Tomoyuki Saitoh

Impact of site-induced mouse caching and transport behaviour on regeneration in Castanea crenata

Abstract Dispersal and retrieval site selection by mice, transport distance, cache depth, and emergence and survival of seedlings of Castanea crenata (Japanese chestnut) were investigated by a magnet-locating experiment in two habitat conditions (gap vs. forest understorey). Magnets were inserted into nuts (n = 450) and the nuts placed in the edge of forest gaps. Although wood mice (Apodemus speciosus and A. argenteus) initially buried nuts singly in shallow surface caches near the nut source, by the following spring these cached nuts were retrieved and re-cached in larger, deeper caches farther from the source, particularly in forest understories, probably to reduce the threat of pilferage. All the nuts cached in the forest understories were consumed, but 4 seedlings emerged in gaps, apparently because of lower foraging activity in the gaps by the mice. Seed size was not correlated with cache depth or cache site selection. With increasing seed size, transport distance increased, particularly in gaps, possibly due to a greater potential energy gain (relative to handling cost to the cacher), or to attempts to prevent density- or mass-dependent loss of caches by other foragers. Variable seed dispersal behaviour based on variation in seed size may influence the chances of colonization and distribution of the light-demanding Castanea trees in mosaic landscapes and may play an important role in community organization and dynamics. Nomenclature: Ohwi & Kitagawa (1983). Abbreviations: FU = Forest understorey; G = Gaps.

Development of microsatellite markers for the dwarf bamboo species Sasa cernua and Sasa kurilensis (Poaceae) in northern Japan.

Ten polymorphic microsatellite markers were isolated from the dwarf bamboo species Sasa cernua and Sasa kurilensis. The applicability of these markers was confirmed by genotyping of open‐pollinated seeds and leaf samples from natural populations. Genotypes of seeds from each culm shared at least one allele from the maternal parent without contradiction. All 10 loci were polymorphic in S. cernua with 2–15 alleles (average HE = 0.532). Eight loci were polymorphic in S. kurilensis with 2–10 alleles (average HE = 0.532). These markers will be useful in detailing the extent of clonal and sexual reproduction in these species.

Female and male fitness consequences of clonal growth in a dwarf bamboo population with a high degree of clonal intermingling

BACKGROUND AND AIMS Although many studies have reported that clonal growth interferes with sexual reproduction as a result of geitonogamous self-pollination and inbreeding depression, the mating costs of clonal growth are expected to be reduced when genets are spatially intermingled with others. This study examined how clonal growth affects both female and male reproductive success by studying a population of a mass-flowering plant, Sasa veitchii var. hirsuta, with a high degree of clonal intermingling. METHODS In a 10 × 10 m plot, genets were discriminated based on the multilocus genotypes of 11 nuclear microsatellite loci. The relationships between genet size and the components of reproductive success were then investigated. Male siring success and female and male selfing rates were assessed using paternity analysis. KEY RESULTS A total of 111 genets were spatially well intermingled with others. In contrast to previous studies with species forming distinct monoclonal patches, seed production linearly increased with genet size. While male siring success was a decelerating function of genet size, selfing rates were relatively low and not related to genet size. CONCLUSIONS The results, in conjunction with previous studies, emphasize the role of the spatial arrangement of genets on both the quantity and quality of offpsring, and suggest that an intermingled distribution of genets can reduce the mating costs of clonal growth and enhance overall fitness, particularly female fitness.