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Posts Tagged ‘loggerhead sea turtle’

loggerhead sea turtle hatching

Recently, I’ve been using this space to play around with the fuzziness of “species.” Hundreds of species concepts exist, and because different researchers have somewhat different perspectives, you will sometimes get real conflicts about whether something is a species or a mere subspecies.

In canids, we get caught up in species discussions that are about what really amounts to very little genetic variation. For example, red wolves, Eastern wolves, gray wolves, dogs, dingoes and coyotes are all lineages that have only radiated in the past 50,000 or so years.

By contrast Old World and North American red foxes, including the ones allegedly derived by those set out by English colonists in the seventeenth and eighteenth, last shared a common ancestor 400,000 years ago.  This finding means that we probably should regard the red fox of North America as Vulpes fulva.

But 400,000 years of divergence is nothing compared to the 3 million years estimated for the Indo-Pacifica and Atlantic-Mediterranean populations of loggerhead sea turtle. There has been some gene flow between the populations. Matrilines have flipped around South Africa, once 250,000 years ago and an once 12,000 years ago.

So researchers who specialize in wolf-like canids are debating over very small genetic differences and relatively recent divergence times.  Red fox researchers are only just now realizing that there are likely two species in what was once thought to be a Holarctic species. And those specializing in loggerhead sea turtles don’t really care that their species has such a deep genetic difference.  The occasional gene flows between populations are enough for them to recognize only one species of loggerhead sea turtle.

This problem gets more interesting when we start talking about “living fossil species.” Take this article on Futurity.org, which is entitled “Evolution Hasn’t Revamped Alligators in 8 Million Years.” This article discusses the findings of some paleontologists at the University of Florida, who have found 8-million-year-old alligator fossils in North America, and they are remarkably similar to the ones we have today.

One of the researchers is quoted in the article says,”We were surprised to find fossil alligators from this deep in time that actually belong to the living species, rather than an extinct one.”

I would be just a hair more careful in my language. Although one can certainly see that these ancient alligators looked and probably behaved very much like the current species, 8 million years is a long time. I doubt that current alligators and those from that time could even interbreed if they encountered each other today. From a biological species perspective, it makes little sense to call them the same species, but from a paleontological perspective, it makes more sense, simply because paleontology is more interested in morphology and ecology over the entire time a population has existed.

So yes, “species” is a nebulous concept, and that is a good thing.  It makes some legal aspects with conservation difficult, because we have an Endangered Species Act that is about a hard and fast definition of a taxonomic entity.  In reality, the whole nebulous side makes for interesting levels of inquiry. If the Neo-Darwinian synthesis correctly describes the origin of biodiversity, then we would expect these discussions and debates to be commonplace.

They certainly are quite common in taxonomy and systematics. They probably always will be. Part of what defines a species are the biases of the classifier, which can often be contradictory.

For example, I have no problem with the new taxonomy of wildcats that posits the European wildcat into a different species than the Near Eastern/North African species. However, I disagree with the position of the domestic cat, which derives fro the Near Eastern/North African species, as its own unique species.

That bias may come from the simple fact that I am more familiar with domestic dog taxonomy, and I have come to accept that domestic dogs are best classified as a divergent form of gray wolf. If the domestic cat derived from its wild ancestor much more recently than the dog derived from its wild ancestor, why would it make any sense to classify the domestic cat as its own species?

So in zoology, we have all these different perspectives on how to classify species. Specialists in sea turtles are able to tolerate a genetically quite divergent species, while experts in wolf-like canids will debate over much more recently divergent lineages. These researchers really don’t talk to each about their ideas.  Indeed, the only time loggerhead sea turtle researchers worry about what specialists on the wolf-like canid side are doing is when they need to figure out how to stop coyotes from destroying the turtles’ nests. But they don’t need to know the complexity of the systematics to find an answer.

However, it is amazing how different specialists come to tolerate variation within one species. That nebulous nature of the various species concepts makes for some interesting variations on what specialists accept as normal.

Specialists often have very different ideas in mind, depending upon what they are used to, and I find it beautiful, even if it a bit confusing at times.

 

 

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