Pre-dispersal seed predation may have important effects on population dynamics and trait evolution in plants. In this review, we first present a conceptual framework of the strength of pre-dispersal seed predation and its variation in space and time. We consider the interaction between plants and their seed predators to be “strong” when it affects plant population dynamics or causes changes in plant trait–fitness relationships, and “weak” when it has no such effects, and propose ways of how to adequately assess these effects. Second, we review the ecological literature between 1991 and 2005 to evaluate documented effects of pre-dispersal seed predation on plants and draw five major conclusions. (1) Pre-dispersal seed predation rates are usually low but sometimes high, and show a considerable variation in space and time. (2) Direct evidence suggests that pre-dispersal seed predation can have a significant effect on recruitment and plant population growth rate. Accumulating evidence of seed-limited recruitment suggests that such effects are common. (3) Pre-dispersal seed predation affects selection on several plant traits, such as flowering phenology and flower number, which are usually interpreted mainly in the context of plant–pollinator interactions. (4) The patterns of variation in the interactions between plants and pre-dispersal seed predators suggest that geographic selection mosaics may be common. (5) Although there are numerous studies estimating seed predation, there are still rather few studies that have aimed at examining the interaction explicitly in terms of effects on plant population dynamics and trait selection. From these we know that seed predators can have important, and often variable, effects on plant population dynamics and trait evolution. However, it still remains to assess how important they are across study systems and relative to other aspects of the plant's biotic and abiotic environment.

Ecological and evolutionary consequences of spatial and temporal variation in pre-dispersal seed predation

Beech regeneration research: From ecological to silvicultural aspects

Genetic diversity and structure in Fagus crenata were studied by analyzing 14 nuclear microsatellite loci in 23 populations distributed throughout the species’ range. Although population differentiation was very low (FST = 0.027; RST = 0.041), both neighbor-joining tree and Bayesian clustering analyses provided clear evidence of genetic divergence between populations along the Japan Sea (Japan Sea lineage) and Pacific (Pacific lineage) sides of Japan, indicating that physical barriers to migration and gene flow, notably the mountain ranges separating the populations along the Japan Sea and Pacific sides, have promoted genetic divergence between these populations. The two lineages of the nuclear genome are generally consistent with those of the chloroplast genome detected in a previous study, with several discrepancies between the two genomes. Within-population genetic diversity was generally very high (average HE = 0.839), but decreased in a clinal fashion from southwest to northeast, largely among populations of the Japan Sea lineage. This geographical gradient may have resulted from the late-glacial and postglacial recolonization to the northeast, which led to a loss of within-population genetic diversity due to cumulative founder effects.

Genetic divergence in nuclear genomes between populations of Fagus crenata along the Japan Sea and Pacific sides of Japan

We used classification tree analysis to develop a climate-based distribution model for Fagus crenata forests in Japan. Four climatic variables judged likely to affect the distribution of the species (summer and winter precipitation, minimum temperature of the coldest month and Kira's warmth index) were chosen as independent variables for the model. Latitudinal and longitudinal information was also used to examine effects of spatial autocorrelation on the model. The climatic factors associated with the distribution of the forests were analysed using a classification tree to devise prediction rules. Predicted areas of high probability for forest occurrence lay mainly on the Sea of Japan side of northern Honshu and southern Hokkaido. This is consistent with actual forest distribution. Some areas with high predicted probabilities of F. crenata forest occurrence were beyond the current natural northern range limits of these forests. Since these areas were widely scattered, it was assumed that the spec...

Climatic controls on distribution of Fagus crenata forests in Japan

Mast seeding and its spatial scale in Fagus crenata in northern Japan

The causes and timing of seed death in early regeneration process of Siebold's beech (Fagus crenata Blume) was studied at 15 sites along a snowfall gradient in Japan, in order to clarify why the seedling density of the species has geographic difference remarkably. Seed production did not significantly differ along the snowfall gradient. Pre-dispersal seed mortality by insect damage was higher at sites with light snowfall than at sites with heavy snowfall, but this only seemed to be a minor factor influencing the population. A large proportion of the viable nuts that fall in autumn ware killed in winter before germination. Winter mortality was much higher at sites with thin snow cover than that at sites with thick snow cover, and this factor was strongly correlated with the geographic variation of seedling regeneration probability. There was little seed mortality by winter desiccation. The main factor contributing to the geographic difference seemed to be a seed predation by rodents in winter. Deep snow cover may reduce the success of rodents finding seeds in winter. Thus the observed relationship between snowpack depth and early mortality may be due to an indirect effect through the process of seed predation.p>

Kenichi Harada

Papers

Geographical variation in the early regeneration process of Siebold's beech (Fagus crenata BLUME) in Japan