Genetic Diversity and Divergence in Populations of the Threatened Grassland Perennial Vincetoxicum atratum (Apocynaceae-Asclepiadoideae) in Japan.

We examined the genetic diversity and structure in populations of the endangered grassland herb Vincetoxicum atratum using 11 polymorphic microsatellite loci. Although the populations were small and disconnected, our molecular data indicated that the species maintains relatively high levels of genetic diversity and connectivity among populations. Population clustering analyses detected 2 to 3 clusters and most of the populations of V. atratum comprised admixture of these genetic clusters. These admixtures likely formed during the process of colonizing habitats that had been disturbed by human activities. However, STRUCTURE clustering detected low-admixtures in populations occurring in rocky maritime sites, which may not be suitable for agriculture/rangeland activities. High genetic diversity and population connectivity suggested that loss of the remaining populations by grassland reduction might be an immediate threat for this species. Small grasslands populations managed by local farmers need appropriate conservation practices. Although our results showed genetic diversity and gene flow among populations of V. atratum were high, it is possible that this resulted from the historical continuous distribution of the species. To examine this hypothesis, further periodical monitoring of the genetic diversity and the genetic differentiation for the species is needed for a conservation action of the species.

Going west - A subtropical lineage (Vincetoxicum, Apocynaceae: Asclepiadoideae) expanding into Europe.

Vincetoxicum sensu lato is a tropical lineage comprising two clades that have reached high northern latitudes. Of the temperate clades, one is restricted to the Far East, the other one (Vincetoxicum s. str. Clade) extends into Europe, but their ranges overlap in Central China and Japan. Three species invasive in North America, V. hirundinaria, V. nigrum and V. rossicum, are members of the Vincetoxicum s. str. Clade. We explore the prerequisites for the range expansion in the Vincetoxicum s. str. Clade performing Bayesian and Maximum Likelihood phylogenetic analyses on sequences of the nuclear internal transcribed spacer (ITS) region, the nuclear external transcribed spacer region (ETS), and five plastid markers. The resulting phylogeny is used to conduct biogeographic analysis using BioGeoBEARS to reconstruct ancestral species ranges. Moreover, we map the known occurrences of two rare characters in Asclepiadoideae, the possession of phenanthroindolizidine alkaloids and reported cases of autogamy onto our phylogeny. Finally, we have conducted ecological niche modelling using Maxent on a total of 220 spatially unique occurrences of nine Vincetoxicum s. str. species spanning more than 4,000 km along the east-west gradient to learn about the climatic conditions along the presumed migration route. Our results indicate a north-westward migration in Vincetoxicum s. str. along the Asian mountain chains to Europe. Climatic preferences of the nine species sampled are dissimilar, except for the common exposure to at least one month of subfreezing temperatures, indicating a rather wide climatic tolerance for the clade as a whole. The three species invasive in North America belong to the northern Eurasian subclade and show the rare combination of phenanthroindolizidine alkaloids and autogamy.

Variation of microsatellite loci in Vincetoxicum Wolf. species in the south-east of Ukraine.

The genetic diversity of 13 Vincetoxicum Wolf species distributed in Ukraine was investigated using 4 of the 8 nuclear microsatellite markers, previously developed for Vincetoxicum atratum from Japan. The number of alleles ranged from 8 to 25. The expected heterozygosities were 0,690­0,938 and observed ones ranged from 0,205 to 0,806. In general, the level of genetic variation in studied representatives of the genus Vincetoxicum from Ukraine proved to be comparable with that of Vincetoxicum atratum. The microsatellite loci Vinc5, Vinc104, Vinc123, Vinc124 can be successfully used to assess intra- and interspecific polymorphisms of species of the genus Vincetoxicum Wolf in Ukraine.