Molecular phylogeny of Bulinus (Gastropoda: Planorbidae) reveals the presence of three species complexes in the Albertine Rift freshwater bodies

A. Nalugwa¹*, A. Jørgensen³, S. Nyakaana¹ and T. K. Kristensen²

¹Makerere University Institute of Environment and Natural Resources: Molecular Biology laboratory P. O. Box 7298, Kampala, Uganda.

²The Mandahl-Barth Research Centre for Biodiversity and Health, DBL-Parasitology, Health and Development, Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 57, DK-1871 Frederiksberg C, Denmark.

³The Molecular Systematic Laboratory, The Natural History Museum of Denmark, Sølvgade 83, DK-1307 Copenhagen K, Denmark.

*Corresponding author. E-mail: nallen@muienr.mak.ac.ug, allennalugwa@yahoo.co.uk. Tel: +246 -414-532789. Fax: +256-414-530134

Accepted 19 July, 2010.

   Abstract

In this study, partial mitochondrial DNA cytochrome oxidase subunit I (mtCOI) sequences (612 bp) of Bulinus snails sampled from 31 freshwater bodies in the Albertine Rift were analyzed to investigate the extent of genetic variation and phylogenetic relationships. Bayesian phylogenetic inferences clustered the samples into three species groups; Bulinus truncatus/ tropicus, Bulinus forskalii and Bulinus africanus. Twenty-two haplotypes were identified within the B. truncatus/tropicus species group which clustered into two well-differentiated lineages; with 2.7% sequence divergence between them. Significant genetic variation was also observed within the B. forskalii group, with the Maramagambo forest haplotype being separated by 55 mutational changes from the rest of the haplotypes. The B. truncatus/tropicus species group showed early divergence from the two B. forskalii and B. africanus species groups which were more closely related. A single species B. globosus in the B. africanus species group was identified in the Albertine Rift. We report the presence of five Bulinus species in the Albertine Rift; two in the B. truncatus/tropicus group, two in the B. forskalii group (one species yet to be identified) and one species in the B. africanus group. The findings of this study highlight the limitations of relying solely on shell characteristics to delineate snail species within the genus Bulinus.

Key words: Bulinus species, cytochrome oxidase c subunit I, mitochondrial DNA, phylogenetic relationships, Albertine Rift.