Fig. 3

Potential distributions of R. flammigerus predicted by MaxEnt using climatic data. Dark gray areas show suitable climatic conditions for the occurrence of flammigerus and icteronotus (a) 6000 years ago and (b) 21,000 years ago (LGM) as estimated employing niche models including all locality data. Light gray depicts climatically suitable areas for their occurrence at present. Note the smaller predicted range during the LGM and that the two forms likely did not exhibit a continuous range along the transect (dotted line) at that time, relative to the more extensive and continuous range modeled for 6000 y.a. and under current conditions. Potential distributions are also shown separately by taxon, as predicted by models excluding intermediate specimens and considering only localities of icteronotus (c and d) and flammigerus (e and f). Note that for both taxa, distributions likely spanned the hybrid-zone transect 6000 years ago but not 21,000 years ago; in the LGM, the potential distribution of flammigerus (f) was dramatically reduced