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Background and Aims Ongoing and previous range expansions have a strong influence on population genetic structure of plants. In turn, genetic variation in the new range may affect the population dynamics and the expansion process. The annual Ceratocapnos claviculata (Papaveraceae) has expanded its Atlantic European range in recent decades towards the north and east. Patterns of genetic diversity were investigated across the native range to assess current population structure and phylogeographical patterns. A test was then made as to whether genetic diversity is reduced in the neophytic range and an attempt was made to identify source regions of the expansion. Methods Samples were taken from 55 populations in the native and 34 populations in the neophytic range (Sweden, north-east Germany). Using amplified fragment length polymorphism markers an analysis was made of genetic variation and population structure (Bayesian statistical modelling) and population differentiation was quantified. Pollen/ovule ratio was analysed as a proxy for the breeding system. Key Results Genetic diversity at population level was very low (mean He = 0·004) and two multilocus genotypes dominated large parts of the new range. Population differentiation was strong (FST = 0·812). These results and a low pollen/ovule ratio are consistent with an autogamous breeding system. Genetic variation decreased from the native to the neophytic range. Within the native range, He decreased towards the north-east, whereas population size increased. According to the Bayesian cluster analysis, the putative source regions of the neophytic range are situated in north-west Germany and adjacent regions. Conclusions Ceratocapnos claviculata shows a cline of genetic variation due to postglacial recolonization from putative Pleistocene refugia in south-west Europe. Nevertheless, the species has expanded successfully during the past 40 years to southern Sweden and north-east Germany where it occurs as an opportunistic

The eu-oceanic therophytic woodland herb Ceratocapnos claviculata has been expanding north- and eastwards into north temperate and subcontinental regions during the past decades. The rapid range expansion of the species may be an example of a species which is strongly profiting from global change. Against this background, in the present paper we review the taxonomy, morphology, distribution, habitat requirements, life cycle and biology of the species.

Habitat fragmentation and reduction of population size have been found to negatively affect plant reproduction in ‘new rare’ species that were formerly common. This has been attributed primarily to effects of increased inbreeding but also to pollen limitation. In contrast, little is known about the reproduction of ‘old rare’ species that are naturally restricted to small and isolated habitats and thus may have developed strategies to cope with long-term isolation and small population size. Here we study the effects of pollen source and quantity on reproduction of the ‘old rare’ bumblebee-pollinated herb, Astragalus exscapus. In two populations of this species, we tested for pollen autodeposition, inbreeding depression and outbreeding depression. Caged plants were left unpollinated or were pollinated with pollen from the same plant, from the same population or from a distant population (50 km). Additionally, we tested for pollen limitation by pollen supplementation in four populations of different size and density. In the absence of pollinators, plants did not produce seed whereas self-pollinated plants did. This indicates a self-compatible breeding system dependent on insect pollination. Both self-pollination and, in one of the two populations, cross-pollination with pollen from plants from the distant population resulted in a lower number of seeds per flower than cross-pollination with pollen from plants from the resident population, indicating inbreeding and outbreeding depression. Pollen addition enhanced fruit set and number of seeds per flower in three of the four populations, indicating pollen limitation. The degree of pollen limitation was lowest in the smallest but densest population. Our results suggest that, similar to ‘new rare’ plant species, also ‘old rare’ species may be at risk of inbreeding depression and pollen limitation.

Question: The eu-atlantic forest herb Ceratocapnos claviculata showed a recent increase in frequency within its native range and an eastward and northward range expansion in Central Europe. To gain deeper understanding of factors affecting the range expansion of the species, we analyzed vegetation relevés at three different scales and asked the following questions: As the species occurs in a wide range of vegetation types, is variation in community composition across the entire range related to climatic environmental zones and tree cover? Are there differences in species composition and habitat characteristics between the native range and the two invaded regions (S Sweden and NE Germany)? Did community composition and habitat characteristics within the native range (The Netherlands) change between ‘before 1970’ and ‘1990 to 2006’? Location: W, C and N Europe. Methods: We analysed vegetation-plot data with C. claviculata from various databases and own surveys using partial CCA, partial DCA, Indicator Species Analysis, MANCOVA and multiple regression. Results: Using vegetation plots from the entire distribution range, climatic environmental zones explained 68.9% of the total canonical Eigenvalue. Differences in floristic composition and habitat characteristics between the two invaded regions were as large as between native and invaded range sites. However, relevés from the invaded range were generally characterized by anthropogenic disturbance. Accordingly, abundance of C. claviculata was positively linked to silvicultural intensity. New relevés from 1990 to 2006 were characterized by higher Ellenberg nutrient indicator values, lower species diversity, higher proportions of neophytic and hemerobic species and showed a lower cover of the study species than old relevés from before 1970. Conclusions: Across the range of C. claviculata, climatic environmental zones determine vegetation composition. Accordingly, the species is charac