Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Genetic Structure of Populations of the Brown Snail (Helix aspersa). I. Microgeographic Variation

Robert K. Selander and Donald W. Kaufman
Evolution
Vol. 29, No. 3 (Sep., 1975), pp. 385-401
DOI: 10.2307/2407252
Stable URL: http://www.jstor.org/stable/2407252
Page Count: 17
  • Read Online (Free)
  • Download ($4.00)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Genetic Structure of Populations of the Brown Snail (Helix aspersa). I. Microgeographic Variation
Preview not available

Abstract

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.

Page Thumbnails

  • Thumbnail: Page 
385
    385
  • Thumbnail: Page 
386
    386
  • Thumbnail: Page 
387
    387
  • Thumbnail: Page 
388
    388
  • Thumbnail: Page 
389
    389
  • Thumbnail: Page 
390
    390
  • Thumbnail: Page 
391
    391
  • Thumbnail: Page 
392
    392
  • Thumbnail: Page 
393
    393
  • Thumbnail: Page 
394
    394
  • Thumbnail: Page 
395
    395
  • Thumbnail: Page 
396
    396
  • Thumbnail: Page 
397
    397
  • Thumbnail: Page 
398
    398
  • Thumbnail: Page 
399
    399
  • Thumbnail: Page 
400
    400
  • Thumbnail: Page 
401
    401