Effects of Habitat Size and Heterogeneity on Anuran Breeding Assemblages in the Brazilian Dry Forest
Habitat size and heterogeneity are among the main factors determining local species richness. However, distinguishing between them is critical to discriminate stochastic from the habitat-driven processes underlying local patterns of species distribution. Here, we test the individual effects and interaction of habitat size and heterogeneity in driving the occurrence of species in water bodies in the Brazilian Caatinga dry forest. We surveyed sites of different sizes and degrees of physical heterogeneity (i.e., margin architecture and plant stratification) and performed univariate and multivariate analyses to test the effect of these factors on species richness and composition. We found a clear habitat size effect but a negligible influence of habitat heterogeneity on the species richness at breeding sites. Specific habitat features may be important for few species, however. Our findings suggest an overall stochastic usage of water bodies by the anurans in the Caatinga and highlight the need of distinguishing the effects of habitat availability from those of habitat heterogeneity when investigating the structure of anuran assemblages.Abstract
Location of the Monumento Natural Grota do Angico (MNGA), Sergipe state, northeastern Brazil.
Partial standardized coefficients depicting the effects of habitat size (A), habitat heterogeneity (B), and the overlap between them (A + B) on anuran species richness at the study site. (C) denotes the unexplained variation in species richness. Note the predominant effect of habitat size and the almost complete dependence of heterogeneity with size.
First and second axes of the CCA involving anuran species and descriptors of heterogeneity of breeding sites in the MNGA, Sergipe, Brazil. Environmental variables (arrows) are: number of vegetation strata (VegStrat); number of margin slope types (MargSlop); number of margin moisture types (MargWet); percent of surface covered by emergent aquatic vegetation (EmergVeg); and percent of surface covered by floating aquatic vegetation (FloatVeg). Species (acronyms) are: Rhinella jimi (Rhji); Rhinella granulosa (Rhgr); Proceratophrys cristiceps (Prcr); Corythomantis greeningi (Cogr); Dendropsophus soaresi (Deso); Hypsiboas crepitans (Hycr); Hypsiboas raniceps (Hyra); Phyllomedusa nordestina (Phno); Scinax pachycrus (Scpa); Scinax x-signatus (Scxs); Leptodactylus fuscus (Lefu); Leptodactylus ocellatus (Leoc); Leptodactylus troglodytes (Letr); Leptodactylus vastus (Leva); Physalaemus cicada (Phci); Physalaemus albifrons (Phal); Pleurodema diplolistris (Pldi); and Dermatonotus muelleri (Demu).
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