Assessing the genetic distinctiveness of Cambarus (Puncticambarus) acuminatus: A recently discovered crayfish in Valley Creek within Valley Forge National Historical Park

Fetzner, James; Crandall, Keith

This investigation into a newly discovered crayfish from Valley Creek, Valley Forge National Historical Park (Chester/Montgomery counties, Pennsylvania; ~30 km NW of Philadelphia), was undertaken in order to help resolve long-standing taxonomic questions related to the Cambarus (Puncticambarus) acuminatus Faxon (1884) species complex, and to help determine the conservation status and geographic origin of Pennsylvania populations assignable to this taxon. The crayfish considered to be a part of this species complex currently range from southeastern Pennsylvania (Valley Creek) in the north, southward to the Saluda River drainage in South Carolina. Morphologically, members of this complex are quite variable across their range, with many populations often lacking the prominent cervical spines Faxon (1884) mentions in his original species description. Taxonomically, the species is difficult to delineate because the type specimens are either lost or degraded to the point where they have no distinguishing characteristics, and is further complicated because the type locality apparently no longer exists; therefore, characterizing which populations of the species complex are most similar to the original type population described by Faxon (1884) cannot currently be determined with available materials, or by recollecting from the type locality. In this report, we attempt to use molecular methods (mitochondrial COI gene sequences) to examine variation from throughout the range of the species complex in order to delimit groups of related populations in the hopes that these data may shed light on the relationships in this group of crayfish and help us to understand their evolutionary history and conservation status. Our results show that the Pennsylvania populations that were sampled (Valley, Pickering and Darby creeks) are closely related to one another, and shared several haplotypes that are unique to Pennsylvania. Interestingly, these Pennsylvania populations appeared to be most closely related to populations sampled from Virginia than they were to the more geographically proximal Maryland populations. DNA sequence divergences averaged 2.4% between PA and VA populations, suggesting that the PA populations share a recent common ancestry with central VA (although some intervening areas were not sampled). The Pennsylvania populations were divergent from what we consider to be the type population from the Saluda River, South Carolina. The magnitude of the divergence suggests they are a different species from “true” C. acuminatus, but the current taxonomic confusion in the genus Cambarus prevents us from defining which species it might represent. In addition, we also identified several other genetically divergent groups in the C. acuminatus complex, indicating that it harbors higher genetic variation than previously thought. Further studies are needed to test if these newly discovered lineages might represent additional undescribed species. We also recommend that additional sampling and analyses should be conducted in order to help sort out the taxonomic issues in this group of crayfish.

Assessing the genetic distinctiveness of Cambarus (Puncticambarus) acuminatus: A recently discovered crayfish in Valley Creek within Valley Forge National Historical Park

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