RufusAtticus

The confusion is arising due to the use of the term "adapt." He is using "adapt" in the non-scientific/original sense: "My pupils adapt to changing light conditions." However, such semantic mistakes do not allow him to challenge the actual scientific usage with respect to evolution.

tgamble

I'm not 100% but I think that point mutations and copying errors are two different things?

scombrid

Mokady, O; Mizrahi, L; Perl-Treves, R; Achituv. 2000. The different morphs of Chthamalus anisopoma: a phenotypic response? Direct molecular evidence. Journal of Experimental Marine Biology and Ecology Vol. 243, no. 2, pp. 295-304. Jan 2000.


Lively, CM. 1986. Competition, comparative life histories, and maintenance of shell dimorphism in a barnacle. SO: Ecology, vol. 67, no. 4, pp. 858-864, 1986


Interestingly it appears that some barnacles do have sufficient plasticity to grow in two morphs in response to predator cues. However, this says nothing of the level (population, individual, gene, ...) of selection that led to such plasticity. Phenotypic plasticity is itself a heritable trait. It’s probably useful to the barnacle. Fecundity and growth are both reduced in bent morphs. It’s pretty useful to the population to only go bent when necessary. Some animals don't show such plasticity.

Arendt, J.D, D.S. Wilson. 1999. Countergradient selection for rapid growth in
pumpkinseed sunfish: Disentangling ecological and evolutionary effects. Ecology 80(8): 2793-2798.

Arnett, A.E., and Gotelli, N.J. 1999. Geographic variation in life-history traits of the ant-
lion, Mymeleon immaculatus: Evolutionary implications of Bergmann’s rule.
Evolution 53(4) 1999. 1189-1188.

Billerbeck, J.M., Lankford, T.E., and D.O. Conover. 2001. Evolution of intrinsic growth
and energy acquisition rates: Trade-offs with swimming performance in Menidia menidia. Evolution 55(9): 1863-1872.

Billerbeck, J.M., and E.T. Shultz. 2000. Adaptive variation in energy acquisition and
allocation among latitudinal populations of the Atlantic silverside. Oecologia 122: 210-219Conover, D.O., and T.M.C. Present. 1990. Countergradient variation in growth rate: Compensation for length of the growing season among Atlantic silversides from different latitudes. Oecologia 83(3): 316-324

Craig, K.J., and C.J. Foote. 2000. Countergradient variation and secondary sexual color: phenotypic convergence promotes genetic divergence in carotenoid use between sympatric anadromous and non-anadromous morphs of sockeye salmon (Oncorhynchus nerka). Evolution 55(2):380-391.


That list of papers deals with countergradient variation. Instead of local adaptation leading to different morphs for different conditions, subtle changes in physiology allow populations inhabiting different environments to look similar. The sockeye and kokanee morphs of Oncorhyncus nerka are a really cool example. Kokanee complete maturity in carotenoid poor oligotrophic inland lakes yet are still able to turn flaming red for mating. If you take the offspring of the sockeye morph(completes maturity on a diet of carotenoid rich krill in the north pacific) and raise them on a carotenoid poor diet a la kokanee they fail to turn red at sexual maturity. The paper above found that there are heritable differences in the uptake efficiency of key carotenoid pigments.

One More:

Storfer, A. 1999. Gene flow and local adaptation in a sunfish-salamander system. Behavioral Ecology and Sociobiology 46(4): 273-279.

If phenotypic plasticity accounted for all of the behavior of salamanders in the presence of and without predation, then geneflow wouldn’t have the effect that it does here.

Background: Salamanders mate on land and spawn in water. Larvae either develop in permanent waters that contain fish or ephemeral ponds without fish. If the different aquatic habitats are within the crawling range of a horny salamander, genes are mixed between habitats.

Prediction: Without geneflow, there should be behavioral differences between salamanders in fishless habitats and salamanders living with fish around. Predator free salamander larvae should be more active during the day and less wary of predators. Because their habitat is ephemeral they must have faster feeding and growth rates to reach their terrestrial adult stage before the pond dries up. Salamanders living in permanent waters containing predators should be more wary and less active. Permanent waters allow them to avoid predators at the expense of growth.

Finding: Where ephemeral habitats and permanent water habitats are sufficiently spatially separated then the above prediction holds. The nearer the habitats, the less local adaptation is observed. Wariness is heritable and selected for on the population level by the relative fitness provided by either escaping sunfish or escaping a drying pond by growing fast.

Individual salamanders are either born wary or not and that decision is made by population history. They do not have plastic behavior in the way that the barnacles change morphs according presence/absence of predators.


Okay so I’m not done yet:

Tussell, GC, and L.D. Smith. 2000. Induced defenses in response to an invading crab predator. An explanation of historical and geographic phenotypic change. Procedings of the National Academy of Sciences. 97(5):2123-2127.


Well it turns out that gastropod shell thickness is plastic. Of course the cretinist drivel that spawned this thread fails to tell the whole story. Plasticity can be selected for on the population level. A population with the ability to thicken its shells when necessary is a lot better off than a population that is only capable of thin shells. Those thick shells are physiologically expensive, it’s nice to be able to not make one unless necessary.

[ November 18, 2002: Message edited by: scombrid ]</p>