Quantitative genetics of extreme insular dwarfing: the case of red deer (Cervus elaphus) on Jersey

Aim: The Island Rule – i.e. the tendency for body size to decrease in large mammals and increase in small mammals on islands has been commonly evaluated through macroecological or macroevolutionary, pattern-orientated approaches, which generally fail to model the microevolutionary processes driving either dwarfing or gigantism. Here, we seek to identify which microevolutionary process could have driven extreme insular dwarfism in the extinct dwarf red deer population on the island of Jersey.

Location: Jersey, UK (Channel Islands).

Taxon: Red deer ( Cervus elaphus)

Methods: We applied an individual-based quantitative genetics model parameterized with red deer life-history data to study the evolution of dwarfism in Jersey’s deer, considering variations in island area and isolation through time due to sea level changes.

Results: The body size of red deer on Jersey decreased fast early on, due to phenotypic plasticity, then kept decreasing almost linearly over time down to the a...