Species, speciation... and definitions

    Defining a species can be very difficult as the concept of a species is extremely complicated. Like many other complicated concepts, there are many ways in which 'species' has been defined. One way in which species has been defined is through the biological species concept. The biological species concept states that interbreeding populations which are reproductively isolated from other such groups defines a species. While this can be a good definition of species, the biological species concept does not account for organisms that reproduce asexually. This is a major complication as there are numerous bacteria, plant, and animal species that do reproduce asexually. 

    Another way to define species is through the evolutionary species concept which states that a species accounts for a single lineage of ancestor dependent populations of organisms which maintains its identity from other such lineages via space and time and has its own evolutionary tendencies and fate. The main issue with the evolutionary species concept is that there is no way of knowing exactly what degree of difference a species needs in order to maintain its identity from other lineages. This can also be an issue with species that are morphologically similar. 

    Another way to define a species is through the phylogenetic species concept which states that a species is an irreducible group whose members are descended from a common ancestor and who possess a combination of certain defining or derived traits. Similar to the evolutionary species concept, one major limitation of the phylogenetic species concept is that it is difficult to determine the level of genetic divergence required to have separate species. This species concept is also limited as it can be difficult to apply in cases of hybridization. 

    Establishing a universal definition of a species would be fairly difficult to do because a species as a concept is quite complex. I believe that it is through combining species concept definitions that a species can be defined. Because the concept of a species is quite complex and there are numerous factors to consider when defining a species, combinations of species concepts are the best way to define a species. There are numerous advantages to the biological, evolutionary, and phylogenetic species concepts but they also have limitations. It is through determining the limitations that you can form combinations with other species concepts that include or touch on the limitation.