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Soft cover. Zustand: Very Good. No Jacket. 1st Edition. Small 4to, pages 217 - 273, 4 black and white plates, 17 figures, blue wrappers with some light wear, contents are fine. Bulletin of the American Museum of Natural History Volume 124, Article 6.

Electrophoretic studies of genetic variation in 14 species of terrestrial slugs of the families Arionidae, Philomycidae, and Limacidae in the eastern United States indicate that self-fertilization, either facultative or obligatory, is the normal breeding system in six of the species. Three of these six species are single monogenic strains; one consists of three monogenic strains; one includes a highly heterozygous form and two monogenic strains; and one has a moderate amount of polymorphism but little heterozygosity and strong linkage disequilibrium. Eight species are outcrossers, being highly polymorphic and panmictic within local populations. Niche breadth, assessed in terms of extent of geographic distribution and variety of habitats occupied and measured on an experimental plot of woodland, is greater in some monogenic strains than in highly heterozygous, outcrossing species. Colonizing success apparently is independent of the amount of genetic variation carried by a species. 5 pp., 4.

Microgeographic population structure in the land snail Helix aspersa was analyzed by determining genotypes at five enzyme loci for 2,218 individuals from 43 estivating colonies on two adjacent 10-acre blocks in Bryan, Texas. An analysis of genotypic proportions yielded no evidence of inbreeding within colonies; but allele frequencies for colonies on the same block were heterogeneous, and there were major differences in mean allele frequencies between blocks. The mean standardized variance (FST) for colonies on a block was .03. Seven demes occupying areas of approximately 500 square meters were identified on each block; the harmonic mean size of the demes was 15 individuals. Deme size in Helix apparently is much smaller than in Cepaea. Variance in allele frequencies among small colonies exceeded that among large colonies, as expected if random genetic drift is a significant factor affecting population structure. An examination of gross features of the habitat types of the colonies yielded no evidence of associations with allele frequencies. Nonrandom features of intercolony variation on blocks could reflect either selection in a spatially heterogeneous environment or incidents of drift occurring in the demographic history of the populations. From the standpoint of genic variation, as indexed by electrophoretically demonstrable protein variation, colonies of Helix on a single block are as heterogeneous as regional populations of Drosophila pseudoobscura in the United States; and the degree of genic differentiation of Helix populations in California may be equivalent to that of the human species as a whole. 7 pp., 4 figs, gr. 8.

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