Book
Preliminary ribosomal RNA phylogeny of gastropod and unionoidean bivalve mollusks
01 Jan 1994
Abstract
Sequences of about 150 nucleotides in the D6 region of the large (28S) ribosomal molecule were obtained from 20 uinionoidean bivalves and gastropods, including a truncatellids, 1 muricid, 1 cancellariid, 1 melongenid, and 1 pleurotomariid. These were analyzed along with sequences from Emberton et al. (1990) for 8 pulmonates, a helicinid and a pomatiopsid. Rates of divergence varied by a factor of two, with unionoidean and the helicinid sequences differing by 15-20'% relative to mouse, pulmonates by 22-24%, neogastropods by 24-27%, and rissooideans by 27-32%. Length variation among sequences occurred mainly in the D6 loop, and complementary mutations were seen in the D6 stem. Cladistic analysis found 24 equally parsimonious trees; the strict consensus supports monophyly of Unionoidea, Rissooidea, Pulmonata and Stylommatophora. Monophyly of Neogastropoda is not contradicted. Some groupings are anomalous when compared to morphology-based phylogenies. Helicinidae groups with Unionoidea, Pleurotomariidae with Neogastropoda, and Geomelania (Truncatellidae) with Pomatiopsidae. In each case, addition of taxa that intersect long branches (e.g. Chitonidae, Patellogastropoda) might show that characters interpreted as synapomorphic are plesiomorphic or convergent. The observed grouping of Muricidae and Cancellariidae is well-supported, indicating the canellariids are a highly derived group within the Stenoglossa. Pleurotomariidae are more closely related to the other gastropods in the analysis than are Helicinidae, supporting Haszprunar's (1988) anatomy-based conclusion. To date, sequence studies of mollusks have not overturned phylogenies based on morphology, but rather have helped in choosing among competing morphology-based hypotheses. Like morphological data, sequence data are subject to problems of convergence, unequal rates of evolution, and choice of taxa. Classifications must be based on all available data to maximize the potential for detecting convergences and correctly resolving phylogenetic relationships.
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Details
- Title
- Preliminary ribosomal RNA phylogeny of gastropod and unionoidean bivalve mollusks
- Creators
- G RosenbergG KuncioG DavisM Harasewych
- Contributors
- S Tillier (Editor)M G Harasewych (Editor)
- Resource Type
- Book
- Language
- English
- Academic Unit
- Biodiversity, Earth, and Environmental Science (BEES); Malacology
- Identifiers
- 991019184036704721