"... counted scales and taken color notes to see if we can find a 'good' morphological character that varies along the same boundaries as the genetic structure."

Thanks Ben -- that sounds like a good approach. If the fundamental concept behind "species" is the degree of reproductive isolation from other populations, I guess that's easier to answer with populations that still have physical contact with their relatives (like Rift Lake cichlids), assuming you have a way measure inter-breeding frequency. For populations that have been physically separated long-term by watersheds or other barriers, especially wide-ranging "species" that still look and behave similar to each other across their range, how do you ever decide when geographically isolated groups are "different enough" to warrant separate species names? In some cases they can and do interbreed freely where one has been introduced into the other's range, e.g., redlip and greenhead shiners in NC. I wonder if we applied to humans the same genetic methods and criteria that we use to split up wide-ranging animals into multiple species (ignoring the social-political fallout) would the major races of humans be defined as species? In other words, are the multiple species that we used to lump into E.spectabile any more distinct genetically than human races were a few hundred years ago before extensive inter-continental travel?

Reproductive isolation is not a requisite for delimiting species, at least for many -ologists anymore. Many of the Rift Lake cichlids do hybridize and there has probably been lots of genetic exchange between species throughout the diversification of those groups. I doubt anyone here would try to lump darter species that hybridize, given there are hybrids between Percina caprodes and several Ethestoma species there would be one very big lump of one or two 'species' of darter. Even if we limited lumping to those that exchanged genes through introgression, which requires some fertile hybrid offspring backcrossing into parental stocks, we'd have to lump Percina sipsi with Percina sciera, and Nothonotus camurus with Nothonotus chlorobranchius and Nothonotus rufilineatus, among others. Identification of reproductive isolation can be used to distinguish species, but reproductive isolation is not required for being identified as a species. As for Homo sapiens I'll leave that to the appropriate taxonomists and as long as they say we're one species, I'm inclined to accept their hypothesis. Comparing levels of genetic diversity or genetic structure across very disparate vertebrate groups will lead to all sorts of misunderstandings, and that brings me back to saying it takes a competent taxonomist/evolutionary biologist to interpret observed differences, morphological and genetic.

I'm not a trained taxonomist, but my understanding of speciation in stony corals is that color has as much to do with species id as the shoe size of the person making the id. The first step in id'ing a stony coral is to bleach off all of the tissue to get a good look at the skeletal structure in order to make the id. Yet if you were to do the same thing to various subspecies of the Common Rat Snake, Elaphe obsoleta, there's enough overlap in the rib counts and such as to make positive identification impossible without seeing the animals skin or knowing where it was collected. Seems that the trained taxonomists should try for a bit more consistency in such matters.

Edited by Subrosa, 06 December 2012 - 06:51 AM.

"Seems that the trained taxonomists should try for a bit more consistency ... Not necessarily. Features that are evolutionarily "plastic" and not very useful in taxonomy in one group of critters (e.g. color in corals) might be evolutionarily "conservative" and therefore useful in another group (e.g. critters that use color cues to select the right mate). It makes sense for taxonomists to use whatever features are evolutionarily significant in that particular group. (Not that we have any sure-fire way of knowing what those are). And of course we are stuck with the old problem that most species were described from preserved museum specimens, lacking color, behavior, and difficult-to-preserve body parts (coral and mussel soft tissue, bird and mammal innards, etc). At least zoologists preserve their smaller critters in jars instead of squashing and drying them on sheets of paper like botanists do. Try ID-ing a Hexastylis (wild-ginger/heartleaf) from a squashed shriveled flower.

