Genetic analysis of the species of sigara s. str. (heteroptera, corixidae) in the Italian peninsula

Abstract

The genetic differences in three populations of Sigara s. str. belonging to S. striata, S. dorsalis, and S. basalis, distributed in northern (Veneto, South Tyrol) and central (Umbria, Molise) Italy, were assayed by horizontal starch electrophoresis. Adult specimens were examined. Twelve enzymes were assayed, eight of which gave satisfactory results. Five of the eight alloenzymes were further investigated to differentiate the three species: phos-phoglucomutase (Pgm-1, Pgm-2), esterase (Est-1, Est-2, Est-3), su-peroxide dismutase (Sod-1, Sod-2), phosphoglucose isomerase (Pgi-1, Pgi-2), isocitrate dehydrogenase (Idh) coding for 10 studied loci. A total of 208 adults of the three taxa (142 for S. basalis, 49 for 5. dorsalis, and 17 for 5. striata) were analysed. Nei's unbiased genetic distances were calculated and values between congeneric species ranged from 0.009 to 0.25, as illustrated in a phenogramme constructed by the unweighted pair-group cluster analysis method. Sigara basalis presented the highest values in comparison with S. striata and S. dorsalis, which had D values of 0.10 and 0.11, respectively. On the basis of these considerations and of morphological and Zoogeographic investigations, it is possible that S. basalis was differentiated in the pre-Quaternary age, while 5. striata and 5. dorsalis are probably ascribable to the same conspecific level, even if laboratory hybridization experiments do not confirm this hypothesis. © 1998 Taylor & Francis Group, LLC.