cichla wrote:At a specific locality almost all modern 'species concepts' (there are more than two dozen serious concepts published) would recognize the same number of species. And all modern species concepts claimed to detect 'natural' entities as species. I am convinced that the so called 'Biological Species Concept' is not the only one which deals with biological units.
I disagree with two things. First, I think different species concepts precipitate in vastly different amounts of species being recognized. I think there is plenty of evidence for this even within the cichlids. Second, not all species concepts deal with the unit "species" as a
natural entity (see Mayr). Sure enough, all species concepts have the goal to categorize the fauna and flora according to some criteria that can be objectively assessed. But the biological species concept is the only one that ties species delineation to a relevant evolutionary mechanism, that being reproductive isolation. Other species concepts build on that, but use indirect metrics (i.e., the phylogenetic species concept). I - coming from the perspective of somebody that studies the
process of speciation - think that this is important to distinguish, as different metrics can lead to vastly different conclusions about species status. On one extreme, you have approaches purely based on phenotypic assessment, which usually completely ignore that a phenotype is actually the product of an interaction between genome and environment and does not necessarily have any implications on reproductive isolation among groups of individuals (recent Australoheros descriptions are a perfect example). On the other extreme you have species definitions purely based on genetic markers. These can provide you with very insightful historical perspectives; groups of organisms that show up as distinct genetic lineages obviously have been reproductively isolated for some time. This, however, ignores a crucial part of the biological species concept ("potentially" interbreeding) and - at least with old school methodology focusing on single markers - underestimates the potential for reticulate patterns of genetic divergence (gene flow patterns at different markers may reveal alternative patterns of divergence). So, the question is what you would like to achieve with recognizing a species. I am well aware this is a systematics related forum, hence the objective is the classification of biodiversity. I come from a slightly different angle. My objective is not what biodiversity is, but how it came to be. That's probably why I rarely have constructive things to say about how to put things into particular boxes (name certain populations one way or the other). The main reason why I somewhat lost my enthusiasm for taxonomy as a student was because it stroke me as awkward that our systematic system does not recognize the dynamic nature of biodiversity (lineages split, merge, and go extinct by myriads of mechanisms). By no means I have a constructive solution to the problem (I'm not sure anybody has so far), but I'd like to advocate that people take a broader perspective. Sometimes I get the feeling that systematics is a business of lawyers rather than biologists, and even if the biological species concept is not most practical for taxonomic purposes, it does illustrate perfectly well that it may be worth thinking about the processes creating what we are all interested in: species. Long rant... I know... but species are real... and they are not easily categorized because they are not static but dynamic entities of biodiversity...
Cheers, m
