A last stand in the Po valley: Genetic structure and gene flow patterns in Ulmus minor and U. pumila

Background and Aims Ulmus minor has been severely affected by Dutch elm disease (DED). The introduction into Europe of the exotic Ulmus pumila, highly tolerant to DED, has resulted in it widely replacing native U. minor populations. Morphological and genetic evidence of hybridization has been reported, and thus there is a need for assessment of interspecific gene flow patterns in natural populations. This work therefore aimed at studying pollen gene flow in a remnant U. minor stand surrounded by trees of both species scattered across an agricultural landscape. Methods All trees from a small natural stand (350 in number) and the surrounding agricultural area within a 5-km radius (89) were genotyped at six microsatellite loci. Trees were morphologically characterized as U. minor, U. pumila or intermediate phenotypes, and morphological identification was compared with Bayesian clustering of genotypes. For paternity analysis, seeds were collected in two consecutive years from 20 and 28 mother trees. Maximum likelihood paternity assignment was used to elucidate intra- and interspecific gene flow patterns. Key Results Genetic structure analyses indicated the presence of two genetic clusters only partially matching the morphological identification. The paternity analysis results were consistent between the two consecutive years of sampling and showed high pollen immigration rates ( 3c0 80) and mean pollination distances ( 3c3 km), and a skewed distribution of reproductive success. Few intercluster pollinations and putative hybrid individuals were found. Conclusions Pollen gene flow is not impeded in the fragmented agricultural landscape investigated. High pollen immigration and extensive pollen dispersal distances are probably counteracting the potential loss of genetic variation caused by isolation. Some evidence was also found that U. minor and U. pumila can hybridize when in sympatry. Although hybridization might have beneficial effects on both species, remnant U. minor populations represent a valuable source of genetic diversity that needs to be preserved

I periodici settecenteschi come luogo di comunicazione dei saperi: prospettive storiche, letterarie e linguistiche

Il presente volume raccoglie ventiquattro saggi, frutto di studi svolti principalmente sui periodici francesi, italiani e tedeschi del XVIII secolo. I contributi si occupano, con taglio di volta in volta storico, letterario e linguistico, di alcuni fra i più rilevanti prodotti del giornalismo settecentesco: i periodici eruditi, le riviste scientifiche, il giornalismo spettatoriale, quello enciclopedico e quello politico. Dai saggi raggruppati in questo volume esce un’immagine senza dubbio rinnovata, per complessità e ricchezza di particolari, dei periodici pubblicati nel XVIII secolo. Pur nella loro eterogeneità, essi sono diventati l’architrave del dialogo culturale europeo anche perché non si sono rivolti solo a un selezionato pubblico di dotti, ma, in alcuni casi, ai lettori semplicemente alfabetizza