Speechless, nearly

Robert Mesibov mesibov at SOUTHCOM.COM.AU
Wed Jul 17 16:33:39 CDT 2002

I reckon most of the participants in the recent, long discussion about
biogeography & phylogeny would have agreed on one thing. We weren't ever
likely to use geological data as the skeleton of an evolutionary
hypothesis. Well, it's a big, often strange world outside TAXACOM, and
someone has done just that:

Monge-Najera, J.  1995.  Phylogeny, biogeography and reproductive trends in
the Onychophora.  Zool. J. Linn. Soc. 114: 21-60.

Monge-Najera calls it "retrovicariant analysis." You start with an area
cladogram from geological results. You then assign to each area the taxon
currently living there. Hey presto! You now have a possible phylogeny for
the taxa, plus (geology willing) dates which are "probable lower time
limit[s] for cladogenesis..." Retrovicariance is used in the paper to come
up with a global-scale phylogeny for a group (Onychophora) which lacks one.
Two summary quotes:

"Retrovicariance biogeography uses area cladograms, produced from
geological data, as the basis for constructing biogeographic, systematic
and even paleontological hypotheses; these can be tested against
non-biogeographical evidence when it becomes available." (p. 40)

"Retrovicariant cladograms are hypotheses: they must be consistent with
their data and make clear taxonomic predictions. For that reason, they can
be tested and refined as new data and interpretations become available
(e.g., new paleogeographic reconstructions, estimations of biochemical
distance and molecular clock analysis)." (p. 41)

Note that Monge-Najera's paper appeared in a Linnean Society journal. Three
years later, the Society again published strange about Onychophora:

Trewick, S.A.  1998.  Sympatric cryptic species in New Zealand Onychophora.
Biol. J. Linn. Soc. 63: 307-329.

In this paper 4 new onychophoran species are described entirely on the
basis of allozyme evidence. All 4 look like Peripatoides novaezelandiae, so
Trewick says, for example for P. kawekaensis sp. nov.:

"Diagnosis.  As for P. novaezelandiae. Distinguished by a unique fast
allelle at the Aat- locus (Table 1). Sympatric with P. sympatrica sp. nov.
at Balls Clearing where it is distinct at three loci: Hk, Mpi and Pgam
(Tables 1, 3). Represented by clade d in the present analysis (Table 2,
Fig. 2)."

Holotypes? Yes, indeed. From the ether-killed animal, "representative
tissue including two to three pairs of legs was dissected from each end and
stored in alcohol." The rest was mashed for enzyme extraction. One wonders
whether the alcohol-preserved "holotypes" can still be used to demonstrate
the diagnostic enzyme bands.

Does Nature's editor know how liberal and "inclusive" the Linnean Society
can be in matters taxonomical?

Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 64371195; 61 3 64371195

More information about the Taxacom mailing list