Asymmetric Male Mating Success in Lek-Breeding Rhinella arenarum

SIMPLE SUMMARY: Reproductive behavior is the result of tactics, which males employ to increase their success in mate acquisition, and of the attempt of females to choose those males, which increase the fitness and survival of their offspring. The aim of our study on pond-breeding neotropical toads (Rhinella arenarum) was to disentangle the interactions of male and female tactics in the mating system. Reproductive behavior took place in a lek, i.e., an assembly area where males advertised and defended suitable spawning habitats. Only one-third of the males present accounted for all matings observed as the result of two male tactics, namely calling and pre-mating fights to defend call positions to obtain access to unpaired females. In turn, females were selective, preferring mates of an adequate size for optimal fertilization success in size-assortative pair-formation. The lek organization of reproduction is unique in the R. marina species group, in which the interception of amplexed pairs is the predominant male tactic. ABSTRACT: Mate choice is the attempt of an individual to gain higher reproductive fitness by preferring to mate with some individuals and not with others. We studied the role of mate choice in the mating system of the neotropical toad Rhinella arenarum by assessing male reproductive tactics for mate acquisition and the contribution of female choice for pair formation. In a shallow pond in central Argentina, we estimated male mating success and the corresponding reproductive tactics by focal observation. The variation of phenotypic and genotypic traits (size and shape, longevity, vocalization features, heterozygosity) was related to the observed mating success in 110 males. The phonotactic response of 21 reproductive females to conspecific advertisement call features was tested in arena experiments. Mating success was limited to 32 males, pair formation was size-assortative. The dominant reproductive tactics were advertising from call positions near suitable breeding sites and pre-mating fights with intruding males, whereas the interception of amplectant pairs and the displacement of mated males were never observed. Female phonotaxis was directed to conspecific choruses but complex and simple call structures were not distinguished. We conclude that the mating system is a lek combining pre-mating fights among males and female choice of slightly smaller males. Fights interfere with female choice, undermining size-assortative mating. This is a unique system in the R. marina species group, in which interception behavior dominates reproduction.