Who is Right?

Susana Ortiz B.

Although it is true the species concept has been controversial and approached from multiple perspectives throughout history, its applicability and acceptance depends on how well to recognize, identify and understand the species in nature hence its relevance in areas like conservation, ecology, evolution, taxonomy and of course systematic. The Biological Species Concept (BSC) is perhaps the most widely accepted species concept in biology, it defines species in terms of interbreeding and reproductive isolation (Mayr, 1963). This lats feature based on barriers to gene flow between populations includes not only geographic isolation but also prezygotic factors such mate choice, and fertilization incompatibilities and postzygotic factors i.e., hybrid inviability and sterility caused by genomic incompatibilities (Dobzhansky, 1937). However, in practice this concept involves some difficulties mainly in relation to hybridization, asexual populations, adimensionality and not distinction between reproductive isolation and the speciation´s process (Mallet, 2007; Fernandez et al., 1994; Templeton, 1989).

In view of this scenario, emerges the Phylogenetic Species Concept (PSC), which stablishes the recognition as criterion for species delimitation through characters; despite the multiple versions, the PSC proposed by Eldredge and Cracaft (1980) and later rephrased by Cracraft (1983) conceives the specie as “…the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent”, the above entails some operational advantages, such as its applicability to fossils and all evolving systems of living things whether sexual and asexual populations and you do not need to know or understand the process driving speciation in order to recognize species (Claridge et al. 1997; Nelson and Placnick, 1981) . Under this concept the pattern of characters distribution in nature provides testable evidence of the existence of species in nature (Wheeler, 1999), additionally it seems to return to typological species concept given its confinement to diagnostic characters, nonetheless, the PSC emphasizes the relationship between unique combination of inherited characters either molecular or morphological and an ancestral–descendant sequence.

According to Cracraft (1989), species defined under this diagnostic criterion are real taxa suitable for phylogenetic analysis and evolutionary studies, being so is necessary to take special care of strict application rather in small groups and polymorphic species if unknown genetics aspects, geographic distribution and demography of the group, this in order to avoid underestimating the intraspecific variation and therefore the wrong multiplication of species (Mallet, 2007; Fernadez et al., 1995); However, to counteract such diagnosable groups have no authentic parental pattern of ancestry and descent (Cracraft, 1989). Another relevant aspect of the diagnostic species concept is the fundament of this diagnosticability that is the characters as synapomorphies or autapomorphies or simply characters as descriptors indistinctly of their historical background. This latest maybe is the most permissive given that it has not conflict in to recognize cladogenesis or anagenesis indistinctly and can be monophyletic or non-monophyletic. On this basis, also the concept is ambiguous because it could behave like synapomorphy, autapomorphy or simplesiomorphy in the same branch, also the major practical difficulties include determining whether shared traits have attained fixation in the population (Wiens and Servedio, 2000) and the inapplicability of this approach to most continuously varying quantitative traits (Willmann and Meier, 2000).

The monophyly criterion of species is an important component in synapomorphic and autapomorphic versions of the PSC, thus, they do not recognize the phyletic change or anagenesis, just the cladogenesis as evolutionary process. Following the above, in cladogenesis from a stem species, subspecies may first appear and then a new species with acquisition of apomorphies, nevertheless, the autapomorphic concept could recognize subspecies as species before the consolidation of the cladogenesis (De Haro, 2005); other problem is that it excludes the existence of stem-species by definition, since these can neither be monophyletic, nor can they possess autapomorphies, relative to its own descendant species since they inherit their "autapomorphies", so that the former autapomorphies of the stem-species become the autapomorphies of the resulting monophylum and thus become symplesiomorphies of the stem-species (Wheeler, 1999; Wheeler and Meier, 2000). On the other hand, the PSC based on synapomorphy, addresses the species problem from a perspective different, perhaps this is synapomorphy and monophyly in terms of relations among species and their characters (Hennig, 1966), but at this level should reflect the branching, or cladistic, relationships among species (Goldstein and De Salle, 2000), ie, the synapomoraphies may show the phylogenetic relationships of two or more species belong to a monophyletic group, then take this group as a single species is inadequate and even more when the historical status may be unresolved. Maybe, monophyly is an ambiguous concept whose problem lies a fundamental distinction between species and monophyletic taxa, where species form mutually exclusive reticulated systems, while higher taxa form inclusive hierarchical systems (Rieppel, 2009).

