**The title, authors, and abstract for this completion report are provided below. For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
Genetic markers to distinguish and quantify the level of gene flow between northern brook and silver lampreys
Margaret F. Docker 1, Nicholas E. Mandrak 2, Daniel D. Heath 1, and Kim T. Scribner 3
1 Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Ave, Windsor ON, N9B 3P4
2 Great Lakes Laboratory for Fisheries and Aquatic Sciences, 867 Lakeshore Rd, Burlington ON , L7R 4A6
3 Department of Fisheries and Wildlife, Michigan State University , 13 Natural Resources Building , East Lansing , MI , 48824
Abstract
The native lampreys of the Great Lakes appear to be declining in parts of the drainages, and the northern brook (Ichthyomyzon fossor) and silver ( I. unicuspis ) lamprey are of particular conservation concern. A major barrier to understanding current distribution and population trends in these species is the difficulty in distinguishing these two species as larvae. They are morphologically indistinguishable, and previous work has shown that they lack fixed species-specific differences in their mitochondrial genome. Mitochondrial restriction fragment length polymorphism (RFLP) assays and microsatellite markers were developed for these species, and indicated that – in some cases, at least – near-diagnostic differences in allele frequencies may permit reasonably accurate identification. This study tested the accuracy of these markers on a broader geographic scale. These markers could notreliably differentiate between northern brook and silver lampreys on a range-wide basis or even within basins. With both the mitochondrial and microsatellite markers, allelefrequency distributions were not significantly different between the species in tributaries to Lake Huron (the only basin in which the two species were sampled from the same streams). Significant differences in allele frequency distributions were observed between them in Lake Michigan tributaries (the only other basin where both species were caught in substantial numbers, but never from the same streams) however, sufficient individual and among-stream variation existed such that accurate species identification using these genetic markers was not possible. When comparing the two species, F ST values were low (-0.0120 and 0.0394, in Lakes Huron and Michigan , respectively), indicating contemporary gene flow between them. Intraspecific variation was as great as orgreater than interspecific variation, indicating that the two species are not monophyletic. Consequently, we suggest that northern brook and silverlampreys are not distinct species and, instead, should be considered different feeding types of the same species (comparable to the different feeding types in other fish species such as smelt, whitefish, and stickleback).