Amplified fragment length polymorphism (AFLP) analysis indicates the importance of both asexual and sexual reproduction in the fissiparous holothurian Stichopus chloronotus (Aspidochirotida) in the Indian and Pacific Ocean

Abstract

Asexual reproduction in the fissiparous holothurian species Stichopus chloronotus from eight populations between Madagascar and the Great Barrier Reef (total N=149) was investigated using Amplified fragment length polymorphism (AFLP) markers; and results compared to previous allozyme studies. Specifically, we tested the hypotheses that (1) genetic diversity in this species is reduced in the West Indian Ocean and that (2) some populations rely nearly exclusively on asexual reproduction. Using 21 polymorphic markers (obtained by two primer combinations) resulted in 51 genotypes in the whole sample, with up to 20 individuals (nearly all within populations) having the same genotype. These repeated genotypes most likely represent clones. In most populations, more than 50% of individuals were inferred to result from asexual reproduction. In two extreme populations, both of which are comprised nearly entirely of male individuals (Great Palm Island, Trou d’eau), only up to 20% of all individuals were sexually produced. Although, the genetic diversity in two populations of La Reunion was reduced, the fact that diversity is high in a third population and on Madagascar showed that low genetic diversity in S. chloronotus is not a general feature of the West Indian Ocean. Cluster analysis using Rogers’ genetic distance did not result in distinct geographic clusters. This supports previous suggestions that although asexual reproduction is important for the maintenance of populations, large distance dispersal of sexually produced larvae provides the genetic link between populations.