Reptile & Amphibian Forums

Since it has indeed been a bit dead around here, I thought I would provide a link to some interesting tidbits leading to the eastern indigo being given full species status. Check out:

http://www.cnah.org/detail.asp?id=117

So Drymarchon couperi it is! Any debates? Rob

As a herpetoculturalist and not a herpetologist, I have two Questions:

A)Why are they are proposing elevating couperi to full species level?

B)Will this in anyway benefit wild populations of couperi?

There are some differences between the subspecies but, there are many more similarities, especially between couperi and erebenus who's natural ranges probably overlapped at one point producing inter-grades.

To me this is no different than kingsnakes or milksnakes both of which have many subspecies.
If an elevation is imminent, maybe they should consider elevating erebenus along with couperi, leaving the central and south American subspecies as they are.

Regardless, species or sub-species, couperi are awesome animals!!

they are invoking the "evolutionary species concept" (as opposed to, for example, the "biological" species concept). basically, they are arguing that there is enough morphological similarity within the range (of couperi) and enough average differences from other related groups to make it a legitimate taxon. in addition, the range of the taxon "couperi" represents a geographically isolationed entity. that is, it will continue to evolve independently of other taxonomically related groups.

remember, these ideas of subspecies, species, and genera are our (human's) best way of categorizing what we see in nature. we make this stuff up because we generally like a neat and ordered world that is easy to explain.

what we often fail to remember is that biology is dynamic over time and populations are still evolving. some populations are becoming more canalized and recognizable as a "species," while others are experiencing increased gene flow and becoming less and less like a "species."

hopefully the important part of this is that by raising couperi to the species level, all of a sudden its range is now only in the US, and it has a much more limited range than it did as a member of corais. arguments could be made for greater protection, due to its limited distribution.

"indigos? -- they don't need protection, we got plenty in texas!"

matt

Also,

I belive that Joe Collins is big on giving species status if there is no natural range overlap between other (former) subspecies OR if there IS range overlap yet no known integration beween the subspecies.

So...the eastern indigo is isolated, and it therefore deserves it's own species. Melanurus subspecies (erebennus, melanurus, orizibensis, rubidus, unicolor) freely integrade from S. TX through Central America...and are therefore all subspecies, not full species.

In S. America, corias / melanurus and caudomaculatus / melanurus have range overlap, yet there is no known integration, so they are therefore givin full species status.

Wuster explains it much better on his indigo systematics page:
http://biology.bangor.ac.uk/~bss166/Taxa/Drymar.htm

don't know why this just occurred to me..I just finished re-reading Wolfgang's article and it spawned many questions, but this one just seemed like I had to ask it...
Why I never thought of it beore, I dunno...
Why are BT's and YT's so close to opposite end images of each other, especially when their ranges overlap? Essentially dark or lite anteriorly and the same caudally(reversed)...
Can anyone think of a logical or, at least, entertaining explanation??
I mean if they inhabit the same areas, what advantage have they with this coloration?
Sorry if anyone burns too many brain cells on this one, but it just seems like a funny adaptation for 2 related animals that live "side by side"
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Carl W Gossett
Garage Door Herps
Monument,Colorado...northern territory of the Great Republic of Texas

"Why are BT's and YT's so close to opposite end images of each other, especially when their ranges overlap? Essentially dark or lite anteriorly and the same caudally(reversed)..."

hey carl,

how about a testable hypothesis? the first thing that came to my mind is predator search and pursuit image. there are a few prey species that rely on the predator forming a search image for pursuit and then changing that image. apparently this confuses some predators enough to cause them to momentarily lose track (bead if you will) of the prey item. i would hypothesize that if a predator catches sight of the anterior portion of the cribo it establishes the image of pursuit (dark head and neck, or light). in a chase, if the prey species is able to move fast enough at the start, then the predator may lose the dark OR light slender focal point and begin a scan for the image. this may, on average, delay the predator enough for it to lose the prey species.

now here's the question i puzzle over quite often. why are couperi mostly black? in light of their preference for relatively low temps, why are they such a dark color?

matt

still doesn't get me anywhere in my small world!! It probably doesn't make any real difference..Just popped into my head..
As for the couperi question, I think we've hit on that in the past and never really come to a good answer either..Anybody out there with a new idea??
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Carl W Gossett
Garage Door Herps
Monument,Colorado...northern territory of the Great Republic of Texas

Many snakes that live in or prefer cooler climes have dark body coloration. This coloration helps them to collect and conserve body heat. The cooler the temperatures they live in, the quicker heat is lost. Black collects heat quickly and holds it longer making it easier for them to effectively thermoregulate. A good example is the Austrailian Tiger Snakes and the North American Rat Snakes. With the Rat Snakes, the further north you go in their range, the darker the coloration until you get into the range of the Black Rat Snakes. Most of the Tiger Snakes are a reddish-brown or yellowish brown banded pattern, but there is one race that lives in a much cooler climate that is solid black and tends to be considerably larger. Darker coloration and more body surface to collect and maintain heat.

I think with the Eastern Indigo it is a combination of the above and the fact that they look so damn good.
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We do not inherit the Earth from our ancestors; we borrow it from our children. Ralph Waldo Emerson

They may be dark to get a head start on the competition. Being dark allows them to get up to operating temperatures quicker.
I read somewhere black head pythons have the black head so they can expose a minimal amount of their body yet warm up more quickly than their prey. Of course it seems safer to expose a black tail than a black head.

Cooperi are high efficiency predators with very active life styles. As such, they need optimum temperatures for metabolism and this is achieved more readily by basking with a BLACK body.
Cooperi also breed in the winter, and this active time for ANY snake requires operating temperatures equal to any other snake species. I have observed cooperi basking in bright sunlight after a night time low of thirty degrees. Upon approach, the animal fled with typical indigo speed, right into an armadillo hole which, upon inspection, contained the warm blooded mammal. Thus the cooperi thermoregulated at night, with the help of the armadillo and ,with sufficient warmth through the cold night, sought females ( or males) and continued thermoregulating with the sun!
I have collected D. rubida at over 5000 Ft. in Mexico. These animals were black as cooperi,they having to deal with even cooler temps than cooperi. Down into the flatlands, rubida interdispursed the black with lighter colors and red on it's flanks. This I do not believe is used as a predator prey defense, but for thermoregulating.

As far as YT's and BT's; Florida coachwhips are patterned this way and I have observed them useing their pattern to hunt birds in the zone between shade and sun around tree boarders in open woodlands, snatching them from low tree branches. All of the Dry's I have collected or observed have been in fairly open habitat were this same pattern mechanism would fall into play.