Integrative taxonomy reveals a new species of freshwater mussel, Potamilus streckersoni sp. nov. (Bivalvia: Unionidae): implications for conservation and management

Abstract

Inaccurate systematics confound our ability to determine evolutionary processes that have led to the diversification of many taxa. The North American freshwater mussel tribe Lampsilini is one of the better-studied groups in Unionidae, however, many supraspecific relationships between lampsiline genera remain unresolved. Two genera previously hypothesized to be non-monophyletic that have been largely overlooked are Leptodea and Potamilus. We set out to resolve supraspecific relationships in Lampsilini and test the monophyly of Leptodea and Potamilus by integrating molecular, morphological, and life history data. Our molecular matrix consisted of four loci: cytochrome c oxidase subunit 1 (CO1), NADH dehydrogenase subunit 1 (ND1), internal transcribed spacer 1 (ITS1), and 28S ribosomal RNA. Secondly, we performed both traditional and Fourier shape morphometric analyses to evaluate morphological differences and finally, we compared our results with available life history data. Molecular data supported the paraphyly of both Leptodea and Potamilus, but nodal support was insufficient to make any conclusions regarding generic-level assignments at this time. In contrast, inference from our integrative taxonomic assessment depicts significant support for the recognition of a new species, Potamilus streckersoni sp. nov., the Brazos Heelsplitter. Our data show clear separation of three taxonomic entities in the P. ohiensis species complex: P. amphichaenus, P. ohiensis, and P. streckersoni sp. nov.; all molecularly, geographically, and morphologically diagnosable. Our findings have profound implications for unionid taxonomy and will aid stakeholders in establishing effective conservation and management strategies. http://www.zoobank.org/urn:lsid:zoobank.org:pub:502647C0-418B-4CC4-85A8-BD89FC3F674F

New freshwater mussel taxa discoveries clarify biogeographic division of Southeast Asia

“…To delimit and diagnose species in our dataset, we used an integrative approach [4][5][6][7][70][71][72][73] based on the phylogenetic and morphological analyses. First, we applied an automatic species delimitation approach to delimit the Molecular Operational Taxonomic Units (MOTUs) that may correspond to biological species.…”

“…All deleterious mutations were retained for the analyses. While numerous recent studies reveal that using an integrative approach for freshwater mussel taxonomic research is rather straightforward [4][5][6][7][70][71][72][73] , its application to freshwater gastropods is more difficult due to several shortcomings such as a possible incongruence in a mitochondrial phylogeny 76,77 and often higher DNA barcoding thresholds between species 46,78,79 . At first glance, the differences between these groups can be explained by slower evolutionary rates of freshwater mussels 20,65 compared with those of freshwater gastropods 80 . nomenclatural acts.…”

Comparative phylogenomics reveal complex evolution of life history strategies in a clade of bivalves with parasitic larvae (Bivalvia: Unionoida: Ambleminae)

“…Highly specific patterns of host use are often associated with equally specialized host infection strategies, including elaborate conglutinates and mantle margins that mimic host prey items (e.g., insect larvae, fish, worms, snails, crayfish), denticulate shell margins to capture hosts, and maternal sacrifice, where brooding females are hypothesized to behave in a manner that increases predation attempts by molluscivorous fishes (Barnhart et al, 2008; Haag, 2012). Morphological and behavioral adaptations for specialized parasitism have strongly shaped the diversity of Ambleminae, and robust evaluations of life history characteristics have been integral to understanding the ecology and evolution of this group (Haag and Warren, 1999; Haag and Staton, 2003; Campbell et al, 2005; Graf and Cummings, 2006; Zanatta and Murphy, 2006; Sietman et al, 2012, 2018; Haag, 2013; Hewitt et al, 2019; Smith et al, 2019; Pfeiffer et al, 2019a, 2019b).…”

“…Life history strategies in this group are generally well studied, but many questions regarding the evolution of these taxa and traits remain unanswered. Previous phylogenetic reconstructions have consistently failed to recover the monophyly of taxa with specialized parasitization of A. grunniens (Campbell et al, 2005; Zanatta and Murphy, 2006; Pfeiffer et al, 2018; Smith et al, 2019). Specifically, the Atlantic coast endemic L. ochracea , which does not use A. grunniens as a host, was nested within a clade otherwise restricted to A. grunniens host use (Johnson, 1970; Kneeland and Rhymer, 2008; Smith et al, 2019).…”

The utility of zooarchaeological data to guide listing efforts for an imperiled mussel species (Bivalvia: Unionidae: Pleurobema riddellii)

“…Zooarchaeological shells are often fragmented and so we developed proxies ( Figure 4) for measurements (i.e., shell length, width, and height) commonly used in morphometric analyses focused on delineating species boundaries for mussels (e.g., Johnson et al, 2018;Smith, Johnson, Inoue, Doyle, & Randklev, 2019). Specifically, umbo thickness (UT) captures width of the shell and is measured from the highest point of the umbo, dorsally, to the interdentum.…”