Centre of origin digression

[Robert Mesibov]

"To give an example, in a book on the crickets of Hawaii, a population from
the island of Molokai was separated specifically from identical ones on Maui
because "all species in this genus are island endemics".

This is taking the idea to an extreme, and using location as the _only_
diagnostic character for the species. On the other hand, knowing how insects
love to baffle taxonomists with cryptic speciation, those geography-based
cricket names could be seen as "placeholders" for genetics-based cricket
names in the near future. It was bad taxonomic practice, but maybe not
totally silly.

I work with poorly vagile, terrestrial animals which typically form
allopatric/parapatric mosaics of closely related forms. If field work shows
that there are, indeed, parapatric or narrow-gap allopatric boundaries
between forms (i.e., after convincing myself that two differing forms from
distant locations don't grade into one another in the intervening country),
I name each form as a species. These I see as "evolutionary species" in the
Wileyian sense. They've differentiated from a common ancestor and in my
judgment are unlikely to fuse again in reticulation. Sometimes there's very
little morphological variation within a mosaic tile, sometimes a fair bit.
I'm thus using geographic AND morphological information to delimit species.

I'm guilty of something else, too. Because I've used geographic information
in coming up with my species concepts, I logically shouldn't be able to do
biogeographical analysis with these species, because that would involve
circular reasoning. I find, however, that there are places where "species"
from different "genera" overlap a lot in range, and that these places are
often bounded by clusters of mosaic tile boundaries. I'd apply the label
"areas of endemism" to these places if I didn't see the "endemism" idea as
vacuous. "Areas of great biogeographical interest" is more to the point.
There often aren't any obvious ecological reasons for these to exist where
they do. The spatial patterning smells more of history, and I'm strongly
tempted to think (as A.R. Wallace did 150 years ago) that forms which are
both morphologically and geographically isolated arose earlier (and are
survivors of a clade which is now largely extinct) and that forms which are
morphologically and geographically closer arose later.

But I'm told there isn't any phylogenetic evidence in distribution
information. What I need to do is win a lottery and pay for a thorough
genetic study of a wide taxonomic and geographic range of individuals. This
will give me an inherent-character phylogeny to compare with the one I've
roughed out from my irresponsible and indefensible use of geographical
information (and some morphological clues, but these are few and tainted
with suspected homoplasy). I could also compare that
molecular-character-based phylogeny with the history of the areas roughed
out for me by my geologist and geomorphologist friends. Their earth-history
stuff fits nicely with my geographically-based thinking, but of course it's
only a geological hypothesis and doesn't have the solidity and scientific
appeal of a character-based phylogenetic analysis.

Must buy that lottery ticket... Wonder if there's a discount for grumpy old
taxonomists?
---
Dr Robert Mesibov
Honorary Research Associate, Queen Victoria Museum and Art Gallery
and School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 6437 1195

Tasmanian Multipedes
http://www.qvmag.tas.gov.au/zoology/multipedes/mulintro.html
Spatial data basics for Tasmania
http://www.geog.utas.edu.au/censis/locations/index.html
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