Variation and mechanisms of life history evolution in insular dwarfism as revealed by a natural experiment

Abstract Islands offer a classic topic for evolutionary studies. Few other subjects have historically raised as much fascination as the island large mammals that having evolved into dwarfs. Consensus has been gained that multivariate ecological causes are behind those changes, but what remains largely unexplored are the mechanisms behind them: how life history (age of reproduction, growth rate, longevity) change with insular dwarfism. Previous studies produced contrasting results difficult to compare, as they concerned different species in single islands. The Japanese Archipelago offers worldwide a unique natural experiment, as in its numerous islands of different sizes the same group of organisms, deer, have evolved into different sizes. Using an extensive examination of bone microstructure, statistical modelling of growth rate and demography, we demonstrate different degrees of change in life history in different islands. We discovered how different life parameters amount to a new, K-strategy contrasting to that of the parent population.