Dwarfing in island elephants and deer: processes in relation to time of isolation

• Main Author: Lister, A M
• Format: Book Part
• Language: English
• Published: Oxford University PressOxford 1996
• Subjects: Wrangel Island; Many Islands
• Online Access: http://dx.doi.org/10.1093/oso/9780198577874.003.0015; https://academic.oup.com/book/chapter-pdf/52421321/isbn-9780198577874-book-part-15.pdf

Abstract Dwarfed populations of large mammal species evolved on many islands in the Pleistocene. Recent discoveries and advances in dating allow us to take the first steps in observing the time scale of dwarfing and the stages by which size reduction and associated morphological changes occurred. Dwarfed red deer on Jersey, and dwarfed woolly mammoths on Wrangel Island, evolved in a few thousand years or less. Their diminution probably occurred by an interplay of ecophenotypic and genetic effects, and was associated with some changes in proportion and morphology. These can be attributed to direct allometric and develop mental effects of size reduction, and may in some cases have been adaptively suboptimal. By comparison, dwarfed deer from Crete, elephants on other Mediterranean islands, and Columbian mammoths from islands off California, had probably been isolated for at least an order of magnitude longer than the Jersey and Wrangel animals. In consequence, they show modifications of cranial, dental, and limb morphology which can be interpreted as adaptive to small body size or the island habitat. Other proportions have readjusted to counter the initial developmental effects of dwarfing. Some forms evolved unique display organs implying biological speciation. In several cases, the morphology appears paedomorphic relative to the full-sized ancestor.