Evolutionary lineages within the Jamaican endemic freshwater crab Sesarma fossarum. Evolutionary lineages of Sesarma fossarum

The freshwater crab Sesarma fossarum is endemic to western central Jamaica in a rainforested limestone area known as the Cockpit Country. It thrives in subterranean and mountain streams where it digs burrows in the banks. Previous studies of genetic connectivity have provided the first evidence of geographic isolation and gene flow in cave systems. Here we aim to use a larger dataset to examine geographic and genetic correlations among 16 populations of S. fossarum throughout its distributional range. Analyses of the genetic population structure of S. fossarum based on cytochrome oxidase subunit 1 mitochondrial DNA revealed a clear separation between the populations from the south and those from the north and northwest of its distribution area. Three independent genetically isolated lineages have evolved among different river systems that are isolated by geographic barriers between hydrological systems. This study emphasizes the need for small-scale local conservation efforts aimed at preserving parts of this threatened habitat and the species that live there and provides further evidence that the Cockpit County harbours unique and significant evolutionary units which evolved over millions of years whose loss would be irreversible.