Humidity levels drive reproductive modes and phylogenetic diversity of amphibians in the Brazilian Atlantic Forest

Authors

  • Fernando Rodrigues da Silva,

    Corresponding author
    1. Departamento de Ciências Ambientais, Universidade Federal de São Carlos, UFSCar, Campus Sorocaba, Rodovia João Leme dos Santos Km 110, CEP 18052-780, Sorocaba, SP, Brazil
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  • Mário Almeida-Neto,

    1. Departamento de Ecologia, Instituto de Ciências Biológicas, Universidade Federal de Goiás (UFG), CEP 74001-970, Goiânia, GO, Brazil
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  • Vitor Hugo Mendonça do Prado,

    1. Departamento de Zoologia, Instituto de Biociências, UNESP, Cx. P. 199, 13506-900 Rio Claro, SP, Brazil
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  • Célio Fernando Baptista Haddad,

    1. Departamento de Zoologia, Instituto de Biociências, UNESP, Cx. P. 199, 13506-900 Rio Claro, SP, Brazil
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  • Denise de Cerqueira Rossa-Feres

    1. Departamento de Zoologia e Botânica, UNESP, Campus de São José do Rio Preto, SP, Brazil
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Fernando Rodrigues da Silva, UFSCar, Campus Sorocaba, Rodovia João Leme dos Santos Km 110, CEP 18052-780, Sorocaba, SP, Brazil.
E-mail: fernandors@ufscar.br

Abstract

Aim  The diversity of reproductive modes among amphibians constitutes a striking example of how differences in the biology of species provide important explanations for species distribution patterns on a broad scale. We hypothesize that sites with a higher humidity level will support more modes of reproduction than drier sites and will consequently exhibit a higher phylogenetic diversity. Furthermore, if there is a gradient in the tolerance of reproductive modes to desiccation, there will be a nested pattern in the composition of reproductive modes among sites.

Location  Twenty-seven forest sites in the Brazilian Atlantic Forest.

Methods  Through a path analysis approach, we evaluated the direct and indirect effects of the humidity level on the number of reproductive modes, as well as the relative importance of both variables on amphibian phylogenetic diversity. A nestedness analysis was used to quantify the extent to which the compositions of both species and reproductive modes in drier sites correspond to subsets of those in sites with higher annual precipitation.

Results  We found that the reproductive modes present in drier sites are non-random subsets of those present in sites with higher humidity levels. Because reproductive modes are phylogenetically conserved among amphibians, sites with a greater number of reproductive modes supported greater phylogenetic diversity. Sites with high precipitation throughout the year provided suitable environmental conditions for a larger number of reproductive modes, whereas sites with low precipitation and typical seasonal climates supported only those reproductive modes specialized to resist desiccation.

Main conclusions  Our results show that humidity-related variables are key environmental factors related to both the richness of reproductive modes and phylogenetic diversity. Our results support the hypothesis that the higher phylogenetic diversity found in moister sites reflects differences in the tolerance to desiccation among different reproductive modes. Given that reproductive modes are associated with susceptibility to desiccation, their incorporation into explanatory models may trigger a significant advance in the understanding of the mechanisms regulating the species richness and composition of amphibian communities.

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