I'm not a qualified person, but for the record, here's my species concept: There is no such thing. For whatever reason, maybe for obvious reasons, the animal clan known as Homo sapiens has an inclination to name things. Maybe it just makes it easier to talk about them on online forums (the named items that is). So we've had to create a concept we call "species" so we will know when a particular creature needs it's own name. The concept really has no meaningful relevance to the nature of the creatures. The creatures are what they are, and are believed to have changed, and to be changing as we speak. They don't require a species concept to carry on with this. Thus, the idea of "species" is meaningless in the context of the progression of the existence of life forms. If a fish can reproduce with another fish and produce viable and fertile offspring, it does so and its genes carry on. It doesn't have to be a defined species to do this. It simply has to do it. If it succeeds, it may result in the existence of new individuals that carry, and sometimes express, its own (the parent's') characteristics. It doesn't need to be a defined species to do this. The only entity that needs it to be a species is one that needs it to have a name that can be reliably used to identify it. And over the long span of time, these names are inherently unreliable... if you accept that species change (evolve) over time. It seems that it is a continuum of change. Not a punctuated process wherein a species appears and remains unchanged (to any lesser or greater degree. There is certainly variation in that regard.) for a certain period during which it really has "accepted" a species concept for itself. So the question then becomes, "Why do we seem to have identifiable 'species' in existence?" Maybe because we are only viewing a very brief snapshot of a very long progression that moves at a glacial pace (probably a bad metaphor given the recent pace of glacial "movement").

If species don't exist, our understanding of biology is really wrong and we could certainly dispense with the Endangered Species Act, etc. Just sayin'...

I agree with almost all of what Mark says except the statement "the idea of "species" is meaningless in the context of the progression of the existence of life forms". Not everything breeds randomly with everything else (although I did have a college roommate once like that) -- there is certainly mate selection in most animals, and reproduction and survival of offspring is very much dependent on joining your gametes with a generally similar and genetically compatible mate. So the species concept IS meaningful, but the boundaries between species (including over time, like Mark says) are blurry, not distinct. Mike Sandel's quote in my signature block below really nails it.

I'm not a qualified person, but for the record, here's my species concept: There is no such thing. For whatever reason, maybe for obvious reasons, the animal clan known as Homo sapiens has an inclination to name things. Maybe it just makes it easier to talk about them on online forums (the named items that is). So we've had to create a concept we call "species" so we will know when a particular creature needs it's own name. The concept really has no meaningful relevance to the nature of the creatures. The creatures are what they are, and are believed to have changed, and to be changing as we speak. They don't require a species concept to carry on with this. Thus, the idea of "species" is meaningless in the context of the progression of the existence of life forms. If a fish can reproduce with another fish and produce viable and fertile offspring, it does so and its genes carry on. It doesn't have to be a defined species to do this. It simply has to do it. If it succeeds, it may result in the existence of new individuals that carry, and sometimes express, its own (the parent's') characteristics. It doesn't need to be a defined species to do this. The only entity that needs it to be a species is one that needs it to have a name that can be reliably used to identify it. And over the long span of time, these names are inherently unreliable... if you accept that species change (evolve) over time. It seems that it is a continuum of change. Not a punctuated process wherein a species appears and remains unchanged (to any lesser or greater degree. There is certainly variation in that regard.) for a certain period during which it really has "accepted" a species concept for itself. So the question then becomes, "Why do we seem to have identifiable 'species' in existence?" Maybe because we are only viewing a very brief snapshot of a very long progression that moves at a glacial pace (probably a bad metaphor given the recent pace of glacial "movement").

