The effect of area and isolation on insular dwarf proboscideans. (11th March 2016)

• Record Type: Journal Article
• Authors: van der Geer, Alexandra A. E.; van den Bergh, Gerrit D.; Lyras, George A.; Prasetyo, Unggul W.; Due, Rokus Awe; Setiyabudi, Erick; Drinia, Hara
• Is Part Of: Journal of biogeography. Volume 43:Number 8(2016:Aug.)
• Page Start: 1656
• Page End: 1666
• Publication Date: 2016-03-11
• Subjects: Elephas -- fossil record -- insularity -- island biogeography -- island rule -- Palaeoloxodon -- Pleistocene -- Stegodon; Biogeography -- Periodicals; 578.09
• DOI: 10.1111/jbi.12743
• Languages: English
• ISSNs: 0305-0270

Abstract

Abstract: Aim: We investigated the hypothesis that insular body size of fossil elephants is directly related to isolation and surface area of the focal islands. Location: Palaeo‐islands worldwide. Methods: We assembled data on the geographical characteristics (area and isolation) of islands and body size evolution of palaeo‐insular species for 22 insular species of fossil elephants across 17 islands. Results: Our results support the generality of the island rule in the sense that all but one of the elephants experienced dwarfism on islands. The smallest islands generally harbour the smallest elephants. We found no support for the hypothesis that body size of elephants declines with island isolation. Body size is weakly and positively correlated with island area for proboscideans as a whole, but more strongly correlated for Stegodontidae when considered separately. Average body size decrease is much higher when competitors are present. Main conclusions: Body size in insular elephants is not significantly correlated with the isolation of an island. Surface area, however, is a significant predictor of body size. The correlation is positive but relatively weak; c . 23% of the variation is explained by surface area. Body size variation seems most strongly influenced by ecological interactions with competitors, possibly followed by time in isolation. Elephants exhibited far more extreme cases of dwarfism than extant insular mammals, which is consistent with the substantially more extended period of deep geological time that the selective pressures could act on these insular populations.