Why Lepisosteus and Atractosteus?

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pagojoe

Feeder Fish
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Jul 4, 2009
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OK Guys,

I know a lot of you probably don't care about taxonomy, so I apologize to you in advance for cluttering the board with this question, but...can anyone tell me what the reasoning was or what the anatomical characteristics were that led to creation of the Atractosteus genus, splitting them from the genus Lepisosteus? It seems the taxonomy has been stable for quite some time, so there must be some solid reasons for having done this, I just don't know what they are.

I know that with many animals, the taxonomy is in a constant state of flux, with new genera being erected every few years, and even family assignments changing as new data becomes available. I personally knew one fellow who did a complete revision of a family, but re-revised his revision a couple of years later after taking into account which species hybridized readily with other species. He had elevated a number of subgenera to full generic status, but had to juggle the genera/subgenera to account for the interbreeding (maybe they were "crossbreeds" and not true hybrids, since some of them were fertile). When I look at the gar species interbreeding, it brings to mind a couple of related questions. Can the offspring of hybrids/crossbreeds in the genus Lepisosteus reproduce? What about the very similar species, such as a Spotted Gar crossed with a Florida Gar? Florida with a Shortnose? How readily do these species interbreed?
If they interbreed easily, do they maintain their identity by spawning under different conditions or at different times, when they inhabit the same water bodies?

I guess the main question I have is this: if Atractosteus species interbreed fairly readily with Lepisosteus species (and they apparently do, as I've personally watched male Alligator Gar swimming with female Longnose Gar, female squirting eggs, male squirting milt, numerous times, and seen the resulting "Croc Hybrids" in the same area), isn't that a pretty good indication that they might belong in the same genus? I know that trans-generic hybridization occurs in nature, but it is very rare, and at least some of the cases involve animals that could or should be, arguably, assigned to the same genus. It seems that this isn't an isolated case of just the right sperm fertilizing just the right egg to produce a hybrid, but a case where you could take a bucket of L. osseus eggs, stir them up with milt from A. spatula, and end up with a cloud of baby "Crocs?"

I'm sure someone has already thought this over and worked it out, but I'm ignorant and haven't really found anything on the internet to satisfy my curiosity about the assignment of the true gar genera. Any enlightenment you gentlemen and ladies can provide, or thoughts on the subject, would be much appreciated.

Thanks, and Cheers,



Don
(PagoJoe)
 
I wasn't aware of the change. Do you have a chart on which species moved to a different genus? I'm sure Sol will enlighten us.
 
Well, Lacepède originally assigned all the gar to the genus Lepisosteus in 1803, then Rafinesque proposed Atractosteus in 1820 for the broad-nosed gar, apparently, during his frenzy of naming, publishing, and inventing (animals). When I search for differences, I seem to only find comments like "broad snout" and "light dorsal stripe," neither of which seems to be much justification for resurrection of a new genus. The fact that Rafinesque's assignment has stood the test of time makes me figure there must be some additional justification out there somewhere? That's really what I'm looking for, since many of Rafinesque's random assignments turned out to be synonyms or were later rejected.

Thanks,



Don
 
hey guys,

good topic of discussion, unfortunately i don't have a ton of time to do it justice, so i will answer in brief for now:

first off, i highly recommend looking up Wiley 1976 dissertation on the Phylogeny and Biogeography of Fossil and Recent Gars. although a pretty old work, this is one of THE gar papers in the literature, and can start to answer most of your questions.

right off the bat, Atractosteus is noted to have shorter, more numerous and ornate gill rakers, whereas Lepisosteus has thinner more elongate gill rakers. there is also the clearly evident prominent second row of teeth in the upper jaw of A, but not as prominent in L genus gars. other differences are covered in that paper, all the way from skull morphology to biogeography and pangeaic distributions/origins.

a lot of species of fishes can hybridize, so bringing up the hybrid issue with gars, or fishes in general is a tricky topic, and the definition of species with fishes is hardly a simple one. that was one of the questions on my prelim exams (for moving forward with my dissertation), i will dig up the answer sometime and post it here (this was several pages).

it is believed that the Lepisosteus genus gars came first, and the Atractosteus species branched off a bit later, but keep in mind we are talking on the order of millions of years here. just based on morphology one can see that the Atractosteus species are more closely related to each other than to the Lepisosteus genus. and similar species, such as the Florida and spotted gar, are considered sister species as well.

i know that's a lot of barely-touched-upon topics introduced, but hopefully it points in the direction that this is a complex topic, but with gars, since there are currently only 7 species, the differences between genera have been fairly solidly established (also keep in mind that they were at one point all in the genus Lepisosteus).

another paper worth looking up is the classic Suttkus 1963, which contains a lot of early classification work on gars. hope that helps get things started!--
--solomon
 
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This is what I could find so far.......
Taxonomic history

Until relatively recently all gars have generally been classified in the genus Lepisosteus Lacepède, 1803. The Alligator Gar had been given the name Atractosteus adamantinus by the eccentric Constantine Samuel Rafinesque-Schmaltz in 1818, and for a long time Atractosteus was simply viewed as a junior synonym of Lepisosteus. E. O. Wiley resurrected this genus in 1976, in his work The phylogeny and biogeography of fossil and Recent Gars.
Based on Wiley's work, after 1976 the Gars were officially split into Lepisosteus and Atractosteus, and ever since then zoos, aquarium books, anglers, and so on have been gradually catching up with the proper terminology.

I checked on getting the book, Amazon.com - $300.95
Barnes&Noble.com - $300.95
Borders - $280.95
 
Excellent, thanks Journey. I need to find a hobby that doesn't cost me 300 bucks every time I need a reference LOL. Hmmm, I wonder if Wiley addressed the crossbreeding issue...I guess I can find out, for a price :)
 
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