lew@ihlpa.UUCP (03/20/87)
In a discussion about possible mechanisms of speciation, the question of genetic compatibility as a criterion for typological classification came up. That is, animals which when cross-bred produced viable, fertile offspring might be classified together. ( I know this is not the definition of species !) I asserted that this criterion doesn't generate an equivalence relation, since there might be populations A, B, and C, such that A is compatible ( by the above criterion ) with B, B is compatible with C, but A is not compatible with C. My question is, is there an example of this intransitivity among known populations of animals? ( N.B. animals, not plants! ) I found some interesting information in Enc. Brit. about trout hybrids and a few other things, but nothing that specifically qualified as a realization of my hypothetical example. Lew Mammel, Jr.
dplatt@teknowledge-vaxc.UUCP (03/20/87)
Lew Mammel, Jr. asks, > My question is, is there an example of this intransitivity among > known populations of animals? ( N.B. animals, not plants! ) I'm not sure about the biological angle (intergroup fertility), but I'm pretty sure that there is at least one known case involving the standard definition of species (intergroup interbreeding). There is a "ring" of species of arctic birds (gulls, I believe) that exhibits this sort of behavior. As I recall, the species are believed to have diverged from one parent stock, by progressive migration in an eastwards direction over a fairly long period of time. Adjacent groups can (and do?) interbreed, with one exception. If you go to the point at which the circle "wraps around" to the point at which it started, you'll find that the species that "wrapped around" has diverged sufficiently from the original variety (which still populates that area) that the two do not (cannot?) interbreed viably. Sorry I don't remember the details on this... I'll see if I can dig them up sometime soon.
bill@ut-ngp.UUCP (03/21/87)
In article <10980@teknowledge-vaxc.ARPA> dplatt@teknowledge-vaxc.ARPA (Dave Platt) writes: >Lew Mammel, Jr. asks, > >> My question is, is there an example of this intransitivity among >> known populations of animals? ( N.B. animals, not plants! ) > >I'm not sure about the biological angle (intergroup fertility), but >I'm pretty sure that there is at least one known case involving the >standard definition of species (intergroup interbreeding). There is a >"ring" of species of arctic birds (gulls, I believe) that exhibits >this sort of behavior. See Raup, _Darwinism Defended_, p. 138. He references an article by M. Ridley, "Who Doubts Evolution?", which appeared in _New Scientist_, 90, 830-832 (1981). Bill Jefferys [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder] [pnews fodder]
g-rh@cca.UUCP (03/21/87)
In article <3353@ihlpa.ATT.COM] lew@ihlpa.ATT.COM (Lew Mammel, Jr.) writes:
] In a discussion about possible mechanisms of speciation, the question
] of genetic compatibility as a criterion for typological classification
] came up. That is, animals which when cross-bred produced viable, fertile
] offspring might be classified together. ( I know this is not the definition
] of species !)
]
] I asserted that this criterion doesn't generate an equivalence relation,
] since there might be populations A, B, and C, such that A is compatible
] ( by the above criterion ) with B, B is compatible with C, but A is not
] compatible with C.
]
] My question is, is there an example of this intransitivity among known
] populations of animals? ( N.B. animals, not plants! )
]
You are talking about clines (a chain of sub species). a specific
example is the herring gull cline consisting of
(1) The British lesser black-backed gull, Larus fuscus graellsii,
(2) Scandanavian lesser black=backed gull, Larus fuscus fuscu,
(3) Siberian vega gull, Larus argentatus vegae,
(4) American herring gull, Larus argentatus smithsonianus,
(5) British herring gull, Larus argentatus argentatus
1 can interbreed with 2, 2 with 3, and so on, but 5 and 1 cannot
interbreed. The difference is one of size -- the British herring
gull is twice as big as the lesser black-backed gull.
--
Richard Harter, SMDS Inc. [Disclaimers not permitted by company policy.]howard@cpocd2.UUCP (03/24/87)
In article <3353@ihlpa.ATT.COM> lew@ihlpa.ATT.COM (Lew Mammel, Jr.) writes: >In a discussion about possible mechanisms of speciation, the question >of genetic compatibility as a criterion for typological classification >came up. That is, animals which when cross-bred produced viable, fertile >offspring might be classified together. > >I asserted that this criterion doesn't generate an equivalence relation, >since there might be populations A, B, and C, such that A is compatible >( by the above criterion ) with B, B is compatible with C, but A is not >compatible with C. > >My question is, is there an example of this intransitivity among known >populations of animals? ( N.B. animals, not plants! ) Yes. The classic example is frogs in the Appalachians. Northern frogs can interbreed with their nearest neighbors, who can interbreed with those a little farther south, ... and so on. But the northernmost and southernmost frogs cannot interbreed. I first heard of this in the late 60's, but I don't have a reference. Note that there may be gender-dependence as well. It is possible that A males could breed with B females, but B males can't breed with A females. (No I don't have an example.) -- Howard A. Landman ...!intelca!mipos3!cpocd2!howard
gagen@bgsuvax.UUCP (03/25/87)
In article <3353@ihlpa.ATT.COM>, lew@ihlpa.ATT.COM (Lew Mammel, Jr.) writes: > > I asserted that this criterion doesn't generate an equivalence relation, > since there might be populations A, B, and C, such that A is compatible > ( by the above criterion ) with B, B is compatible with C, but A is not > compatible with C. > > My question is, is there an example of this intransitivity among known > populations of animals? ( N.B. animals, not plants! ) Yes. There are several. There is at least one group of frogs. There is a group of snakes. I will see if I can locate the articles. Kathi Gagen Dept. of Biological Sciences Bowling Green State Univ. Bowling Green Ohio 43402 gagen@bgsuvax