Finally, although in many contexts the PSC emphasizes a diversity of mechanisms that can give rise to real species in nature and that are not all recognized by the BSC (Claridge et al. 1997), operational difficulties exist for the identification of distinct historical entities in nature regardless of the phylogenetic species concept applied (Frost and Kluge, 1995), however, seems that the most adequate species concept is perhaps the autapomorphic concept in despite of its difficulties, without this meaning that it is the right or the universal criteria by which species may be delimited, it is just a good approximation to define and recognize the diversity of life.

References

Claridge, M. F., H.A. Dawah, and M. R.Wilson. 1997a. Practical approaches to species concepts for living organisms. Pp. 1–15 in Species: The units of biodiversity. Edited by M. F. Claridge, H. A. Dawah, and M. R. Wilson. London: Chapman & Hall.

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

Cracraft, J. (1989). Speciation and its ontology: The empirical consequences of alternative species concepts for understanding patterns and processes of differentiation. In Speciation and its Consequences (D. Otte and J. A. Endler, Eds.), pp. 28–59. Sinauer Associates, Sunderland, MA

Dobzhansky, T. 1937. “Genetics and the Origin of Species.” Columbia Carpenter, J. M. (1992). Random cladistics. Cladistics 8, 147–153.

Eldredge, N., and J. Cracraft. 1980. Phylogenetic patterns and the evolutionary process. New York: Columbia University Press.

Fernández, F., Hoyos J. M. and D. R. Miranda. 1994. Biodiversidad, Extinciones y el Problema de la la Especie. Colombia: Ciencia y Tecnología. 12 (4).

Fernández, F., Hoyos J. M. and D. R. Miranda. 1995. Especie. Innovacion y Ciencia. 32-37.

Frost D. R. and A. G. Kluge. 1995. A consideration of epistemology in systematic biology, with special reference to species. Cladistics 10:259-294.

Goldstein, P. Z., DeSalle, R., Amato, G., and Vogler, A. P. 2000. Phylogenetic Species, Nested Hierarchies, and Character Fixation. Cladistics 16, 364–384.

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

Mallet, J. 2007. Species Concepts Of. University College London Trans. Encyclopedia of Biodiversity. 10, 294–299

Mayr, E. 1963. Animal species and evolution. Cambridge: Belknap Press of Harvard University Press.

Murphy, F. A., C. M. Fauquet, D. H. L. Bishop, S. A. Ghabrial, A. W. Jarvis, G. P. Martelli, M. A. Mayo, and M. D. Summers (ed.). 1995. Virus taxonomy: classification and nomenclature of virus, p. 415±421. Spring-Verlag, New York, N.Y.

Nelson, G., and N. I. Platnick. 1981. Systematics and biogeography: Cladistics and vicariance. New York: Columbia University Press.

Rieppel, O. 2009. Species monophyly. Journal of Zoological Systematics and Evolutionary Research. 48 (1), 1-8.

Templeton, A. R. 1989. The meaning of species and speciation: A genetic perspective. In “Speciation and Its Consequences” (D. Otte and J. A. Endler, Eds.), pp. 3–27. Sinauer Associates, Sunderland, MA.

Van Regenmortel, M. H. V. 1990. Virus species, a much overlooked but essential concept in virus classification. Intervirology 31:241±254.

Wheeler, Q. D. 1999. Why the phylogenetic species concept? -elementary. Journal of Nematology 31:13–141.

Wheeler, Q. D., and R. Meier, eds. 2000. Species concepts and phylogenetic theory: A debate. New York: Columbia University Press.

Willmann, R., and R. Meier. 2000. A critique from the Hennigian Species Concept Perspective. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 101-108, Columbia University Press, New York.

Wiens, J. J., and M. R. Servedio. 2000. Species delimitation in systematics: inferring diagnostic differences between species. Proc. R. Soc. London, Ser. B 267:631-636.

Species Concept: position

D.F.Silva

Pluralism of concepts: the PCS

D.F.Silva

There are three basic concepts phylospecies. one of them, initially defined by Hennig, is the Henniano species concept (Meier & Willmann 2000). Henniana convention: if new species arise from division from a parent species, then I would say the parental species is not monophyletic (now paraphyletic), has been lost and now there are two new species. The second concept is called phylospecie Concept synapomorphic. A species is one in which no beyond there taxonomic division or subdivision is the phylogenetic analysis unit. The version of Mishler adds it on this concept, the vision of that species should be monophyletic. The phylospecie third concept of the so-called Autopomorphyic concept, according to one version of Wilkins. The concept is called diagnosis. this concept is derived from the work tends to Rosen.este rely on the diagnosis of taxa or is a completely epistemological notion of species. All concepts that rely on autapomorficos species is the terminal taxon in a cladogram.

