Biogeographic variation in genetic variability, apomixis expression and ploidy of St. John's wort (Hypericum perforatum) across its native and introduced range.

BACKGROUND AND AIMS: St. John's wort (Hypericum perforatum) is becoming an important model plant system for investigations into ecology, reproductive biology and pharmacology. This study investigates biogeographic variation for population genetic structure and reproduction in its ancestral (European) and introduced (North America) ranges. METHODS: Over 2000 individuals from 43 localities were analysed for ploidy, microsatellite variation (19 loci) and reproduction (flow cytometric seed screen). Most individuals were tetraploid (93%), while lower frequencies of hexaploid (6%), diploid (<1%) and triploid (<1%) individuals were also identified. KEY RESULTS: A flow cytometric analysis of 24 single seeds per individual, and five individuals per population demonstrated opposite patterns between ploidy types, with tetraploids producing more apomictic (73%) than sexual (24%) seed, while hexaploids produced more sexual (73%) than apomictic (23%) seed. As hexaploids are derived from tetraploids, these data imply that gene dosage, in addition to the effects of hybridization, influences the switch from apomictic to sexual reproduction. No significant differences in seed production were found between Europe and North America. An analysis of population structure based upon microsatellite profiling demonstrated three major genetic clusters in Europe, whose distribution was reflective of Pleistocene glaciation (e.g. refugia) and post-glacial recolonization of Europe. CONCLUSIONS: The presence of pure and mixed populations representing all three genetic clusters in North America demonstrates that H. perforatum was introduced multiple times onto the continent, followed by gene flow between the different gene pools. Taken together, the data presented here suggest that plasticity in reproduction has no influence on the invasive potential of H. perforatum.

Isolation and characterization of microsatellite loci from apomictic Hypericum perforatum (Hypericaceae).

PREMISE OF THE STUDY: Microsatellite markers were developed to study the origins and evolution of apomictic Hypericum perforatum, a polyploid invasive perennial herb indigenous to Europe that produces compounds of medicinal/pharmaceutical importance. METHODS AND RESULTS: Eleven primer sets were developed using a non-radioactive protocol. All loci were polymorphic, showing from 2 to 9 alleles per locus. Observed and expected heterozygosity averaged 0.861 and 0.772, respectively, across four studied populations. Most primers also amplified successfully in eight other Hypericum species. CONCLUSIONS: Markers developed in this study provide genetic tools for studies of apomixis and invasiveness, both on the intra- and interspecific levels.

Genomic resources for wild populations of the house mouse, Mus musculus and its close relative Mus spretus.

Wild populations of the house mouse (Mus musculus) represent the raw genetic material for the classical inbred strains in biomedical research and are a major model system for evolutionary biology. We provide whole genome sequencing data of individuals representing natural populations of M. m. domesticus (24 individuals from 3 populations), M. m. helgolandicus (3 individuals), M. m. musculus (22 individuals from 3 populations) and M. spretus (8 individuals from one population). We use a single pipeline to map and call variants for these individuals and also include 10 additional individuals of M. m. castaneus for which genomic data are publically available. In addition, RNAseq data were obtained from 10 tissues of up to eight adult individuals from each of the three M. m. domesticus populations for which genomic data were collected. Data and analyses are presented via tracks viewable in the UCSC or IGV genome browsers. We also provide information on available outbred stocks and instructions on how to keep them in the laboratory.