Consequences of dispersal limitation and habitat fragmentation for the Brazilian heart-tongued frogs (Phyllodytesspp.)

Abstract

Poorly known species may be cryptically endangered, especially when they inhabit fragmented and threatened habitats. Heart‐tongued frogs (genus Phyllodytes, family Hylidae, Lophyohylinae) comprise 17 species of poorly known frogs that have obligatory associations with tank bromeliads. The distributions of all species are restricted to a small, extremely fragmented, region of Atlantic Forest in eastern Brazil. We model climate and tank bromeliad distributions to better understand frog distribution limits. Using records from several sources for frogs and bromeliads with climate data from WorldClim, we modelled the distribution of Phyllodytes using maximum entropy. We compared climate and altitude within the distribution and nearby to test how climate may limit distribution. Climate together with bromeliad distributions provided the best model and predicted the smallest suitable area for Phyllodytes that was larger than that occupied, from the state of Paraiba in the north to Rio Grande do Sul in the south. Phyllodytes occurs in lower elevations that are warmer, wetter and less variable than the surrounding regions where it does not occur, and dispersal is apparently limited by the surrounding, inhospitable, region. Dispersal limitation and habitat fragmentation have relegated Phyllodytes to many very small habitat fragments. With many species in this genus being known from a single or few samples, this unfortunate combination of limitation and fragmentation suggests that some or all species of Phyllodytes may be threatened with extinction, especially if habitat fragmentation continues at its present pace in eastern Brazil.