[Taxacom] Metapopulation lineage species concept

[Stephen Thorpe]

> Just because there are many alternative species concepts does not throw doubt on the One True Species concept (which in my opinion is:  there isn't any, and systematics exists to classifiy species, not 
> necessarily to figure out how they variously originated).

This statement is a big confusion! 

>systematics exists to classifiy species, not necessarily to figure out how they variously originated

The species concept determines what it is that systematics is supposed to classify ... it isn't just about how species originated. In fact, it had better NOT make assumptions about that - assumptions that could turn out to be false ...

There are two ways of understanding "alternative species concepts": one reading ("subjectivist") is that we can simply choose an alternative and do systematics with it. The other (my understanding) is that the alternative species concepts are each competing theories on what it is that we mean by species when we do systematics.

Needless to say, I still think the BSC is it...


________________________________________
From: taxacom-bounces at mailman.nhm.ku.edu [taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard Zander [Richard.Zander at mobot.org]
Sent: Sunday, 18 October 2009 4:56 a.m.
To: Jody Haynes; taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Metapopulation lineage species concept

A small splash, a wavelet:

Just because there are many alternative species concepts does not throw doubt on the One True Species concept (which in my opinion is:  there isn't any, and systematics exists to classifiy species, not necessarily to figure out how they variously originated).

The phrase "separate evolutionary trajectories" is loaded. If you feel that all (molecular or morphological) lineage splits are followed by gradualist accumulation of important traits in the daughter lineages, then you have separate evolutionary trajectories, but gradualist evolution in all taxa (based on expressed traits) is contradicted by fact. Taxa commonly remain in expressed-trait stasis for hundreds of thousands or millions of years. An ancestral taxon theoretically might have many daughter taxa that have separate evolutionary trajectories, but remain static. In any cladogram, you can have n minus 1 ancestral taxa.

Practically, two isolated populations may not have separate evolutionary trajectories if stabilizing selection is the same for both. Suggesting that neutral traits can accumulate differentially in each is an okay explanation for some situations of geographically isolated species-pairs, but many long-isolated populations stay identical (in expressed traits, though accumulating non-coding traits) for geologically long periods. The observation for these should be that neutral traits do not accumulate for some reason (e.g. for that particular habitat, any neutral traits possibile within phyletic contraint of structure and habitat are quickly stomped on).

Sometimes, sometimes a new approach simplifies scientific work, reveals a True Path based on fact, betters facility of reason, and is celebrated. Most times, new approaches are quick fixes or cartoons.

_______________________
Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org


________________________________

From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Jody Haynes
Sent: Wed 10/14/2009 7:43 AM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Metapopulation lineage species concept



Thanks, Alex. Point taken.

As a non-taxonomist who has described new species and who has struggled his entire professional life with various species concepts, I find de Queiroz's simplistic and elegant explanation of "the species problem" both refreshing and illuminating. Specifically, according to my understanding of the "general metapopulation lineage concept of species," the fact that two groups of connected populations are evolving separately is sufficient for them to be considered separate species, regardless of whether the two groups have acquired any or all of the properties that those who adhere to any of the 20+ contemporary species concepts would consider as 'necessary' for the two groups to be considered valid species (i.e., intrinsic reproductive isolation, monophyly, ecological distinctness, diagnosability, etc.). The actual 'contingent' properties involved (or recognized as 'important') are irrelevant; rather, it is the very fact that the two groups currently have separate evolutionary tr
 ajectories that is sufficient for them to be considered distinct species. >From a conceptual standpoint, this generalized species concept represents a significant paradigm shift away from the 20+ myopically focused (and admittedly biased) 'species concepts' and toward a unified concept that is more inclusive and more general-with the 20+ myopic concepts now appropriately relegated to nothing more than specific examples of the general concept. In application, I see this as a significant advance as well. because now one simply needs to present (and justify) a testable hypothesis as to how any given group (metapopulation lineage) is distinct from other such groups as a means of identifying (or circumscribing) a species. Different approaches of study (and types of data gathered) will obviously focus on different 'contingent' properties, but the ultimate goal is simplified because one simply needs to show how a given group of populations are connected genetically and evolving sepa
 r
 ately from other such groups.



Bracing for the tsunami...



Jody



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