SREL Reprint #1904
Phylogenetic analysis of eleven species of Biomphalaria Preston, 1910
(Gastropoda: Planorbidae) based on comparisons of allozymes
SUSAN M. BANDONI,1,2 MARGARET MULVEY,1 AND ERIC S. LOKER 2
1Savannah River Ecology Laboratory, Drawer E, Aiken, SC, 29802, U.S.A.
2Department of Biology, University of New Mexico, Albuquerque, NM, 87131,
USA.
Freshwater snails in the genus Biomphalaria transmit Schislosoma mansoni in Africa, South
America and the Caribbean region. Although considerable attention has been given to the
identification of species, little is known of' evolutionary relationships among the species. A
phylogenetic analysis of' 25 populations representing 11 species was performed on 25 enzyme loci
examined using starch gel electrophoresis. A phylogenetic analysis of' the individual populations
produced 60 trees of equal length. 'I've 60 trees have a consistency index value of' 75.9% and a
retention index value of 76.5%. The phylogenetic analysis provided strong support for the
monophyly of Biomphalaria with either 14 or 15 synapomorphics uniting all of' the species included
and separating them from the outgroup, two species of' Helisoma. Four nominal species
represented by multiple populations formed monophyletic groups. Populations of' B. sudanica, B.
choanomphata, and B.alexandrina were interspersed. 'Ten arrangements were obtained for the
populations of' these three species. A variety of' ingroup taxa were used to root the trees, and all
provided support for tile use of' Helisoma species as an outgroup. In all of' the trees obtained, the
African species together formed a monophyletic group. In none of' the trees obtained did the
neotropical species form a monophyletic group. A constrained analysis requiring the monophyly of'
the neotropical species as well as the African species resulted in 90 trees just two steps longer than
the shortest trees. Analysis of' the species from either hemisphere alone resulted in decreased
resolution, as measured by an increase in the number of' trees obtained. 'This finding suggests that
further comparisons of' species from the two hemispheres will be of considerable value. Finally, two
species which are resistant to infection with S. mansoni were included among the eleven studied.
Neither of' these species formed the sister group to all of' the other species included, indicating that
susceptibility is the plesiomorphic state, and that resistance is derived. Similarly, in none of' the trees
obtained did the two resistant species fall out as sister taxa, indicating that resistance arose
independently twice.
ADDITIONAL KEY WORDS: freshwater gastropods - phylogeny - coevolution - biogeography
- Schistosoma mansoni
SREL Reprint #1904
Bandoni, S.M., M. Mulvey, and E.S. Loker. 1995. Phylogenetic analysis of eleven species of Biomphalaria Preston, 1910 (Gastropoda: Planorbidae) based on comparisons of allozymes. Biological Journal of the Linnean Society 54:1-27.
