JOURNAL OF PLANKTON RESEARCH | VOLUME 3 | NUMBER 4 | PAGES 509-529 | 1981
© Oxford University Press
research-article |
Nouvelles formulations des règles écologiques connues sous le nom de rèegle de Bergmann et loi de Jordan
Amendments of the ecological rules known as Bergmann's and Jordan's rules
Laboratoire de Biologie animale (Plancton), Université de Provence Marseille, France
Received on May 1, 1980; accepted on February 1, 1981 Measurements of populations of planktonic and micronektonic species from the Atlanto-mediterranean region (about 10,000 specimens) have lead to improvements in Bergmann's rule relating to the increase in size with latitude.
There are three cases : Mediterranean specimens may be smaller (e.g. the mysid Eucopia hansent), equal to (e.g. the decapod crustacean Gennadas elegans) or larger than Atlantic ones (e.g. the thecosomatous genus Cymbulia).
All the species in the last group have their principal distribution in warm ocean waters. In the Atlantic, tropical species (e.g. the euphausiid Euphausia gibboides) decrease in size in the northern parts of their range while temperate species (e.g. the decapod crustacean Sergesles corniculum) decrease in size towards both the pole and the equator.
The comparison with the number of vertebrae of fish, which increases as does the size according to Jordan's rule, is interesting: though correct for cold water species (e.g. Merlucdus merluccius), this rule cannot be applied to warm water species (e.g. Merluccius senegalensis).
Thus, these rules must be corrected like this:- "a species reaches its maximal size in high, intermediate or low latitudes of its area if it has a boreal, temperate or tropical distribution";
- "the number of vertebrae increases with latitude for boreal fish and decreases for tropical ones".