Hennig is often read as: species cease to exist when they are divided bone when relationships end hologenetics be a simple set. hennig but assumes that species are reproductive communities genes harmonic butler, as he had said Dobzhansky, and that species are reproductive groups as Mayr said, however hennig assumes that species are reproductive lineages. but the most important aspect of the definition lies in the dimencion hennig time where the note that species have to be bounded by speciation event "The limits of the species in a longitudinal section through time could therefore be determined by two processes of speciation: one which rise as an independent reproductive community and one which travez the descendants of these initial populations ceased to exist as one homogeneous reproductive community. When some of the relationships between individuals tokogenetics of a species no longer exist, that breaks into two species and ceases to exist.

The criticisms have not been expected and appeared to be a delineation somewhat arbitrary to species taxa. this has come to call Hennig convention. the Hennig the concept of the species has been expanded by Meier & Willmann. hennnig proposed a modified concept: species are natural populations reproductively isolated groups of wild populations. they originate by way of the dissolution of the stem species of speciation events and cease to exist travez of speciation or extinction. hennig basically the concept of species is a concept of biomolecules as has hennig accepted that reproductively isolated species were exposed and that the criteria used identifying relevant edges of the clades are phylogenetic simply those of biospecies or BCS. The extinction is a taxonomic extinction.

Synapomorphic species

The Concept is special because although Brent Mishler has defined Cracraft the species taxon as the smallest diagnosable cluster organisms within which there is a pattern of ancestry or descent. Mishler and monophyletic version: a species is the most inclusive taxon recognized in a classification into which organisms are grouped together because evidence of monophyly (usually, but not restricted to the presence of synapomorphies) such that it is positioned as a species because it is the smallest lineage important. and redefine monophyly: A monophyletic taxon is a group that contains all and only descended from a common ancestor originandoce in the same event.

Synapomorphic species are usually based on historical lines ancestry current offspring that are represented in a cladogram. as a phylogenetic taxon species is a synapomorphy shared by agupada for individuals that show monophyly .The definition of Mishler and Theriot: a species is the most inclusive taxon recognized in a formal phylogenetic classification. As with all levels levels of taxa in such classifications grouped organisms within species because of evidence of monophyly. taxa are classified as species because they are the groups phylogenetic smaller. monophyletic conception here is explicit. dual nature of the epistemic and the ontological aspects are expressed notably marked and the range of species lineages is restricted to biologically important. De Queiroz and Donoghue [1988, 1990] do not think that species have to be monophyletic because the monophyly of the populations does not provide a way to specify which is the basis of the range.

Autapomorphyc Species or diagnostic.

Diagnosis of the species has been embroiled in a debate. species have diagnostic autapomorphies whereas higher taxa are synapomorphies Rosen noticed that the subspecies are by definition unobservable and indefinable. since they have no apomorphies. Nelson and Platnick tratarona species as shows just the smallest of organisms detected own perpetuation that have unique set of character . (Wheeler & Platnick 2000; 56) Almost contemporaneously Eldredge & cracaraft defined a species as a diagnosable cluster of individuals who within which there is a pattern of ancestry and descent.

PHYLOGENETIC SPECIES CONCEPT

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

Phylogenetic Species Concept

Gualdrón-Diaz J. C.

Several Phylogenetic Species Concept have been proposed. The first in applied cladistic methods to the species problem was Rosen (1978), who defined species as "a geographically constrained group of individuals with some unique apomorphous characters, is the unique evolutionary significance", after de Queiroz and Donogue (1988) argued that species should be based on monophyly and the grouping of populations supported on sinapomorphies. Although an ancestor must have existed ans must have been a species in its own time, an ancestral species according to phylogenetic theory has no autapomorphies in relation to their own descendant species (Wheeler 1999). According to this concept of the species are defined from the point of view phenotype, the level of state support monophyletic, nevertheless sometimes there is no evidence on monophyletic status of a group.

Also, Eldredge and Cracraft (1980) and Nelson and Platnick (1981) proposed similar species definitions, later amplified by Nixon and Wheeler (1990) and Wheeler and Platnick (2000); All based on defining species a unique combination of diagnosable characters; moreover, some of these concepts have in mind a pattern in the ancestor-descendant. Nevertheless this approach does emphasis in the capacity that is had to distinguish to a species of other one, which is a problem of the taxonomist and of the systematic one, which does not concern the existing organism in the nature (Haro 1999).

