Is Diet Quality an Overlooked Mechanism for Bergmann’s Rule?

• Published in: The American naturalist 2010-02, Vol.175 (2), p.269-276
• Main Authors: Ho, Chuan‐Kai, Pennings, Steven C., Carefoot, Thomas H.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Aplysia; Aplysia - physiology; Biological and medical sciences; Body length; Body size; Body Size - physiology; Body temperature; Botany; Demography; Diet; Ecosystem; Flowers & plants; Fundamental and applied biological sciences. Psychology; General aspects; Grasshoppers - physiology; Hemiptera - physiology; Herbivores; Marine; Notes and Comments; Orchelimum; Plant growth; Plants; Precipitation; Prokelisia; Tibia; Tropical regions
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/649583

Bergmann’s rule (body size increases with latitude) has long interested biologists; however, its mechanism remains unclear. An overlooked mechanism (latitudinal variation in plant quality) might help explain Bergmann’s rule. We studied three herbivores. In the field, the planthopperProkelisiaand the sea hareAplysia, but not the long‐horned grasshopperOrchelimum, were larger at high latitudes, following Bergmann’s rule. In the laboratory, all three species grew larger or faster on high‐latitude plants. High‐latitude diets increasedProkelisiasize andAplysiagrowth rates by 8% and 72%, respectively, enough to explain the increase in field body size toward high latitudes. Therefore, latitudinal variation in herbivore body size could be influenced by latitudinal variation in plant quality, which may directly or indirectly also affect body size in detritivores, parasitoids, and predators. Studies of Bergmann’s rule should consider the influence of biotic factors on body size in addition to abiotic factors such as temperature and precipitation.