Intraspecific Phylogeography of the American Brook Lamprey, Lethenteron appendix (DeKay, 1842)

Variation at two mitochondrial DNA regions was used to assess the phylogeographic history of the American brook lamprey, Lethenteron appendix, a widespread and typically non-parasitic species in eastern North America. Little differentiation (<0.2%) was observed among populations throughout its range. Specimens of putatively parasitic individuals had sequences identical to non-parasitic individuals. Additional sequences from other members of the genus Lethenteron also demonstrated little or no differentiation with American brook lamprey (<1.2%). These results support the hypothesis of a recent range expansion of the American brook lamprey. Further, the absence of variation among several of the species of Lethenteron suggests a recent origin of multiple non-parasitic species with insufficient time for lineage sorting or ongoing gene flow among populations of a trophically polymorphic species. This study calls into question the current species diversity of Lethenteron.