2015/08/14 by Dan Strickland, D. Ryan Norris · 1 citation
Environmental Science · Earth and Planetary Sciences · #Wildlife Ecology and Conservation #Animal Ecology and Behavior Studies #Evolution and Paleontology Studies
paper · pdf · doi:10.1002/ece3.1557
openalex publication_date 2015/08/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23
The island rule refers to the tendency of small vertebrates to become larger when isolated on islands and the frequent dwarfing of large forms. It implies genetic control, and a necessary linkage, of size and body-mass differences between insular and mainland populations. To examine the island rule, we compared body size and mass of gray jays (Perisoreus canadensis) on Anticosti Island, Québec, located in the Gulf of St. Lawrence, with three mainland populations (2 in Québec and 1 in Ontario). Although gray jays on Anticosti Island were ca 10% heavier, they were not structurally larger, than the three mainland populations. This suggests that Anticosti jays are not necessarily genetically distinct from mainland gray jays and that they may have achieved their greater body masses solely through packing more mass onto mainland-sized body frames. As such, they may be the first-known example of a proposed, purely phenotypic initial step in the adherence to the island rule by an insular population. Greater jay body mass is probably advantageous in Anticosti's high-density, intensely competitive social environment that may have resulted from the island's lack of mammalian nest predators.