Place in taxonomy (finish?)
jrg13 at PSU.EDU
Wed Jul 3 23:48:35 CDT 2002
I haven't followed the place in taxonomy postings as closely (only so much
time in the day) but I concur with the latest observations by Robert
Mesibov. His examples illustrate how knowledge of the geographic
positioning of taxa can contribute information of phylogenetic significance
that is not present in a purely biological cladogram. I found it
interesting to read the examples cited. There is so much empirical work
going on in biogeography I find it a daunting task to keep track (no pun)
of even part of it.
In the panbiogeography book we have an entire chapter on geography and
systematics titled "Mapping the Trees of Life" subtitled "Panbiogeography,
phylogenetic systematics, and evolutionary processes".
The introductory statement is as follows:
"An understanding of geographical evidence is basic to interpreting the
phylogeny, systematics, and taxonomy of species and higher taxa. the use of
geographical distribution and other biogeographical data as a source of
classificatory characters and phylogenetic evidence is a time-honored
practice among systematists (citations from the 1800's to 1995)".
We note De Candolle as one of the first systematists to note the value of
geographical distribution, and Wallace's recognition that the natural
sequence of affinities of species was geographical, and Darwin made
comments on the value of using geographic evidence. A number of examples
are briefly cited including the use of geography to help delineate taxa in
a study of copper butterflies by Johnson and Balogh 1977.
There is one aspect of this that may be of general interest with respect to
the 'heritability' of geographic characters. I think there was a comment in
an earlier posting that inheritance was purely biological. Russell Gray and
others have argued for an extended concept of inheritance where
developmental information is in circuit rather than being localized within
internal or external factors:
"An alternative approach to genes and environments is a developmental
systems or constructionist approach in which genes are recognized as just
one resource that is available to the developmental process. Although
particular resources may have different roles, there is nothing dividing
the resources into fundamentally differing kinds such as genes and
environment. Phenotypic traits require both genetic and environmental
inputs. The fundamental unit of evolution becomes the developmental system.
This is a set of organismic and environmental features interacting to
produce an outcome capable of replicating the developmental process
(Grifiths 1992, Griffiths and Gray 1994). Characters are constructed
through epigenetic processes that are no less a codeterminant of characters
than genes (Oyama 1985, Ho 1988). Evolution is the differential replication
of these systems."
At 10:28 AM 7/4/02 +1000, you wrote:
>Pierre Deleporte has asked how, specifically, you can extract historical
>evidence from distributional data. Unfortunately I have no Method (note the
>capital) and no software package (Geoclade?) to offer, but here are 3
>recent papers to think about:
>(1) The 3 conifers Athrotaxis cupressoides, A. laxifolia and A.
>selaginoides are all endemic to Tasmania. Each has its own set of
>morphological and ecological character-states, and each produces fertile
>pollen. It's a straightforward exercise to devise 3-species cladograms from
>character-states, and you can then fiddle with statistical tests to see
>which of the cladograms is most likely. All the cladograms are wrong.
>Genetic evidence (RAPD & SSCP analysis of total genomic DNA) shows clearly
>that laxifolia is a stable, interspecific hybrid of cupressoides and
>selaginoides, and selaginoides may well be the only pollen parent (Aust J
>Bot 48:753-758, 2000). Now let's expand on that "endemic to Tasmania".
>Mapping Athrotaxis distributions on a fine scale, you find that laxifolia
>occurs ONLY where cupressoides and selaginoides are sympatric. Here the
>best evidence for clarifying the phylogenetic relationships between 3
>species comes from genetic and spatial data, not from a taxon-by-character
>(2) In a fascinating study of grasshoppers in the genus Chitaura on
>Sulawesi (Biol J Linn Soc 72:373-390, 2001), 4 types of data were
>available: exact locations for samples from 60 sites, maximum parsimony
>cladograms for colour pattern, a mtDNA cladogram and a morphometric data
>set from males analysed using PCA, HANOVA and a Mantel test (with
>geographic distance). There are 10 named Chitaura species and the character
>data certainly support the conclusion that the Chitaura lineage has
>branched repeatedly over the past few million years. However, it is far
>from obvious how a conventional tree can be constructed which satisfies all
>the data. Instead the authors focus on spatial relationships (especially
>what happens at contact zones on the island) to illuminate tree "details".
>Read the paper to see how complicated the story is.
>(3) A preliminary analysis has recently been made of the connections
>between species range size/position and hypothesised phylogeny (Amer Nat
>155:419-434, 2000). In the groups studied, range size asymmetry was
>associated with relatively recent splits, suggesting that peripatric
>(allopatric) speciation was the split mechanism, and sympatry seems to have
>resulted from post-speciation dispersal. The hint here is that the geometry
>of a set of ranges contains phylogenetic information which would not be
>evident in a simple presence/absence summary of locations.
>In an earlier post I pointed out that spatial information becomes less
>important (more blurred) as you go up the taxonomic hierarchy. A reckless
>generalisation: spatial information is essential in studying populations,
>very useful for species, important for genera and helpful for families.
>This shouldn't be seen as a limitation which reduces the importance of
>"place" overall, any more than mtDNA analysis should be dismissed because
>it doesn't help us understand basal arthropod phylogeny.
>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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