RT Journal Article
SR Electronic
T1 Variation and process of life history evolution in insular dwarfism as revealed by a natural experiment
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.12.23.424186
DO 10.1101/2020.12.23.424186
A1 Shoji Hayashi
A1 Mugino O. Kubo
A1 Marcelo R. Sánchez-Villagra
A1 Hiroyuki Taruno
A1 Masako Izawa
A1 Tsunehiro Shiroma
A1 Takayoshi Nakano
A1 Masaki Fujita
YR 2021
UL http://biorxiv.org/content/early/2021/09/04/2020.12.23.424186.abstract
AB Background 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 processes involved. Recent studies focused on associated change of body size and life history (age of reproduction, growth rate, longevity) – a key to understand the process of insular dwarfism. 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. We investigated eight deer populations exhibiting body size variation, both extant and fossil, to clarify the effect of insularity on life history traits.Results We applied several methods to both extant and extinct populations for resolving life history change among deer populations. Skeletochronology using lines of arrested growth successfully reconstructed body growth curves and revealed a gradual change in the growth trajectories reflecting degree of insularity: slower growth with prolonged growth periods in more isolated deer populations. An extensive examination of bone microstructure further corroborated it, and clearly indicated much slower growth and later somatic maturity in fossil insular deer, which had been isolated for more than 1.5 Myr. Finally, mortality patterns revealed by demographic analysis varied among deer populations and life history of insular populations shifted toward “slow-life” of K-strategists.Conclusion We clarified the evolutionary and ecological process behind insular dwarfism, which occurred in conjunction with life history shifts. The process initiated with phenotypic plasticity responding to the resource-limitation on predator-free islands after the settlements of islanders. Under the insular environments, natural selection favored K-selected animals and the life history traits were genetically fixed. Extreme K-strategy found in fossil dwarfs on islands would make them vulnerable to anthropogenic changes, that would explain termination of insular dwarfs after human arrival on islands.Competing Interest StatementThe authors have declared no competing interest.