Abstract
Understanding the climatic and historical factors shaping species richness is a major goal of ecology and biogeography. Consensus on how climate affects species richness is still lacking, but four potential and non-exclusive explanations have emerged: water–energy, where diversity is determined by precipitation and/or temperature; seasonality, where diversity is determined by seasonal variation in climate; heterogeneity, where diversity is determined by spatial variability in climate; and historical climatic stability, where diversity is determined by changes in climate through evolutionary time. Climate–richness relationships are also mediated by historical processes, such as phylogenetic niche conservatism and lineage diversification across regions. We evaluated the effect of climate on species richness gradients of Anolis lizards and tested the role of phylogenetic niche conservatism and regional diversification in the origin and maintenance of climate–richness relationships. Climate had a strong nonstationary relationship with species richness, with strong shared effects among several climate axes. Regional differences in climate–richness relationships suggest different assembly processes between regions. However, we did not find evidence for a role of evolutionary factors, such as phylogenetic niche conservatism or regional diversification, underlying these relationships. We suggest that evolutionary processes affecting climate–richness relationships in Anolis were probably obscured by high dispersal rates between regions.
Highlights
Understanding the causes of variation in species richness across regions and clades is a fundamental goal of ecology (Wiens & Donoghue 2004; Gotelli et al 2009)
For climatic predictors of species richness, four main hypotheses have been considered (Evans et al 2005; Field et al 2009; Tello and Stevens 2010; Gouveia et al 2013): water-energy, where diversity is hypothesized to be determined by overall precipitation and/or temperature levels in a region; seasonality, where diversity is hypothesized to be determined by seasonal variation in climate; heterogeneity, where diversity is hypothesized to be determined by spatial variability in climate; and historical climatic stability, where diversity is hypothesized to be determined by changes in climate over millennia
We evaluated whether parameters (R2, slopes, and residuals) from full Geographically Weighted Regression (GWR) models for Last Glacial Maximum (LGM) and Last Inter-Glacial (LIG) varied between regions using a spatial ANOVA
Summary
Understanding the causes of variation in species richness across regions and clades is a fundamental goal of ecology (Wiens & Donoghue 2004; Gotelli et al 2009). The strong relationship between species richness and climate across continents, globally, and through time, suggests a causal effect of climate on species richness at multiple spatial scales (Currie et al 2004; Vázquez-Rivera & Currie 2015), as well as a historical and evolutionary fingerprint on these patterns and relationships (Mittelbach et al 2007; Wiens et al 2010) The existence of both geographic and evolutionary aspects implies that understanding how climate shapes richness gradients would be advanced by pursuing two components: first, studies must identify the climatic variables that predict species richness; second, phylogenetic patterns linking climate and richness must be explored. For evolutionary effects (Mittelbach et al 2007), phylogenetic niche conservatism (PNC; Wiens & Donoghue 2004; Wiens et al 2010) and geographic variation in diversification rates (Weir & Schluter 2007; Rolland et al.39 2014) currently are the most prominent hypotheses to explain contemporary diversity gradients and its relationship with climate
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