Departures from the Energy-Biodiversity Relationship in South African Passerines: Are the Legacies of Past Climates Mediated by Behavioral Constraints on Dispersal?

Res Altwegg,Guillaume Péron

doi:10.1371/journal.pone.0133992

Abstract

Legacies of paleoclimates in contemporary biodiversity patterns have mostly been investigated with global datasets, or with weakly dispersive organisms, and as a consequence been interpreted in terms of geographical or physical constraints. If paleoclimatic legacies also occurred at the regional scale in the distributions of vagile organisms within biomes, they would rather suggest behavioral constraints on dispersal, i.e., philopatric syndromes. We examined 1) the residuals of the regression between contemporary energy and passerine species richness in South African biomes and 2) phylogenetic dispersion of passerine assemblages, using occupancy models and quarter-degree resolution citizen science data. We found a northeast to southwest gradient within mesic biomes congruent with the location of Quaternary mesic refugia, overall suggesting that as distance from refugia increased, more clades were lacking from local assemblages. A similar but weaker pattern was detected in the arid Karoo Biomes. In mobile organisms such as birds, behavioral constraints on dispersal appear strong enough to influence species distributions thousands of years after historical range contractions.

Highlights

Macroecological patterns theoretically result from the interaction of biogeographic history and evolutionary events [1] on the one hand, and contemporary ecological constraints [2] on the other hand
Net relatedness indexes obtained using null model 2 (NRI2) consistently indicated more taxonomic dispersion than NRI1 (Fig 1D, Table 1), as expected since locally available species are more likely to be represented in local assemblages than species from further afield
Using crowdsourced data and occupancy models, we found a northeast to southwest gradient in both species debt and taxonomic dispersion (NRI1) of the passerine assemblages of South African wooded biomes, especially the assemblages of the Savanna Biome

Summary

Introduction

Macroecological patterns theoretically result from the interaction of biogeographic history and evolutionary events [1] on the one hand, and contemporary ecological constraints [2] on the other hand. Locally-available energy constrains both contemporary community carrying capacity [6,7] and long-term rates of speciation and extinction [8,9], so both pathways could shape observed species richness patterns [10]. For this reason, the residuals of the regression between species richness and energy should harbour phylogeographic signals of interest.

Methods

Results

Conclusion