Low reproductive skew despite high male-biased operational sex ratio in a glass frog with paternal care.

BACKGROUND: Reproductive skew, the uneven distribution of reproductive success among individuals, is a common feature of many animal populations. Several scenarios have been proposed to favour either high or low levels of reproductive skew. Particularly a male-biased operational sex ratio and the asynchronous arrival of females is expected to cause high variation in reproductive success among males. Recently it has been suggested that the type of benefits provided by males (fixed vs. dilutable) could also strongly impact individual mating patterns, and thereby affecting reproductive skew. We tested this hypothesis in Hyalinobatrachium valerioi, a Neotropical glass frog with prolonged breeding and paternal care. RESULTS: We monitored and genetically sampled a natural population in southwestern Costa Rica during the breeding season in 2012 and performed parentage analysis of adult frogs and tadpoles to investigate individual mating frequencies, possible mating preferences, and estimate reproductive skew in males and females. We identified a polygamous mating system, where high proportions of males (69 %) and females (94 %) reproduced successfully. The variance in male mating success could largely be attributed to differences in time spent calling at the reproductive site, but not to body size or relatedness. Female H. valerioi were not choosy and mated indiscriminately with available males. CONCLUSIONS: Our findings support the hypothesis that dilutable male benefits - such as parental care - can favour female polyandry and maintain low levels of reproductive skew among males within a population, even in the presence of direct male-male competition and a highly male-biased operational sex ratio. We hypothesize that low male reproductive skew might be a general characteristic in prolonged breeders with paternal care.

Characterisation of nine new polymorphic microsatellite loci in the reticulated glass frog Hyalinobatrachium valerioi (Centrolenidae).

Here we document the development of thirteen novel microsatellite markers for the reticulated glass frog Hyalinobatrachium valerioi (Centrolenidae). Nine of those markers were polymorphic and contained between 4 and 34 alleles per locus (mean = 20.3) in 138 individuals (91 males, 47 females) from the field site 'La Gamba', Costa Rica. Average observed heterozygosity was 0.76. Two loci (Hyval19 and Hyval21) significantly deviated from Hardy-Weinberg equilibrium. We did not find evidence for linkage disequilibrium among any of the loci. These markers will serve to identify the genetic mating system in H. valerioi, investigate gene flow between local populations, and reconstruct parent-offspring relationships for studies on individual mating and reproductive success. Therefore, these markers will serve to answer a wide range of scientific questions in conservation, behavioural ecology, and also evolutionary biology.