Species, Speciation.... and Definitions

Species, Speciation... and Definitions

The biological species concept defines species as members of populations that have the ability to interbreed. Their appearance does not affect whether they could be deemed as the same species, as some animals within a species look similar and some look different. One of the difficulties with this concept is that some organisms within the same species have qualities that allow them to physically mate with each other, but are held back by a barrier of some sort (maybe a mountain or a highway separates them). How big would this separation have to be to consider them two different species. The distances between species becomes a strong question in the case of ring species. Ring species are a series of populations that live in the form of a ring, in which they all interbreed with populations near them, except for populations on the far ends of the rings. This then poses the question, are each their own species, or are the ones that interbreed a species and the ones that dont a different species? The answer is unclear and proves how daunting the task of defining a species truly is. 

The morphological species concept determines species based on their observable traits, or morphology. A major limitation to this is that convergent evolution has lead many varying populations to look similar. Dogs and wolves, although have many similar morphologies oftentimes could not even be safely around each other. Considering each of these to be in the same species seems to be a stretch. Although the reasoning behind this makes sense, I find this concept the least appealing. There leaves a large amount of grey area because looking similar to another thing is on a spectra. There is not a way to quantify, calculate, test, or prove such findings outside of your opinion. Finding a baseline of percentage similarity seems to difficult of a task and neglects many important factors. I believe for animals to be a species, their ability to interact and mate seems to be pretty important. Some animals may not look the exact same, but are still able to interbreed. My point does bring up another conflict which is asexual organisms. If organisms reproduce on their own and without another organism, then the morphological species concept seems to be more appealing. I still think factoring in location and closeness would be helpful to add into the morphological species concept.

The phylogenetic species concept does not look at physical characteristics or breeding ability, rather their ancestry, In this case, a species would be a group of organisms that share a common ancestor and form a distinct lineage on a phylogenetic tree. An advantage to this concept is that species can be pretty easily divided, as phylogeny trees are pretty easily divided, however, I believe that not every animal with a common ancestor should be considered a part of the same species. This concept is still slightly subjective, because looking at phylogenetic trees, at the very end you could say that 2 organisms have a common ancestor and are therefore a part of the same species. Or you could look further back in their lineage and find even more organisms before them which would also be considered a common ancestor. The question with this is how detailed or how broad we want species to be. With evolution occurring successfully over the years, animals that once had a common ancestor may look entirely different now, have absolutely no ability to interbreed, and may be located on the other side of the Earth. For example, whales and hippopotamus are morphologically very distinct organisms, yet are believed to have once shared a land dwelling common ancestor.  

A barrier for all three of these concepts are animals that are involved in hybrid zones. These are areas where two distinct populations overlap and are able to breed, exchange genetic material, and produce hybrids. Although the populations may remain separated outside of the hybrid zones, the formation of a hybrid causes trouble for each of these concepts. Would the new hybrid animals be a new species distinct from the separated populations? Or would both of the populations be considered a part of the same species because they have the capacity to interbreed, even though they don't all do it. 

Defining a species is so difficult because there are so many different ways that organisms interact with each other, and they are continually moving, evolving, adapting, and mutating. Given the fluid nature of life and evolution, creating harsh speciation lines between organisms will never be a clear-cut process, and will always have some ambiguity. Creating too few species fails to highlight the rich biodiversity that is to be found here. Creating too many species can overlook the meticulous trait differences evolution, mutations, and fitness have created. Although clarity in species mapping would be helpful when studying evolution and displaying biodiversity, the fluidity of life keeps that from being a simple and obtainable solution. Not having a universal definition of a species hinders us from objectively studying predator-prey relationships, understanding evolutionary processes, and even assessing biodiversity. As many organisms are misclassified, this can result in a complete misunderstanding of their ecosystem and role within it.