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Ecology and evolution of Blackfin cisco populations in an outflow system of proglacial Lake Algonquin
J. Turgeon2, M.S. Ridgway3
2Département de biologie Université Laval, Québec, QC, Canada G1V 0A6
3 Harkness Laboratory of Fisheries Research, Aquatic Research and Monitoring Section, Ontario Ministry of Natural Resources & Forestry; Trent University, Peterborough, ON K9L 0G2 Canada
Ciscoes resembling the nigripinnis form formerly found in the Laurentian Great Lakes was captured in several lakes of Algonquin Provincial Park, as well as Lake Memesagamesing. For convenience, they are referred to as blackfin, rather than Blackfin cisco. The morphology of blackfin is similar to that of nigripinnis from Lake Nipigon, yet they often possess more gill rakers. These fish are predominantly benthic, with peak occupancy between 20-25m rather than more profundal available depths in some lakes such as L. Hogan and L. Cedar. The presence of Mysis as a prey item in some lakes of APP is a key element. Cisco in the park afford the opportunity to examine niche space expansion given differences in diel migrators, habitat use and phenotypic diversity. Given that blackfin populations are located in the Fossmill outlet, a temporary drainage of proglacial Lake Algonquin, it was hypothesized that they could be a remnant lineage of the Great Lakes nigripinnis. Neutral genomic data (ca. 6000 SNPs) on 600 fish from 14 lakes of this area indicates that it is not the case: blackfin diverged independently from cisco in several lakes. Across lakes, there was a continuum of ecological, morphological and genetic differentiation that could be associated with alternative resources and lake characteristics. Unexpectedly, all fish from this area belonged to the Atlantic refugial lineage, with no trace of admixture with the western lineage now characterizing ciscoes from the Upper Great Lakes. Review of published genetic data and new data in critical areas near the GL suggest that the Atlantic lineage reached the GL before any other lineages. The western lineage may have dispersed from the Missourian refuge instead of the Mississippian refuge. Hence the colonization of APP could have been by the Atlantic lineage arriving from the GL area at a time when it was the only lineage present in Lake Algonquin.