repopulated by a bird fauna different from that of other islands in the area which were not depopulated by the volcanic activity. The difference in species composition has apparently affected the body sizes of two species of honeyeaters.
Nine cases are known in which two species of the same genus are found living on the same newly populated island. In only one of these nine cases the two species do not occur together on any other island. In only this case individuals from Long Island differ in size as compared to individuals from other islands where the two species do not coexist. The larger species has increased in size on Long Island, while the smaller species has decreased in size. This appears to be a case of character displacement, in which size has changed in response to competition pressures, preventing one species from out-competing and eliminating the other species from the island. This change could not have taken longer than four centuries, and might have taken much less time.
RAPID CHANGE IN INSECTS
Mallet J. 1989. The evolution of insecticide resistance: have the insects won? Trends in Evolution and Ecology 4:336-340.
Summary. Resistance of insects to chemical pesticides has developed rapidly. Mechanisms of resistance include adaptations that increase behavioral avoidance, reduce cuticle permeability, increase the rate of destruction of insecticide molecules, and decrease sensitivity to the insecticide. Most of these mechanisms seem to depend on single genes, or very few genes, contrary to the expectations of neo-Darwinian theory. “Standard population genetic models have been of little use....” Mutations in regulatory genes seem more important than mutations in structural genes.
RAPID OIL FORMATION
Didyk BM, Simoneit BRT. 1989. Hydrothermal oil of Guaymas Basin and implications for petroleum formation mechanisms. Nature 342:65-69.
Summary. Oil being released in association with hydrothermal vent activity in the Gulf of California has been radiocarbon dated at less than 5000 years. The oil has similar chemical and physical properties to ordinary crude oil.
SPECIATION AND MUTATIONS
Paigen K. 1989. Experimental approaches to the study of regulatory evolution. American Naturalist 134:440-458.
Summary. Regulatory polymorphisms have been described for the genes for production of beta-globin in man and beta-glucuronidase in mice. Several steps in the regulatory process could potentially be modified by mutation, but only a limited number of such mutations is actually found. The types of mutations differ in different systems, and the regulatory differences between closely related species can be different from the polymorphisms found within a species. The types of mutations actually known in the condition called thalassemia are listed. Single substitutions accounted for 28 out of the 37 mutants known. Addition or deletion of one or a few bases were found in nine cases, the longest being a 25-base genetic deletion. The results suggest that speciation events may involve genetic mechanisms beyond those normally observed within populations.
SPECIATION, BOTTLENECKS AND ENVIRONMENTAL STRESS
Carson HL, Wisotzkey RG. 1989. Increase in genetic variance following a population bottleneck. American Naturalist 134:668-673.
Summary. A laboratory population of an endemic Hawaiian species of Drosophila was accidentally subjected to sustained high temperatures which killed most of the flies. The population was reconstituted from about a half dozen larvae which survived. After this population bottleneck, new combinations of chromosome 4 inversions were noted. This increase in genetic variance is the opposite of the decrease generally expected after a population bottleneck. The author does not discuss the possible effect of the high temperature, which has been reported to increase the rates of recombination in Drosophila (see Parsons 1988, Biological Journal of the Linnaean Society 35:49-68).
TAPHONOMY, FOSSILS AND CATASTROPHES
Greenstein BJ. 1989. Mass mortality of the West-Indian echinoid Diadema antillarum (Echinodermata: Echinoidea):