A population genetic study on Holothuria polii from the Maltese Islands

Abstract

Randomly amplified polymorphic DNA (RAPD) analysis was used to assess the genetic variation of the sea cucumber Holothuria pollii population from the Maltese archipelago. 176 individuals of the sea cucumber H. polii, were sampled from 24 sites. The specimens were collected from 3 different habitats namely sandy (31%), rocky (38%) and reefs (31%). Of the 176 individuals 48% were female, 34% were males. The remaining 18% could not be classified either because they were juveniles or individuals that had already spawned. A total of 33 loci were chosen from the 7 primers used. However, in order to correct for the fact that RAPDs are dominant markers, loci pruning was carried out according to Lynch & Milligan ( 1994) Tile resultant B loci showed a genetic diversity of 42% to 44% and the average expected heterozygozity s 0.465. A lower average expected heterozygosity was found in a previous study carried out on the same species using allozyme markers (Spiteri, 2007) Tho Gtudy alGo revealed that there is divergence between sub-populations found on the east coast and the west coast of Malta, especially at the Anchor Bay site (I = 0.7; D = 0.3) where the 15 individuals collected from this locality showed a genetic divergence from the other sub-populations. On the other hand, Delimara's sub-population showed a high homozygozity and less effective alleles (H = 0.214, N0 = 1.295), possibly due to a decline in numbers, as a result to new selection pressures. A similar result was reached in a study carried out in 2007 (Spiteri, 2007) that showed a high level of inbreeding in this location.