ANALYSIS OF STACKED SPECIES DISTRIBUTION MODELS PROVIDES A NEW PERSPECTIVE ON BIOGEOGRAPHY AND CONSERVATION OF PHILIPPINE AMPHIBIANS

Abstract

In regions of the megadiverse tropics where biodiversity information is scarce, species distribution models have become important tools for conservation. Use of models, generated individually, for many species or an entire fauna enables researchers to quantify measures of diversity through the use of a Presence-Absence Matrix (PAM). In this study we calculated two biodiversity indices (species richness and average locality range size) for 96 native Philippines amphibian species based on all globally available occurrence data from biodiversity repositories. We then investigated Philippine amphibian biodiversity patterns and examined how these patterns change in relation to the geological components of the archipelago (island groups), its many volcanic elevational gradients, and finally to the Philippine government protected areas. The results of our study suggest that the species richness peaks at intermediate elevation, a result consistent with recent field transect studies. The Mindanao and Luzon Pleistocene Aggregate Island Complexes have the highest species richness and are inhabited by species that on average have markedly large geographical ranges. The central portion of the geologically distinct Palawan Island (and, to a lesser extent, Mindoro Island) has high to intermediate species richness but is inhabited by species that have much smaller average geographical ranges. We are encouraged by a general congruence between Philippine protected areas and biodiversity areas of highest amphibian diversity, but we also note several geographical pockets of high amphibian diversity that currently are unprotected, as well as protected area coverage of low-diversity sites. This analysis, the first of its kind for any terrestrial vertebrate group in the Philippines, demonstrates the practical utility of PAM analysis of stacked distribution models, and Range-Diversity ordination for biogeographical studies, ecological applications, and conservation planning.