Yeah, apparently there is selection and an advantage for an individual that can find a mate with whom to produce viable and fertile offspring. This is the rationale for the existence of populations of similar individuals that have been identified by us as species. But when you start splitting these similar groups of individuals into smaller and smaller subgroups with the only apparent purpose to name new species, then you're creating an artificial concept that doesn't really have much meaning from the perspective of the animals themselves. The end result being that a species is, as has been mentioned earlier, just whatever any particular taxonomist says it is. If there is no agreement and not much constistency from one taxonomist to another, then the notion that the species concept is pretty nebulous is just reinforced. So is it important to recognize similar groups of animals as species? That's a pretty broad and intricate question. If the purpose is to provide more and more protection of existing life forms, then naming new species could likely advance this cause. If the intent is to really get at the nature of life and animal forms, then identifying species perhaps does not really address the true essence of the developmental process and the real significance of animal diversity, variation and genetic and morphological change. It's nice, and in ways helpful, to have names to identify the many forms that we can observe. But that doesn't really validate the "species" concept. I'm having trouble coming up with another concept that would accurately characterize the state of the many varied forms that exist. But I think the overriding idea is that it is a continuum, rather than a series of discreet, distinct, forms that arise and perists until they go extinct. So again, I'm thinking of the snapshot concept as more true. A one time cross section, faunal transect. A sample in a fixed time frame that can tell us something about what exists on December 12th 2012 in North America on planet Earth. But that doesn't really tell us anything about what will exist in the same sample if it is drawn at a later or earlier time. So maybe the species concept can serve as an inventory tool, but one that is only valid for a single time frame, never repeatable. Does that mean that every identified species should be protected at any cost? It seems hard to argue that. Maybe it's more important to gather the data about what lives now, what has lived in the past, and to try to come to an understanding of what this tells us about the nature of the planet and the universe. In the words of Jefferson Airplane, (or was it Starship?) "Life is change."

Species aren't immutable, that's one of the major conceptual changes since Darwin and Wallace published their key works in 1859 on evolutionary processes. But some form of "species" does exist in nature. This is the basis of how to choose an optimal mate, as well as the basis of what pollinators are drawn to what flowers. In both cases much variation from a certain range is sub-optimal and probably won't be successful. Hybrids exist and can define hybrid contact zones in any sorts of multicellular eukaryotes. But such exceptions tend to prove the rule.

The species concept becomes easier to accept when you you let go of the old idea of a bunch of separate boxes, where every individual organism must be assigned to one specific box. Instead, think of the orangethroat darters group (or maybe the orangethroats and rainbow groups combined) as one big box with a bunch of loose piles (populations) and a little mixing at the edges of the piles; or maybe a lot of mixing when somebody kicks the box. Some biologists use the term "evolutionarily significant units" for populations that are distinct in some way (geography, morphology, behavior, etc) but it's unclear whether they should be designated as "species". Yes, taxonomy is certainly an artificial construct, but it does (hopefully) reflect realities in nature. Should we not give names to rocks, since they're all a jumble of different minerals that can be combined and recombined in virtually any combination? Does granite not exist? The politics and conservation implications of assigning species names is a whole 'nother issue, or at least it should be, but yeah you're probably right that some scientists may push species recognition as a protection tool.

Another species concept I've heard: "It's a statistical cloud"

As someone who's only dabbled in phylogentic sequencing(used MEGA, PAUP, MrBayes for my Phylogentics class in my first year of grad-school for some "newbie" phylogentic work), I'm far from being an expert, but I've always considered the combination of both morphological and genetic divergences to be necessary for speciation. I personally like seeing a combination of multiple loci being examined, not just the cyt b or Nd5 or whatever the researcher has chosen, when I read papers making the case for speciation, as well as the noted morphology differences. The real grey area lies in how much genetic divergence is significant, which is left to the eye of the beholder(taxonomist).

That being said...I'm ready to go collect Etheostoma clinton and Etheostoma teddyroosevelt!

That being said...I'm ready to go collect Etheostoma clinton and Etheostoma teddyroosevelt!

Oh no! Not this again.

Oh no! Not this again.

Ha, yeah I take it from reading this board there isn't a lot of love for the name. I'm personally indifferent, but I think the evidence splitting the speckled up is pretty solid, although I would like to see more about how the phylogeny resolves in some genetic analyses (what I read was mostly based on morphometry). I only brought it up because this group was also mentioned earlier in the thread. (sorry to highjack the thread, I'll stick to my stream ecology and GIS expertise, I ain't no dang taxonomist!)

Edited by justinoid, 12 February 2013 - 03:27 PM.