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. 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). 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.
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. Reproductive isolation, even thought it is strong evidence of lineage independence it is the hardest to obtain, almost never available. 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. 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. 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. Sites and Marshall4 present a review with nine methods with empirical examples to delimite ES. 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. 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.Įvolutionary species can be delimited by a number of methods, I will present some works in which ESC is used and ES are delimited. The SC that are operational are thus not species concepts, should be reinterpreted as delimitation methods of ES 2. The ESC is not relaxed in the true nature of species, and is only answering the first question. Several authors have argued for the distinction of these two questions considering it the root of the “species problem”1, 2,3. The species concepts should answer the question of what is a species? rather than, How can we delimite species?.
Species Concepts and Phylogenetic Theory: A Debate. Populations, Genetic Variation, and the Delimitation of Phylogenetic Species Systematic Biology, 1992, 41, 421-435 But on observational features, the unique combination of character states of the PSC gives us a testable hypothesis. The way we could distinguish among species is the unique combination of character states.Īs the species are not external, and our knowledge about the organisms is not immaculate, we need a concept not based on abstract or unpractical characteristics (i.e., niche, reproductive isolation, percentage rules). The PSC (sensu Wheeler & Platnick, 2000), has the advantage that is not worried about the evolutionary mechanisms that have caused the species, but the way how could we distinguish them. The inference about the history of the groups is an after activity to its delimitation (Davis & Nixon, 1992). That system or classification needs to reflect the history of the group, in which the species are contained.Īlthough the delimitation of the species is related to the classification, they are not the same. As the species are the basic units which different biological programs work with, (and not all the researchers are experts in the groups) a feasible way to communicate its necessary. The transference of the knowledge is part of any activity, and the basic research in biology is not the exception.