Global richness patterns of venomous snakes reveal contrasting influences of ecology and history in two different clades |
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Authors: | Levi Carina Terribile Miguel Ángel Olalla-Tárraga Ignacio Morales-Castilla Marta Rueda Rosa M Vidanes Miguel Ángel Rodríguez José Alexandre Felizola Diniz-Filho |
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Institution: | 1. Programa de Pós-Gradua??o em Biologia Animal, Universidade de Brasília, Campus Universitário Darcy Ribeiro, 70.910-900, Brasília, DF, Brazil 3. Departamento de Biologia Geral, ICB, Universidade Federal de Goiás, CP 131, 74.001-970, Goiania, GO, Brazil 2. Department of Ecology, University of Alcala, 28871, Alcalá de Henares, Spain
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Abstract: | Recent studies addressing broad-scale species richness gradients have proposed two main primary drivers: contemporary climate
and evolutionary processes (differential balance between speciation and extinction). Here, we analyze the global richness
patterns of two venomous snake clades, Viperidae and Elapidae. We used ordinary least squares multiple regression (OLS) and
partial regression analysis to investigate to what extent actual evapotranspiration (AET; summarizing current environmental
conditions) and biogeographical regions (representing evolutionary effects) were associated with species richness. For viperids,
AET explained 45.6% of the variance in richness whereas the effect of this variable for elapids was almost null (0.5%). On
the other hand, biogeographic regions were the best predictors of elapid richness (56.5%), against its relatively small effect
(25.9%) in viperid richness. Partial regressions also revealed similar patterns for independent effects of climate and history
in both clades. However, the independent historical effect in Elapidae decreased from 45.2 to 17.8% when we excluded Australia
from the analyses, indicating that the strong historical effect that had emerged for the global richness pattern was reflecting
the historical process of elapid radiation into Australia. Even after excluding Australia, the historical signal in elapid
richness in the rest of the globe was still significant and much higher than that observed in viperid richness at a global
scale (2.7% after controlling for AET effects). Differences in the evolutionary age of these two clades can be invoked to
explain these contrasting results, in that viperids probably had more time for diversification, generating richness responses
to environmental gradients, whereas the pattern of distribution of elapid richness can be more directly interpreted in an
evolutionary context. Moreover, these results show the importance of starting to adopt deconstructive approaches to species
richness, since the driving factors of these patterns may vary from group to group according to their evolutionary history.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Evolutionary history Latitudinal gradient Snakes Species richness Water energy hypothesis |
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