Well, this will be sort of confusing without a total understanding of evolutionary biology, so bare with me.

One of the most fundamental, yet widely disputed concepts in biology is what is a species? Unfortunately, for years and years, the convention was that a species is a set of organisms that can reproduce to create fertile offspring. Well that’s just stupid. Different species of sunfish do it. Hell, Hitch probably do too. But we know that a green sunfish is not the same species as a bluegill. Countless plants do it too. I am actually starting to get involved with in the philosophical debate over species concepts, and have spent a lot of time reading and discussing the issue. I feel that the best definition of a species is that it is an entity comprised of organisms that maintain genetic cohesion through time. This accounts for asexual reproducing species, and hybridization. Hybrids exist in nature, but rarely. Why? Because if they hybridized all the time indescriminantly, they would just be a species, they would not show two distinct lineages through time – there would be no green sunfish or bluegill, their would just be their hybrid.

Anyways, so the thing that people don’t like about that species concept is that any time that the best evidence shows that there is genetic isolation occurring, it may be a new species. So, technically, if you can bring forward evidence that bass in one lake will never share genetic information with bass from another lake, one could potentially name it a new species. That’s taking it a little far, but a good example is a fish im working with right now. A suckerfish that was in the Rio Grande basin, but maybe 20,000 years ago the headwaters in mexico were captured via geologic activity, and now belong to a pacific draining river. They are genetically isolated, and arguably a new species that diverged from the Rio Grande lineage.

I would also like to mention, most organisms do change over time. A coelacanth from 100,000,000 years ago, I bet, it genetically way different than one today, probably morphologically as well. Things change as environments change. Also just randomly. If a mutation occurs that is neither beneficial nor deleterious, than it can easily become fixed in the species over time. This is called genetic drift. Sometimes a random trait like a set of pigmentation on the body somewhere might be linked with another gene that is more important, and thus this random gene hitchhikes through evolutionary time with the important gene.

Which of those pieces of progress (shouldn’t say progress necessarily, it’s a random response to a changing environment, not a purifying or constantly improving process) is considered an element of biodiversity? I would say whatever one is alive at the time. We are limited in our abilities to understand biodiversity in that we only have the current snapshot of it.

The question of which element of biodiversity is of greater value is where my objectivity as a scientist ends, and my personal politics began. But personally, I believe that the hypothesis of a novel species is more supported when there is a relatively long-term evolutionary background. This can mean thousands of years for vertebrates, while only a few weeks for bacteria. Its relative to generation time. A man made pond with a distinct variety of mosquito fish doesn’t do it for me. Although under the species concept I mentioned it may be argued that it is a new species, I don’t think there is any value in recognizing or protecting it. I feel that there is a functional role to natural elements of biodiversity. Every organism is like a cog in a machine. You can trace energy through systems and find that every organism plays a unique role in uptake and redistribution throughout the system. When a lot of dams in CA were built, the soils far up in the hills became deprived of a certain isotopic signature of Nitrogen that came from salmon. Because the salmon were food to bears, and we all know the answer to the age old question, Does a bear #### in the woods?.

Im rambling again....

In summary, biodiversity can be assumed to be current snapshot of species that are extant (not extinct) today regardless of how they may have changed and will continue to change over time. The divergent patterns of evolution will continue to cause genetic isolation in a variety of ways, as we move forward through time. The best we can do to classify units of biodiversity (species) is to make hypotheses that certain sets of organisms are maintaining themselves as a cohesive groups through time. When these hypotheses are falsified, then we reevaluate the group and make a new hypothesis using current information.

I hope this was somewhat useful?

Ryan Thoni


If people concentrated on the important things in life there would be a shortage of fishing poles.
~Doug Larson