Hi all,
Re Phylogenetic and Biological Species.
Michael Wink & I wrote in our 2004 paper:
The interpretation of morphological and genetic data depends to some degree
which species concept is favoured by an author. For example, Robertson and
Nunn (1998) published an important paper examining the phylogenetic
relationships among members of the albatross family (Procellariiformes:
Diomedeidae) on the basis of complete mitochondrial DNA cytochrome b
sequences. This resulted in the splitting of the previously accepted 13
albatross species to form 24 species. Important in evaluating the proposed
species splits is the fact that Robertson and Nunn (1998: 2-3) declared
their acceptance of a version of the Phylogenetic Species Concept (PSC), the
hallmark of which is the application of the label 'species' to the terminal
taxa of the evolutionary tree.
There are, of course, several versions of the PSC. As Haffer (in del Hoyo
et al. 1997: 15) pointed out, at least two versions of the PSC, including
that of Hennig (1966), and the so-called 'monophyly version, PSC2', accept
the possibility of subspecies within species. The third version, PSC1
(Cracraft 1983; Zink and McKitrick 1995; and Zink 1996, 1997), assigns
species status to any population that is morphologically diagnosable, and
thus elevates most subspecies to species rank. It is this narrow species
concept that Robertson and Nunn (1998) embrace.
Haffer (1997: 15 - 16) emphasized some strongly subjective aspects of PSC1:
'The term "phylogenetic species" subsumes taxa of conspicuously varying
biological differentiation from those at early stages of speciation to taxa
that have already reached phylogenetic independence. Another problem under
PSC1 is that the number of species taxa recognized is a matter of the
resolving power of the analytical tools available...; therefore species
limits are highly subjective. Numerous small populations or even groups of
individuals may be 'diagnosable' with improved laboratory techniques and
would thus qualify as species.'
(continued in Part 2)
John Penhallurick
86 Bingley Crescent
FRASER, A.C.T. 2615
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