Disentangling direct and indirect effects of water availability, vegetation, and topography on avian diversity

Vladimír Remeš,Lenka Harmáčková

doi:10.1038/s41598-018-33671-w

Vladimír Remeš, Lenka Harmáčková

Open Access

https://doi.org/10.1038/s41598-018-33671-w

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Journal: Scientific Reports	Publication Date: Oct 19, 2018
Citations: 12	License type: open-access

Affiliation: Palacký University, Olomouc

Abstract

Climate is a major driver of species diversity. However, its effect can be either direct due to species physiological tolerances or indirect, whereby wetter climates facilitate more complex vegetation and consequently higher diversity due to greater resource availability. Yet, studies quantifying both direct and indirect effects of climate on multiple dimensions of diversity are rare. We used extensive data on species distributions, morphological and ecological traits, and vegetation across Australia to quantify both direct (water availability) and indirect (habitat diversity and canopy height) effects of climate on the species richness (SR), phylogenetic diversity (PD), and functional diversity (FD) of 536 species of birds. Path analyses revealed that SR increased with wetter climates through both direct and indirect effects, lending support for the influence of both physiological tolerance and vegetation complexity. However, residual PD and residual FD (adjusted for SR by null models) were poorly predicted by environmental conditions. Thus, the FD and PD of Australian birds mostly evolved in concert with SR, with the possible exception of the higher-than-expected accumulation of avian lineages in wetter and more productive areas in northern and eastern Australia (with high residual PD), permitted probably by older biome age.

Highlights

Current climatic conditions, especially energy and precipitation, are major determinants of species richness[1,2,3]
We (i) mapped the geographical distribution of the residual phylogenetic diversity (PD) and residual functional diversity (FD) of Australian and Tasmanian birds adjusted for species richness (SR) by null models and identified areas deviating from our null expectations, and (ii) fitted path models to link SR and residual PD and residual FD to water availability, topography, canopy height, and habitat diversity
There was a strong spatial gradient in the species richness (SR) of Australian birds, varying four-fold in 1 × 1 degree squares: it was highest in eastern Queensland and New South Wales and lowest in west-central deserts; it was low on Tasmania (Fig. 3a)

Summary

Introduction

Especially energy and precipitation, are major determinants of species richness[1,2,3] This effect can be direct, due to a subset of species tolerating harsh climates (the physiological tolerance hypothesis)[4] or indirect due to wetter and warmer environments facilitating more complex habitats providing more ecological niches (the vegetation structure hypothesis)[5,6]. By using path models (Fig. 1a), we quantified both the direct and indirect effects of a major climatic variable driving Australian environments, namely water availability, to provide comprehensive insights into the processes determining the accumulation and maintenance of biodiversity in Australian and Tasmanian avifauna. It should be noted that we focused only on the current climate and environment as potential explanations for bird diversity, because finding data of sufficient detail and scope for past climates and environments was not possible

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Results

Conclusion