Living in a tiny world: reproductive biology and population ecology of the Neotropical miniature frog Euparkerella aff. brasiliensis (Terraranae, Strabomantidae)

Miniaturisation is an important evolutionary trend for amphibians and has occurred several times in independent anuran lineages. Most miniaturised frogs live in the leaf litter of tropical forests and have terrestrial reproductive modes. They are expected to have reduced fecundity in number of eggs than larger-bodied related species, but little is known about reproductive cycles and proportion of reproductive females. Lower vagility is also assumed, however, as they are difficult to observe, there is little empirical evidence about their dispersal. We studied the reproductive biology (sex ratio, sexual size dimorphism and fecundity parameters) and population ecology (growth, dispersal, and phenology) of the miniature Guanabara Frog Euparkerella aff. brasiliensis (≤20 mm). We collected and analysed 75 specimens of E. aff. brasiliensis, of which 27 were adult females with vitellogenic oocytes in their ovaries. Fecundity was low for number of eggs (average number = 9.7), but only one adult female had no vitellogenic oocytes. Sex ratio was relatively balanced among sexes, being female-biased (0.92) for all individuals and male-biased (1.17) for adults. Juveniles and ovigerous females were observed throughout the year during the two years of mark-recapture study, which indicates continuous breeding. We captured 121 individuals, of which 12% were recaptured in their original collection sites, suggesting low vagility. We discuss our findings considering the current knowledge about the ecology of miniaturised frogs and other Terraranae and suggest future directions for ecological studies and conservation planning.