Jordan’s and other ecogeographical rules, and the vertebral number in fishes
Article first published online: 10 DEC 2007
© 2007 The Author
Journal of Biogeography
Volume 35, Issue 3, pages 501–508, March 2008
How to Cite
McDowall, R. M. (2008), Jordan’s and other ecogeographical rules, and the vertebral number in fishes. Journal of Biogeography, 35: 501–508. doi: 10.1111/j.1365-2699.2007.01823.x
- Issue published online: 10 DEC 2007
- Article first published online: 10 DEC 2007
- Bergmann’s rule;
- Jordan’s rule;
- vertebral count;
- Williston’s rule
Aim To explore variation in the number of vertebrae in fishes in the context of Jordan’s rule and other ecogeographical rules.
Methods The study is based on literature review.
Results The number of vertebrae varies very widely across the diversity of fishes. Jordan’s rule states that vertebral number increases with latitude, and this is widely attributed to ambient temperatures during ontogeny of individual fishes. However, the number of vertebrae may depend on both the ontogenetic environment and inheritance. Diverse other aspects of fish development and ecology are suggested as influencing vertebral number, including fish size, phyletic position, body shape and swimming mode.
Main conclusions The number of different factors that influence the number of vertebrae in fishes makes for highly complex patterns of variation, and means that unravelling causes is difficult. The question needs to be addressed at the population/species/species group scale; moreover, the lack of discrimination between environmental and inherited causes of variation adds to the complexity.