Are there any herpetologists here? Is the Prairie Lizard found in northern New Mexico a subspecies of the Eastern Fence Lizard (Sceloporus undulatus consobrinus) or is it a separate species (Sceloporus consobrinus)? I have seen it described both ways in many different sources. Who gets the final say on this? Do I even know what I am talking about? Maybe its some other lizard altogether. I read the Wikipedia article so we can skip that unless you think it might help other readers get an idea of what I am talking about.
My father got a PhD in herpetology and his response is: well if it’s Western it’s probably considered a separate species. He says sometimes, though it really turns into a matter of opinion as to whether it is a subspecies or a species. So take that for what it’s worth.
Herpetological systematists as a group I find have tended to lean towards the evolutionary species concept in recent decades( or at least they certainly did when I was deeply into this stuff in the 1990’s). Under that criterion it is S. consobrinus. Basically they are reproductively isolated enough from other populations to the point where they are on ‘separate evolutionary trajectories.’
However this is hardly a universally accepted concept and it occasionally makes geography key to field identification which some object to. If they look pretty much the same and are doing the same thing in similar habitats and would probably happily interbreed if they weren’t spatially separated are they really distinct? So I think it is fair to treat them as synonyms. You truly can make an argument in either direction.
I do happen to kinda like the ESC so I’d go with what seems to be the loose consensus and split them. But I don’t think there is anything wrong with arguing otherwise and I’m sure many herpetologists still do. Systematists/taxonomists love to argue over this stuff. Sometimes collegially, sometimes not 
.
There isn’t any global authority that has the “final say” on whether a particular population is a full species, or just a subspecies of a wider species. Even for birds, which are better known than most groups, there are four different widely accepted global species lists (Clements/eBird, Birdlife International/Handbook of the Birds of the World, International Ornithological Committee, and Howard & Moore). These lists recognize anywhere from 10,175 to 11,126 species.
Basically you have to decide which authority you’re going to follow. I don’t know offhand what are regarded as the most authoritative lists for reptiles. But basically if some authority recognizes the species as distinct, you can choose to follow that.
Fortunately, I’m not going to lose any sleep over this one.
Birders do, however, eagerly awaiting the annual revision of their list-of-choice to find if they have gained or lost species from their life lists due to splits or lumps.
Surprisingly few people keep life lists of the lizards they’ve seen.
Personally, I think that speciation ought to be regarded as being a property of organisms, not of geography. If two populations are separated by a geographic barrier that physically prevents them from interbreeding, and we therefore call them two species, then what do we say when that barrier is somehow removed, the populations mix again, and happily breed freely with each other? Did the two species merge into one again? I would rather say that, in that situation, they never were two different species to begin with.
To use a concrete example, for many thousands of years there was no or almost no contact between the human populations of the Americas and of Eurasia/Africa. Were we, during that time period, separate species? We’re certainly all one species now.
One thing is for certain. The lizards themselves don’t care.
Scientists don’t classify two populations as different species merely because of geographic separation. There are many examples of isolated populations that are regarded as part of the same species.
But you have identified one of the major problems in species classification, that of allopatric populations, that is, those isolated from other related populations. When populations are sympatric (occurring in the same place) or parapatric (having adjacent ranges), it is easy to see whether (and how much) they hybridize in nature. (Even in such cases, however, it can be a judgement call as to how much hybridization to accept before lumping the species. Contrary to the popular conception, many good species are perfectly capable of producing fertile hybrids on occasion. It’s whether or not hybridization is common or widespread that’s the criterion under the Biological Species Concept.)
In practice, isolated populations are evaluated on the basis of whether or not they differ to the same degree as sympatric species in the same group. And characteristics that are important in breeding, such as color pattern, vocalizations, and behavior are given special weight. Likewise the genetic difference is evaluated relative to the average interspecific difference in the group.
These decisions on the part of taxonimists used to be highly subjective. Today there is more of an effort to make the criteria more objective. For example, in birds, a kind of “point system” has been developed to give weight to differences in plumage, other morphology, vocalizations, and genetics.
That’s not a good example of isolated populations, since those of the Americas were connected to those of Europe/Africa by a continuous series of interbreeding populations (even across the Bering Strait). No modern taxonomist would classify those populations as separate species on that basis. No population of modern humans (sapiens) has been sufficiently isolated from any other for a period sufficient for speciation to take place.
(Although Neanderthals are now known to have interbred with sapiens, that doesn’t mean they were the same species. The evidence indicates that the interbreeding was limited in time and space, and did not occur anywhere (or anywhen) the two groups overlapped. So by modern species concepts, they would qualify as separate species.)
