ECOLOGICAL SPECIATION OF A LANDLOCKED POPULATION OF RAINBOW SMELT (Osmerus mordax) IN LOCHABER LAKE, NOVA SCOTIA

Abstract

The process of speciation still remains one of the most debated issues in evolutionary biology. Studying sympatrically speciated pairs of fish, found in post-glacial lakes, may provide a unique insight into speciation, as populations are recently diverged. A landlocked sympatric pair of Rainbow Smelt (Osmerus mordax) found in Lochaber Lake, Nova Scotia is diverged into a small microphagous form and a large macrophagous form. Both forms have phenotypic differences associated with different trophic niches. Besides being phenotypically diverged they are also genetically differentiated suggesting reproductive isolation that is stable over time; however, results from this study provide evidence for gene flow between the two morphs. Hybrids were also observed in the adult and the larval Rainbow smelt providing further evidence that gene flow between the two morphs does exist, despite being selected against.