Species: What exactly IS a species?
My friend Forrest Mims, one of the 50 best brains in science, according to Discover Magazine, writes to say,
Your post on "DNA analysis means death of taxonomy (determining what a "species" is)?"Speaking for myself, I have long been confused by the concept of "species" because it seems to be used in different ways.
This is a significant post that should be of interest to the ID community.
I have considerable experience with this, having studied for 7 years variants of the baldcypress found along Texas Hill Country streams and rivers. Let us go so far as to assume that all baldcypress are the same species: Taxodium distichum, including T. mucronatum, the national tree of Mexico. This leaves the problem of assigning scientific names to the variants of the species, including those I study that have a very different appearance from the common baldcypress. Even the annual growth rings and distribution of tannin in the rings is obviously different.
In a future book I'll discuss some of my extensive correspondence with the new/old generations of botanists about my findings. The old generation is confident of the findings, but the young generation refuses to look at the actual specimens and wants only to see its DNA.
My main web site has a photo of the common baldcypress and the variants I study. Go here and scroll to end of page. The photo is low res on my site, but anyone can see the obvious difference that the molecular biologist I dealt with refused to acknowledge.
Everybody agrees that beetles and butterflies belong to different species, but no one needs special training to see that.
But are dogs, wolves, and coyotes really different species? It's no secret that they can interbreed. Most sources discourage interbreeding because wolves, coyotes, and their offspring are not desirable domestic companions compared to dogs.
Should behaviour count in relation to species?
Horses and donkeys can also interbreed, but the resulting mules and hinnies are not fertile. So with them we have a clearer idea of what a species might be. (Note: Mules are generally larger than hinnies because their mothers are (horse) mares and their fathers are jack asses. Hinnies are smaller because their mothers are jenny asses, a naturally smaller breed, and their fathers are (horse) stallions.)
Some animals that are generally considered members of the same species - Chihuahuas and Newfoundland Rescue Dogs - may not be able to interbreed for logistic reasons (size difference).
But before we go making a big "evolution" argument out of that, we need to stop and remember that those animals were bred by humans for specific tasks, and would probably not be viable in nature.
Maybe the best long run solution would be a figure for the type and amount of genetic difference that should prompt us to classify a given life form as a different species from another.
(Note: The Discover editors, to their credit, did not back down when challenged over their choice of Mims, due to his ID sympathies. Indeed, they were wise to stand their ground. If they dump "best brains" due to politically incorrect sympathies, they must replace them with "second best" brains, at least in their own honest opinion. In short, having the correct opinion becomes more important than adding to knowledge. That is a classic recipe for cultural stagnation that they did well to avoid. As I said at the time, "Science motors along on facts, so political correctness is not one of the branches of science." )
Here is Forrest's comment, published at Science (free registration wall):
The Twilight of Taxonomy
by Forrest Mims III
[Comment posted 2009-06-03 12:22:04]
Bob Grant's piece on the fading of taxonomy (http://www.the-scientist.com/2009/06/1/32/1/) deserves a wide audience while there is still time to salvage what is left. The National Science Foundation should especially acknowledge this serious problem.
We have entered an era when some molecular biologists seem more interested in extracting DNA from museum specimens than in adding to the collections. A classic example is the destruction of very rare specimens preserved in amber to attempt DNA extraction (Mims, 1993).
For 7 years I have studied variants of the baldcypress found along Texas Hill Country streams and rivers. Let us go so far as to assume that all baldcypress are the same species: Taxodium distichum, including T. mucronatum, the national tree of Mexico. This leaves the problem of assigning scientific names to the variants of the species, including those I study that have a very different morphology than the common baldcypress. Even the annual growth rings and distribution of tannin in the rings is obviously different. While the old generation of botanists I have consulted is intrigued by these findings, the young generation has a very different view based solely on DNA.
Satellite remote sensing technology can lead to issues analogous to the twilight of taxonomy. For example, a decade ago colorful sunsets accompanied by extended twilights were observed from South Texas. These twilight glows looked much like those that followed the volcanic eruption of Mount Pinatubo and suggested a new aerosol layer in the stratosphere. After I posted these observations on the Internet, two experienced twilight observers were among the respondents who reported seeing the same phenomenon. I then sent an inquiry to a team charged with measuring optical depth from a remote sensing satellite. Their response was that the twilights were probably caused by smoke from Mexican power plants, an impossibility due to the stratospheric altitude suggested by the lengthy duration of the twilight s. I suggested to the team that they simply go outdoors to watch the twilights with their own eyes, but persistent sulfate smog over their location blocked their view.
In the end, the high-tech satellite completely missed the phenomenon. Observations by much older lidars in Cuba and California confirmed the new aerosol layer that was first discovered simply by measuring the duration of twilight glows using unaided eyes and a watch (Mims, et al., 1996).
Forrest M. Mims III
F. M. Mims III, Save the Amber, Nature 362, 389 (1993).
Ibid., et al., Lidar data from Cuba, Germany, and Hawaii; aerosol layer with unknown source, Bulletin of the Global Volcanism Network (Atmospheric Effects), http://www.volcano.si.edu/reports/bulletin/contents.cfm?issue=atmospheric, (February 1996).
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