Reproductive biology of an endemic Physalaemus of the Brazilian Atlantic forest, and the trade-off between clutch and egg size in terrestrial breeders of the P. signifer group

Abstract

Physalaemus crombiei is a small foam-nesting frog endemic to the Atlantic forest. It is a member of the P signifer group known only from its type locality in Santa Teresa, State of Espirito Santo, and from another locality in the State of Bahia, Brazil. Most Physalaemus species are aquatic breeders, and species in the P signifer group are the only ones exhibiting a tendency toward terrestrial reproduction in the genus. Here we describe the reproductive period, breeding site and reproductive modes of P crombiei from a third population in the Atlantic forest, southeastern Brazil. We also investigated reproductive effort and size fecundity relationships in females. Reproductive traits were compared to other species in the genus Physalaemus, especially those included in the P signifer group. Physalaemus crombiei is a prolonged breeder, reproducing throughout the year with a peak of activity during the most rainy months (October March). Males called from the humid forest floor and eggs embedded in foam nests were deposited in the water as well as on the humid floor amidst the leaf litter, or inside fallen leaves or tree holes containing rainwater on the forest floor. As expected, P crombiei exhibited three alternative reproductive modes, as described for other species of the P signifer group. The number of eggs produced per female varied from 91 to 250. Female body size is positively correlated both with ovary mass and clutch size (number of eggs per clutch). Variation in the number and size of eggs observed in Physalaemus species may be explained not only by female size, but also by the terrestrial reproductive mode exhibited by the species in the P signifer group.