Rapid radiation in the barley genus Hordeum (Poaceae) during

Abstract Evidence was found for a rapid radiation of the grass genus Hordeum in the Americas during the last 2 million years, accumulating 23 species in South and North America, while only 10 Hordeum species occur in other regions of the world. The differences in species richness are caused by distinct evolutionary mechanisms in the Americas and Eurasia, as recovered by the integration of phylogenetic and phylogeographic analyses with modeling of ecological niches. The Eurasian region is mainly characterized by a loss of biodiversity during the Pleistocene glaciations, while vivid speciation took place in the Americas during this time period. Thus, speciation in Eurasia was mainly affected by severe genetic bottlenecks probably due to small populations surviving in ice-age refugia, while such restrictions in New World species groups seem less pronounced. Particularly in southern Patagonia, speciation was due to multiple geographical subdivisions of relatively large populations during the last million years, without measurable reduction of genetic diversity or population sizes. This together with long-distance colonization of remote areas was the main cause of species diversity in the New World

The Relictual Fern Genus Loxsomopsis

Volume: 91Start Page: 13End Page: 2

Ecotypes and genetic structure of Rhinanthus alectorolophus (Orobanchaceae) in southwestern Germany

European annual species of the genus Rhinanthus often exhibit seasonal ecotypic variation, a phenomenon also known from related genera of hemiparasitic Orobanchaceae. Populations with different flowering times exist, correlated with differences in a number of morphological characters. The present study evaluates the correlation of morphological characters and genetic differentiation of populations of Rhinanthus alectorolophus. Thirty-nine populations of three different subspecies from southwestern Germany were sampled. A total of 798 individuals were used for morphological analyses and 187 of these for AFLP analyses. Principal component analysis showed that morphological variation is mostly continuous. In a discriminant analysis based on morphological characters, only 89.7 % of all individuals were correctly assigned to their previously determined subspecies, indicating that subspecies identification is ambiguous for some populations. Using AFLP data and Bayesian assignment analysis, the sampled individuals could be grouped in three genetic clusters which do not correspond to the three subspecies. Instead, the clustering shows a clear geographic pattern and a Mantel test likewise revealed a significant correlation between genetic and geographic distances. Correlations of genetic distances with differences in morphological characters were weak and mostly insignificant. The results indicate that the subspecies of R. alectorolophus do not form discrete entities and that the character combinations distinguishing them are homoplastic