In spite of the different concepts proposed with relation to the phylogeny, the goal for developing a phylogenetic species concepts is to support the aims of phylogenetics systematics as the elements for reconstruction of phylogenetic history, distinguish among kinds of organisms, describe and predictively classify the diversity biological, and permit the study of evolution and comparison of clades (Wheeler and Platnick 2000).

References

Eldredge, N., and J. Cracraft. 1980. Phylogenetic patterns and the evolutionary process. New York: Columbia University Press.

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

Nelson, G., and N. I. Platnick. 1981. Systematics and biogeography: Cladistics and vicariance. New York: Columbia University Press.

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

Rosen, D. E. 1978. Vicariant patterns and historical explanation in biogeography. Systematic Zoology 27: 159±188.

Wheeler, Q. D. 1999. Why the phylogenetic species concept? -elementary. Journal of Nematology 31:13–141.

Wheeler, Q. D., and Platnick, N. I. 2000. A critique from the Wheeler and Platnick Phylogenetic Species Concept Perspective: Problems with Alternative Concepts of Species. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 133-145, Columbia University Press, New York.

de Queiroz, K., and M. J. Donogue. 1988. Phylogenetic systematics and the species problem. Cladistics 4:317-338.

An approach from phylogenetic species concept

Susan@ Ortiz B.

Even though the species concept is an important topic in the recognition and conservation of biological diversity, presently there are no a universal concept and choosing one in particular is controversial in all cases. Perhaps, just like Wheeler (1999) mentioned, there are more species concepts in use today than any other time; however, the Phylogenetics Species Concept (PSC) could be considered a good approach. According to cladistic principles, the PSC suggested by Rosen (1978), is focused to population or group of populations geographically constrained defined by one on more unique apomorphous features. After a decade, a modified version was proposed by Queiroz and Donoghue (1988), as the smallest unit determined cladistically at least one specific character. Evidently, this concept is based on autapomorphic background and therefore the species are defined under monophyly criterion. However, some practical difficulties arise about recognition of ancestral species based on autapomorphies, since, the character becomes a synapomorphy and the ancestral taxon actually differs from its descendant due to lack of the evolutionary novelty. Additionally the PSC point out against BSC the absence of reproductive isolation as a plesiomorphic character inappropriate in the delimitation of species (Wheeler and Meier, 2000) and the absence of reproductive boundaries between ancestral and descendant populations (Hennig, 1966).

On the other hand, Eldredge and Cracraft (1980) and Cracraft (1983) addressed the PSC towards diagnosable characters, establishing the specie as a diagnosable cluster or the smallest diagnosable cluster of individuals within which there is a parental pattern of ancestry and descent. Afterwards Nelson and Wheeler (1990) redefine it as the smallest aggregation of populations or lineages diagnosable by a unique combination of character states. As well this concept also is based on the relationships between species and its characters, although not necessarily imply monophyly, being that the autapomorphic characters are diagnosable, but no all diagnosable characters can be autapomorphies. This approach seems to evoke the Typological Species Concept with regard to constant diagnostic differences to identify species (Mayr, 1991); nonetheless the measure is less arbitrary because it follows a parental pattern of ancestry and descent. A critique against this concept indicates that the species exist in nature independently of the systematic’s ability to diagnose them (Haro, 1999). Obviously, diagnosable apomorphies must be sought, but this is a systematic’s problem that does not affect the organism as real entity. Another difficulty is to define the boundaries of diagnostic in polytypic species with a wide variety, which could lead to false increases in diversity and underestimation of intraspecific variation (Fernandez et al., 1995).

Despite the above, the PSC is an operational concept compatible with phylogenetic theory designed to recognize and define the groups for any characteristic, from morphological to molecular. Some fundamental components of the PSC are the weighting of the recognition against reproductive isolation and lack of a temporal dimension under BSC (Willmann and Meier, 2000), its applicability to all evolving systems, whether sexual or asexual (Balakrishnan, 2005) and the recognition that species based on observable, testable characters simply avoid the confusion imparted by considerations of modes of speciation (Wheeler, 1999). Likewise, according to Balakrishnan (2005) the major practical troubles include determining whether shared traits have attained fixation in the population (Wiens and Servedio, 2000), determining how many diagnostic traits to consider and the inapplicability of this approach to most continuously varying quantitative traits (Willmann and Meier, 2000). Finally, although PSC has not completely solved the conflict between the real species existing in nature and the criteria and tool to recognize, it constitutes an attractive approach and a step in this direction. Also emphasize the diversity of mechanisms that can give rise to real species in nature and that are not all recognized by the BSC.

