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.

Sympatric Sea Shells along the Sea's Shore: The Geography of Speciation in The Marine Gastropod Tegula

Michael E. Hellberg
Evolution
Vol. 52, No. 5 (Oct., 1998), pp. 1311-1324
DOI: 10.2307/2411301
Stable URL: http://www.jstor.org/stable/2411301
Page Count: 14
  • 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.
Sympatric Sea Shells along the Sea's Shore: The Geography of Speciation in The Marine Gastropod Tegula
Preview not available

Abstract

Uncertainty and controversy surround the geographical and ecological circumstances that create genetic differences between populations that eventually lead to reproductive isolation. Two aspects of marine organisms further complicate this situation: (1) many species possess planktonic larvae capable of great dispersal; and (2) obvious barriers to movement between populations are rare. Past studies of speciation in the sea have focussed on identifying the effects of past land barriers and on biogeographical breakpoints. However, assessing the role such undeniable barriers actually play in the initial divergence leading to reproductive isolation requires phylogenetic studies of recent radiations living in varying degrees of sympatry and allopatry to see which barriers (if any) tend to separate sister species. Here I infer phylogenetic relationship between 23 species of the marine snail Tegula using DNA sequences from two regions of the mitochondrial genome: cytochrome c oxidase I (COI) and the small ribosomal subunit (12S). These snails possess planktonic larvae with moderate dispersal capabilities and have speciated rapidly, with over 40 extant species arising since the genus first appeared in the mid-Miocene (about 15 M.Y.B.P.). Trees constructed from the COI and 12S regions (which yielded 205 and 137 phylogenetically informative sites, respectively) were robust with respect to tree-building method, bootstrapping, and the relative weightings of transitions, transversions, and gaps. Within clades where all extant species have been sampled, five of six identified sister species pairs broadly coexist on the same side of biogeographical boundaries. These data suggest strong geographical barriers to gene flow may not always be required for speciation in the sea; transient allopatry or even ecological barriers may suffice. A survey of the geographic distributions of marine radiations suggests that coastal distributions may favor the sympatry of sister taxa more than island distributions do.

Page Thumbnails

  • Thumbnail: Page 
1311
    1311
  • Thumbnail: Page 
1312
    1312
  • Thumbnail: Page 
1313
    1313
  • Thumbnail: Page 
1314
    1314
  • Thumbnail: Page 
1315
    1315
  • Thumbnail: Page 
1316
    1316
  • Thumbnail: Page 
1317
    1317
  • Thumbnail: Page 
1318
    1318
  • Thumbnail: Page 
1319
    1319
  • Thumbnail: Page 
1320
    1320
  • Thumbnail: Page 
1321
    1321
  • Thumbnail: Page 
1322
    1322
  • Thumbnail: Page 
1323
    1323
  • Thumbnail: Page 
1324
    1324