Makiko Mimura

High‐dispersal rates in heterogeneous environments and historical rapid range expansion can hamper local adaptation; however, we often see clinal variation in high‐dispersal tree species. To understand the mechanisms of the species’ distribution, we investigated local adaptation and adaptive plasticity in a range‐wide context in Sitka spruce, a wind‐pollinated tree species that has recently expanded its range after glaciations. Phenotypic traits were observed using growth chamber experiments that mimicked temperature and photoperiodic regimes from the limits of the species realized niche. Bud phenology exhibited parallel reaction norms among populations; however, putatively adaptive plasticity and strong divergent selection were seen in bud burst and bud set timing respectively. Natural selection appears to have favoured genotypes that maximize growth rate during available frost‐free periods in each environment. We conclude that Sitka spruce has developed local adaptation and adaptive plasticity throughout its range in response to current climatic conditions despite generally high pollen flow and recent range expansion.

While habitat fragmentation is a central issue in forest conservation studies in the face of\ud broad-scale anthropogenic changes to the environment, its effects on contemporary\ud mating patterns remain controversial. This is partly because of the inherent variation in\ud mating patterns which may exist within species and the fact that few studies have\ud replication at the landscape level. To study the effect of forest fragmentation on\ud contemporary mating patterns, including effective pollen dispersal, we compared four\ud native populations of the Australian forest tree, Eucalyptus globulus. We used six\ud microsatellite markers to genotype 1289 open-pollinated offspring from paired fragmented\ud and continuous populations on the island of Tasmania and in Victoria on\ud mainland Australia. The mating patterns in the two continuous populations were similar,\ud despite large differences in population density. In contrast, the two fragmented\ud populations were variable and idiosyncratic in their mating patterns, particularly in\ud their pollen dispersal kernels. The continuous populations showed relatively high\ud outcrossing rates (86–89%) and low correlated paternity (0.03–0.06) compared with the\ud fragmented populations (65–79% and 0.12–0.20 respectively). A greater proportion of\ud trees contributed to reproduction in the fragmented (de ⁄ d ‡ 0.5) compared with the\ud continuous populations (de ⁄ d = 0.03–0.04). Despite significant inbreeding in the offspring\ud of the fragmented populations, there was little evidence of loss of genetic\ud diversity. It is argued that enhanced medium- and long-distance dispersal in fragmented\ud landscapes may act to partly buffer the remnant populations from the negative effects of\ud inbreeding and drift