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 need an accessible version of this item please contact JSTOR User Support

Distribution of Freshwater Mussels: Coastal Rivers as Biogeographic Islands

J. John Sepkoski, Jr. and Michael A. Rex
Systematic Zoology
Vol. 23, No. 2 (Jun., 1974), pp. 165-188
DOI: 10.2307/2412130
Stable URL: http://www.jstor.org/stable/2412130
Page Count: 24
  • Download ($42.00)
  • Cite this Item
If you need an accessible version of this item please contact JSTOR User Support
Distribution of Freshwater Mussels: Coastal Rivers as Biogeographic Islands
Preview not available

Abstract

Coastal rivers are isolated habitats that can be studied as biogeographic islands. Forty-nine rivers of the North American Atlantic and Eastern Gulf of Mexico Coastal Plains and their freshwater mussel (Unionidae) faunas are analyzed as a discrete island biogeographic system. Cluster analyses group the rivers on the basis of faunal similarity into five intergrading zoogeographic provinces. Distributional patterns in these provinces are strongly influenced by the proximity of species source rivers. Independent variables measuring stepping-stone distances (number of intervening rivers) from species source rivers, area of river drainage basins, and water quality parameters were tested in multiple regression models for their ability to predict numbers of species. Area of drainage basins is the best predictor of numbers of species. The species-area effect is greatest for provinces containing important source rivers and is lower for provinces in which rivers were colonized primarily by stepping-stone dispersal. The influence of stepping-stones on dispersal was assessed by constructing a stochastic model that uses immigration and extinction probabilities on serially arranged islands. Simulations of the model demonstrate that numbers of species on the islands should decrease approximately geometrically with distance from the species source. Numbers of freshwater mussels in the coastal rivers display a similar geometrical decline. The species-area and stepping-stone dispersal effects are combined in a descriptive model that stresses an interaction between area and distance from source rivers in determining species numbers. When combined with measures of environmental quality (hydronium concentration, amount of dissolved solids, and nitrate concentration), this model explains up to 80 percent of the variance in unionid species numbers among the coastal rivers.

Page Thumbnails

  • Thumbnail: Page 
165
    165
  • Thumbnail: Page 
166
    166
  • Thumbnail: Page 
167
    167
  • Thumbnail: Page 
168
    168
  • Thumbnail: Page 
169
    169
  • Thumbnail: Page 
170
    170
  • Thumbnail: Page 
171
    171
  • Thumbnail: Page 
172
    172
  • Thumbnail: Page 
173
    173
  • Thumbnail: Page 
174
    174
  • Thumbnail: Page 
175
    175
  • Thumbnail: Page 
176
    176
  • Thumbnail: Page 
177
    177
  • Thumbnail: Page 
178
    178
  • Thumbnail: Page 
179
    179
  • Thumbnail: Page 
180
    180
  • Thumbnail: Page 
181
    181
  • Thumbnail: Page 
182
    182
  • Thumbnail: Page 
183
    183
  • Thumbnail: Page 
184
    184
  • Thumbnail: Page 
185
    185
  • Thumbnail: Page 
186
    186
  • Thumbnail: Page 
187
    187
  • Thumbnail: Page 
188
    188