Edge-Related Loss of Tree Phylogenetic Diversity in the Severely Fragmented Brazilian Atlantic Forest

Bráulio A Santos,Víctor Arroyo-Rodríguez,Claudia E Moreno,Marcelo Tabarelli,Jerome Chave

doi:10.1371/journal.pone.0012625

Abstract

Deforestation and forest fragmentation are known major causes of nonrandom extinction, but there is no information about their impact on the phylogenetic diversity of the remaining species assemblages. Using a large vegetation dataset from an old hyper-fragmented landscape in the Brazilian Atlantic rainforest we assess whether the local extirpation of tree species and functional impoverishment of tree assemblages reduce the phylogenetic diversity of the remaining tree assemblages. We detected a significant loss of tree phylogenetic diversity in forest edges, but not in core areas of small (<80 ha) forest fragments. This was attributed to a reduction of 11% in the average phylogenetic distance between any two randomly chosen individuals from forest edges; an increase of 17% in the average phylogenetic distance to closest non-conspecific relative for each individual in forest edges; and to the potential manifestation of late edge effects in the core areas of small forest remnants. We found no evidence supporting fragmentation-induced phylogenetic clustering or evenness. This could be explained by the low phylogenetic conservatism of key life-history traits corresponding to vulnerable species. Edge effects must be reduced to effectively protect tree phylogenetic diversity in the severely fragmented Brazilian Atlantic forest.

Highlights

Understanding how habitat alteration affects biodiversity is a main challenge for ecologists and conservation biologists
Mean phylogenetic distance (MPD) and Mean nearest taxon phylogenetic distance (MNTD) are expressed in million years; net related index (NRI) and nearest taxon index (NTI) are in units of standard deviation
One of the major conclusions of this study is that the local extirpation of tree species from forest edges results in a significant loss of tree phylogenetic diversity

Summary

Introduction

Understanding how habitat alteration affects biodiversity is a main challenge for ecologists and conservation biologists. Empirical evidence from plants, amphibians, birds, and mammals worldwide indicates that extinction and vulnerability to extinction are taxonomically selective [13,14,15,16,17,18] These nonrandom extinctions have been attributed to evolutionary causes that determine the patterns of rarity across taxonomic groups of different sizes, and to critical aspects of species’ life history that constrain their abundance and distribution. These forces are not mutually exclusive given that ecological groups may be phylogenetically clustered, but the ecological causes of nonrandom extinctions are expected to be relevant at smaller spatial scales, especially in species-rich communities with high levels of endemism and species turnover [19]. An increasing number of papers document drastic reductions in both tree species richness and the diversity of tree life-history traits in fragmented tropical rainforests [20,21,22,23,24,25], to date no studies are evaluating how these changes affect the phylogenetic diversity of the remaining tree assemblages

Methods

Results

Conclusion