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Hybrid Darters

Started by Guest_smbass_* , Jan 30 2008 02:21 AM

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27 replies to this topic

#1 Guest_smbass_*

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Posted 30 January 2008 - 02:21 AM

Ok so I know some of you have enough of a fit when someone posts a hybrid sunfish so how does this look/sound...

Matt D. and I were out today along with Marc K. and Thom R. We sampled two locations in SW Ohio and at the first location, which was a ditch through a farm field, we found one man made riffle at a gravel ford for farm equipment. It seems this must be the only suitable spawning habitat for the orangethroat and rainbow darters in the area. We found a bunch of male darters in this one tiny riffle and they were obviously crosses and back crosses and who knows what. We got the full spread from orangethroats, almost orangethroats, some where in the middle, almost rainbows, and 2 that actually looked like male rainbows. I kept and took pics of 5 of the hybrids.

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This guy almost looks like an orangethroat but notice the little bit of orange pigment on the anal fin.

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These all seem to be somewhere in the middle, most have a little more body coloration of a rainbow but the anal fin has too much blue and the color of blue is much more teal than usual. They also have fewer and wider vertical bars and the bars do not extend all the way around the body like they should if they were rainbows. They also apear to have an orange belly, which you often see in male orangethroats.

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I did put two of these into my stream tank because even though they are freaks they are still colorful. The first three pics are the same fish and the 4th is the other one.

The other curious thing about all this was it seemed all the females we found looked prety much like normal orangethroats. I know that with sunfish a very high % of hybrids are males, I wonder if this is also the case with darters. Does anyone have any insight on this?

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#2 Guest_farmertodd_*

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Posted 30 January 2008 - 11:28 AM

Awesome. I've been looking for them in the Blanchard and Auglaize without finding any that were convincing. It's interesting to see how the phenotypes play out. What watershed? (HUC8 is good enough, I can see this getting exploited

As far as sex ratio... You've got me on that one. Maybe this is how Trevor can pay us back. I'll send this along to him and see what he thinks. He might not be so interested in our redsides then lol.

Todd

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#3 Guest_Irate Mormon_*

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Posted 30 January 2008 - 10:13 PM

"Rainbows" are highly variable darters. FWIW. No experience here with O-throats.

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#4 Guest_Skipjack_*

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Posted 30 January 2008 - 10:24 PM

We see these fish all the time. Two of our most common darters. I am confident that these are hybrids. Without being there, and seeing the habitat and fish in the flesh, I can understand why one might be skeptical, but either way, they are at the OSU fish lab right now. Sure it will be sorted out.

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#5 Guest_Skipjack_*

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Posted 30 January 2008 - 10:35 PM

Thom, I took the liberty of posting two of your habitat shots.

Notice no suitable spawning habitat for rainbow, or orangethroat darters.

In the second photo, the crossing is the riffle. Cannot really be seen in photo. Seemed to be the only gravel riffle for miles, the rest was muck, a bit of sand, and vegetation. With both species present, and spawning on such a small riffle (twenty feet long, five feet wide) it is easy to see that a male of either species releasing milt could inadvertently be fertilizing eggs of the other species downstream. Or outright spawning with them.

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#6 Guest_fundulus_*

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Posted 30 January 2008 - 11:20 PM

Maybe I'm being a wiseguy, but has anyone ever hybridized these two species for sure? Are their karyotypes even close? I honestly don't know; I'm inclined to agree with Martin that we're looking at an unusual population within either rainbows or the orangethroat complex.

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#7 Guest_truf_*

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Posted 31 January 2008 - 12:45 AM

Maybe I'm being a wiseguy, but has anyone ever hybridized these two species for sure? Are their karyotypes even close? I honestly don't know; I'm inclined to agree with Martin that we're looking at an unusual population within either rainbows or the orangethroat complex.

I would say purposefully hybridizing them in the lab would settle it once and for all. Perhaps Brian, you can accomplish this? Or - perhaps if anyone else is up for the challenge?
-Thom

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#8 Guest_daveneely_*

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Posted 31 January 2008 - 02:50 AM

It wouldn't settle anything, as it's not relevant to what things do in the wild.

Hybrids happen, nobody is disputing that (and anyone that's done any mtDNA sequencing will have lots of fun stories...). It's just that some people have used calling things a hybrid as an easy way out of a tough ID, or an excuse to ignore natural variation between populations.

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#9 Guest_smbass_*

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Posted 31 January 2008 - 10:03 AM

As I suspected the same usual skeptics but there is no doubt in my mind about what these fish are. Like Matt pointed out we see these two species a lot in the western part of our state and as I mentioned there were normal individuals of both species found as well.

Todd I like the idea of getting some genetic samples of these guys, it would not be hard to get a good sample there were probably as many hybrids as there were normal orangethroats and there were only two rainbows that we were sure of. This was in a ditch way up in the Paint creek watershed, I can give you an exact location later. By the way it was loaded with least darters as well, way more of them than up in the population west of you, and we did find a few creek chubsuckers as well.

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#10 Guest_amiacalva_*

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Posted 31 January 2008 - 10:28 AM

With regards to the lab hybrid query, this has been done in our lab by a former student of Ted Cavender but most of the specimens were...mixed up. We have the wild hybrids determined by Ted and Milton and can use them to check against Brian's wild caught individuals for what that's worth. Will let you know what turns up.

