2020 MUSSELp Publications & Presentations

A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus

by Inoue, Cummings, Tiemann, Miller, Johnson, Smith & Randklev

Published 2020, Zootaxa 4816(4): 457-490. Click here for online access.

The Gulf coastal drainages of central Mexico are a faunal transition zone between North and South America and harbor a unique assemblage of freshwater mussels (Bivalvia: Unionida). However, little information is available regarding the taxonomy, distribution, and evolutionary history of the Mexican mussel fauna due to limited sampling over the last 100 years. To address these knowledge gaps, we evaluated species-level diversity in the genus Popenaias Frierson, 1927, in Mexican Gulf coastal drainages as part of a larger effort to inform conservation efforts for members of this genus both in Mexico and the United States of America. Based on our analyses, we describe Popenaias berezai n. sp. from the Río Valles of the Río Pánuco basin, San Luis Potosí, Mexico. We also provide presumptive distributional range, phylogenetic structure, and molecular and morphological diagnoses of the new species and provide comments on the other species currently in Popenaias. Our findings highlight the high levels of endemism among freshwater mussels in Mexican Gulf coastal drainages and will help guide impending conservation actions for P. popeii, which is listed as “endangered” in the United States.

The conservation status of the world’s freshwater molluscs

by Böhm et al. (including D.L. Graf & K.S. Cummings and 48 others)

Published 2020, Hydrobiologia: 24 pp. Click here for online access.

With the biodiversity crisis continuing unchecked, we need to establish levels and drivers of extinction risk, and reassessments over time, to effectively allocate conservation resources and track progress towards global conservation targets. Given that threat appears particularly high in freshwaters, we assessed the extinction risk of 1428 randomly selected freshwater molluscs using the IUCN Red List Categories and Criteria, as part of the Sampled Red List Index project. We show that close to one-third of species in our sample are estimated to be threatened with extinction, with highest levels of threat in the Nearctic, Palearctic and Australasia and among gastropods. Threat levels were higher in lotic than lentic systems. Pollution (chemical and physical) and the modification of natural systems (e.g. through damming and water abstraction) were the most frequently reported threats to freshwater molluscs, with some regional variation. Given that we found little spatial congruence between species richness patterns of freshwater molluscs and other freshwater taxa, apart from crayfish, new additional conservation priority areas emerged from our study. We discuss the implications of our findings for freshwater mollusc conservation, the adequacy of a sampled approach and important next steps to estimate trends in freshwater mollusc extinction risk over time.

Status of freshwater mussels (Unionidae) of the Río Conchos basin, Chihuahua, Mexico

by Tiemann, Inoue, Rodríguez-Pineda, Hart, Cummings, Naranjo-García & Randklev

Published 2020, Southwestern Naturalist 64(3/4): 180-186. Click here for online access.

Before this study, researchers had not systematically surveyed the Río Conchos, a tributary of the Rio Grande located in northern Mexico, for freshwater mussels. The Texas hornshell, Popenaias popeii, an endangered species under the United States Endangered Species Act, occurs in the main stem of the Rio Grande near its confluence with the Río Conchos. The Texas hornshell's proximity to the Río Conchos prompted us to survey to determine whether P. popeii also occurs within the Conchos basin. Additionally, previous researchers described the Conchos disk, Disconaias conchos, from the Río Conchos but, to date, no one has reported live individuals of this species. The goal of this study was to determine the status of mussels within the Río Conchos basin and to provide a baseline for future monitoring efforts. We qualitatively surveyed 11 sites within the Río Conchos basin in May 2018. In total, we found two live individuals of the paper pondshell, Utterbackia imbecillis, at one site in the Río San Pedro, a tributary of the Conchos River, and as shells of recently live individuals at two sites in the Río Conchos. We found D. conchosas relict shells only at three sites, two in the Río Conchos and one in a tributary of the river at Coyame. The lack of live or fresh-dead material suggests that D. conchos is extinct. We also found live individuals of nonnative Asian clams (Corbicula spp.) at 10 sites. Sand and gravel mining, high organic pollution, and inadequate instream flows were evident throughout the basin and might explain the general absence of mussels.

A Biodiversity Informatics Approach to Family-group Level Classification of Freshwater Mussels (Bivalvia: Unionoida)

by Daniel L. Graf

Presented at the virtual annual meeting of the American Malacological Society, 13-14 July 2020.

Abstract. The MUSSEL Project Database (Graf & Cummings, http://mussel-project.net/) was developed as a resource for studying freshwater bivalve systematics. The MUSSELpdb is distinguished from similar biodiversity informatics initiatives and rendered awesome by the inclusion of “taxonomic opinions.” A taxonomic opinion relates three items: 1) a taxonomic work, 2) a named taxon, and 3) a valid taxon that circumscribes the nominal taxon in that publication. For the 958 valid freshwater mussel species and their >4000 synonyms, the MUSSELpdb reports more than 65,000 taxonomic opinions, providing the history of classification that underpins current usage.

Taxonomic opinions regarding genera and species are relatively easy to manage. At minimum, any reference to a binomial species also refers to a genus. But, traditionally, supra-generic taxonomy has been restricted to works that dealt explicitly with family-group level classification. Nowadays, the basis for taxonomy is found in cladograms that result from phylogenetic analyses. However, branching diagrams do not align easily with the data structure of taxonomic opinions the way that synonymies do.

To solve this problem, I am developing a database structure in FileMaker Pro, with analysis resources coded in Python. I have captured cladogram topologies from each of the 213 publications (from 1989 to 2020) with phylogenetic information on freshwater mussels. These works account for 369 cladograms and 6488 clades (i.e., nodes with descendant terminal species-group lineages). Half of these freshwater mussel phylogenetic studies have been published since 2015, and this period coincides with a new phase of vigorous post hoc revisions and clade-naming based on phylogenetic results. My talk will explore how these informatics tools can facilitate comparisons among cladograms to identify conflicting phylogenetic signals and to highlight opportunities for fruitful research.