They only had the Reader's Digest version on tape, and I was looking for the unabridged version. Journey, I couldn't find the $280 listing on Borders, how did you find the listing there?
Thanks,
Don
Thanks,
Don
Why Lepisosteus and Atractosteus?
- Thread starter pagojoe
- Start date
One thing to remember is that genera and other higher taxonomic categories have no meaning in nature; they are strictly a human categorizing concept. So, in a small group like gars with two evident clades, it is natural to elevate both clades to genus level. Two similarly differentiated clades in a more diverse group might only be treated as subgenera or species groups. Looked at another way, if all living gars are placed in Lepisosteus, than Lepisosteus and Lepisosteidae are somewhat redundant. The family placement has already told us that they're gars; we may as well use the genus placement to give us some finer taxonomic resolution.
Hi Noto,
Thanks for your comments. I was thinking exactly that on my way home, that the taxonomic hierarchy is really artificial, since the animals don't know the difference, and that the cladists wouldn't have a problem with the different relationships. I also realize that the divisions are rather subjective, and vary mostly with how well-studied a family is: the more scrutiny, the greater the likelihood that more genera and subgenera will be created/elevated/resurrected. It's gotten to the point with some families that almost every species has its own genus, which somewhat defeats the purpose of illustrating relationships between species in the first place, or at least hinting at them.
I think it's the inconsistency involved that makes me uneasy. Everything you say makes sense, but if generic assignments are so random, it makes the phrase "rare, trans-generic hybrid" pretty much meaningless. I don't come from a fish background, but to me, there should be some fairly serious differences before consideration is given to moving species from one genus to another (not accusing Wiley of failing to do this, I haven't read the paper yet and I'm sure he has lots of good reasons). I want the taxonomy to give me the best picture possible of the relationship between two species. I can see that a Florida Gar is very similar to a Spotted Gar, and I can see that an Alligator Gar doesn't share nearly as many characteristics with these species as they share with each other. But, if you tell me you've assigned two animals to different genera, and they share as many overall characteristics as say, L. oculatus shares with A. spatula, you draw me a picture that paints them as more different than they actually are. The spine/tail, teeth, scales, internal organs, etc., are remarkably similar, and they share so many similarities that a kindergartner could place them in the same family. I don't see how assigning a different genus for the sake of avoiding redundancy really helps accurately illustrate such a relationship, even if the goal is to easily indicate that there are two clades within a family. If I see two genera, and every member of each genus is capable of interbreeding with every member of the other genus, it just screams to me that the two clades can't be very different genetically, and again, that placing them in different genera may accomplish the goal of noting that there are two groups within a family, but may less accurately depict their actual relationships.
Please understand that I'm not arguing, just musing.
I appreciate all the commentary, and hope to have a copy of the Wiley paper in my hands soon. I'm sure I'll have plenty more to muse about after I've read it.
Cheers,
Don
Thanks for your comments. I was thinking exactly that on my way home, that the taxonomic hierarchy is really artificial, since the animals don't know the difference, and that the cladists wouldn't have a problem with the different relationships. I also realize that the divisions are rather subjective, and vary mostly with how well-studied a family is: the more scrutiny, the greater the likelihood that more genera and subgenera will be created/elevated/resurrected. It's gotten to the point with some families that almost every species has its own genus, which somewhat defeats the purpose of illustrating relationships between species in the first place, or at least hinting at them.
I think it's the inconsistency involved that makes me uneasy. Everything you say makes sense, but if generic assignments are so random, it makes the phrase "rare, trans-generic hybrid" pretty much meaningless. I don't come from a fish background, but to me, there should be some fairly serious differences before consideration is given to moving species from one genus to another (not accusing Wiley of failing to do this, I haven't read the paper yet and I'm sure he has lots of good reasons). I want the taxonomy to give me the best picture possible of the relationship between two species. I can see that a Florida Gar is very similar to a Spotted Gar, and I can see that an Alligator Gar doesn't share nearly as many characteristics with these species as they share with each other. But, if you tell me you've assigned two animals to different genera, and they share as many overall characteristics as say, L. oculatus shares with A. spatula, you draw me a picture that paints them as more different than they actually are. The spine/tail, teeth, scales, internal organs, etc., are remarkably similar, and they share so many similarities that a kindergartner could place them in the same family. I don't see how assigning a different genus for the sake of avoiding redundancy really helps accurately illustrate such a relationship, even if the goal is to easily indicate that there are two clades within a family. If I see two genera, and every member of each genus is capable of interbreeding with every member of the other genus, it just screams to me that the two clades can't be very different genetically, and again, that placing them in different genera may accomplish the goal of noting that there are two groups within a family, but may less accurately depict their actual relationships.
Please understand that I'm not arguing, just musing.
I appreciate all the commentary, and hope to have a copy of the Wiley paper in my hands soon. I'm sure I'll have plenty more to muse about after I've read it.Cheers,
Don
I found the listing using google to search out the name of his book. The listings popped up in a sidebar. I checked my local library and apparently they can't afford a copy either.
LOL thanks Journey. I guess I could blackmail someone for a copy, but it's probably less trouble to shell out the 300 bucks...
As far as I know the only person to try to legitimize a standard rationale for defining genera was E. D. Cope (of Bone Wars fame) back at the turn of the 20th century. He considered species to be of different genera if they showed heterochronic differences, that is differences in timing and degree of development. If Cope had been the one to elevate Atractosteus, he might have used the hypermorphosis shown by Atractosteus as justification; that is, Atractosteus travel further along the morphological trajectory from slim, narrow-snouted juveniles to massive, broad-snouted adults (I'm not claiming this is really the case, just that it's the sort of rationale Cope would use).
Cope's definition never really caught on, for a handful of reasons. First, Cope's rationale was rooted in his own non-Darwinian evolutionary views. Second, heterochronic definitions hit some serious walls when you look at things like tiger salamanders, where several degrees of heterochrony may be found within a single population. Third, Cope's ideas led to the creation of numerous monotypic genera, which was endlessly annoying to non-taxonomists. Finally, since Cope's time most taxonomists have agreed that taxonomy's most important purpose is to reflect evolutionary relationships, which Cope's style did not.
Since that time, genera are essentially whatever the leading experts declare them to be. There is no standard measure of differentiation that is used to define them. So yes, they are rather arbitrary. Genus assignments often tell more about extinction patterns than anything else; two closely related genera would often be considered one if species intermediate between the two were extant.
Cope's definition never really caught on, for a handful of reasons. First, Cope's rationale was rooted in his own non-Darwinian evolutionary views. Second, heterochronic definitions hit some serious walls when you look at things like tiger salamanders, where several degrees of heterochrony may be found within a single population. Third, Cope's ideas led to the creation of numerous monotypic genera, which was endlessly annoying to non-taxonomists. Finally, since Cope's time most taxonomists have agreed that taxonomy's most important purpose is to reflect evolutionary relationships, which Cope's style did not.
Since that time, genera are essentially whatever the leading experts declare them to be. There is no standard measure of differentiation that is used to define them. So yes, they are rather arbitrary. Genus assignments often tell more about extinction patterns than anything else; two closely related genera would often be considered one if species intermediate between the two were extant.
Thanks for the explanations and informative response, Noto. I'm having to reprogram my brain a bit when it comes to the higher (and maybe lower) taxonomic levels, but I'm learning a lot here. I appreciate you guys on the forum taking the time to give me such great answers.
Cheers,
Don
Cheers,
Don
