domingo, 16 de septiembre de 2007

Rebuttal from the ESC
The species concepts should answer the question of what is a species? rather than, How can we delimite species?. Several authors have argued for the distinction of these two questions considering it the root of the “species problem”1, 2,3. The ESC is not relaxed in the true nature of species, and is only answering the first question. The SC that are operational are thus not species concepts, should be reinterpreted as delimitation methods of ES 2. The fact that ESC does not provide a clear delimitation criteria is not a weakness, it is indeed one of the advantages of this SC that permits to use not only one delimitation method but almost all methods are suitable for this purpose 4.

Evolutionary species can be delimited by a number of methods, I will present some works in which ESC is used and ES are delimited. Wiens and Penkrot5 review three approaches for species delimitation (tree-based with DNA data and tree-based and character-based with morphological data) in Sceloporus lizards, Also as in my previous empirical post and other works 6,7,8,9 genealogical concordance of multiple gene trees is a criteria to delimit ES, the results of this analysis are independent lineages regardless of whether in the analyses one looks for pattern or for process. Sites and Marshall4 present a review with nine methods with empirical examples to delimite ES. Disagreement between species boundaries inferred from different data types raises several important questions 5, each particular case has its own way to approach delimitation, and the decision of assigning species boundaries and hierarchy implicit in it should be based on the previous knowledge of the study group and its variability, as well as availability of the data.

It is a misunderstanding when ESC is equated to BSC, they are enormously different SC, first, the universality of the concept, ESC is applicable to all the forms of life, and BSC only to sexual forms. Second, ESC does not have as the only and predominant method for species delimitation the biological criteria, it is not the goal to find reproductive isolation or genetic distances, the goal is to identify independent lineages, with all the evidence available. Reproductive isolation, even thought it is strong evidence of lineage independence it is the hardest to obtain, almost never available. The strength of this concept is precisely to be open about evidence and methods, and surely we can not restrict ourselves to reproductive isolation as the only evidence.

When I stated that under the PSC ( sensu Wheeler and Plantnik ) every subpopulation will be named a species, I was not worried about number of resulting species, but the relationships among them, i.e. tokogenetic relationships within a species, following Hennig’s emphasis in differentiating tokogeny (parent-offspring relationships) from phylogeny, descent relationships among certain groups of organisms (i.e., species). In a ES there shouldn’t be tokogenetic relationships, is in this way (allowing species within there is tokogenetics relationships), that there is a genealogy denial in the PSC, no matter if in the posterior phylogenetic analyses this presents a problem or not.
References
  1. Wheeler, Q. D. and Meier, R. (Editors). 2000. Species Concepts and Phylogenetic Theory: A Debate. New York: Columbia University Press.
  2. de Queiroz, K. 2005. Different species problems and their resolution. Bioessays 27:1263-1269.
  3. Wiens, J. J., M. R. Servedio. 2000. Species delimitation in systematics: Inferring diagnostic differences between species. Proc. R. Soc. London Ser. B. 267:631–636.
  4. Sites J. W., Marshall. C. J. 2003 Delimiting species: a Renaissance issue in systematic biology Trends Ecol. Evol. 18: 462
  5. Wiens, J.J. and Penkrot, T.A. 2002.Delimiting species using DNA and morphological variation and discordant species limits in spiny lizards (Sceloporus). Syst. Biol. 51, 69–91
  6. Templeton, A. R. 2001. Using phylogeographic analyses of gene trees to test species status and processes. Mol. Ecol. 10:779–791.
  7. Dettman, J. R., D. J. Jacobson, and J. W. Taylor. 2003. A multilocus genealogical approach to phylogenetic species recognition in the model eukaryote Neurospora. Evolution 57:2703-2720.
  8. Starrett J. and Marshal H. (2007) Multilocus genealogies reveal multiple cryptic species and biogeographical complexity in the California turret spider Antrodiaetus riversi (Mygalomorphae, Antrodiaetidae). Molecular Ecology 16:3, 583–604.
  9. Taylor, J. W., D. J. Jacobson, S. Kroken, T. Kasuga, D. M. Geiser,D. S. Hibbett, and M. C. Fisher. 2000. Phylogenetic species recognition and species concepts in fungi. Fungal Genet. Biol. 31:21–32.