Ah, but they should. Although species classification is basically a way for scientists to pigeonhole organisms, it actually does have real-world consequences. In particular, it can strongly influence conservation of a population. Populations classified as species get a lot more attention than those that are “mere” subspecies.
As one example, the Coiba Spinetail is a small brown bird found only on Coiba Island off the coast of Panama. However, when it was first described in 1957, it was as a subspecies of Rusty-backed Spinetail, found thousands of miles away in the Amazon Basin, because it was very similar in plumage.
Despite this, many references recognized it as a separate species, and the Red List of the International Union for the Conservation of Nature (IUCN) classified it as “near-threatened” on the basis of its very small global range. Then in 2006 the IUCN decided to follow the classification system of the American Ornithologists’ Union (AOU), which still regarded Coiba Spinetail as a subspecies of Rusty-backed Spinetail. Its conservation status was dropped to “non-threatened,” because the combined species has an enormous range.
Fortunately some genetic work was done that showed that the two forms were not closely related. On this basis I wrote a proposal to the AOU to split them, and this was accepted in 2015. The IUCN followed suit, and it went back to “near-threatened.” I and a colleague are currently in the process of publishing a paper on the species that shows that, in addition to genetics, Coiba Spinetail differs from Rusty-backed Spinetail in vocalizations, nest construction, foraging, and habitat.
I am currently working on getting some other isolated populations in Panama, currently recognized as subspecies, recognized as full species in order to upgrade their conservation classification. Some of them are found in areas of severe deforestation and are seriously threatened, but not classified that way.
I’m sure all of the posters in this thread know this already but for the benefit of others I would like to point out that the whole concept of species is an artificial concept created by humans. Mother Nature doesn’t give a flip about what we think is the same species or a different species.
I don’t agree with this. “Species” are real things that exist in the real world. In one location, at one time, there is virtually no problem in recognizing which organisms are distinct species (at least of sexual organisms.) “Mother Nature” cares very much about speciation, because that is the basis of future evolution and biodiversity. The question is where exactly where we draw the line in the case of closely related populations, not whether species as evolutionary entities in general exist. In fact, “species” is about the only taxonomic category that is subject to objective definition, other grouping like genus, family, and order being more arbitrary.
Colibri: Then I apologize for putting words in your mouth. Sorry about that. I still stand by my original statement. Can we just agree to disagree and not get mad at each other over it?
You said [about the lizards], “Ah, but they should know.” Maybe they should know but how can we communicate that to the lizards? OK, now I’m just getting silly. I need to turn the computer off and go for a nice, long ride in the countryside. Maybe I’ll go birdwatching. Mammals, arthropods, and reptiles are welcome on my daily list as well. Amphibians are also welcome but I probably won’t see any today.
I’m not sure why you would think I was mad. I was just clarifying. While in some cases there is a degree of arbitrariness to where exactly we draw the line between related populations, in the majority of cases there is no disagreement. Regarding the four bird checklists I mentioned, they agree on 86% of all species. The majority of species are objective entities.
Species are the basic units of evolution. Until a population acquires reproductive isolation from others, it can’t undergo independent evolution and fine-tune its adaptations to its environment. This is the reason biologists are so interested in defining them.
Due to limitations in the Biological Species Concept, several additional species concepts have been developed, such as the Evolutionary Species Concept mentioned by Tamerlane and the Phylogenetic Species Concept. From the point of view of conservation, the concept of an Evolutionarily Significant Unit has been developed which doesn’t depend so much on species designations.
I just didn’t want anyone (not just you) to get mad and derail this very informative discussion.
Dammit. I see it’s been an hour since I said I was going outside and I’m still here. I’m really leaving this time!
I get pretty mad at the AOU sometimes when they reject my proposals but I’m not mad at anyone here.
I have a big list of “it was small and brown” birds…does that count?
Known in the trade as LBJs (“Little Brown Jobs”). I love when people describe one of these and want me to identify it. (Identification always depends on some detail they didn’t notice.)
I have an old bird guide that has one page with just illustrations of five or six different species of sparrows. It reminds me a lot of one of those puzzle books I had as a child that said, “One of these birds is different from the others. Can you find it?”.
You really don’t want to look at the plates on tyrant flycatchers in the field guide to the Birds of Colombia then. They have 40+ species of little brown/little gray jobs. There are lots of species of flycatchers that can’t be told apart in the field even by experts unless they are calling.