LE3 .A278 2008

2008

Stewart, Don

Acadia University

Master of Science

Masters

Biology

Biology

The freshwater mussels 'Pyganodon cataracta' and ' Pyganodon fragilis' are both found in Atlantic Canada but their taxonomic status and exact geographic distribution is uncertain. Phenotypic plasticity and convergence of shell characteristics has created difficulties in delineating unionids based on morphological traits. Our study will utilize the mitochondrial cytochrome c oxidase (COI) gene, the nuclear internal transcribed spacer region (ITS-1) gene and a multi locus marker, amplified fragment length polymorphisms (AFLPs), in conjunction with morphological data to determine if 'P.cataracta ' and 'P. fragilis' are two distinct species, just one species, or a mixed hybridizing population. Mussels collected from Newfoundland, Nova Scotia, New Brunswick and Prince Edward Island displayed low levels of genetic variability and extremely low divergence values for both the COI and ITS-1 sequence data, forming a single monophyletic group. Population genetic structure inferred from 235 AFLP loci, showed a moderatelevel of geographic structuring based on province, however no genetic differentiation among the putative species was observed. Common morphological characteristics used to distinguish the species in question were found to be unreliable. Our holistic approach of combining morphology, mitochondrial and nuclear data clearly indicates that 'P. cataracta' and 'P. fragilis' are not distinct species and should be regarded as a single species, with ' P. cataracta' having nomenclatural priority. These data also have implications for understanding the historical biogeography of 'P. cataracta ' and for conservation strategies for this species in eastern Canada.

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https://scholar.acadiau.ca/islandora/object/theses:2758