miércoles, 21 de julio de 2010


Jiménez- Silva C. L.

The ratings are the historical framework for interpreting the patterns of similarities between taxa, ecological interactions and their geographic distribution (Brooks, 1981; Cracraft, 1983; Eldredge and Cracraft, 1980; Farris, 1979) The species has been considered the foundation in construction of classifications of the trees evolutivos.Las different versions of the phylogenetic species concept is characterized by accepting the evolutionary and biological conception and to delimit the species in one way or another. Hennig defined the species as "groups of individuals who are interconnected by tocogèneticas relations are called species (Hennig 1996). Then Hennig believed that: "The species should then be defined as a complex of spatially distributed reproductive communities, or if we call this relationship in the" vicariance "as a vicariant complex communities of reproduction" (Hennig 1966)

The species can be considered a species level, among all those available in the hierarhy filogenética. Only monophyletic groups can be recognized and formally named taxa. This principle is based on the groups which include all the descendants of a single common ancestor are the only groups with real and natural existence in relation to the evolutionary process (De Luna and Mishler, 1996). The phylogeny or the search for parsimonious cladograms formal and robust only to discover monophyletic groups and build a classification according to Mishler. Mishler and Donoghue (1982) also split two operational aspects of species recognition. First, agencies may be grouped into species based over monofilesis evidence (autopomorphies), as is the case in the other taxonomic levels. The criteria for crossover in particular should not be used for purposes of grouping. Second, the criteria to assign species status to certain monophyletic groups should be pluralistic, ie, they vary in different organisms. Theriot is, agree to the taxa at the species level should be distinguished by discrete apomorphic states rather than by total or plesiomorphic similarity (Theriot, 1992).

Other authors such as Wiley says, "An evolutionary species is a single lineage of ancestral-descendant populations which maintains its identity from other lineages and have their own evolutionary tendencies and historical fate" (Wiley 1978). In this case the species is formed by organsmos evolve independently, while maintaining the identity to other lineages, which is maintained through relations that are generated lattice throught mating among similar organizations. From this it follows that the species is well defined independent biological units to be guided by evolution and that holds it together through reproduction (De Haro 1999)

Cacraft states that a species diagnosable smaller group of individual organisms in which there is a pattern of parental ancestor descendant (Cacraft 1983). To this author is an indispensable part of the definition to diagnose the species in question. For some like De Haro (1999) this is beyond the interest of the dynamics of the process since we are not able to diagnose the species exist and our limitations do not affect the process.

The phylogenetic species concept as Nixon and Wheeler: "the smallest aggregation of populations (sexual) or lineages, (asexual) diagnosable by a unique combination of character states in comparable individuals (semaforontes)" (Nixon and Wheller 1990). This definition of species differs little from the Cacraft in depth, but it is operationally more precise phylogenetic studies, which are those that may eventually shed light on these patterns of segregation and on the basis of which should be the separation of the species and is the grouping of these terminals evolving information which may eventually define a more precise and natural supraspecific categories. This definition creates a working tool for the detection of minimal terminals for phylogenetic analysis (Davis and Nixon 1992). Species are groups of organisms that evolve together and are able to maintain its own identity distinct from grups. These other species are different because they have diverged evolutionarily and not because they are different according to the human eye.

Haro, J.J. 1999. ¿Qué es una especie?.Bol. S.E.A. 26:105-112

Nixon, K. C., and Q. D. Wheeler. 1990. An amplification of the phylogenetic species concept. Cladistics 6:211±223

Cracraft, J. 1983. Species concepts and speciation analysis. Current Ornithology 1:159±187.

Hennig, W. 1966. Phylogenetic systematics. Urbana, IL: University of Illinois Press.

Wiley, E. O.,1978. The evolutionary species concept reconsideres. Syst. Zool., 27: 17-26.

Mishler, B. D., and E. de luna. 1997 Sistemática Filogenética y el concepto de especie.Bol. Soc. Bot. México 60: 45-57