Contrasting female mate preferences for red coloration in a fish

Abstract

Understanding how animals select their mates requires knowing the factors that shape mate preferences. Recent theoretical and empirical considerations suggest that female mating status can influence the degree to which a female engages in mate choice, with virgin females predicted to be less choosy than mated females. In this study, we investigated mate choice in both virgin and mated females in the pygmy halfbeak Dermogenys collettei. Halfbeaks are small, live-bearing, internally fertilizing freshwater fish that live in mixed-sex groups where females have ample opportunity to engage in mate choice. Using a dichotomous choice assay, we quantified and contrasted in virgin and mated females mate preferences for differences in male body size, beak size, and area of yellow and red coloration. We also examined how mating status influenced the amount of time a female associated with the first male encountered and the relative amount of time a female associated with each male. We demonstrate that mate preferences of female halfbeaks are driven primarily by the size of red coloration present on males. Females showed contrasting preferences based on mating status, with virgin females preferentially associating with drab males whereas mated females preferentially associate with males possessing large areas of red. Contrary to expectations, female mating status did not influence how females associate with the first males encountered or how females biased their association time among males. Although the precise drivers of these effects need further studying, our finding highlights a possible explanation for how variation in male ornamentation can be maintained.

Male–male behavioral interactions drive social-dominance-mediated differences in ejaculate traits

“…Males were photographed 1 day prior to the start of the experiment using a photo chamber (30 × 20 × 20 cm) fitted with a scale. Using these images, body length (from the tip of the lower beak to the caudal peduncle; see Reuland et al 2019 ) was measured and size-matched pairs of males, henceforth called dyads, were created. Males in each dyad were statistically indistinguishable in total body length (average absolute difference within dyad ± standard error [SE]: 0.44 ± 0.10 mm, n = 32; paired two-sample t -test assuming equal variance: t (31) = 0.30, P = 0.77).…”

Behavioral Variation in the Pygmy Halfbeak Dermogenys collettei: Comparing Shoals With Contrasting Ecologies

“…Pygmy halfbeaks are sexually dimorphic in body size, with adult females being larger than males, and sexually dichromatic, with adult males expressing more red and yellow coloration than females, particularly on their modified anal fins (Greven, 2010). Females choose mates on the basis of the amount of red coloration displayed by a male (Reuland et al, 2020a), while male mate choice is based on the size of a sex-specific orange gravid spot on the female's abdomen that varies in size with the reproductive cycle (Ogden and Fitzpatrick, 2019). Sexual dimorphism, along with sex-specific behaviors, allows the sexes to be easily identified in natural populations.…”

Does brain size affect mate choice? An experimental examination in pygmy halfbeaks

“…All females were presented with a pair of males in a dichotomous choice chamber; pairs either had a larger difference in red area on their fins and beak or a smaller difference in red area. The amount of red coloration on males is the main (and seemingly only) visual factor influencing female preference in pygmy halfbeaks during dichotomous trials ( Reuland et al 2019 ). Experiments were carried out in two blocks, and classifications of female brain size (i.e., large vs. small) were determined for each block separately.…”

“…Halfbeaks live in mixed-sex shoals ranging from 6 to 128 individuals, and males in shoals spend nearly one third of their time directing courtship behaviors toward females ( Devigili et al 2021 ). Halfbeaks are sexually dichromatic, with males displaying strong red coloration that females use to exert mating preferences ( Reuland et al 2019 ). However, female preference is influenced by mating status in a counter-intuitive fashion: previously mated females prefer males with a large amount of red, whereas virgin females prefer males with a small amount of red ( Reuland et al 2019 ).…”

“…Halfbeaks are sexually dichromatic, with males displaying strong red coloration that females use to exert mating preferences ( Reuland et al 2019 ). However, female preference is influenced by mating status in a counter-intuitive fashion: previously mated females prefer males with a large amount of red, whereas virgin females prefer males with a small amount of red ( Reuland et al 2019 ). Halfbeaks also have semi-transparent heads, with a clear dorsal outline of the brain visible through the skull (including the dorsal outline of the optic tectum and telencephalon), allowing for noninvasive external estimates of both total brain size and the size of individual brain areas (sensu Näslund 2014 ).…”