Guppy males distinguish between familiar and unfamiliar females of a distantly related species

Prioritizing Sex Recognition Over Learned Species Recognition: Hierarchical Mate Recognition in an Invasive Fish

Mate recognition is the process of identifying and assessing the appropriate species, sex or population of another individual for their suitability as a potential mate. Recognition may be innate or learned. Learning, the acquisition of knowledge or skills through experience, involves a relatively long-term change in behavioral responses. In this study we examined learned and innate mate recognition in invasive male mosquitofish, Gambusia holbrooki, interacting with female conspecifics and male and female native toothcarp, Aphanius iberus. Male mosquitofish directed no mating attempts at male toothcarp whereas numerous attempts were made toward female toothcarp. Male mosquitofish therefore differentiated between males and females, but initially did not distinguish between con- and heterospecific females. Neither the presence of a male toothcarp, nor the presence of a refugia affected the number of mating attempts received by females. However, by the second day males appeared to learn to more accurately direct their mating attempts, with larger female mosquitofish receiving the most attention, though smaller toothcarp females were still harassed. We propose that male mosquitofish, with a coercive mating system, are selected for persistence despite rejection by potential mates. In this scenario, the pool of potential mates may include heterospecifics whose avoidance of mating attempts may be ignored by male mosquitofish. It may thus be adaptive for male mosquitofish to prioritize sex recognition over species recognition: if one sex is recognized as a “non-mate” this will cut 50% from the pool of potential mates whereas recognition of a single species will remove many fewer potential mates from the pool. This innate sex recognition together with rapid learning of species identity may be a factor in the invasive success of mosquitofish.

Consistent female preference for rare and unfamiliar male color patterns in wild guppy populations

How genetic variation is maintained in ecologically important traits is a central question in evolutionary biology. Male Trinidadian guppies, Poecilia reticulata, exhibit high genetic diversity in color patterns within populations, and field and laboratory studies implicate negative frequency-dependent selection in maintaining this variation. However, behavioral and ecological processes that mediate this selection in natural populations are poorly understood. We evaluated female mate preference in 11 natural guppy populations, including paired populations from high- and low-predation habitats, to determine if this behavior is responsible for negative frequency-dependent selection and to evaluate its prevalence in nature. Females directed significantly more attention to males with rare and unfamiliar color patterns than to males with common patterns. Female attention also increased with the area of male orange coloration, but this preference was independent of the preference for rare and unfamiliar patterns. We also found an overall effect of predation regime; females from high-predation populations directed more attention toward males than those from low-predation populations. Again, however, the habitat-linked preference was statistically independent from the preference for rare and unfamiliar patterns. Because previous research indicates that female attention to males predicts male mating success, we conclude that the prevalence of female preference for males with rare and unfamiliar color patterns across many natural populations supports the hypothesis that female preference is an important process underlying the maintenance of high genetic variation in guppy color patterns.

Social familiarity relaxes the constraints of limited attention and enhances reproduction of group-living predatory mites

In many group-living animals, within-group associations are determined by familiarity, i.e. familiar individuals, independent of genetic relatedness, preferentially associate with each other. The ultimate causes of this behaviour are poorly understood and rigorous documentation of its adaptive significance is scarce. Limited attention theory states that focusing on a given task has interrelated cognitive, behavioural and physiological costs with respect to the attention paid to other tasks. In multiple signal environments attention has thus to be shared among signals. Assuming that familiar neighbours require less attention than unfamiliar ones, associating with familiar individuals should increase the efficiency in other tasks and ultimately increase fitness. We tested this prediction in adult females of the group-living, plant-inhabiting predatory mite Phytoseiulus persimilis. We evaluated the influence of social familiarity on within-group association behaviour, activity, predation and reproduction. In mixed groups (familiar and unfamiliar), familiar predator females preferentially associated with each other. In pure groups (either familiar or unfamiliar), familiar predator females produced more eggs than unfamiliar females at similar predation rates. Higher egg production was correlated with lower activity levels, indicating decreased restlessness. In light of limited attention theory, we argue that the ability to discriminate between familiar and unfamiliar individuals and preferential association with familiar individuals confers a selective advantage because familiar social environments are cognitively and physiologically less taxing than unfamiliar social environments.

Avoidance of interspecific mating in female Syrian hamsters is stronger toward familiar than toward unfamiliar heterospecific males

Adult Syrian hamster females (Mesocricetus auratus) learn to discriminate against familiar heterospecific males (Turkish hamster, M. brandti). We investigated whether females learn to avoid any heterospecific male after exposure to just one heterospecific male. We predicted that, after being exposed to one heterospecific male, a female would avoid mating not only with that familiar male but also with any unfamiliar heterospecific male. We exposed females to a heterospecific male across a wire-mesh barrier for 8 days and then paired the female with (a) that same heterospecific male or (b) an unfamiliar heterospecific male. Females exhibited lordosis faster and for a longer duration toward the unfamiliar than toward the familiar heterospecific male. However, females were similarly aggressive toward familiar and unfamiliar heterospecific males. Perhaps exposure to stimuli from several heterospecific males (a likely scenario in the wild) would result in females behaving similarly toward familiar and unfamiliar heterospecific males.

Male fish use prior knowledge about rivals to adjust their mate choice

Mate choice as one element of sexual selection can be sensitive to public information from neighbouring individuals. Here, we demonstrate that males of the livebearing fish Poecilia mexicana gather complex social information when given a chance to familiarize themselves with rivals prior to mate choice. Focal males ceased to show mating preferences when being observed by a rival (which prevents rivals from copying mating decisions), but this effect was only seen when focal males have perceived rivals as sexually active. In addition, focal males that were observed by a familiar, sexually active rival showed a stronger behavioural response when rivals were larger and thus, more attractive to females. Our study illustrates an unparalleled adjustment in the expression of mating preferences based on social cues, and suggests that male fish are able to remember and strategically exploit information about rivals when performing mate choice.

Adult female hamsters avoid interspecific mating after exposure to heterospecific males

When females mate with a heterospecific male, they do not usually produce viable offspring. Thus, there is a selective pressure for females to avoid interspecific mating. In many species, females innately avoid heterospecific males; females can also imprint on their parents to avoid later sexual interactions with heterospecific males. However, it was previously unknown whether adult females can learn to discriminate against heterospecific males. We tested the hypothesis that adult females previously unable to avoid interspecific mating learn to avoid such mating after being exposed to heterospecific males. Syrian hamster (Mesocricetus auratus) females not previously exposed to Turkish hamster (Mesocricetus brandti) males can discriminate between odors of conspecific and heterospecific males, but they mate with either type of male. However, when we exposed adult females to both a conspecific male and a heterospecific male through wire-mesh barriers for 8 days, and then paired them sequentially with the two males, females were more receptive to conspecific males and more aggressive to heterospecific males. When females were paired with the heterospecific male first and the conspecific male second, no female was receptive and all were aggressive to heterospecific males. When females were paired with the conspecific male first, only 43% of females were then aggressive toward the heterospecific male. That is, interactions with conspecific males may decrease a female's ability to properly avoid heterospecific males. Our study clearly shows for the first time that females can learn during adulthood to avoid interspecific mating just by being exposed to stimuli from heterospecific males.