Prey, populations, and the pleistocene: evidence for low COI variation in a widespread North American leech
Phylogeographic study published in Mitochondrial DNA Part A (2019)
Abstract
Placobdella rugosa has long presented challenges to leech biologists. Its extreme morphological variability and similarity to some congeneric species has confounded classification for over a century. Recent molecular analyses revealed a surprising lack of genetic variation among morphologically disparate, geographically widespread specimens of P. rugosa. Given the lack of any obvious mechanism by which this species could disperse between distant habitats, it was expected that widespread populations would be genetically isolated from each other. In the present study, we investigate the relationship between geographic distance and genetic diversity in P. rugosa using COI sequences from specimens collected across Canada and the United States. Although we find preliminary evidence for a barrier to gene flow between eastern and western collecting localities, our vastly expanded dataset largely corroborates prior studies, showing minimal phylogeographic signal among the sequences and negligible levels of genetic isolation by distance. A recent range expansion following the last ice age and/or host-mediated dispersal are discussed as potential explanations for this unexpected phylogeographic pattern.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Low COI variation in widespread North American Erpobdella leech populations across Canada and United States, attributed to recent range expansion following the last ice age and/or host-mediated dispersal.
Why This Matters for Hirudotherapy
This study examined phylogeographic patterns in the North American leech Placobdella rugosa using COI mitochondrial DNA sequences from specimens collected across Canada and the United States, finding minimal genetic variation and negligible isolation by distance despite wide geographic distribution. Possible explanations discussed include post-glacial range expansion and host-mediated dispersal. For ASH's domain, the work is tangentially relevant in that it advances understanding of leech population genetics, biogeography, and species boundaries—knowledge that could inform sustainable collection practices and species verification for leech-based applications. However, P. rugosa is not a species used in hirudotherapy, the study involves no therapeutic application or secretome analysis, and the findings are purely taxonomic and phylogeographic. The relevance to hirudotherapy is therefore indirect at best.
Citation
Prey, populations, and the pleistocene: evidence for low COI variation in a widespread North American leech.
Mack J et al. · Mitochondrial DNA Part A, 2019
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