Phenotypic and genetic divergence among island populations of sika deer (Cervus nippon) in southern Japan: a test of the local adaptation hypothesis

Abstract

Transplant and common garden experiments have been used in studies on local adaptation, but are diicult to be conducted for large animals with long life span. A previous study on the southern Japanese islands demonstrated that relative limb lengths of sika deer (Cervus nippon) were short on islands with steep slopes. We hypothesized that this morphological variation was evidence for local adaptation, and tested this hypothesis by comparing phenotypic divergence with neutral genetic divergence among eight populations of the sika deer in the southern Japanese islands. Divergence patterns difered between the phenotypic and neutral genetic features. Genetic similarity was high among individuals on Kyushu (OI, KGS, and KGK). Individuals on Tanegashima (TN) and Yakushima (YK) also constituted a group, whereas individuals on Tsushima (TS), Wakamatsujima (WM), and Kuchinoerabujima (KE) formed a genetically distinct group. Phenotypic data indicated that individuals from TS, OI, KGS, and KGK exhibited similarity, whereas individuals on YK formed an isolated group that was separated from the other populations. The degree of phenotypic divergence was larger than that of neutral genetic divergence between TN and YK. These results suggest that divergent selection worked between two of the eight island populations (TN and YK). The morphological trait of captive-bred individuals from TN and YK, which had never experienced their original environments, retained their original morphological features. By combining the results of multiple analyses, we found that the diference in relative limb length between the two populations was consistent with local adaptation hypothesis, although conclusive results were not obtained for the other populations.

High variation of mitochondrial DNA diversity as compared to nuclear microsatellites in mammalian populations

“…Sato et al (2017) reported such populations of wood mice ( Apodemus speciosus ) on Hakatajima island, the haplotype diversity of which diverged from the general relationship between haplotype diversity and island size. A similar pattern was observed in sika deer ( Cervus nippon ) on Yakushima island (Table S1, Terada & Saitoh, 2018). The nested population structure hypothesis predicts that the structure of populations with higher haplotype diversity is more complex than that of those with standard haplotype diversity.…”

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

“…The next step of life history evolution would be illustrated by the Yakushima Island deer, which also showed slower growth rate and intermediate histological features, coupled by a moderate shift of survivorship curve toward those of K -selected species. Contrary to the situation of the Kerama deer, the slower growth rate of Yakushima deer is considered to have a genetic basis because 1) Yakushima deer are not malnourished and have enjoyed a recent population increase [43] and 2) some of their macromorphological features have a genetic basis [44, 45]. A long-term field observations of Yakushima deer also supported our finding that the life history traits of this population is shifting to K -strategist (Agetsuma and Agetsuma-Yanagihara, personal communication).…”

“…Yakushima Island was possibly connected to Kyushu Island by a land bridge during the Last Glacial Maximum (ca. 25,000 ya), but the genetic differentiation between the two populations implies a much longer period of isolation for Yakushima deer (Nagata et al 1999, Terada andSaitoh 2018). The complete skeleton of each individual has been stored at Tochigi Prefectural Museum (TPM), Utsunomiya, Japan.…”

Plant constituents affecting food selection by sika deer

“…The body size of Yaku sika deer is considerably smaller than other subspecies of Japanese sika deer (e.g., Kyushu sika deer [ C. n. nippon ], Honshu sika deer [ C. n. centralis ], Ezo sika deer [ C. n. yesoensis ]; Whitehead ). Terada () showed that the dwarfing of Yaku sika deer was genetically linked, potentially because of food limitation from high population density through predator release (Kay , Lomolino ). Under these food limitation conditions, deer may have evolved the ability to detoxify phenolics to expand the range of foods they can consume.…”