Sunday Spinelessness – Each thing by its right name

By David Winter 06/05/2012

In Dr Zhivago Boris Pasternak describes an epiphany that sneaks up on one of his characters thus:

For a moment she rediscovered the purpose of her life. She was here on earth to grasp the meaning of its wild enchantment and to call each thing by its right name…

It’s probably not spoiling the story to tell that Lara doesn’t dedicate her life to taxonomy at this point of the novel.I can’t say I really know what Pasternak was getting at with these sentences, but I’ve always liked them because they really do describe the driving force that makes taxonomists and lovers of natural history seek to understand and even name the wild diversity of life on earth.

I’ve recently learned the name of two species that turned up on these pages unnamed. So, let me introdue you to Thalassohelix igniflua (last seen in “they’re alive!”):

And Phenacohelix pilula (seen in Incertae sedis)

The drive that naturalists feel to call each thing by its right name can seem oddly obsessive to people that aren’t pulled by the same forces. But species are the fundamental units of biodiversity, and thus a natural point of comparison for studies in ecology, evolution and many other fields. If we want to understand biology we need to know about species, and if we want to know something about a species the we need to have a name that uniquely identifies that species in any scientific work. The species above got its name from Lovell Reeve and, being a New Zealand endemic invertebrate, only a little information has been tacked on that name since. Even so, knowing the name of this species is enough for me to learn that it is widespread across New Zealand, and down here in the southern end of the South Island it can co-exist with a close relative called P. mahlfelda. (From this last fact we can infer that it’s likey that P. mahlfeldae and P. pilula occupy slightly different ecological niches, as it is generally though two species can’t co-habitate while trying to take up the same sopt in nature’s economy).
I can also look at an unpublished study by the late Jim Goulstone, who collected snails from all around Dunedin and the surrounding patches of bush, and learn that its a bit of a surprise that our urban garden (we are 400 m away from the Octagon, Dunedin’s answer to a town square) has such a thriving population of this snail. Goulstone only found P. pilula at two sites in Dundedin, both in old-growth forests on the slopes of Mt Cargill. In both of those sites he only records one shell for P. pilula. Land snail distributions are notoriously patchy, but it’s still interesting to wonder how what seems like a fairly rare and habitat-restricted species ended up as the only native land snail in our garden.