References

Balakrishnan, R. 2005. Species Concepts, Species Boundaries and Species Identification: A View from the Tropics. Syst Biol.2005; 54: 689 -693.

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

Eldredge, N., and J. Cracraft. 1980. Phylogenetic patterns and the evolutionary process. New York: Columbia University Press.

Fernández, F., Hoyos J. M. and D. R. Miranda. 1995. Especie. Innovacion y Ciencia. 32-37.

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

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

Mayr , E. 1991. One long, argument, Charles Darwin and the genesis of modern evolutionary thought. Harvard University Press, Cambridge, Mass.

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

Rosen, D. E. 1978. Vicariant patterns and historical explanation in biogeography. Systematic Zoology 27: 159±188.

Wheeler, Q. D. 1999. Why the phylogenetic species concept? -elementary. Journal of Nematology 31:13–141.

Wheeler, Q. D., and R. Meier. 2000. Species Concepts and Phylogenetic Theory. Columbia University Press, New York. pp. 133-145.

Willmann, R., and R. Meier. 2000. A critique from the Hennigian Species Concept Perspective. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 101-108, Columbia University Press, New York.

de Queiroz, K., and M. J. Donogue. 1988. Phylogenetic systematics and the species problem. Cladistics 4:317±338.

Pluralism of concepts: the BSC

D.F. Silva

The idea that there is no single, right species definition, is known as pluralism, this being one response to the multiple species definitions (Maclaurin & Sterelny.2008). This pluralism is reflected in the diversity of species concepts. (Wilkins 2002) has listed 26 distinct species concepts along with synonyms. Here, I include one concepts broadly used and debated, in order to consider how to recognize species.

The BSC (biological species concept), is considered as an interbreeding concept or reproductive isolation concept (Lee 2003; Wilkins 2009 ) . The basis for this consideration lie in the concept´s specifications: Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups (Mayr 1942),

So the reproductive isolation in nature, was the key factor in identifying and maintaining species as discrete entities (Claridge 2009). But this key factor, was the principal trouble at the time to recognize the species. Thus, in practice the BSC would recognize that different species are characterized by distinct barriers, isolating mechanism or by the SMRS (the Specific Mate Recognition System of Paterson). However the species taxa are only rarely recognized by direct studies of the SMRS (Claridge 2009). Further, neither asexual nor Parthenogenetic organism can be considered under the BSC because they don’t have a functional system of mate that leads to the fusion of gametes and the reproductive isolation. The geographical variation of the populations vary from almost nothing to large differences but the reproductive isolation in the field can be determined only for sympatric populations , then the allopatric forms began to be recognized with a pragmatic approach as subspecies (Mallet 2005).

Perhaps one of the principal problems with the BSC is the practical impossibility of establish the reproductive isolation between natural populations (Balakrishnan 2005). Another point of criticism, including lack of temporal dimensión, the BSC defines the species only in some point in time (Lee 2003; Balakrishnan 2005). Under the BSC, as the other concepts related to the interbreeding concepts, the species at a given point in time are groups of organisms which interbreed with each other and are reproductively isolated from other species. Likely employing gene flow would tend to delimit the same taxa as species, and thus to depict the boundary of the species rank in the same place (Lee 2003).

Claridge, M. 2009. Species Are Real Biological Entities. In: Contemporary debates in Philosophy of Biology. (Ed. F. Ayala and R. Arp). Wiley-Blackwell. p 91-109

Lee, M. S. 2003 Species concepts and species reality: salvaging a Linnaean rank. J. Evol. Biol. 16. Blackwell Publishing ltda.

Maclaurin, J. & Sterelny, K. 2008. What is biodiversity?. The University of Chicago Press, Ltd., London. p 31.

Mallet, J. 2005. Species Concept. p367-373.

Mayr, E. 1942. Systematics and the Origin of Species from the Viewpoint of a Zoologist. Columbia University Press: New York.

Wilkins, J. 2002. Summary of 26 species concepts. Copyright © 2002 John S. Wilkins

Wilkins, J. 2009. Species: A History of the Idea. University of California Press, Ltd. London.p 197- 201.

Biological Species Concept

Jimenez Silva, C. L.

