Evolving Thoughts

I was going to write a killer piece on the naming of a species of spider for Stephen Colbert, but that rat bastard Carl Zimmer, who I am convinced never actually sleeps, beat me to it. So instead I will ignore the layers of irony that the naming of a spider for a fictional conservative offers to semantic strip mining, and discuss the species concept that Jason Bond ("Bond. Jason Bond") and his collaborator Amy Stockman used to identify and discriminate these species. But first, here's the interview (or "sketch", as the Colbert writers call it) between Colbert and Bond (which I can't access because of its popularity, I guess, or the US-Australian link being confused about the date):

In the paper - the full citation for which is

Bond, J., Stockman, A. (2008). An Integrative Method for Delimiting Cohesion Species: Finding the Population-Species Interface in a Group of Californian Trapdoor Spiders with Extreme Genetic Divergence and Geographic Structuring. Systematic Biology, 57(4), 628-646. DOI: 10.1080/10635150802302443

the authors discuss at great length the conception of species they are employing here. The first paragraph is this:

Although it is generally accepted that species comprise lineages (De Queiroz, 1999, Sites and Marshall, 2004), how lineages are diagnosed or recognized as species remains a strong point of contention (Wake, 2006). It is this point of contention that has captured the interest, thought, and imagination of many practicing systematists and evolutionary biologists because species constructs, by definition, convey an almost immeasurable number of questions and hypotheses—Are populations isolated reproductively? Are they ecologically interchangeable? Does migration occur and at what frequency? Are lineages genealogically exclusive (what genes or subset of genes are exclusive)? Does introgression occur when populations come into contact? Despite the complexity of questions raised by virtually any species construct, many of them lack the requisite rigor they seemingly imply. For example, many species hypotheses are based on a single character system (e.g., genitalia) or single class of characteristics (somatic morphology) and are sometimes based on very few individual specimens (in some cases only one; see Huber, 2003, for a summary of spider examples). Delimiting species that represent real evolutionary lineages that summarize a set of well-founded hypotheses requires an integrative approach that accounts for multiple lines of evidence, if informed decisions regarding conservation of habitat and populations are to be made, and if we are to study speciation pattern, diversification, and process in a rigorous manner.

So what conception do they use? The so-called "cluster concept" or Alan Templeton's 1989 "demographic replaceability" concept . Unlike Mallet's later version (1995), which is based solely on genetic loci (and which is in my view properly called the Cluster conception - Templeton's I think of as the Two Criteria conception - niche adaptation and genetic similarity), Bond and Stockman use a number of criteria, including geographical range, sexual morphology and so on to identify whether or not the group is one species or many, and they divide previously named species into several on this basis.

Usually, taxonomic inflation, as this is sometimes called, is based on a version of the phylogenetic species conception that I call the Diagnostic species conception. A similar effect is based here on the use of diagnosis - by introducing novel (or colalting in a novel way previously used) criteria for identifying species, both the Cluster Concept and the Diagnostic Concept introduce more discriminata, and if you can discriminate it, then it is a new "species" in the logical sense. The inflation results from having more ways to cut the species pie, to coin a phrase.

So, did Colbert get a new species named after him or not? Is his "species" just a morph or variety of the old species? Therein lies the problem. Species is not, I think, an absolute rank or grade of organization, so there really is no simple fact of the matter. That being so, a species is what you notice when a number of lineages - of genes, haplotypes, populations, morphotypes, and so on, all tend to coincide. Reality being unkind to systematists and philosophers, there are many cases in which there is a lack of perfect coincidence, and this is one of them. So Colbert is just going to have to reconcile himself to ambiguity, something real conservatives tend to find disquieting...

Refs

Mallet, J. 1995. The species definition for the modern synthesis. Trends in Ecology and Evolution 10 (7): 294-299.
Templeton, Alan R. 1989. The meaning of species and speciation: A genetic perspective. In Speciation and its consequences, edited by D. Otte and J. Endler. Sunderland, MA: Sinauer: 3-27.