Contrasting patterns of population structure and reproduction strategies of three sympatric species of Cladophoraceae endemic to Lake Baikal

Abstract

ABSTRACT The endemic Cladophoraceae of Lake Baikal are a group with high species richness, monophyly, and apparently recent speciation, making them ideal for the study of the genetic structure of an alga in this large freshwater environment. We analysed the population genetics of Chaetomorpha (= Ch.) moniliformis, Cladophora (= Cl.) compacta and Cl. kursanovii, using a set of eleven microsatellites coded as allelic phenotypes. The genetic variability of the populations was estimated by calculating the number of alleles in each population, mean values of unbiased diversity, and proportion of unique genotypes. Analyses of molecular variance were performed to account for the partitioning of the genetic variation between populations. The genetic structures of the species were inferred using clustering methods. The analyses revealed patterns of genetic variation and structure that suggest different reproductive strategies and dispersal abilities in the three species. In Ch. moniliformis the analysis suggested asexual reproduction and long-distance dispersal across the lake, due to the high proportion of identical genotypes and weak population structure. Cladophora compacta was likely to reproduce sexually due to its high proportion of unique genotypes and high gene flow within and between populations. Cladophora kursanovii showed intermediate diversity compared to the other two species, but with high differentiation between some populations. Results demonstrated that contrasting biological characteristics may arise in closely related species. Finally, this study can contribute more broadly to the understanding of the evolution and diversification in other taxa of the family Cladophoraceae, as few studies have been done to date.