Population structure of modern-day Italians reveals patterns of ancient and archaic ancestries in Southern Europe.

European populations display low genetic differentiation as the result of long-term blending of their ancient founding ancestries. However, it is unclear how the combination of ancient ancestries related to early foragers, Neolithic farmers, and Bronze Age nomadic pastoralists can explain the distribution of genetic variation across Europe. Populations in natural crossroads like the Italian peninsula are expected to recapitulate the continental diversity, but have been systematically understudied. Here, we characterize the ancestry profiles of Italian populations using a genome-wide dataset representative of modern and ancient samples from across Italy, Europe, and the rest of the world. Italian genomes capture several ancient signatures, including a non-steppe contribution derived ultimately from the Caucasus. Differences in ancestry composition, as the result of migration and admixture, have generated in Italy the largest degree of population structure detected so far in the continent, as well as shaping the amount of Neanderthal DNA in modern-day populations.

Arbuscular mycorrhizal fungal community differences among European long-term observatories.

Arbuscular mycorrhizal fungal (AMF) communities have been demonstrated to respond to a variety of biotic and abiotic factors, including various aspects of land management. Numerous studies have specifically addressed the impact of land use on AMF communities, but usually have been confined to one or a few sites. In this study, soil AMF assemblages were described in four different long-term observatories (LTOs) across Europe, each of which included a site-specific high-intensity and a low-intensity land use. AMF communities were characterized on the basis of 454 sequencing of the internal transcribed spacer 2 (ITS2) rDNA region. The primary goals of this study were (i) to determine the main factors that shape AMF communities in differentially managed sites in Europe and (ii) to identify individual AMF taxa or combinations of taxa suitable for use as biomarkers of land use intensification. AMF communities were distinct among LTOs, and we detected significant effects of management type and soil properties within the sites, but not across all sites. Similarly, indicator species were identified for specific LTOs and land use types but not universally for high- or low-intensity land uses. Different subsets of soil properties, including several chemical and physical variables, were found to be able to explain an important fraction of AMF community variation alone or together with other examined factors in most sites. The important factors were different from those for other microorganisms studied in the same sites, highlighting particularities of AMF biology.

Arbuscular mycorrhizal fungal communities and Rhizophagus irregularis populations shift in response to short-term ploughing and fertilisation in a buffer strip.

Short-term effects of soil physical disturbance by ploughing and nitrogen and phosphate fertilisation on arbuscular mycorrhizal fungal (AMF) communities and on intraspecific populations of Rhizophagus irregularis in a buffer strip surrounded by arable fields were studied. Pre-grown Plantago lanceolata plantlets were transplanted into fertilised and/or ploughed experimental plots. After 3 months, the glomeromycotan communities in the roots of these trap plants were analysed using 454 pyrosequencing of a fragment of the RNA polymerase II gene (RPB1). Intraspecific populations of R. irregularis were studied by restriction fragment length polymorphism (RFLP) analysis of the mitochondrial large ribosomal subunit (mtLSU) gene. Soil disturbance significantly increased the diversity of species-level molecular taxa (MTs) and altered community structure, whilst fertilisation alone had no significant effect, unless coupled with ploughing. At the population level, the expected shift from genotypes of R. irregularis typically found in grasslands to those usually found in arable sites was only partially observed. In conclusion, in the short-term, physical soil disturbance, as well as nitrogen fertilisation when coupled with physical soil disturbance, affected AMF community and to a smaller extent population composition.