Females sample more males at high nesting densities, but ultimately obtain less attractive mates

Background: Sexual selection is largely driven by the availability of mates. Theory predicts that male competition and female choice should be density-dependent, with males competing more intensely at relatively high density, and females becoming increasingly discriminating when there are more males from whom to choose. Evidence for flexible mating decisions is growing, but we do not understand how environmental variation is incorporated into mate sampling strategies. We mimicked threespine stickleback (Gasterosteus aculeatus) breeding conditions in pools with high and low densities of nesting males and allowed females to search for mates to determine whether 1) mate search strategies change with the density of breeding males and 2) pre-copulatory components of mate choice (signalling, competition, search patterns, and mating decisions) are modified in parallel. Results: While females sampled more males at high male density, suggesting greater opportunity for sexual selection, the expanded search did not result in females choosing males with more attractive sexual signals. This is likely because red throat colouration was twice as great when half as many males competed. Instead, females chose similarly at high and low male density, using a relative strategy to compare male traits amongst potential suitors. Reduced throat colour could reflect a trade-off with costly male competition. However, we did not observe more intense competition at higher relative density. Density-dependent signalling appears largely responsible for females associating with males who have more attractive signals at low density. If we lacked knowledge of plasticity in signalling, we might have concluded that females are more discriminating at low male density. Conclusions: To understand interactions between mate choice and population dynamics, we should consider how components of mate choice that precede the mating decision interact

Females sample more males at high nesting densities, but ultimately obtain less attractive mates

Background: Sexual selection is largely driven by the availability of mates. Theory predicts that male competition and female choice should be density-dependent, with males competing more intensely at relatively high density, and females becoming increasingly discriminating when there are more males from whom to choose. Evidence for flexible mating decisions is growing, but we do not understand how environmental variation is incorporated into mate sampling strategies. We mimicked threespine stickleback (Gasterosteus aculeatus) breeding conditions in pools with high and low densities of nesting males and allowed females to search for mates to determine whether 1) mate search strategies change with the density of breeding males and 2) pre-copulatory components of mate choice (signalling, competition, search patterns, and mating decisions) are modified in parallel. Results: While females sampled more males at high male density, suggesting greater opportunity for sexual selection, the expanded search did not result in females choosing males with more attractive sexual signals. This is likely because red throat colouration was twice as great when half as many males competed. Instead, females chose similarly at high and low male density, using a relative strategy to compare male traits amongst potential suitors. Reduced throat colour could reflect a trade-off with costly male competition. However, we did not observe more intense competition at higher relative density. Density-dependent signalling appears largely responsible for females associating with males who have more attractive signals at low density. If we lacked knowledge of plasticity in signalling, we might have concluded that females are more discriminating at low male density. Conclusions: To understand interactions between mate choice and population dynamics, we should consider how components of mate choice that precede the mating decision interact

Effects of Human Land Use on Prey Availability and Body Condition in the Green Anole Lizard, \u3cem\u3eAnolis carolinensis\u3c/em\u3e

Lizards frequently occur in disturbed habitats, yet the impacts of human activity on lizard biology remain understudied. Here, we examined the effects of land use on the body condition of Green Anole lizards (Anolis carolinensis) and the availability of their arthropod prey. Because human activity generally alters abiotic and biotic habitat features, we predicted that areas modified by humans would differ from areas with natural, intact vegetation in arthropod abundance and biomass. In addition, because biological communities in high use areas are often relatively homogenized, we predicted that higher human land use would result in lower prey diversity. Regardless of land use, we also predicted that areas with greater prey availability and diversity would support lizards with higher body condition. We studied anoles in six plots with varying levels of human modification in Palmetto State Park in Gonzales County, Texas. We quantified arthropod abundance, biomass, and diversity in each plot via transects and insect traps. We also determined lizard body condition using mass:length ratios and residuals, fat pad mass, and liver lipid content. We found that, although arthropod abundance did not differ across plots, arthropod biomass was higher in natural than in disturbed plots. Diversity indices showed that the plots varied in their arthropod community diversity, but not in relation to disturbance. Female (but not male) lizard body condition differed across plots, with body condition higher in natural plots than disturbed plots. Together, these results suggest that land use is associated with lizard body condition, but not through a direct relationship with prey availability

Females Sample more Males at High Nesting Densities, but Ultimately Obtain Less Attractive Mates

Background: Sexual selection is largely driven by the availability of mates. Theory predicts that male competition and female choice should be density-dependent, with males competing more intensely at relatively high density, and females becoming increasingly discriminating when there are more males from whom to choose. Evidence for flexible mating decisions is growing, but we do not understand how environmental variation is incorporated into mate sampling strategies. We mimicked threespine stickleback (Gasterosteus aculeatus) breeding conditions in pools with high and low densities of nesting males and allowed females to search for mates to determine whether 1) mate search strategies change with the density of breeding males and 2) pre-copulatory components of mate choice (signalling, competition, search patterns, and mating decisions) are modified in parallel. Results: While females sampled more males at high male density, suggesting greater opportunity for sexual selection, the expanded search did not result in females choosing males with more attractive sexual signals. This is likely because red throat colouration was twice as great when half as many males competed. Instead, females chose similarly at high and low male density, using a relative strategy to compare male traits amongst potential suitors. Reduced throat colour could reflect a trade-off with costly male competition. However, we did not observe more intense competition at higher relative density. Density-dependent signalling appears largely responsible for females associating with males who have more attractive signals at low density. If we lacked knowledge of plasticity in signalling, we might have concluded that females are more discriminating at low male density. Conclusions: To understand interactions between mate choice and population dynamics, we should consider how components of mate choice that precede the mating decision interact

What Determines Paternity in Wild Lizards? A Spatiotemporal Analysis of Behavior and Morphology

Mating behavior in animals can be understood as a sequence of events that begins with individuals encountering one another and ends with the production of offspring. Behavioral descriptions of animal interactions characterize early elements of this sequence, and genetic descriptions use offspring parentage to characterize the final outcome, with behavioral and physiological assessments of mates and mechanisms of copulation and fertilization comprising intermediate steps. However, behavioral and genetic descriptions of mating systems are often inconsistent with one another, complicating expectations for crucial aspects of mating biology, such as the presence of multiple mating. Here, we use behavioral and genetic data from a wild population of the lizard Anolis cristatellus to characterize female multiple mating and the potential for sexual selection through female mate choice in this species. We find that 48% of sampled females bore offspring sired by multiple males. Moreover, spatiotemporal proximity between males and females was associated with whether a male sired a female\u27s offspring, and if yes, how many offspring he sired. Additionally, male body size, but not display behavior, was associated with reproductive outcomes for male-female pairs. While much remains to be learned about the mechanisms of mating and targets of sexual selection in A. cristatellus, it is clear that female multiple mating is a substantial component of this species\u27 mating system in nature