcome of copulatory and post-copulatory processes. It has been shown that polyandrous Tribolium castaneum females discriminate among males before mating based on olfactory cues, and also exert cryptic choice during mating through several mechanisms. This study tested whether a male's relative attractiveness predicted his insemination success during copulation. Bioassays with male olfactory cues were used to rank two males as more and less attractive to females; each female was then mated to either her more attractive male followed by less attractive male, or vice versa. Dissections immediately after second copulations revealed a significantly higher percent of successful inseminations for females that remated with more attractive males compared with those that remated with less attractive males. These results indicate that cryptic female choice during copulation reinforces precopulatory female choice in T. castaneum, and suggest that females could use cryptic choice to trade up to more attractive males, possibly gaining better phenotypic or genetic quality of sires.     

Sexual selection in a lekking bird: the relative opportunity for selection by female choice and male competition

Leks are classic models for studies of sexual selection due to extreme variance in male reproductive success, but the relative influence of intrasexual competition and female mate choice in creating this skew is debatable. In the lekking lance-tailed manakin (Chiroxiphia lanceolata), these selective episodes are temporally separated into intrasexual competition for alpha status and female mate choice among alpha males that rarely interact. Variance in reproductive success between status classes of adult males (alpha versus non-alpha) can therefore be attributed to male-male competition whereas that within status largely reflects female mate choice. This provides an excellent opportunity for quantifying the relative contribution of each of these mechanisms of sexual selection to the overall opportunity for sexual selection on males (I males). To calculate variance in actual reproductive success, we assigned genetic paternity to 92.3% of 447 chicks sampled in seven years. Reproduction by non-alphas was rare and apparently reflected status misclassifications or opportunistic copulations en route to attaining alpha status rather than alternative mating strategies. On average 31% (range 7-44%, n=6 years) of the total I males was due to variance in reproductive success between alphas and non-alphas. Similarly, in a cohort of same-aged males followed for six years, 44-58% of the total I males was attributed to variance between males of different status. Thus, both intrasexual competition for status and female mate choice among lekking alpha males contribute substantially to the potential for sexual selection in this species.     

Evolution of female mating preferences in stalk-eyed flies

Sensory exploitation predicts that female mate preferences existbefore the evolution of exaggerated male ornaments. We testedthis prediction by estimating female preference functions, rematingintervals, and copulation durations for three species of stalk-eyedflies. Two species, Cyrtodiopsis whitei and C dalmanni, exhibitextreme sexual dimorphism in eye span, with eye stalks exceedingbody length in large males. In contrast, C quinqucguttata ofboth sexes possess short eye stalks. Maximum parsimony analysisof 437 basepairs of the 16S mitochondrial ribosomal RNA genefrom 6 Malaysian diopsids reveals that short, sexually monomorphiceye stalks are plesiomorphic in Cyrtodiopsis. Observations ofmultiple copulations by females in paired-choice mating chambersindicated that female C whitei and C. dalmanni exhibit relativepreferences for longer eye stalks such that preference intensityincreases linearly with the difference in eye stalk length betweenmales. Females from the sexually monomorphic species showedno detectable preference for male eye stalk length. Female matingpreferences of bodi sexually dimorphic species exhibited significantrepeatability, as expected if genetic variation underlies thepreference. In addition, female C whitei and C. dalmanni exhibitedshorter copulations, mated more frequently, and rejected fewermating attempts than female C quinqueguttata. Thus, opportunitiesfor sperm competition have increased with acquisition of femalepreferences. We conclude that female sensory bias for maleswith long eye span did not exist in a common ancestor to thesespecies. Instead, female preference and remating propensityeither coevolved with eye span dimorphism or evolved after maleeye stalks elongated.     

Genes, copying, and female mate choice: shifting thresholds

Recent experimental work on guppies (Poecilia reticulata) hasexamined the strength of genetic and cultural (copying) factorsin determining female mate choice. Using females from a populationwith a heritable preference for the amount of orange body colorpossessed by males, prior work discovered that a threshold differencein orange color among males existed below which females wouldchoose a less orange male if they observed another female choosethat male, but above which they consistently preferred the moreorange of the males, regardless of whether they viewed anotherfemale prefer the less orange male. I tested whether this thresholdcan be shifted by increasing the amount of mate-copying informationavailable to a female. I demonstrate that when a female hasthe opportunity to see two different model females independentlyprefer the less orange of two males or a single female neara drab male for a longer period of time (twice as long as inprior work), the observer female prefers this drab male evenwhen males dramatically differ in orange coloration.     

