Post-Pleistocene Dispersal Explains the Rapoport Effect in North American Salamanders

Aims: In many taxa, the latitudinal span of species’ geographic ranges is positively correlated with median latitude (i.e., a Rapoport effect). This is frequently explained as adaptation to contemporary climate, however, variability in postglacial range expansion among species could also explain this pattern. Here, we analyze geographic data for North American salamanders to test the causes of Rapoport effects.

Location: Temperate North America

Taxon: Salamanders (order Caudata)

Methods: Using range maps, we tested for a Rapoport effect. We then manipulated species’ latitudinal ranges and species pools to test for an impact of postglacial range expansion in forming a Rapoport effect. In addition, we built ecological niche models for species found south of the Wisconsin Ice Sheet during the Last Glacial Maximum and transferred these models to postglacial areas. If dispersal is important in forming a Rapoport effect, then some species may be able to tolerate northern climates but...