Universidad Industrial de Santander
The biological species concept defeat the "typological thinking", Mayr's foundations to refute it was the population biology vision, with which reverses the meaning of species as type and replaced with a statistical group approach. the Population biologist emphasizes the uniqueness of each thing in the organic world. Individuals, or any kind of organic entity, build populations from which we can determine the arithmetic mean and the statistical variation. Averages are merely statistical abstractions, only individuals have actually made up of those populations. For the typology, the type (eidos) is real and the variation an illusion, while for the population biologist the type (average) is an abstraction and only the variation is real. (MAYR, E. 1959)

A population forms a "specie" only with respect to other populations. Belonging to a different specie is not about differences, it is about distinguish and relate. The Biological interpretation introduce to the multidimensional concept of species, which means that it should be considered as a group of stocks that actually or potentially interbreed. Such species, to preserve their identity, can't coexist in the same place at the same time, applying the concept to allopatric species is determined on the possibility of mutual intersection. As the concept of "species" as Mayr that applies to biological individual, acquires a double meaning: on the one hand it refers to the dimensionless-that Mayr interpreted as the reproductive continuum, and secondly, concerns to the multidimensional condition, whereby the possibility of gene flow can be almost unlimited. It also includes raising Population meaning: "The species are natural population groups really or potentially interbreeding , reproductively isolated from other similar groups" MAYR, E. (1942). Comparable to those proposed by Dobzhansky, 1941, stating: "A species is a reproductive community wider ... of sexual individuals and that fertilize each other, they share a common gene pool".

One of the problems of the species is limited to the consequences of consider it was the result of a "category of thought" taking it to an artificial incompatible condition with the biological reality. Mayr criticizes the taxonomists, who believe that this concept treats individuals as an aggregate of inanimate objects, taking it as inappropriate for the dynamic behavior of a population change. Affirming that "The species is therefore a dynamic concept, population, inextricably tied to genetic recombination events, whose meaning makes possible the emergence or splitting of one species into another" (MAYR, E 1968). Defending and a realistic notion of species derived from their interactions with the environment and other species. MAYR, E. (1949) In the biological species concept, although two species are morphologically indistinguishable, each one has a genetic system, behavioral and ecological separate, isolated by a real biological discontinuity in a meaningful context specific population based on genetic transformation.


DOBZHANSKY, T.-: (1941) Genetics and the Origins of Species. Columbia, Biological Series, N.XI, 2a

MAYR, E.: (1959) Species concepts and definitions. En E. MAYR, E.: The species problem (Amer. Assoc. Adv. Sci. Publ. No. 50), 1-22.

MAYR, E.: Animal Species and Evolution., Ariel, 1968. p. 32

MAYR, E.: (1942 ) T(Systematics and the Origin of Species. Columbia University Press. New York.

MAYR, E.: (1949) Speciation and selection. Proc. Amer. Phil. Soc. 93:514-519.

Biological Species Concept and Species Boundaries

Gualdrón-Diaz Juliette

Almost all studies in biology, whether at the level of molecules, cells, individuals or populations, are typically referenced to the level of the species. In the field of conservation biology, assessments of biodiversity are made at the level of the species: typical criteria include species richness, numbers of endemic species and the number or presence of endangered species in given areas (Myers et al. 2000). The accurate identification of species is crucial both to research in all areas of biology and to biodiversity conservation. Classical taxonomists classified individuals as members of a species based on a suite of shared morphological characters that were diagnostic and differentiated them from other such morphologically defined groups. In recent times, behavioural and ecological characters have also been increasingly used (Balakrishnan 2005).

One of the species concepts has been almost universally adopted by students of behavior, by most ecologist and those animal taxonomists, as well as by the molecular biologists (Avise and Ball 1990) is the Biological Species Concept (BSC). The BSC is most closely associated with Ernst Mayr (1942), who defines species based on their ability to interbreed: species are considered as “natural” entities distinguishable from other species by the criterion of reproductive isolation and not overall phenotypic similarity. The BSC has been criticised for several reasons: its inapplicability to asexual taxa (Mishler and Theriot 2000; Wheeler and Platnick 2000), lack of a temporal dimension (Willmann and Meier 2000), logical fallacy and the difficulty of applying it to allopatric populations (Mallet 1995).

