Biodiversity at Ecogenetic Level in Three Species of Beach Fleas

Abstract

Patterns of fine-scale niche diversification were investigated in three co-generic species of littoral amphipods. Population samples of Orchestia montagui, O. gammarella and O. mediterrmea were collected from the same sampling site, in the Venice Lagoon, and analysed by means of protein electrophoresis and RAPD techniques. The three species exhibited significant differences at the protein and the nuclear DNA level. Specific markers were identified that allow the correct species assignment of females, that are morphologically indistinguishable. Two species, O.montagui, that occurs under vegetal debris, and O. mediterranea, found on muddy infra-littoral substrates, were further investigated with regard to the resistance to high temperature and to glucose-phosphate isomerase (GPI) biochemical activity. The two species were found to have different resistance to high temperatures, with O. montagui showing the higher survival rate. The thermal stability of the common GPI genotype and the biochemical activity of this enzyme was higher in O. montagui. Our results strongly suggest that a relationship exists between habitat preference and metabolic properties that can explain the competition avoidance in these animals.