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Thursday, October 8, 2009

BRYONET: Re: Lichen species & speciation

BRYONET

Hi all,
Thanks to everyone for these interesting comments about the age-old
question "what if anything is a species?". I know Brent would love to
see them, but I doubt he subscribes to lichens-l. Since we've been
talking about him (his ears are probably burning), I'm copying this to
him and other bryonetters to see if we can get them to comment.

All best,
Jim

James D. Lawrey
Department of Environmental Science and Policy MSN 5F2
George Mason University
4400 University Drive
Fairfax, Virginia 22030-4444
U.S.A.

Phone: (703) 993-1059; (703) 993-3462
Fax: (703) 993-1046; (703) 993-1066
Email: jlawrey@gmu.edu
Lab website: http://mason.gmu.edu/~jlawrey/biography/

----- Original Message -----
From: Robert Lucking <rlucking@FIELDMUSEUM.ORG>
Date: Thursday, October 8, 2009 4:54 pm
Subject: Re: Lichen species & speciation

> Hi all,
>
> I agree with Brendan, specifically in the importance of the biological
> species concept and its practical difficulties (which do not
> diminuish its
> value). The fact that something is difficult to demonstrate does
> not make it
> less valid; else we would reduce nature to a very anthropomorphic
> view. I
> would think that phylogeny, morphology etc. are ways to test
> biologicalspecies concepts, because based on BSC we can predict
> certain phylogenetic
> and morphological processes and patterns. Asexual "species" are not
> necessarily excluded from a "biological" species concept, they are
> by all
> means biological but their mechanisms of propagation are different.
>
> The idea of a coherent force "holding together" species is a very
> importantone. It is the force that ensures that individuals of a
> species recognize
> each other. Without that force, the whole theory of evolution
> would not
> work, because the recognition is the base of mating selection. If that
> recognition is primarily visual, the result is a strong degree of
> uniformity, as we see usually in animals. If no visual senses are
> developed,recognition is mostly chemical, which allows a much
> higher level of
> morphological variation. This is why no single plant or fungus of
> a given
> species looks like another. That phenomenon makes morphological
> speciesrecognition in plants and fungi more difficult than in
> animals (plants and
> fungi are "open" systems, whereas animals are "closed" systems
> with respect
> to their "bauplan").
>
> For me, evolution of species is like Cladonia verticillaris: if
> you look
> along a lineage, you always start with a small founder population that
> expands horizontally in time (within-species radiation) and then
> individualpopulations become isolated and genetically distinct
> (genetic "anagenesis")
> and expand again. A species along that lineage would then be the
> "interval"between founder population and expansion, before a new
> "anagenesis" happens.
> That this is something real and not abstract is shown by about 10-
> 30 million
> examples of organisms living on earth. This "verticillaris"
> concept even
> accomodates asexual lineages, because they show the same pattern
> of founder
> populations subsequently expanding (if one excludes asexual forms
> that are
> not really lineages but just parts of a complex life cycle of a single
> species).
>
> One must then also recognize that species are open systems in
> evolutionaryterms, as they always evolve from other species and
> give raise to other
> species. Here the concept of paraphyly comes to life, because
> evolution is
> not possible without paraphyly. That species can be, and are,
> paraphyletic,is a proven fact and also theoretically undeniable,
> so for me the statement
> that there is no such thing as species, by a cladist, is a way of
> workingaround the paradox of paraphyly: if you cannot explain away
> paraphyly in
> species, then just explain away the existence species to get rid
> of the
> problem. In practice, this does not solve anything because the
> underlyingphylogeny is exactly the same and the problem is
> basically one of
> terminology. Lineages can be nested within other lineages, but
> according to
> cladists, taxa cannot be nested within other taxa. This is because
> taxa are
> entities that group together horizontal sections through lineages
> that all
> have the same common ancestor. So, strictly speaking, if species
> are taxa,
> they cannot be accepted as such because they are nested within
> each other.
> If we recognize species as expanding lineages instead of taxa,
> then we solve
> that problem. The problem is also solved if taxa are defined as
> equivalentsof portions of lineages, not as groups of horizontal
> sections.
> Hybridization and other "crazy" things, as Brendan mentioned, add
> anotherdimension to the problem. Coincidentally, I recently heard
> a bryophyte talk
