Diversidade e densidade de anuros de serralheria num gradiente altitudinal na mata atlantica costeira

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Here I present and discuss data about the diversity and abundance ofleaf-litter frogs along an altitudinal gradient (0-1.000 m) in Ubatuba, São Paulo, (Southeastem Brazil). I sampled the area in three transects, with 64 fenced plots (8 x 8 m) in the summer and 32 in the winter. I considered 11 altitudinal strips, from the plains to the top of the hills. In an analysis of , b-diversity I considered the presence/absence of the species in each altitudinal strip. I looked for correlations between 12 environmental variables and the distribution of the eight more abundantldisperse species using the Canonical Correspondence Analysis (ACC). I looked for evidences of interspecific interactions through the analysis of Covariance of Abundances. I evaluated the pattem of spatial distribution of the frogs through the Index ofDispersion. I recognized 21 regular species in the area (16 genera, 5 families). Brachycephalus sp. presented microgeographic variation, mainly in coloration. The estimated richness of the summer was larger than tOOt of winter; the diversity index did not vary among the seasons. The richness dropped on1y beyond 550 m Dominance was not correlated with the altitude. In the coastal plains the richness was higher (15 spp.) than tbat of higher areas. Eleutherodactylus parvus was abundant in the whole gradient and dominant in the slope; Brachycephalus sp. was found only beyond 450 m and dominated above 750 m Density and biomass were larger in the summer. The spatial distribution of the individuaIs was aggregated, in both seasons. The abundance of E. parvus correlated positively with tbat of the three most abundant species. The richness in the plotswas positively correlated with the total density of individuais, with tbat of E. parvus and with the leave layer depth. The total density in the summer was not correlated with the elevation; tbat of Brachycephalus sp. was. The ACC indicated tbat 31 % of the total variance in the distribution ofthe species can be explained by three ofthe environmental variables, 23% by. elevation. Ubatuba is very rich in genera and species of leaf-litter ftogs. My data corroborated the expected decline in richness with increasing elevation. Species turno ver along the gradient should indicate habitat preferences. In Ubatuba, the existence of bodies of water for reproduction should determine the higher richness in the coastal plains. The decrease in density in the winter may be reflecting the decrease in humidity. The aggregated distribution of the individuaIs may indicate areas with higher, and seasonally stable, humidity. The pattern of positive covariances and the wide overlap in the altitudinal distribution among the species indicate that, in the study area, interspecific competitive interactions do not determine the spatial distribution of the species. As a mo deI of populational differentiation of Brachycephalus sp., I propose that the high parts of the hills work as islands where each population is restricted ftom lower lands and seasonally drier zones

ASSUNTO(S)

diversidade biologica anfibio mata atlantica

ACESSO AO ARTIGO

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