One of the major problems, not only in BSC, but in any species concept is criterion for differentiating and delimiting species. If one accepts reproductive isolation as a sufficient criterion for delimiting species, then how recognize and delimit species using reproductive isolation?, a solution to this problem is delineate species boundaries using morphology, for this is necessary to examine the concordance between morphological and “biological” species boundaries (Balakrishnan 2005). Nevertheless, in certain groups is relatively easy such as crickets because the calling songs of cricket species are often reliable indicators of reproductively isolated populations (Shaw, 1999). Therefore the concordance in such behavioural and morphological characters would imply that phenetic clusters based on morphology correctly reflect the species boundaries defined by reproductive isolation. But for taxa that do not possess such behavioural associated with morphological is difficult to define species by BSC. In practice, even strong adherents of the BSC use phenetic similarities and discontinuities for delimiting species. If the organisms are phenotypically similar, they are considered conspecific until a reproductive barrier is demonstrated. However a practical difficulty encountered is that some populations may acquire reproductive isolation but minimal morphological difference, whereas other populations may acquire conspicuously different morphologies but no isolating mechanisms (Mayr 2000). Reproductive isolation may thus be looked upon as a sufficient but not necessary condition for delimiting species boundaries.

Although the BSC is the species concept most widely adopted, and is potentially useful in the analysis of speciation from the perspective of population genetics (Templeton 1989), it has some serious difficulties that make it inadequate, besides question unresolvable using the biological definition. As a result, most taxonomists, even those that accept the biological species concept, continue to use morphology and other phenotypic characters in order to delineate species boundaries.

References

Avise, J.C., Ball, R.M., 1990. Principles of genealogical concordance in species concepts and biological taxonomy. Oxford Surv. Evol. Biol. 7, 45–67.

Balakrishnan, R. 2005. Species concepts, species boundaries and species identification: A view from the tropics. Systematic biology. 54: 689-693.

Mallet, J. 1995. A species definition for the Modern Synthesis. Trends Ecol. Evol. 10:294-299.

Mayr, E. 1942. Systematics and the Origin of Species from the Viewpoint of a Zoologist. Columbia University Press: New York.

Mayr, E. 2000. A critique from the Biological Species Concept Perspective: What Is a Species, and What Is Not?. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 133-145, Columbia University Press, New York.

Mishler, B D., and Theriot, E. C. 2000. A critique from the Mishler and Theriot Phylogenetic Species Concept: Monophyly, Apomorphy, and Phylogenetic Species Concepts. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 119-132, Columbia University Press, New York.

Myers, N., Mittermeier, R. A., Mittermeier, C. G., da Fonseca, G. A. B., and J. Kent. 2000. Biodiversity hotspots for conservation priorities. Nature 403:853-858.

Shaw, K. L. 1999. A nested analysis of song groups and species boundaries in the Hawaiian cricket Genus Laupala. Mol. Phylogenet. Evol. 11:332-341.

Templeton, A. R. 1989. The meaning of species and speciation. A genetic perspective. In: Otte D, Endler J A (eds.) Speciation and its Consequences. Sinauer Associates, Sunderland, MA

Wheeler, Q. D., and Platnick, N. I. 2000. A critique from the Wheeler and Platnick Phylogenetic Species Concept Perspective: Problems with Alternative Concepts of Species. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 133-145, Columbia University Press, New York.

Willmann, R., and Meier, R. 2000. A critique from the Hennigian Species Concept Perspective. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 101-108, Columbia University Press, New York.

A perspective from the Biological Species Concept

Susana Ortíz B.

The hight biodiversity and complexity of the biological systems, is one of the greatest challenges at the time to recognize and delimit species as real entities in nature (Shcherbakov, 2010; Purvis and Hector, 2000; Sites and Crandall, 1997). Efforts to describe and identify these entities have resulted in the formulation of multiples species concepts contrasting with differents philosophical and epistemological approaches. Perhaps, the most widely discussed concept is the Biological Species (BSC). This concept stipulates the specie as a group of interbreeding natural populations that are reproductively isolated from other such groups and share a common place (Mayr 1942-1996). Although, the concept has been widely adopted in various areas is controversial and unyokeable under certain context. Criticism have been focused against some aspects including its lack of universality (Balakrishnan, 2005). This limitation is manifest by its inapplicability to sexual taxa (Wheeler and Platnick, 2000), and fossils; the latter, given the impossibility of identify its reproductive potential.

The capacity of interbreeding is the main criterion to define species in the BSC, which in theory implies that species no interbreed with members of other species, and they are reproductively isolated (Ayala, 2010). However, this does not mean only geographical isolation, structural and behavioral barriers could be considered prevent interbreeding. Based on the above, the concept is not clear in defining the causal order between interbreeding and reproductive isolation. This is consistent with the formation of hybrids and also the practical difficulty of determining a specie in allopatric populations, ignoring the potential to interbreed with other species under contingent conditions and the ability to produce real fertile offspring (Mallet, 1995). So, because mechanisms of reproductive isolation differ among taxa, the BSC cannot be absolute in the determination of species (Claridge, 1997).

