Genetic structure and diversity of the island-restricted endangered land crab, Johngarthia lagostoma (H. Milne Edwards, 1837)

The land crab, Johngarthia lagostoma, occurs exclusively on Ascension Island and the Brazilian oceanic islands of Trindade, Atol das Rocas, and Fernando de Noronha. Like other gecarcinid crabs, it retains a marine planktotrophic larval phase, and as in some other gecarcinids the Megalops migrate inland into fully terrestrial habitats before moulting to the first crab instar. Due to their limited geographical distribution and their biological characteristics, the populations of J. lagostoma are especially vulnerable to environmental disturbances. The aim of this study was to assess, through analyses of mitochondrial DNA sequences, the genetic structure and diversity of J. lagostoma on the four islands where it occurs. The large differentiation observed indicates that three discrete land crab evolutionary significant units should be considered: Ascension Island, Trindade, and Atol das Rocas/Fernando de Noronha.