Avoidance of extinction through nonexistence: the use of museum specimens and molecular genetics to determine the taxonomic status of an endangered freshwater crayfish

We investigated the endangered status and taxonomic status of the freshwater crayfish Procambarus ferrugineus, a crayfish species considered for the candidate list of the Endangered Species Act. This species has a narrow distribution from central Arkansas, USA and is codistributed with its presumed sister species, Procambarus liberorum. We sampled extensively throughout the ranges of both primary burrowing species and collected mitochondrial DNA from a hypervariable fragment of the 16S gene from 109 individuals across 22 sites. We also collected data from a variable region of the 12S gene from a subset of the resulting 16S haplotypes. Due to our inability to sample what we considered P. ferrugineus in the field, we included museum specimens from the United States Natural History Museum of both P. ferrugineus and P. liberorum. Analyses of the resulting data suggested that these two species are indeed the same and we therefore synonymize them under the name of priority—P. liberorum. Additionally, our sampling discovered three new cryptic species from southwestern Arkansas all from the genus Procambarus. Nested clade phylogeographic analysis coupled with population genetic analyses suggested that P. liberorum has had three rounds of range expansion throughout the inferred evolutionary history. Using IUCN Red List criteria for conservation assessment, we conclude that the species P. liberorum should be considered stable, but with special concern because of habitat fragmentation and urbanization, small restricted range, and a moderate level of genetic diversity. Procambarus reimeri should be considered endangered due to its limited geographic range and the potential for a decline in suitable habitat. The three potentially newly discovered species should be considered data deficient until more information is obtained on their distributional limits and habitat requirements. Our study highlights the importance of thorough geographic and taxonomic sampling coupled with the utility of collecting data from museum specimens to reach robust taxonomic and conservation conclusions for endangered species.