An important aspect addressed in all conceptualizations of species is related to the definition of its status as a class or as individual. According to Goldstein & DeSalle (2000)the BSC defines the species as a class, which provides an ambiguous criterion to group organisms and result in the BSC might not be monophyletic (Donoghue, 1985). However, according to Dobzhansky (1950), the biological specie is the largest and most inclusive mendelian population then recognizes the evolution and thus the species as fundamental units of evolution, while higher taxonomic categories such as gender, cataloging families and orders are artificial, made for convenience and do not necessarily reflect evolutionary relationships (Jody, 2001). Moreover, the BSC concept is conceived in a population notion, where "populations" are seen as reproductive units which share a common gene pool in a context of reproductive isolation. Although the concept frames the unique properties of biological systems such as reproduction and crossover potential, other properties are not directly unlink, for example, recognition of conspecifics and gene flow (Mallet, 1995).

Additionally, the concept dispose that the taxonomy of natural species should be the conceptual schema of genetic populations, because a community of organisms that cross, is a gene pool which gives an identity that makes relatively recognizable species (Dobzhansky, 1937), but this appears not be the case in cryptic species. In despite of the mechanisms that can give rise to real species in nature and that are not recognized by the BSC, it have a strong theoretical component, which as Mayr (1996) said not only refers to the description and recognition of the species in nature, but the causes and processes associated with them.

Finally, the species concept can be extended to virology, but maybe the BSC is not the most adecuate; In the first place, viruses are genetic and evolutionary entities but is impetuous to affirm that are biological entities. Nonetheless, some features of BSC are applicable, for example, the specie is the evolutionary face, also as the BSC the members of a species resemble one another, and differ from other species. The difference between BSC and specie in viruses lies in some processes and mechanisms responsible of this identity. Obviously, viruses do not interbreed, but the recombination could be considered loosely as a mechanism that similarly allows genetic exchange, although this event is quite rare in viruses (Lai, 1992). To conclude, clearly these are just some aspects and implications of the BSC in virology, but probably there are many issues to be adressed in this and others areas, for now, even though the BSC is an important conceptual and operational base, it cannot offer universal yardstick to delimit species in nature.

References

Ayala, F., J. & Arp, R. 2009. Contemporary Debates in Philosophy of Biology. John Wiley and Sons.426p

Balakrishnan, R. 2005. Species Concepts, Species Boundaries and Species Identification: A View from the Tropics. Syst Biol.2005; 54: 689 - 693.
Dobzhansky, T. 1937. Genetics and the Origin of Species. Columbia University Press, New York.

Dobzhansky, T. 1950. Mendelian populations and their evolution. Am. Natur. 84:401-418.

Donoghue, M. J. 1985. A critique of the biological species concept and recommendations for a phylogenetic alternative. Bryologist 88:172-181.

Goldstein P.Z, DeSalle R.2000 Phylogenetic species, nested hierarchies, and character fixation. Cladistics. 16, 364–384.

Jody, H. 2001. Genes, Categories, and Species: 2001. The Evolutionary and Cognitive Causes of the Species Problem. Oxford University Press US. 217p

LAI, M. M. C. 1992. RNA recombination in animal and plant viruses. Microbiol. Rev. 56:61–79.

Mallet, J. 1995. A species definition for the modern synthesis. Trans. Ecol. Evol. 10:294–299.

Mayr, E. 1996. What is a species and what is not? Phil. Sci. 63:262-277.

Mayr, E. 1942. Systematics and the Origin of Species from the Viewpoint of a Zoologist. Columbia University Press: New York.

Purvis, A. & Hector, A. 2000. Getting the measure of biodiversity. Nature. 405: 212-219.

Shcherbakov. V., P. 2010. Biological species is the only possible form of existence for higher organisms: the evolutionary meaning of sexual reproduction. Biology Direct. 5:1-14.

Sites, J. W., Jr., and K. A. Crandall. 1997. Testing species boundaries in biodiversity studies. Cons. Biol. 11:1289-1297.

Wheeler, Q. D., and N. I. Platnick. 2000. A critique from the Wheeler and Platnick Phylogenetic Species Concept Perspective: Problems with Alternative Concepts of Species. In: Species Concepts and Phylogenetic Theory (Ed. Q. D. Wheeler and R. Meier), pp. 133-145, Columbia University Press, New York.

Claridge, M. F., H. A. Dawah, and M. R.Wilson. 1997b. Species:The units of biodiversity. London: Chapman & Hall.