CLONAL DIVERSITY IN THE SUBMERGED MACROPHYTE POTAMOGETON PECTINATUS L. INFERRED FROM NUCLEAR AND CYTOPLASMIC VARIATION

Genetic variation within a worldwide collection of Potamogeton pectina tus L. was investigated by analyzing randomly amplified polymorphisms of nuclear DNA anti restriction fragment length polymorphisms of chlor oplast DNA. Of the 51 plants investigated, 50 exhibited unique multi-l ocus nuclear genotypes. Analysis of chloroplast DNA revealed four uniq ue haplotypes, as well as distinct cytonuclear genotypes in population s from geographically isolated regions (e.g., Donana, Spain and Pechor a Delta, Russia). Based on the distributional pattern of P. pectinatus , previous studies have assumed that dispersal between populations is frequent and genotypes are distributed according to the island model o f genetic structure. In contrast, we found that genetic distances and geographic distances were significantly correlated, indicating that th e observed population structure can better be explained by stepping st one or isolation by distance models. Although no distinction of histor ic factors, such as founder effects, and current processes, such as en vironmental conditions, can be derived from this data set, we found in dications for the impact of migrating water-fowl on plant distribution al patterns. (C) 1998 Elsevier Science B.V. All rights reserved.