Female Preference for Males Varies with Resource Availability for Reproduction in the Freshwater Goby Tridentiger brevispinis

Animals with resource-based breeding systems show varying sexual selection modes driven by resource availability. Males of the freshwater goby Tridentiger brevispinis (Pisces: Gobiidae), which are larger, with a longer dorsal-fin, than females, make nests under stones, and provide exclusive parental care of eggs in the nests. For this goby, the nest sites are crucial resources for reproduction. Laboratory experiments that controlled for nest-site abundance were conducted to investigate the effects of nest-site availability on male-male competition and female mate choice. Nest-holding males were on average larger than the average size of all males combined under conditions of low nest-site availability. This result indicates a greater advantage for large males in intrasexual competition for nest sites under conditions of low nest-site availability. Furthermore, egg-guarding males under conditions of low nest-site availability were larger than nest-holding males without eggs. Under conditions of high nest-site availability, the dorsal-fin length of nest-holding males with eggs were longer than those without eggs. These findings suggest that female preference for mates varies qualitatively with nest-site availability. This variation in female preference might result from mate availability that depends upon nest-site availability. The current study concludes that in nest-spawning fishes, nest-site availability can affect the intensity of male-male competition and cause variations of female preference for mates.

Resource acquisition and pre-copulatory sexual selection

Sexual selection influences the evolution of phenotypic traits and contributes to patterns of biodiversity. In many animals, mating involves sequential steps. Often, individuals must secure resources that are essential for mating (nests, territories, food), and then after securing a resource, individuals engage in competition for access to limited opposite sex mates and gametes. A large body of empirical research and some verbal models have illustrated that resource acquisition can influence sexual selection. In general, though, we lack a priori predictions of when and how resource acquisition will influence sexual selection. Here, we use a mathematical framework to explore the link between resource acquisition and sexual selection on an advantageous mate‐acquisition trait across biologically relevant trade‐off scenarios. Our findings provide a set of testable predictions of how resource acquisition can influence sexual selection on mating traits. In general, selection on mate‐acquisition traits is expected to be heavily influenced by: (1) the episode of selection considered, and in particular, whether one considers selection associated with the mating pool only or selection associated with both the mating pool and pre‐mating pool; (2) whether resource‐acquisition and mate‐acquisition traits are positively associated or whether they trade off; and (3) the proportion of males with the resource‐ and mate‐acquisition traits.

Woe is the loner: Female treefrogs prefer clusters of displaying males over single "hotshot" males

Communal displays such as leks and choruses are puzzling phenomena, as it is not obvious why signalers or choosers should aggregate. It has been hypothesized that signalers in leks enjoy higher per-capita reproductive success because choosers prefer to sample among dense configurations ("clusters") that are easier to compare. Although female preferences as well as the signal features of attractive males are well characterized in many chorusing species, we know little about how mate sampling is influenced by the spatial dynamics within communal displays. Here, we ask how female Eastern Gray Treefrogs (Hyla versicolor) respond to isolated and clustered call stimuli in a simple one versus three playback design. We explored (i) whether females exhibit a general preference for call clusters, (ii) whether spatial preference is robust to call-feature preference, and (iii) how this affects the relative success of attractive and unattractive males in different spatial combinations. We found generalized spatial discrimination against lone callers but did observe fine-scale assessment of call features within clusters. The prominence of the spatial preference impacts the attractiveness of males, conferring particular advantage to attractive callers within clusters, while reducing attractiveness of isolated males regardless of their acoustic features. Our findings indicate that female frogs navigate complex choruses by initially orientating toward clusters of calling males, and then assess call features within them. This study provides novel insight into the mate choice heuristics involved in animal choruses.

Leave me alone: solitary females attract more mates in a nocturnal insect

Spatial distributions of sexual competitors and potential mating partners have a large impact on sexual selection and mating systems. Typically, such effects are investigated with regard to male aggregations. However, females may also need to compete for mating opportunities. Here, we investigated the consequences of clustering and rival attractiveness on female mate attraction success under field conditions in a nocturnal beetle, the common glowworm, Lampyrus noctiluca. We placed dummy females of two glow intensity (attractiveness) levels either alone or in clusters of varying attractiveness compositions. We found that, by displaying alone rather than in a cluster, females have a higher probability of mating and greater potential to exercise mate choice. Within clusters, females of both attractiveness levels had the highest probability of mating when having neighbors of only the less attractive type. These results show that both the presence and attractiveness of rivals can strongly influence females’ mate attraction. The findings also suggest that the typical distribution of glowing females in the wild is better explained by female than male benefits. Hence, the results highlight the important links between spatial distribution of females, male mate searching, and sexual selection.