Mussel of the Month

In the age of molecular phylogenetics, there have been shake-ups in the taxonomy of long-recognized, well-studied, species-rich genera of North American freshwater mussels. The whole Fusconaia-Reginaia and Quadrula-Cyclonaias sagas are good examples. The former Elliptio has had Eurynia and Parvaspina carved out of it. Hamiota was pulled out of Lampsilis, and Pleuronaia was forged from shards of Pleurobema, Fusconaia, and the old Lexingtonia. There are definitely other examples. Furthermore, though the current concepts of the genera Lampsilis and Pleurobema have recently changed, they are likely to need some more revision. Simply put, those genera are typically not recovered as monophyletic in recent phylogenetic studies.

This can be seen by examining the Cladomics page for the genus Pleurobema on this web site.* The most comprehensively sampled phylogeny of Pleurobema to-date is that of Inoue et al. (2018), but there are several other relevant papers as well (many are cited below). The results differ from study to study, but the gist is that Pleurobema lineages are often not recovered as monophyletic.

There is a large group of species that typically cluster with Pleurobema clava (the type species of Pleurobema), and another clade of species that includes P. sintoxia. The latter species is significant because it is the type species of the senior available genus-group name that could be used for that other “Pleurobema” clade should the need arise: Sintoxia Rafinesque, 1820.

We have chosen Pleurobema sintoxia as Mussel of the Month to draw attention to this issue.

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* There is a Cladomics page for Lampsilis as well.