Reproductive success and distance to conspecific adults in the sparsely distributed tree Kalopanax pictus

Lineage admixture during postglacial range expansion is responsible for the increased gene diversity of Kalopanax septemlobus in a recently colonised territory

We aimed to reveal the effects of range expansion and subsequent lineage admixture from separated glacial refugia on genetic diversity of Kalopanax septemlobus in Japan, by combining nuclear microsatellite data and ecological niche modelling. Allelic richness and gene diversity were compared at the population and regional level. We also statistically examined these indices as a function of population accessibility to the last glacial maximum (LGM) palaeodistribution reconstructed by ecological niche modelling to test a simple range expansion scenario from glacial refugia. Genetic diversity was highest in the populations of southern Japan and gradually decreased towards the north. However, an additional centre of genetic diversity, when measured as gene diversity, was found in northern Honshu Island, where distinct lineages were shown to be in contact. Positive effects of population accessibility to the LGM range were detected in both diversity indices at different spatial scales. The combined data support independent postglacial range expansions towards the north from the edge populations on the exposed coastal shelf of Pacific and Sea of Japan in northern Honshu during the LGM, which subsequently resulted in markedly low genetic diversity in the northernmost extant range, Hokkaido. The regional increase in gene diversity in northern Honshu is likely to be the result of postglacial lineage admixture. Relative difference in the spatial scales best relating population genetic diversity with the LGM distribution can be explained by a higher rate of allelic richness diversity loss during range expansions and stronger effects of lineage admixture on gene diversity.

Neighborhood aggregation effect and its effective scale on reproductive success in Shorea laxa (Dipterocarpaceae)

This study investigated whether reproductive success is affected by the intensity of neighborhood aggregation of adults in the tropical tree Shorea laxa. We focused on three processes in the early reproductive stages: seed maturation; seed survival (categorizing sound seed, predation by insects and predation by vertebrates) in pre-seed dispersal; and seedling survival in the post-seed dispersal stage. We used a model selection procedure to examine the aggregation effect on reproductive success. The intensity of neighborhood aggregation was represented by the neighborhood aggregation index, which contains the adult number within a specific radius and the distances to neighboring adults (weight of proximity). Then, we evaluated the models exhaustively with the aggregation index having different scales (radius and weight of proximity) to assess the scale on which aggregation had significant effects. In particular, the best effective neighborhood scale, which is defined as the scale of the index in the model with minimum Akaike information criterion, was examined to compare those scales among processes. We found that the probability of seed maturation, seed survival and seedling survival decreased with the aggregation index at specific scales. This suggests that aggregation influenced reproductive success negatively in both the pre- and post-seed dispersal stages. However, the selected radii differed among processes: >200 and 130 m in pre- and post-seed dispersal stages, respectively. The selected weight of proximity also seemed to have a weak effect on all processes and was not different among processes.