Interbreeding question

Dedicated exclusively to field herping.

Moderator: Scott Waters

Post Reply
simus343
Posts: 566
Joined: March 30th, 2014, 12:16 pm
Location: Okaloosa ca, Fla.

Interbreeding question

Post by simus343 » October 17th, 2015, 11:19 am

So, I have a question about cottonmouth interbreeding. In the coastal plain of the southeast, we get both Agkistrodon piscivorus conanti and Agkistrodon piscivorus piscivorus.

Being a subspecies, not a separate subspecies, and frequently occupying the same areas in almost equal abundance (at least in my stomping grounds), could they interbreed? Has it ever been documented? What would a cross-breed look like or would one subspecies' phenotype dominate the other subspecies'?

I understand that interbreeding between species is rare, but not rare between subspecies (as is the case where rat snake subspecies overlap) yet I have never heard anything about it in Florida and Eastern cottonmouths.

Coluber Constrictor
Posts: 1164
Joined: June 7th, 2010, 6:25 am
Location: Mobile, AL

Re: Interbreeding question

Post by Coluber Constrictor » October 17th, 2015, 11:28 am

If you are in the intergrade zone wouldn't they all just be considered intergrades? I think that's what the ones in Baldwin County, AL are (eastern/western, maybe some Florida Cottonmouth influence as well).

User avatar
Stohlgren
Posts: 603
Joined: November 6th, 2010, 9:59 am
Location: Athens, GA (Columbia, MO)

Re: Interbreeding question

Post by Stohlgren » October 18th, 2015, 7:39 am

^What he said. In general (though there are exceptions), you should not have two separate subspecies of the same species occupying an area. They are just intergrades.

User avatar
Noah M
Posts: 2289
Joined: November 3rd, 2012, 6:00 pm
Location: Gainesville, FL
Contact:

Re: Interbreeding question

Post by Noah M » October 18th, 2015, 11:16 am

I think a component here is how subspecies are designated. Are they genetically different from one another, and if so by how much? I thought subspecies desgination was based on phenotypic traits, and to some degree location. That is, animals that look a certain way tend to live in a certain region (or animals that live in a certain region tend to look a certain way). But because subspecies can and do interbreed, we're talking about a continuum.

So in overlap areas, we're looking the "gray" in an otherwise "black" and "white" division.

User avatar
Stohlgren
Posts: 603
Joined: November 6th, 2010, 9:59 am
Location: Athens, GA (Columbia, MO)

Re: Interbreeding question

Post by Stohlgren » October 19th, 2015, 5:46 am

You are correct. Subspecies are typically described based on morphology. Which often times does not line up with the genetics (see rat snakes for an example). We attempt to put boundaries on these subspecies, but as you mention, they usually occur as a gradient.

User avatar
walk-about
Posts: 567
Joined: June 14th, 2010, 11:04 am
Location: 'God's Country' aka western KY
Contact:

Re: Interbreeding question

Post by walk-about » October 19th, 2015, 4:34 pm

I would agree that attempting to navigate map boundaries as shown in Conant for example, can be at times too simplistic and too 'black' and 'white'. Or as Stohgren said, these areas often are reflected in 'gradients'. Intergradation between one or more subspecies is very common. And hybridization between species is not as rare as you might think. Where you have a zone of intergradation for example, you will have 'pockets' of often, notable physical characteristics representing a melding of these features, representative of both or more. Conant is a great reference and starting point, but in the end, one's eyes (what you actually see in your area - as a field researcher and observer) are the best.

Dave

simus343
Posts: 566
Joined: March 30th, 2014, 12:16 pm
Location: Okaloosa ca, Fla.

Re: Interbreeding question

Post by simus343 » October 20th, 2015, 5:19 pm

Okay thanks all. I ask because in some areas I got I see a rather even intergrade of cottonmouths without the vertical dark marks on the rostrum and ones with the vertical dark marks on the rostrum. Other spots I see almost all of one, and only a few of the other, and vise-versa. I am in an intergrade zone though, my entire "stomping grounds" is in the intergrade zone for eastern and florida. If I push another 10 miles west I could possibly add the western cottonmouth into my intergrade stomping grounds.

User avatar
BillMcGighan
Posts: 2302
Joined: June 7th, 2010, 8:23 am
Location: Unicoi, TN

Re: Interbreeding question

Post by BillMcGighan » October 21st, 2015, 4:08 am

in some areas I got I see a rather even intergrade of cottonmouths ...... Other spots I see almost all of one, and only a few of the other, and vise-versa.
If you look at the range maps of older field guides (e.g. Conant's 1958), species/subspecies ranges tended to be general, almost like political boundaries.
As time progressed and data increased, using this field guide series as an example, the range maps were less general, more irregular borders, and, in some cases, you could see an animal's range follow a geographical feature, a river, a mountain range, etc.

As Dave said
Where you have a zone of intergradation for example, you will have 'pockets' of often, notable physical characteristics representing a melding of these features, representative of both or more.

Point being, you may be seeing morphological, or even genetic characteristics, that are tied to physical features, past or present.
Sometimes you have to look at how the habitat was and not how it is today.

Post Reply