Age-specific mating strategies and reproductive senescence

While males gain obvious direct advantages from multiple mating, the reproductive capacity of females is more constrained. The reason why polyandry evolved in females is therefore open to many conjectures. One hypothesis postulates that females gain indirect benefits by increasing the probability of siring young from high quality males. To explore this hypothesis, we used the natural variation of the reproductive value that males and females undergo through age. The age-related variation of phenotypic performance might then induce variations in mating strategies in males and females. Using the common lizard (Lacerta vivipara) as our model system, we showed that reproductive immaturity and senescence created variability in both male and female reproductive success (including survival of offspring). Consistent with theory, males at their best-performing phenotype adopted a polygynous strategy. These males were of an intermediate age and they produced offspring of higher viability than younger and older males. In contrast, females at their best performing phenotype, also of an intermediate age, were less polyandrous than other less-performing females. Middle-aged females tended to mate with males of an intermediate age and produced litters with higher viability independently from their reproductive strategy. Males of an intermediate age enhanced their fitness by additional matings with young or old females. Young and old females increased their fitness by being more polyandrous. Polyandry therefore appears as means to seek for good males. A positive correlation between males and their partners' fitness disagree with the idea that polyandry is the result of a sexual conflict in this species.     

Constrained mate choice in social monogamy and the stress of having an unattractive partner

In socially monogamous animals, mate choice is constrained by the availability of unpaired individuals in the local population. Here, we experimentally investigate the physiological stress endured by a female (the choosy sex) when pairing with a non-preferred social partner. In two experimental contexts, female Gouldian finches (Erythrura gouldiae) socially paired with poor-quality mates had levels of circulating corticosterone that were three to four times higher than those observed in females that were paired with preferred mates. The elevated level of this stress hormone in response to partner quality was observed within 12 h of the experimental introduction and maintained over a period of several weeks. Our findings demonstrate the extent of intra-individual conflict that occurs when individuals are forced to make mate-choice decisions that are not perfectly aligned with mate-choice preferences. The elevated level of corticosterone also suggests a mechanistic route through which females might adaptively manage their responses to intersexual conflict over reproductive investment.     

The role of functional constraints in nonrandom mating patterns for a dance fly with female ornaments

Most hypotheses to explain nonrandom mating patterns invoke mate choice, particularly in species that display elaborate ornaments. However, conflicting selection pressures on traits can result in functional constraints that can also cause nonrandom mating patterns. We tested for functional load‐lifting constraints during aerial copulation in Rhamphomyia longicauda, a species of dance fly that displays multiple extravagant female‐specific ornaments that are unusual among sexual traits because they are under stabilizing selection. R. longicauda males provide females with a nuptial gift before engaging in aerial mating, and the male bears the entire weight of the female and nuptial gift for the duration of copulation. In theory, a male's ability to carry females and nuptial gifts could constrain pairing opportunities for the heaviest females, as reported for nonornamented dance flies. In concert with directional preferences for large females with mature eggs, such a load‐lifting constraint could produce the stabilizing selection on female size previously observed in this species. We therefore tested whether wild‐caught male R. longicauda collected during copulation were experiencing load‐lift limitations by comparing the mass carried by males during copulation with the male's wing loading traits. We also performed permutation tests to determine whether the loads carried by males during copulation were lighter than expected. We found that heavier males are more often found mating with heavier females suggesting that whereas R. longicauda males do not experience a load‐lift constraint, there is a strong relationship of assortative mating by mass. We suggest that active male mate choice for intermediately adorned females is more likely to be causing the nonrandom mating patterns observed in R. longicauda.     

Differential mating success of virgin female katydidsRequena verticalis (Orthoptera: Tettigoniidae)

Male katydids (Orthoptera: Tettigoniidae) invest in offspring through nutrients provided in a large spermatophore. Previous research with Requena verticalishad shown that almost all of the investment of males mating with recently mated (4 days previously) females is in eggs fertilized by the female's previous mate. Thus males are predicted to discriminate against such females as mates. In experiments placing males with both a virgin and a female mated 4–5 days previously, virgin females obtained almost all matings. Although male discrimination of mates was noted in the experiments, there was no evidence that such discrimination was against nonvirgins in both this experiment and one in which a single virgin or mated female was placed with a male. Instead, the results suggest that the differential mating was a result of interfemale competition. The mating advantage held by virgin females over nonvirgins appeared to be lost once the latter had oviposited. Finally, there was no evidence from both single- and paired-female experiments that males preferred larger females as mates.     

