Global richness patterns of venomous snakes reveal contrasting influences of ecology and history in two different clades

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.

Lizard species richness patterns in China and its environmental associations

“…Among the considerable number of hypotheses that aim to explain species richness patterns (reviewed by Gaston 2000;Hawkins et al 2003a), many ecological (environmental) hypotheses have been widely discussed and accepted (Terribile et al 2009). …”

“…Three alternative variants of ecological hypothesis, the species-energy, contemporary climate and habitat heterogeneity hypotheses, have received a great deal of attention as the primary determinants of species richness (Currie 1991;Kerr and Packer 1997;Kerr et al 2001;Rahbek and Graves 2001;Terribile et al 2009). The species-energy hypothesis includes at least two versions, the ambient energy and productive energy hypotheses (Hawkins et al 2003a).…”

“…However, the knowledge of the determinants of reptile richness remains insufficiently documented among terrestrial vertebrates (Qian et al 2007;Terribile et al 2009;McCain 2010). It is urgency to understanding the drivers of reptile richness patterns due to global warming impact on species distribution and abundance (Pounds et al 1999;Gibbons et al 2000;Qian et al 2007).…”

Polychromatism of populations of Corallus hortulanus (Squamata: Boidae) from the southern Amazon Basin, Brazil

“…Such phenotypic variation can be explained by a set of environmental factors, which may influence its behavior and gene flow rate among populations (Henderson 1997). According to some studies, its polymorphism may be linked to different variables such as behavior, thermoregulation, metabolism, interactions with environment, predator-prey interactions through mimicry, aposematism and camouflage, and higher occupancy of habitat; besides indicating resilience/ age of the species (Terribile et al 2009;Farallo and Forstner 2012;Pizzatto and Dubey 2012).…”

Filogenia molecular das espécies de Bothrops do grupo neuwiedi(Serpentes, Viperidae)

“…Os viperídeos compreendem cerca de 270 espécies, com ampla distribuição em todos os continentes, exceto Austrália e Antártida (Ferrarezzi, 1994;Terribile et al, 2009) …”