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#11 Guest_ashtonmj_*

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Posted 31 January 2008 - 10:37 AM

I'd be interesetd to see what the lab investigations reveal but I'm falling on the side of skeptical based on visual examination. I really just see orangethroats with alot of variation in them. The tiny speck of orange between an anal ray isn't really convincing to me. The bars, the dorsal fin coloration, and the caudal peduncle coloration all say orangethroat to me too. Really only one picture has substantial orange/red in the anal fin. I saw darters formerly known as spectabile with this kind of variation pretty frequently on the Cumberland Plateau with and without the presence of rainbows.

I don't think a lack of "suitable" spawning habitat except for the man made riffle ultimately means or drives them to hybridize either. I'm sure that ditch has been that way for decades, maybe even over a century now, and the fish have probably since long shifted to less "optimal" habitat for spawning. I'm sure there are plenty of seasonally available patches of coarse sand with some pebbles that function as spawning substrate.

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#12 Guest_daveneely_*

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Posted 31 January 2008 - 10:37 AM

As I suspected the same usual skeptics but there is no doubt in my mind about what these fish are.

hey now... for the record, I think you're right, and at least y'all KEPT the things rather than making it a purely hypothetical question! Work that Nick Lang (now at the Field Museum in Chicago) has been doing suggests that there's been a long and sordid history of hybridization in Etheostoma, with both occasional isolated events as well as complete fixation of the "wrong" mtDNA in some species...

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#13 Guest_bpkeck_*

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Posted 31 January 2008 - 11:37 AM

Clark Hubbs did a lot of experimental crosses and one of the more accessible publications is a 1957 Experimental Zoology paper (Hubbs & Strawn) on the survival of F1 crosses. This includes E. spectabile and E. caeruleum, although not the same populations as being discussed here. I can provide the pdf if anyone is interested. Etheostoma caeruleum X E. spectabile is by orders of magnitude the most common Etheostoma hybrid from putative museum specimens and literature review.

Experimental crosses (e.g. stripping eggs and milt; aka 'love in a petri dish') can tell you about the genetic component to isolating barriers and whether or not the cross can happen (this one can). Additionally, results from experimental crosses can tell you if there may be a sex bias or other patterns and can help with expectations for wild occurrences. However, behavior isolating barriers like female mate choice must be overcome as well for hybridization to occur in higher frequencies than would occur by chance meeting of gamates alone in the wild. Even though there are hybrids does not mean that genetic exchange will occur, but it has in darters and researchers are starting to look at the effects of this exchange, or at the least document its occurrence.

I agree with Dave that there have no doubt been researchers that took the easy way out and identified variation as hybridization. I don't know if I would call this example an easy way out, but for a time researchers called Nothonotus vulneratus a hybrid between N. chlorobranchius and N. rufilineatus. However, I would say that hybrids have been overlooked more often because of systematist's natural need to put things into discreet categories and want to explain things by simple bifurcating patterns. Even when genetic exchange is documented it is often regarded as inconsequential and ignored by saying it is not a part of the 'true' species relationship.

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#14 Guest_farmertodd_*

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Posted 31 January 2008 - 12:22 PM

And... If that BLUE TEARDROP from the field photos doesn't tell all (expression of both parental characteristics), I dunno what will convince you, and I'm not going to bother to argue it

I'm curious if anyone has looked at the mechanism of disturbance on hybridization. I mean we know it happens... But what is the mechanism? Does the homogenization flip some switch that says "Hey, mix in all the genes you can!" within darters and sunfish? Or is it like a smokey bar on a crazy night, where you go to bed at 2 with a "10" and wake up at 10 with a "2"? Hey, I like that hypothesis. It just seems the disturbance makes the females WAY less picky.

And man, those grass buffer strips are doing thier job! Look at how clear that water is!

Todd

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#15 Guest_ashtonmj_*

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Posted 31 January 2008 - 12:37 PM

Just grind the fish up already and spit out the info! :mrgreen:

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#16 Guest_smbass_*

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Posted 31 January 2008 - 12:45 PM

hey now... for the record, I think you're right,

I wouldn't consider you one of the usual skeptics...

Anyways 2 of the specimens have been catalogged into the Museum collection as OSUM 105231, along with an entire fin off of each in 95% etoh so if anyone wants to look into the genetics it is possible for 2 of these.

Todd I'm sending you the location so if you want to go back and get more some time, let me know.

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#17 Guest_Skipjack_*

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Posted 31 January 2008 - 09:19 PM

It just feels good when Dave Neely agrees with you doesn't it?

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#18 Guest_bpkeck_*

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Posted 01 February 2008 - 12:06 PM

Very time appropriate for this topic, J. Ray et al. just had a paper published on introgression in E. uniporum from E. caeruleum. It's a pretty cool paper and the first darter paper that talks a lot about mitochondrial capture and fixation. I have the pdf if anyone needs it and it's in this months Journal of Fish Biology if you have access.

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#19 Guest_mikez_*

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Posted 01 February 2008 - 12:15 PM

And man, those grass buffer strips are doing thier job! Look at how clear that water is!
Todd

Don't want to divert this thread but, man was I impressed to see that habitat!
If you showed my those photos and and asked me what lived in the ditches I'd have responded mosquitos and green frogs and that's it. If those ditches were in MA that's all that WOULD be found. It amazes me that you can find 2 or 3 [or 2.5] species of darter in water like that.
How come the crop fertilizer doesn't turn the ditches into stagnant algae factories?

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#20 Guest_smbass_*

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Posted 01 February 2008 - 12:58 PM

There was actually more than that in there. We got Rainbow and orangethroat darters as previously stated but we also got least darters, creek chubsuckers, creek chub, bluntnose minnows, central stoneroller, striped shiners, tadpole madtom, blackstripe topminnow, hmm Matt and Thom am I forgetting any?

Rockbass