Generic reclassification and species boundaries in the rediscovered freshwater mussel ‘Quadrula’ mitchelli (Simpson in Dall, 1896)

Abstract

The Central Texas endemic freshwater mussel, Quadrula mitchelli (Simpson in Dall, 1896), had been presumed extinct until relict populations were recently rediscovered. To help guide ongoing and future conservation efforts focused on Q. mitchelli we set out to resolve several uncertainties regarding its evolutionary history, specifically its unknown generic position and untested species boundaries. We designed a molecular matrix consisting of two loci (cytochrome c oxidase subunit I and internal transcribed spacer I) and 57 terminal taxa to test the generic position of Q. mitchelli using Bayesian inference and maximum likelihood phylogenetic reconstruction. We also employed two Bayesian species validation methods to test five a priori species models (i.e. hypotheses of species delimitation). Our study is the first to test the generic position of Q. mitchelli and we found robust support for its inclusion in the genus Fusconaia. Accordingly, we introduce the binomial, Fusconaia mitchelli comb. nov., to accurately represent the systematic position of the species. We resolved F. mitchelli individuals in two well supported and divergent clades that were generally distinguished as distinct species using Bayesian species validation methods, although alternative hypotheses of species delineation were also supported. Despite strong evidence of genetic isolation within F. mitchelli, we do not advocate for species-level status of the two clades as they are allopatrically distributed and no morphological, behavioral, or ecological characters are known to distinguish them. These results are discussed in the context of the systematics, distribution, and conservation of F. mitchelli.

Phylogeny of Mesoamerican freshwater mussels and a revised tribe‐level classification of the Ambleminae

“…Despite the morphological disparity of these sympatric taxa (all individuals were collected from just three sites in the same drainage), they are, for all intents and purposes, genetically indistinguishable in our analyses. The average pairwise COI uncorrected p‐distance among those terminals, 0.163%, was less than our expectations for interspecific variation in amblemines (Pfeiffer, Johnson, Randklev, Howells, & Williams, ; Pfeiffer, Sharpe, Johnson, Emery, & Page, ) and below the general DNA barcode cut‐off to delimit species (Hebert, Cywinska, & Ball, ). Our sampling from those species and genera was neither geographically nor taxonomically comprehensive (Table ), and, as such, our conclusions are necessarily limited.…”

Conservation of freshwater bivalves at the global scale: diversity, threats and research needs

“…More powerful genetics and morphometric tools are also increasingly available, for instance, new statistical tools for species delimitation using molecular and/or other types of data such as morphometry and anatomical traits (e.g. Froufe et al, 2016b;Pfeiffer et al, 2016). These tools are particularly important owing to the fact that many species present hidden cryptic diversity (Froufe et al, 2016b;Pfeiffer et al, 2016).…”

“…Froufe et al, 2016b;Pfeiffer et al, 2016). These tools are particularly important owing to the fact that many species present hidden cryptic diversity (Froufe et al, 2016b;Pfeiffer et al, 2016). Additionally, nextgeneration sequencing is now allowing for quicker and less expensive robust phylogenies using methods like whole-transcriptome and whole-mitogenome analyses with a wide range of markers (Guerra et al, 2017;Lopes-Lima et al, 2017c).…”

Editorial: The importance of integrated taxonomy to freshwater conservation

“…Most papers suggest that COI or ND1 mtDNA genes typically differ by at least 2.0% (i.e. they exhibit a substitution rate or probability of mutation of 0.02) between most mussel species (Johnson et al, ; Pfeiffer, Johnson, Randklev, Howells, & Williams, ). Some studies have reported differences as high as 4–5% (Smith et al, ; Zanatta & Harris, ), however, for some shorter‐lived taxa (e.g.…”