Plant selection and seasonal patterns of vocal activity in two populations of the bromeligen treefrog Scinax perpusillus (Anura, Hylidae)

An interesting case of reproductive specialization among anurans is found in bromeligen species that have reproductive cycles associated with bromeliads. In these species, male reproductive activity might be related not only to macroclimatic patterns but also to the availability of suitable microhabitats in bromeliads. This research focuses on one bromeligen species from Southeastern Brazil, Scinax perpusillus, that is territorial and uses bromeliads as retreat and oviposition sites. Two populations were studied (Intervales State Park and Boraceia Biological Station, both in the state of Sao Paulo, Brazil). Available bromeliads vary substantially in morphology and position in the forest. Thus, we examined whether mate frogs (1) select plants with specific eco-morphological traits, (2) call at specific time periods within the reproductive season, and (3) call more actively under certain temperature and humidity conditions. Patterns of male calling activity within the reproductive season varied between years and between populations, but calling was not more intense during warmer or more humid periods. It seems, then, that subtle patterns of phenology might vary significantly between populations and across years. Bromeliad choice was non-random. Males chose bromeliads that were larger, clustered, closer to the ground, and had higher reservoir pH, features that probably reflect the quality of the plants as oviposition sites and that might confer social advantages by reducing conflict with neighboring males.