The Phoenix Rises: Reversal of Cave Adaptations in the Blind Cave Salamander, Proteus anguinus?

Abstract

Six isolated populations of the Blind Cave Salamander, Proteus anguinus are thought to represent six species distributed in the Dinaric Karst of Central Europe. Five of these are troglobitic “white” forms, with little or no pigment and vestigial eyes, and are currently assigned to the subspecies P. a. anguinus. A single population of pigmented, non‐troglobitic “black” Proteus with fully developed eyes is currently assigned to a separate subspecies, P. a. parkelj, that is thought to resemble the common ancestor from which the troglobitic forms evolved. Recent comparative molecular studies, however, reveal that the dark Proteus is more closely related to a geographically adjacent population of white Proteus than that population of white Proteus is to other populations of white Proteus. Thus, either the troglobitic form has evolved multiple times independently, or the black form evolved from a white ancestor. In this study we show that the most parsimonious hypothesis is that the common ancestor of living Proteus was a white troglobitic form, and that the black form evolved once from a white ancestor by reversing troglobitic transformations to re‐adapt to surface habitats. We discuss the possible genetic mechanisms that may have been involved in this case of “reverse evolution”. This research was supported in part by a Faculty Research Grant from Hartwick College and a grant from the National Science Foundation (NSF # 0966085) to S.K.S., and by a grant from the Ministry of Higher Education, Science and Technology, Republic of Slovenia (contract grant number: P1‐0184) to B.B. and L.B.M.