Genetic consequences of Last Glacial-Holocene changes in snowfall regime in Arnica mallotopus populations: A plant confined to heavy-snow areas of Japan.

PREMISE: Snow is an important environmental factor affecting plant distribution. Past changes in snowfall regimes may have controlled the demographies of snow-dependent plants. However, our knowledge of changes in the distribution and demographies of such plants is limited because of the lack of fossil records. METHODS: Population genetic and landscape genetic analyses were used to investigate the response of population dynamics of Arnica mallotopus (Asteraceae)-a plant confined to heavy-snow areas of Japan-to changes in snowfall regimes from the Last Glacial Period to the Holocene. RESULTS: The population genetic analysis suggested that the four geographic lineages diverged during the Last Glacial Period. The interaction between reduced snowfall and lower temperatures during this period likely triggered population isolation in separate refugia. Subpopulation differentiation in the northern group was lower than in the southern group. Our ecological niche model predicted that the current distribution was patchy in the southern region; that is, the populations were isolated by topologically flat and climatically unsuitable lowlands. The landscape genetic analysis suggested that areas with little snowfall acted as barriers to the Holocene expansion of species distribution and continued limiting gene flow between local populations. CONCLUSIONS: These findings indicate that postglacial population responses vary among regions and are controlled by environmental and geographic factors. Thus, changes in snowfall regime played a major role in shaping the distribution and genetic structure of the snow-dependent plant.

Identification of management units in threatened populations of Arnica mallotopus Makino (Asteraceae) using novel EST-SSR markers.

Arnica mallotopus is a perennial herb endemic to the snowy regions of Japan. At the southern edge of its distribution, in Kyoto Prefecture, overgrazing by sika deer and decreased snowfall have resulted in the rapid decline of A. mallotopus populations. Therefore, there is an urgent need for a conservation genetic analysis of the remaining local populations. In this study, we first developed 13 EST-SSR markers to evaluate genetic variation in A. mallotopus. The average number of alleles per locus was 5.33. Genetic analysis using these markers showed that the investigated samples were classified into two groups corresponding to landscape structure. One group isolated from a tributary of the Yura River showed a strong population bottleneck signal, likely resulting from founder effects and subsequent drifts. On the other hand, the genetic diversity of the second group in the main distribution along the Yura River was higher and less inbred. Overall, our assessment suggested recognizing the two genetic groups as management units in conservation programs for the threatened populations.

Altitudinal variation of flavonoid content in the leaves of Fallopia japonica and the needles of Larix kaempferi on Mt. Fuji.

Ultraviolet-B radiation is harmful to plants, and its intensity increases at altitude. So plants growing at high altitude possess UV protection systems. Flavonoid is known as a major UV protectant because it absorbs UV radiation and scavenges UV-induced free radicals in plant tissues. Japanese knotweed (Fallopia japonica) and Japanese larch (Larix kaempferi) grow at a wide range of altitudes on Mt. Fuji, the highest mountain in Japan, while the two plants harbor a homogeneous genetic structure. In the present study, a total of 14 flavonol 3-O-glycosides were isolated from both species. Furthermore, quantitative HPLC analyses revealed that flavonoid levels in the leaves of F. japonica and the needles of L. kaempferi increased with increasing altitude of their growing sites. The altitudinal trend of UV-absorbing antioxidants of herbal and woody plants was simultaneously revealed for the first time. These results suggest that both species have chemically acclimatized to high altitude regions, in which severe environmental conditions such as higher UV radiation exist.

Flavonoids and their qualitative variation in Calystegia soldanella and related species (Convolvulaceae).

Coastal species are exposed to severe environmental stresses, e.g. salt and UV-B. The plants adapt themselves to such harsh environment by controlling morphological features and chemical defense systems. Flavonoids are known as efficient anti-stress polyphenols produced by plants. Most flavonoids show antioxidant activity, and their properties are important for plants to survive under high-stress conditions such as those in a coastal area. Among the compounds, ortho-dihydroxylated flavonoids act as strong antioxidants. In this survey, we elucidated the flavonoid composition of a seashore species Calystegia soldanella, which is distributed not only on the seashore, but also by the inland freshwater lake, Lake Biwa. Seven flavonol glycosides, i.e. quercetin 3-0- rutinoside, 3-O-glucoside, 3-O-rhamnoside and 3-O-apiosyl-(1-->2)-[rhamnosyl-(1-->6)-glucoside], and kaempferol 3-O-rutinoside, 3-O-glucoside and 3-0- rhamnoside were isolated from the leaves of C. soldanella. In addition, it was shown that the quercetin (Qu) to kaempferol (Km) ratio of coastal populations was higher than that of lakeshore populations. In general, these differences of Qu/Km ratio depend on flavonoid 3'-hydroxylase (F3'H) transcription. RT-PCR analysis suggested that F3'H of C. soldanella is regulated translationally or post-translationally, but not transcriptionally. Furthermore, quantitative and qualitative differences in flavonoid composition occurred among three Calystegia species, C. soldanella, C. japonica and C. hederacea.

Genetic differentiation and genetic diversity of Castanopsis (Fagaceae), the dominant tree species in Japanese broadleaved evergreen forests, revealed by analysis of EST-associated microsatellites.

The broadleaved evergreen forests of the East Asian warm temperate zone are characterised by their high biodiversity and endemism, and there is therefore a need to extend our understanding of its genetic diversity and phylogeographic patterns. Castanopsis (Fagaceae) is one of the dominant tree species in the broadleaved evergreen forests of Japan. In this study we investigate the genetic diversity, genetic structure and leaf epidermal morphology of 63 natural populations of C. sieboldii and C. cuspidata, using 32 Expressed Sequence Tag associated microsatellites. The overall genetic differentiation between populations was low (GST = 0.069 in C. sieboldii and GST = 0.057 in C. cuspidata). Neighbor-joining tree and Bayesian clustering analyses revealed that the populations of C. sieboldii and C. cuspidata were genetically clearly differentiated, a result which is consistent with the morphology of their epidermal cell layers. This suggests that C. sieboldii and C. cuspidata should be treated as independent species, although intermediate morphologies are often observed, especially at sites where the two species coexist. The higher level of genetic diversity observed in the Kyushu region (for both species) and the Ryukyu Islands (for C. sieboldii) is consistent with the available fossil pollen data for Castanopsis-type broadleaved evergreen trees during the Last Glacial Maximum and suggests the existence of refugia for Castanopsis forests in southern Japan. Within the C. sieboldii populations, Bayesian clustering analyses detected three clusters, in the western and eastern parts of the main islands and in the Ryukyu Islands. The west-east genetic differentiation observed for this species in the main islands, a pattern which is also found in several plant and animal species inhabiting Castanopsis forests in Japan, suggests that they have been isolated from each other in the western and eastern populations for an extended period of time, and may imply the existence of eastern refugia.