Does macrohabitat differentiation explain patterns of allopatry and sympatry in widely distributed woodland salamanders (<i>Plethodon</i>)?

Abstract Species can vary in range size and overlap because of physiological differences, competitive interactions, or historical climatic shifts since the last glacial period. However, these factors are rarely considered in the same study to explain distributional interactions. We estimated ecological niche models for three morphologically similar and relatively wide-ranging species of woodland salamanders that exhibit complex patterns of allopatry and sympatry (Plethodon cinereus, Plethodon electromorphus, and Plethodon richmondi). All three species had less estimated niche overlap than expected, although we found differences even when using a subset of the phylogeographical diversity of P. cinereus or a dataset that combined the sister species P. electromorphus and P. richmondi, suggesting sensitivity to the phylogenetic and geographical decisions in the occurrence data. Palaeoclimate projections implied rapid turnover in climatically suitable habitat in the recent past, particularly for P. richmondi, in which a best-fitting model projected no suitable habitat in its present distribution as recently as the Late Holocene epoch (4.2–0.3 kya). Using survey and topographic data within Ohio, variation in sympatry/allopatry was explained mostly by spatial autocorrelation rather than habitat differences. Our results suggest that a combination of niche differentiation, spatial interactions, and historical range shifts explain distributional patterns across coarse spatial scales.