Despite being close to the mainland, the Island of Jersey in front of the French coast was the stage for one of the quickest cases of extreme reduction of body size that we know of. Red deers shrank to about a 5th of their original size (more than 80% reduction) in about 5,000 years after the island became disconnected from the continent at the beginning of the last glaciation. In a paper just published in the July issue of Journal of Biogeography, Diniz-Filho and collaborators show that the fast extreme dwarfism observed in Jersey red deer fossils is a plausible outcome of a combination of well-established ecological and evolutionary processes. We modelled red deer body size evolution based on realistic assumptions of different aspects of their life history (such as polygamous mating mode leading to low levels of inbreeding) and high immigration rates, which together with high mutational variance and high phenotypic plasticity in a wide adaptive landscape lead to body size evolution trends similar to the observed in the fossil record.
Picture: Red deer stag (Cervus elaphus) with velvet antlers in Glen Torridon, Scotland, by Mehmet Karatay (CC license).