高知県室戸市で確認されたカミガモソウGratiola fluviatilis（ゴマノハグサ科）の新産地とその生育状況

A new locality of Gratiola fluviatilis Koidz.（Scrophulariaceae）, a threatened species endemic to Japan, was discov-ered in a mountain bog in Muroto City, Kochi Prefecture, southwestern Japan, in 2004. Sixty-three patches of G. flu-viatilis were recorded at the site, with most patches being distributed under the canopy of trees growing around the bog. Extrapolating from the area of the patches and the density of individual plants, the total number of individuals was estimated at ca. 47,000. In conclusion, the study site represents the largest population of G. fluviatilis in Japan. To maintain habitat conditions suitable for the growth and reproduction of this threatened species, a comprehensive investigation of plant life history strategy, environmental requirements and habitat disturbance regime is urgently re-quired

Comparative analysis of spatial genetic structures in sympatric populations of two riparian plants,Saxifraga acerifoliaandSaxifraga fortunei

PREMISE: The genetic structure between plant populations is facilitated by the spatial population arrangement and limited dispersal of seed and pollen. Saxifraga acerifolia, a local endemic species in Japan, is a habitat specialist that is confined to waterfalls in riparian environments. Its sister species, Saxifraga fortunei, is a generalist that is widely distributed along riverbanks. Here, we examined sympatric populations of the two Saxifraga species to test whether the differences in habitat preference and colonization process influenced regional and local genetic structures. METHODS: To reveal genetic structures, we examined chloroplast microsatellite variations and genome-wide nucleotide polymorphisms obtained by genotyping by sequencing. We also estimated the gene flow among and within populations and performed landscape genetic analyses to evaluate seed and pollen movement and the extent of genetic isolation related to geographic distance and/or habitat differences. RESULTS: We found strong genetic structure in the specialist S. acerifolia, even on a small spatial scale (<1 km part); each population on a different waterfall in one river system had a completely different predominant haplotype. By contrast, the generalist S. fortunei showed no clear genetic differentiation. CONCLUSIONS: Our findings suggest that the level of genetic isolation was increased in S. acerifolia by the spatially fragmented habitat and limited seed and pollen dispersal over waterfalls. Habitat differentiation between the sister taxa could have contributed to the different patterns of gene flow and then shaped the contrasting genetic structures