Repeatability of mate choice in female red jungle fowl

We staged female mate choice trials between pairs of males andrepeated the process for each female to determine the repeatabilityof female preference for males in red jungle fowl (Gallus gallus)in the first and second half of the breeding season. We measuredmale morphological traits (the size and color of the comb andthe brightness of the hackle feathers) that females are knownto use in choosing a mate. In the first half of the breedingseason, females showed repeatability in their choices of matewith respect to the male's comb characters. Females did notshow a repeatable preference with respect to male hackle feathers,and we found no repeatability of mate choice in the second halfof the season. Females seem to primarily look at the male'scomb when choosing a mate, and other ornaments seem only ofsecondary importance.[Behav Ecol 7: 243-246 (1996)]     

Roving females and patient males: a new perspective on the mating strategies of chimpanzees

Mating strategies are sets of decisions aimed at maximizing reproductive success. For male animals, the fundamental problem that these strategies address is attaining mating access to females in a manner that maximizes their chances of achieving paternity. For chimpanzees (Pan troglodytes), despite substantial interest in mating strategies, very little attention has been paid to the most fundamental problem that mating strategies need to solve: finding mates. Only a single model, Dunbar's general model of male mating strategies, exists to explain mate‐searching behaviour in chimpanzees. Under this model, males in most populations are regarded as pursuing a ‘roving’ strategy: searching for and sequestering fertile females who are essentially passive with respect to mate searching. The roving mating strategy is an assumption deeply embedded in the way chimpanzee behaviour is considered; it is implicit in the conventional model for chimpanzee social structure, which posits that male ranging functions both to monitor female reproductive state and to ward these females from other groups of males through collective territoriality: essentially, ranging as mating effort. This perspective is, however, increasingly at odds with observations of chimpanzee behaviour. Herein, I review the logic and evidence for the roving‐male mating strategy and propose a novel alternative, a theoretical framework in which roving is a strategy pursued by female chimpanzees in order to engage successfully in promiscuous mating. Males, unable to thwart this female strategy, instead maximise the number of reproductive opportunities encountered by focusing their behaviour on countering threats to health, fertility and reproductive career. Their prolonged grooming bouts are seen, in consequence, as functioning to mitigate the negative impacts of socially induced physiological stress. In this new framework, the roving‐male strategy becomes, at best, a ‘best of a bad job’ alternative for low‐ranking males when faced with high levels of competition for mating access. Male chimpanzees do not search for mates, but for one another, for food, and, at times, for rivals in other communities. To the extent that female promiscuity functions to counter infanticide risk, mate searching by female chimpanzees—and any associated costs—can be seen as an unavoidable consequence of male sexual coercion. This novel framework is a better fit to the available data than is the conventional account. This review highlights the desperate need for additional work in an area of chimpanzee biology that has been somewhat neglected, perhaps in part because assumptions of roving males have remained unquestioned for too long. It also highlights the need, across taxa, to revisit and revise theory, and to test old assumptions, when faced with contrary data.     

STORM: software for testing hypotheses of relatedness and mating patterns

Storm is a software package that allows users to test a variety of hypotheses regarding patterns of relatedness and patterns of mate choice and/or mate compatibility within a population. These functions are based on four main calculations that can be conducted either independently or in the hypothesis-testing framework: internal relatedness; homozygosity by loci; pairwise relatedness; and a new metric called allele inheritance, which calculates the proportion of loci at which an offspring inherits a paternal allele different from that inherited from its mother. STORM allows users to test four hypotheses based on these calculations and Monte Carlo simulations: (i) are individuals within observed associations or groupings more/less related than expected; (ii) do observed offspring have more/less genetic variability (based on internal relatedness or homozygosity by loci) than expected from the gene pool; (iii) are observed mating pairs more/less related than expected if mating is random with respect to relatedness; and (iv) do observed offspring inherit paternal alleles different from those inherited from the mother more/less often than expected based on Mendelian inheritance.