Ecological specialization promotes diversity and diversification in the Eastern Mediterranean genus Ricotia (Brassicaceae)

Despite its amazing biodiversity, the Eastern Mediterranean remains a highly understudied region when compared withthe Western Mediterranean, restricting our understanding of diversity across the entire Mediterranean. Here we use a combination of molecular markers and presence/absence data from all species of the Eastern Mediterranean genus Ricotia collected across its full geographic range to determine historical, ecological, and evolutionary factors responsible for lineage-specific diversification in the Eastern Mediterranean. Network analysis based on molecular data revealed a high genetic structure within all lineages, and phylogenetic reconstructions based on the multispecies coalescent showed that within-lineage diversification corresponded to the onset of the Mediterranean climate. Reconstruction of ancestral histories indicates that the genus originated within Anatolia and spread across the Eastern Mediterranean and Levant using the Taurus mountains. Ecological niche models suggest that local populations did not go through any major distributional shifts and have persisted in present-day habitats since the Last Glacial Maximum. Furthermore, niche differentiation tests revealed significant differences between closely related species and showed the main variables predicting species limits to be different for each species. Our results give crucial information on the patterns and processes shaping diversity in the Eastern Mediterranean and show the main factors promoting diversification to be local environmental dynamics and ecological specialization and not large-scale latitudinal movements, as often reported for southern Europe. By determining local and regional patterns of diversification in an Eastern Mediterranean genus, we further our understanding of the major trends influencing plant diversity in the Mediterranean basin as a whole.     

Rearing conditions influence refuge use among over-wintering Atlantic salmon juveniles

At low population densities, both hatchery- and wild-reared Atlantic salmon Salmo salar , which were progeny of a common genetic stock, occupied sub-gravel shelters alone. However, at high population densities, hatchery-reared fish occurred within shelters in significantly higher numbers than wild-reared fish. There was a significant effect of time after introduction to the experimental arenas on the proportion of hatchery-reared fish sheltering. These results show that rearing environment influences the behaviour of Atlantic salmon parr during winter and may also affect the carrying capacity of their environment.