Distribution of cave-dwelling Aegla spp. (Decapoda: Anomura: Aeglidae) from the Alto Ribeira karstic area in southeastern Brazil based on geomorphological evidence

Abstract

In this study, we assess the main ecological and evolutionary causes of the current distribution of cave dwelling species of Aegla from the Alto Ribeira karstic province, southeastern Brazil. Based on field surveys conducted over several years and on examination of scientific collections, we discuss herein how processes of colonization, dispersal, and vicariance could have resulted in the present pattern of distribution of these species. Given the extensive area of continuous limestone lenses interrupted by insoluble rocks, the distribution of aeglids from Alto Ribeira is limited by stratigraphic barriers, possibly due to difficulty in accessing other underground compartments and low vagility of juveniles. Sympatric speciation is unlikely, since molecular evidence does not support a strong sister-group relationship between extant troglophilic and troglobitic species with sympatric distribution in the study area. Under differing sources of evidence, we hypothesize that Pleistocene climatic fluctuations and drainage changes is the main cause of vicariance in the study area, while the fragmented nature of the limestone lenses probably hindered subsurface dispersion. Troglobites could be relicts of extinct epigean ancestrals, while the extant troglophiles did not achieve reproductive isolation after vicariance events, resulting in the present co-distribution with species less closely related.