Validation of a Method for Quantifying Male Mating Preferences in the Guppy (Poecilia reticulata)

Male and female mating preferences are commonly inferred from association times spent with potential mates in a dichotomous-choice test. However, this assessment method is rarely validated, particularly so for male matin

Do male Trinidadian guppies adjust their alternative mating tactics in the presence of a rival male audience?

Males in polygamous mating systems may inadvertently transmit information regarding their mating preferences to bystanding sexual competitors, thereby permitting bystanders to use this information to enhance their own mating success by copying the mate choice of signallers. If males are at risk of having their mate choice copied and consequently face a higher risk of sexual competition, then selection should favour males that reduce conspicuous mating behaviours in the presence of an audience of sexual competitors. In the current study, we used the Trinidadian guppy (Poecilia reticulata), a species that exhibits alternative male mating tactics, to test this sexual competition avoidance hypothesis and the predictions that males would decrease their overall mating effort and exhibit fewer conspicuous courtship displays relative to more inconspicuous sneak mating attempts in the presence of either one or two sexual rivals compared to the absence of any audience. Male guppies significantly reduced their overall mating effort in the presence of increasing numbers of rival audience males. This was reflected in similar monotonic decreases in the frequencies of courtship displays and sneak mating attempts and in the proportional use of courtship displays (relative to sneak mating attempts) across treatments. These findings are consistent with the sexual competition avoidance hypothesis. Our novel results contribute to an increasing body of knowledge showing that the social environment can influence the mating effort and mating decisions of individuals and thus have important implications for sexual selection and evolution

Concurrent effects of sperm competition and female quality on male mate choice in the Trinidadian guppy (Poecilia reticulata)

Males are generally expected to be discriminating in their choice of mates when females vary in quality and when under sperm competition from rival males. However, how sperm competition and female quality interact to influence male mating decisions remains poorly understood. Here, we explored the concurrent effects of sperm competition and female body length on male mating decisions in the Trinidadian guppy (Poecilia reticulata) as a model system. We used female body length as a proxy for fecundity and manipulated the relative size difference of paired stimulus females concurrently with sociosexual cues (i.e., presence of rival males) that may predict sperm competition. When all else was equal, males preferred the larger female when the paired females differed considerably in body length. The presence of either 1 or 2 rival males near, and sexually interacting with, the initially preferred female reduced a focal male's preference for that female and increased the probability that he would reverse his initial mate preference. However, focal males were more likely to reverse their initial preference when the females were similar in body length than when they differed considerably in body length after observing initially preferred females interacting with 1 rival male. Our novel results suggest that male guppies simultaneously evaluate sperm competition and female quality when making mating decisions

Spatial separation from family in the mobile young of a biparental fish: Risks and dynamics of returning home

In species with extended parental care, mobile dependent young are potentially more vulnerable to predators when they stray and become separated from their parents. We would expect that the likelihood of, and latency time for, a separated young to safely return to its 'family unit' (i.e. parents and brood mates) to be, respectively, inversely and positively related to the initial distance of separation and potentially mediated by its age or body size. Using the biparental convict cichlid fish (Amatitlania siquia), we tested these predictions by capturing individual young and displacing them at varying distances from their family unit in both the field and laboratory. As expected, displaced fish were less likely, and took longer, to return to their family with increasing separation distance from the family unit. The body length of displaced young mediated these relationships and their antipredator behaviour; larger young refuged more than smaller ones and were also less likely to be eaten by predators. These results suggest that selection should favour strong affiliative behaviour in mobile young animals towards their brood mates and protective parents because straying from the family unit leads to increased exposure to predation and a reduced likelihood of returning home with increasing separation distance

Sperm competition risk and mate choice in male Trinidadian guppies, Poecilia reticulata

Sperm competition theory predicts that males should be sensitive to socio-sexual cues that provide information about the risk of sperm competition at any mating and correspondingly adjust their mating tactics in a manner that maximizes their reproductive success. Here, we investigated male mating preferences in response to socio-sexual cues as predictors of sperm competition risk (SCR) in the Trinidadian guppy, Poecilia reticulata, as a model study species. In a natural Trinidadian population, we observed that free-ranging females were most commonly pursued sexually by only one male at a time, which presumably represents a SCR associated with that female from the vantage of a nearby male observer. We tested whether wild-caught male guppies would modify their initial mating preference for either of two stimulus females presented by experimentally increasing the male's apparent SCR. This was done by allowing focal males to observe a rival male either placed near (but not physically interacting nor copulating with) or sexually interacting with their initially preferred female. In the absence of any apparent increase in SCR, the preference of focal males for either of the two stimulus females presented remained consistent. However, males significantly reduced their preference for their initially preferred female after having observed her either sexually interact with or merely in the vicinity of a rival male. Our results indicate that male guppies are sensitive to perceived SCR and adjust their mate choice behaviour in an apparently adaptive manner, as predicted by sperm competition theory