> in which the presenter had difficulties to accept a paraphyletic
> genus. He
> had no difficulties at all to accept species that clearly were
> demonstratedto be the origin of hybridization. I think there is no
> way around accepting
> the fact that hybridization can create species. But then, a hybrid
> has two
> ancestral species, which not only makes the ancestors paraphyletic by
> definition but also the hybrid polyphyletic. Is it logical to accept
> paraphyletic and polyphyletic species without naming them so, but
> at the
> same time deny the existence of paraphyly in nature, especially if all
> higher taxa are ultimately based on species events?
>
> Robert
>
>
>
> On Thu, Oct 8, 2009 at 2:03 PM, Brendan Hodkinson <
> brendan.hodkinson@duke.edu> wrote:
>
> > OK, John, I'll take the bait. There is no question that sexual
> > reproduction creates forces that maintain uniformity (and keep
> members of
> > 'species' morphologically and molecularly similar to one
> another). When
> > these forces break down permanently because of some reproductive
> barrier, we
> > generally call that a 'speciation' event. This is obviously
> based on a
> > Biological Species Concept (BSC), but from my perspective, that
> is the only
> > 'real,' justifiable species concept; however, other species concepts
> > (phylogenetic, morphological) are perfectly valid in that they
> provide> excellent insight into what the biological species are
> likely to be
> > (biological species are very hard to demonstrate experimentally,
> especially> for cryptogams, so the BSC is not practical for our
> purposes).>
> > Of course, this leaves out asexual organisms, and those must be
> > pigeon-holed based on similarity, because the species are not
> 'real' but are
> > merely names for phylogenetic entities possessing unique
> innovations that
> > have altered the course of their evolutionary history (no
> different from
> > genera, families, etc.).
> >
> > We must also not forget hybridization, polyploidy, etc., which
> can throw a
> > wrench in the system. These events can have major effects and
> cause instant
> > 'speciation' (reproductive isolation) even though they are
> seemingly quite
> > rare. In some cases you can get new species with multiple
> progenitor> species. I don't think we really have a good idea of
> how big a role this
> > plays in fungi yet, but I really wouldn't be surprised to find
> all sorts of
> > crazy things going on in lichen-forming fungi!
> >
> > People like Brent Mischler are valuable in academia because they
> challenge> us to think in different ways. If your perspective is
> only phylogenetic,
> > then it is true that the word 'species' means nothing. However,
> if you can
> > use a combination of molecular and morphological features of
> organisms, you
> > can begin to infer biological species by assuming that there are
> forces> maintaining some degree of uniformity within each unit
> (but as I implied
> > above, this is not always a sound assumption).
> >
> > You've thrown out red meat here, and I recognize that now I'm
> just piling
> > it on!
> >
> > All the best,
> > Brendan
> >
> > http://www.duke.edu/~bph8/
> >
> >
> > On Thu, Oct 8, 2009 at 1:31 PM, <Johngguccion@aol.com> wrote:
> >
> >> Dear Lichenonetters,
> >>
> >> I wonder how many of you are aware of a parallel universe on
> the internet
> >> called Bryonet. You
> >> can join it free of charge at bryonet-l@mtu.edu For the second
> time in
> >> as many years, professional
> >> bryologists have begun a vigorous discussion and debate about
> the nature
> >> of bryophyte species and
> >> speciation. And it all began this time when a graduate student
> from Spain
> >> rather meekly inquired if
> >> anyone knew something about local bryophyte endemics. The
> debate became
> >> quite interesting when
> >> one professional bryologist said, "there is no such thing as
> "species" or
> >> "speciation" in contrast to
> >> another bryologist who said that his main objective was to identify
> >> species daily! I encourage you all
> >> to follow this rather rambling but very interesting discussion on
> >> Bryonet. I think that a discussion of
> >> lichen species and speciation is long overdue, especially in
> light of the
> >> apparent recent importance of
> >> such things as ascus tips and DNA sequencing! So where do you
> stand>> lichenonetters? Are you with Brent Mischler who believes
> "there is no such
> >> thing as "species" or "speciation"? Or are you with David
> >> Wagner who has spent much of his lifetime learning to identify
> every plant
> >> species in Oregon?
> >>
> >> Cheers,
> >>
> >> John G. Guccion
> >>
> >
> >
>
>
> --
> Robert L�cking, PhD
> Collections Manager and Adjunct Curator
> Department of Botany
> The Field Museum
> 1400 South Lake Shore Drive
> Chicago, IL 60605-2496
> USA
> Phone: 1-312-665-7154
> Fax: 1-312-665-7158
>

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