Mussel of the Month

Back in March 2008 when Ensidens ingallsianus was the Mussel of the Month, the genus was regarded to be composed of only two species (Graf & Cummings, 2007). But that wasn’t the only word on the subject. Brandt (1974) had considered Ensidens to be a single species (with two subspecies), and as recently as last year, we listed Ensidens with 3 species on this web site (Graf & Cummings, 2021). But now, that tally has been boosted to six species — including Ensidens dugasti.

The current consensus came into view relatively recently when the purveyors of densely sampled molecular phylogenies started having trouble shoehorning their mitochondrial lineages into only two species (Bolotov et al. 2017 and all the references that re-used those sequences). Muanta et al. (2019) recovered two clades that they regarded as representative of the classic two-species system: E. ingallsianaus and E. sagittarius, but in each case, those two species sensu lato could be divided into multiple subclades. It fell to Pfeiffer et al. (2021) to revise the taxonomy and circumscribe the type specimens and published sequences into the six species we recognize today.

You can see the clade topology of Ensidens as resolved in the trees published by Pfeiffer et al. (2021) (or any other publication that mentions Ensidens species) by going to the Ensidens Cladomics page. This is a new feature of the MUSSELp web site (described at the recent AMS meeting) wherein phylogenetic results are summarized for genera and family-group level taxa. For any taxon, just click the cladomics link to be instantly planted in the forest of relevant cladograms. Cladomics is still in the experimental phase, so it is probably clunkier now than it will be once people start using it.