The Iberian Peninsula contains the majority of the Paleartic land slug species of the genus Arion, which exhibits diverse taxonomic problems. The present study investigated Arion taxonomy on the basis of analyses of the mitochondrial ND1 gene and nuclear internal transcribed spacer 1 (ITS1) sequences. The Iberian endemic species were monophyletically clustered in two divergent sister clades. The topotype specimens of Arion lusitanicus and the closely related species Arion nobrei and Arion fuligineus, as well as Arion hispanicus and Arion flagellus, were grouped into an ÔAtlanticÕ clade, whereas Arion baeticus, Arion gilvus, Arion anguloi, Arion wiktori and Arion paularensis were included in a ÔContinental-MediterraneanÕ clade. Calibration of mutation rate in the ND1 gene suggested that the divergence of these two clades occurred around the Pliocene-Pleistocene boundary, with subsequent speciation events during the Pleistocene. A group of ancestral and divergent endemic species with distribution centred in the Pyrenean mountain range (Arion molinae, Arion lizarrusti, Arion antrhacius and Arion iratii) arose in the Pliocene and survived through the Pleistocene in geographically confined small populations. Arion lusitanicus showed up to be polyphyletic: specimens, sampled outside the geographic range of the topotype in the north-western Iberian Peninsula, were included in a non-monophyletic clade together with the widely distributed species Arion ater and Arion rufus. The divergent species with a wide European distribution (Arion subfuscus, Arion hortensis, Arion fagophilus and Arion intermedius) were located in basal positions in all topologies. The evolutionary history of these slug species (highly sensitive to climatic factors, with capacity for both outcrossing and selfing, and with low dispersal ability) appears to have been moulded by Pliocene-Pleistocene climate events and by the rugged topography of southern Europe, giving rise to repeated cycles of population isolation during periods of glaciation alternating with interglacial expansions limited by geographic barriers.

No abstract

Clonally transmissible cancers are tumour lineages that are transmitted between individuals via the transfer of living cancer cells. In marine bivalves, leukaemia-like transmissible cancers, called hemic neoplasia (HN), have demonstrated the ability to infect individuals from different species. We performed whole-genome sequencing in eight warty venus clams that were diagnosed with HN, from two sampling points located more than 1000 nautical miles away in the Atlantic Ocean and the Mediterranean Sea Coasts of Spain. Mitochondrial genome sequencing analysis from neoplastic animals revealed the coexistence of haplotypes from two different clam species. Phylogenies estimated from mitochondrial and nuclear markers confirmed this leukaemia originated in striped venus clams and later transmitted to clams of the species warty venus, in which it survives as a contagious cancer. The analysis of mitochondrial and nuclear gene sequences supports all studied tumours belong to a single neoplastic lineage that spreads in the Seas of Southern Europe.

Microbial communities of natural subaerial biofilms developed on granitic historic buildings of a World Heritage Site (Santiago de Compostela, NW Spain) were characterized and cultured in liquid BG11 medium. Environmental barcoding through next-generation sequencing (Pacific Biosciences) revealed that the biofilms were mainly composed of species of Chlorophyta (green algae) and Ascomycota (fungi) commonly associated with rock substrata. Richness and diversity were higher for the fungal than for the algal assemblages and fungi showed higher heterogeneity among samples. Cultures derived from natural biofilms showed the establishment of stable microbial communities mainly composed of Chlorophyta and Cyanobacteria. Although most taxa found in these cultures were not common in the original biofilms, they are likely common pioneer colonizers of building stone surfaces, including granite. Stable phototrophic multi-species cultures of known microbial diversity were thus obtained and their reliability to emulate natural colonization on granite should be confirmed in further experiments.