Population Genetics of Egyptian Biomphalaria alexandrina (Gastropoda, Planorbidae)

Abstract

Biomphalaria alexandrina has recently spread its range from the Nile Delta region of Egypt to upstream sites as far as Aswan, approximately 950 km to the south. This study of allozyme variation in B. alexandrina revealed that colonization of the upper Nile involved a stepwise series of founder events that resulted in losses of allelic diversity at several polymorphic loci. Additionally, peripheral populations that inhabit irrigation canals in Alexandrina and near the Suez Canal also exhibit some reduction in allelic diversity compared to a dense cluster of populations that inhabit irrigation canals near Cairo. Parent-offspring analysis revealed that, although selfing is possible in these hermaphroditic snails, the progency of wild snails were produced by outcrossing.