MEPS 228:153-163 (2002)  -  doi:10.3354/meps228153

Carnivore/non carnivore ratios in northeastern Pacific marine gastropods

James W. Valentine1,*, Kaustuv Roy2, David Jablonski3

1Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, California 94720, USA
2Ecology, Behavior and Evolution Section, Division of Biology, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093 0116, USA
3Department of Geophysical Sciences, University of Chicago, 5734 Ellis Avenue, Chicago, Illinois 60637, USA

ABSTRACT: For 2321 species of shelled gastropods of the northeastern Pacific, the ratio of carnivorous to non-carnivorous species (C/NC ratio), computed for each degree of latitude, reveals striking spatial changes, with tropical and arctic areas characterized by high values and with the mid-latitudes having the lowest ratios. This latitudinal trend is markedly different from trends for terrestrial clades. The zonal variation in C/NC ratios within bins is largely due to differences in geographic ranges of the groups; for example, tropical carnivorous species range farther than non-carnivorous ones, thus overlapping them in more latitudinal bins. Differences in the distribution and diversity of carnivorous and non-carnivorous species may arise from a number of sources, including variability of primary production in the tropical eastern Pacific, patchiness of substrates to which non-carnivores are adapted, narrow dietary specializations of tropical carnivores, and higher provinciality found in extratropical regions.

KEY WORDS: Trophic ratios · Latitudinal diversity trends · Provinciality · Variable productivity

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