We chose Anemina fluminea as the Mussel of the Month for May because it is emblematic of the challenges that still exist in freshwater mussel taxonomy and systematics*. The upshot is that we know of very little science that would allow us to answer the question, "Upon what characteristics (synapomorphies) is Anemina based?" Anemina is a hypothesis about the evolutionary relationships of the five species in the genus. What is the evidence that supports that hypothesis? The short answer: it is pretty slim.
Until only about a decade ago, there was only a single species in the genus Anemina: A. arcaeformis, the type species. Lindholm (1925) created the genus Haasiella for Anodon arcaeformis Heude 1877 because the species was reported to lack the larval thread and hooked margin found in typical anodontine glochidia. However, Haasiella was preoccupied by a genus of myriapod, so Haas (1969) provided a replacement name, the subgenus Anemina — Anodonta (Anemina) arcaeformis.**
Then, out of the blue, Prozorova et al. (2005) put four additional species in Anemina: A. euscaphys, A. globosula, A. angula, and (our Mussel of the Month) A. fluminea. This was a bit of a shift in taxonomy since these four species had previously been either synonymized with Sinanodonta woodiana, omitted, or were unknown to Haas (1969). Is it reasonable to assume that these mussels also have the larval characteristics of A. arcaeformis? If so, it is certainly worth noting that Prozorova et al. (2005) placed the type of Anemina in a different genus: Buldowskia arcaeformis.
This is where we enter the story (Graf & Cummings, 2007). In trying to sort of the global freshwater mussel species diversity, we simply followed Prozorova et al. (2005) in classifying the other four species in Anemina, and we included A. arcaeformis because the rules of nomenclature required it. If there is an Anemina, then A. arcaeformis is one. Our treatment of Anemina was subsequently applied by Bogan (2010) and then mostly copied verbatim from a previous iteration of this web site by He & Zhuang (2013).
So, this is where we are at. A. fluminea resides in Anemina because Prozorova et al. (2005) put it there. However, those authors didn't classify the type of Anemina in Anemina, so their taxonomy is suspect. One could put the blame on us for floating the current concept of Anemina, but since subsequent authors have not attributed their taxonomy to us, perhaps we can take their use of the name as confirmation rather merely following. For now, we will keep Anemina.
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* And we chose this particular species of Anemina because it had a nice looking picture. Normally, we would use the type species of a particular genus(A. arcaeformis), but the picture of the type for that mussel isn't as nice as this one.
** The Soviet "Comparatory" School of Malacology split A. arcaeformis into multiple genera. Their practice of over-splitting has been discussed on this web site and in print (Graf, 2007). We regard this digression as something to be ignored rather than an interesting wrinkle in this story. |
