Inconsistent interspecific and intraspecific differentiation of climate envelopes in a subtropical tree.
Aims: Comparisons of climate envelopes among species have shown that niche conservatism tends to break down over time. Here, we use the Asian tree genus Platycarya (Juglandaceae) as a case study to test this tendency at relatively short timescales in a single lineage. This, together with a reanalysis of the extant literature, should help evaluate prospects of using correlations between climate and species occurrence data to infer evolutionary processes. Methods: We rely on species distribution models (SDMs) and multivariate analyses to compare current and past (Last Glacial Maximum ∼21 ka) climatic envelopes between the two extant Platycarya species (Platycarya strobilacea and Platycarya longipes) and between mainland and Taiwan populations of P. strobilacea, paying particular attention to autocorrelation issues. We also review interpretations provided in similar studies comparing climate envelopes between and within species, including in studies involving native and introduced populations of the same species. Important Findings: We find intraspecific but not interspecific differentiation in climate envelopes of Platycarya, despite the prediction that niche differentiation should be stronger between older groups. Our review also suggests that differentiation in climate envelopes need not imply rapid evolutionary divergence. Whereas SDMs can be used to raise evolutionary hypotheses to be validated with other data, we conclude that it should not be used to directly infer short-term evolutionary processes.