kinman at HOTMAIL.COM
Wed Jul 17 21:04:23 CDT 2002
The trouble with terrestrial onychophorans (euonychophorans) is that we
still know so little about their fossil history. And I imagine Poinar's
discovery of footless forms (no pads or claws) in Tertiary amber (especially
in Baltic amber) would throw a whole new light on both the phylogenetics and
biogeography of euonychophorans.
I haven't seen Poinar's 2000 paper (in Invert. Biol.), but the question
that immediately jumps into my mind is whether these Tertiary
clawless/padless forms are primitively clawless (which would have enormous
implications), or whether they are secondarily clawless for some strange
Either way, I can certainly see why
biogeographers would be attracted to onychophorans.
>From: Robert Mesibov <mesibov at SOUTHCOM.COM.AU>
>Reply-To: Robert Mesibov <mesibov at SOUTHCOM.COM.AU>
>To: TAXACOM at USOBI.ORG
>Subject: Speechless, nearly
>Date: Wed, 17 Jul 2002 16:33:39 +1000
>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,
>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
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