[Taxacom] Phylogenetic classification?

[Stephen Thorpe]

To expand a little on my former comment about paraphyletic species:
Probably the concepts of 'monophyly', 'paraphyly', etc. are wrongly  
applied to species. GROUPS OF SPECIES are monophyletic or  
paraphyletic, not the species themselves. When we talk about  
decendants being included, we don't mean individuals decended from  
other individuals by parent-offspring relationships, we mean species  
decended from other species by speciation events. Even if we do  
somehow apply the concepts to species, there is no reason to "dislike"  
paraphyletic species in the same (Hennigian) way as for paraphyletic  
groups. For all we know, and I am convinced that this is true,  
probably most if not all cases of speciation renders a "parent  
species" "paraphyletic" in the sense we are talking about. I see  
abundant evidence for founder effect speciation! Just compare, say,  
the fauna of the Three Kings Islands with that of the adjacent New  
Zealand mainland. A small population of a widely distributed species  
becomes isolated on the islands, and evolves quickly (being a small  
population) into a distinct new species, while the mainland ones  
remain largely unchanged...

Stephen

Quoting Michael Heads <michael.heads at yahoo.com>:

> Dear Ken et al.,
>  
> In their book 'Speciation' (2004: 401) Coyne & Orr concluded that ‘there is
> little evidence for founder effect speciation’. Note that  
> these authors are not rabid
> cladists or wacky vicariance biogeographers but  
> eminently respectable population
> geneticists who can be taken seriously.
>  
> Michael Heads
>
> Wellington, New Zealand.
>
> My papers on biogeography are at: http://tiny.cc/RiUE0
>
> --- On Sat, 8/1/09, Kenneth Kinman <kennethkinman at webtv.net> wrote:
>
>
> From: Kenneth Kinman <kennethkinman at webtv.net>
> Subject: [Taxacom] Phylogenetic classification?
> To: taxacom at mailman.nhm.ku.edu
> Date: Saturday, August 1, 2009, 2:45 PM
>
>
>
> Hi Richard,
>        Such an expectation by some cladists that
> ancestor-daughter species "inexorably" become sister species seems to be
> largely wishful thinking. This might tend to occur in cases where the
> daughter species has a population that is not greatly smaller than the
> population of the mother species. However, such an expectation seems
> rather unlikely in frequent speciation where there some element of
> "founder effect", especially when the mother species is highly
> polytypic. This would be most evident in extreme cases where the founder
> is a single pregnant female (such as for metazoans) or even a single
> seed (for plants) which manages to survive in a new environment and is
> reproductively isolated.         
>       The paraphyly is even more evident when one adds the time
> dimension and considers the earlier history of the mother species (which
> would usually be broader both genetically and phenotypically) than it
> was at the later time when it gave rise to its daughter species.  If I
> was a strict cladist, I would find it VERY disturbing to conceive of one
> sister species having perhaps evolved a considerable period earlier than
> its sister species.  Given the lack or sparsity of a fossil record
> (along the stem between nodes) leading to most such species pairs,
> having no good evidence of relative age makes it even more problematic.   
>        Extinction and a poor fossil record is truly a double-edged sword
> that can make the recognition of clades both useful in the face of that
> lack of information, but often only temporarily useful and subject to
> destablizing challenges to that cladistic recognition when fossil
> intermediates are eventually discovered.  The trick is to occasionally
> use paraphyly where cladistic assumptions seem likely to be overturned
> by new information (fossil or otherwise).  Paraphyletic speciation (and
> paraphyly at higher taxonomic levels) is too common for strict cladism
> to continue hoping that it won't cause them any major problems (and
> classificatory unstability for us all).  Stability and usefulness
> require the occasional use of paraphyletic taxa at appropriate points in
> the Tree of Life.
>       ---------Ken Kinman
>
> ----------------------------------------------
> Richard Zander wrote:
>           As far as I can figure it out,
> phylogeneticists expect a species that is paraphyletic (many exemplars
> with a different species coming out of the middle of the lineage of
> exemplars) to eventually become a sister group (reciprocally
> monophyletic is the phrase). Therefore, a paraphyletic species should be
> considered different from the autophyletic species because it will
> inexorably become a sister group to it as exemplars get their act
> together and homogenize their molecular data through recombination and
> gene conversion and whatnot.
>
>
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