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A MOLECULAR PHYLOGENY OF NORTH AMERICAN PLEUROCERIDAE (GASTROPODA: CERITHIOIDEA) BASED ON MITOCHONDRIAL 16S rDNA SEQUENCES

2000; Oxford University Press; Volume: 66; Issue: 2 Linguagem: Inglês

10.1093/mollus/66.2.233

1464-3766

Wallace E. Holznagel, Charles Lydeard,

Myxozoan Parasites in Aquatic Species

The Pleuroceridae Fischer, 1885, is one of three freshwater gastropod families currently recognized in the superfamily Cerithioidea Férussac, 1819 (Mollusca: Caenogastropoda Cox, 1960). Despite considerable literature justifying various proposed generic names of North American pleurocerids, no study has been conducted examining phylogenetic relationships of the recognized genera. In an effort to expand our understanding of evolutionary relationships of North American pleurocerid genrea, we examined a large portion of the mitochondrial 16S rRNA gene among 32 extant North American taxa. Multiple sequence alignment of the amplified region for our taxa resulted in a matrix consisting of 900 nucleotides including insertions and deletions. Based on analysis of nucleotide substitution patterns, we employed two approaches in our phylogenetic analysis: (1) all substitutions received equal weighting and (2) transversions were weighted 2X and 4X transitions to compensate for transition saturation among distantly related taxa. The molecular phylogeny based on the mitochondrial 16S rDNA sequences supports the monophyly of Pleurocera Rafinesque, 1819, Elimia H. & A. Adams, 1854, and Juga H. & A. Adams, 1854, but depicts the genera Lithasia Haldeman, 1840, and Leptoxis Rafinesque, 1819, as polyphyletic. The genus Pleurocera is sister to Elimia, which in turn is sister to a paraphyletic assemblage including representatives of Leptoxis, Lithasia, and the monotypic genus Io Lea, 1831. Juga, a genus restricted to west of the North American continental divide is the basal-most clade and is sister to all the aforementioned genera found east of the continental divide.