Access

You are not currently logged in.

Access JSTOR through your library or other institution:

login

Log in through your institution.

Geographic Distance, Environmental Difference, and Divergence Between Isolated Populations

Robert T. Dillon, Jr
Systematic Zoology
Vol. 33, No. 1 (Mar., 1984), pp. 69-82
DOI: 10.2307/2413133
Stable URL: http://www.jstor.org/stable/2413133
Page Count: 14
  • Download ($42.00)
  • Cite this Item
Geographic Distance, Environmental Difference, and Divergence Between Isolated Populations
Preview not available

Abstract

Evolutionary theory predicts that population divergence should be correlated with both geographic distance and environmental difference. This prediction was tested using 25 populations of Goniobasis proxima (Say), a snail restricted to small creeks in the piedmont and mountains of the southern Appalachians. Geographic distance was measured both over land and through water. Genetic difference was measured in three ways: an analysis of allozyme frequencies at seven polymorphic enzyme loci using gel electrophoresis, and two measures based on different variance components from 23 specially-screened morphological variables. Three measures of environmental difference were also calculated: one based on 11 water chemical variables; a second based on standardized water chemical variables plus four physical and biological variables; and a third based on diatom floral similarity. The correlations between all pairs of the resulting eight symmetric matrices were examined by calculating Kc statistics and tested using permutation. Population divergence was found highly correlated with geographic distance by all measures. Morphological divergence was also correlated with environmental difference. Isolation may, however, have precluded a correlation between divergence in allozyme frequencies and environmental difference. Thus, allozyme divergence among isolated populations seems more a function of gene flow restriction or time since isolation than selection.

Page Thumbnails

  • Thumbnail: Page 
69
    69
  • Thumbnail: Page 
70
    70
  • Thumbnail: Page 
71
    71
  • Thumbnail: Page 
72
    72
  • Thumbnail: Page 
73
    73
  • Thumbnail: Page 
74
    74
  • Thumbnail: Page 
75
    75
  • Thumbnail: Page 
76
    76
  • Thumbnail: Page 
77
    77
  • Thumbnail: Page 
78
    78
  • Thumbnail: Page 
79
    79
  • Thumbnail: Page 
80
    80
  • Thumbnail: Page 
81
    81
  • Thumbnail: Page 
82
    82