Pollen-mediated gene flow in a highly fragmented landscape: consequences for defining a conservation strategy of the relict Laperrine's olive.

In the present central Saharan conditions, the Laperrine's olive regeneration has never been observed and its populations are locally threatened. The production of plants originating from seeds was proposed as a multiplication strategy. In order to determine the impact of sexual reproduction, seeds issued from ten mothers (sampled from four locations in the Hoggar, Algeria) were genotyped using microsatellites. Compared to the initial population, a significant lost of allelic richness was revealed, indicating that our seed sampling was not representative of the local gene diversity. Paternity analyses allowed measurement of the effective pollen-mediated gene flow within patches. Preferential mating between some genotypes was revealed. A trend for a higher multipaternity on seeds collected on trees from relatively large patches was also observed. Lastly, seedlings issued from trees of small patches displayed low growth performance. The implications of our observations in the development of an efficient conservation strategy by seeds are discussed

Biogeography of the date palm (Phoenix dactylifera L., Arecaceae): insights on the origin and on the structure of modern diversity

AGAP : équipe Génomique évolutive et gestion des populations (GE²pop)The biogeography of the date palm (Phoenix dactylifera L.), the origin, structure and dynamics of its agrobiodiversity, and the relationships to other species of Phoenix are reviewed. Phoenix dactylifera is confirmed as a distinct species and has closest affinities with P. sylvestris and P. atlantica. Multiple origins of domestication are likely, within two highly distinct primary gene pools, one oriental (Middle East) and one occidental (south-western Europe and north-western Africa), subsequently partially admixed, especially in the intermediate zone of North Africa. A rationale to identify wild populations of P. dactylifera, using a combination of chloroplast barcoding and nuclear microsatellite genotyping is proposed. A domestication model is presented and the domestication syndrome is described, as well as the nature of cultivars. All data indicate a strong geographic structure of the genetic diversity of the date palm at all scales (local, regional, global), and the importance of both isolation and intraspecific gene flow in shaping the present day agrobiodiversity, while there is no evidence of interspecific hybridization in the cultivated gene pool

Genetic structure of the date palm (Phoenix dactylifera) in the Old World reveals a strong differentiation between eastern and western populations

Background and Aims Date palms (Phoenix dactylifera, Arecaceae) are of great economic and ecological value to the oasis agriculture of arid and semi-arid areas. However, despite the availability of a large date palm germplasm spreading from the Atlantic shores to Southern Asia, improvement of the species is being hampered by a lack of information on global genetic diversity and population structure. In order to contribute to the varietal improvement of date palms and to provide new insights on the influence of geographic origins and human activity on the genetic structure of the date palm, this study analysed the diversity of the species. Methods Genetic diversity levels and population genetic structure were investigated through the genotyping of a collection of 295 date palm accessions ranging from Mauritania to Pakistan using a set of 18 simple sequence repeat (SSR) markers and a plastid minisatellite. Key Results Using a Bayesian clustering approach, the date palm genotypes can be structured into two different gene pools: the first, termed the Eastern pool, consists of accessions from Asia and Djibouti, whilst the second, termed the Western pool, consists of accessions from Africa. These results confirm the existence of two ancient gene pools that have contributed to the current date palm diversity. The presence of admixed genotypes is also noted, which points at gene flows between eastern and western origins, mostly from east to west, following a human-mediated diffusion of the species. Conclusions This study assesses the distribution and level of genetic diversity of accessible date palm resources, provides new insights on the geographic origins and genetic history of the cultivated component of this species, and confirms the existence of at least two domestication origins. Furthermore, the strong genetic structure clearly established here is a prerequisite for any breeding programme exploiting the effective polymorphism related to each gene pool

Projected distributions of novel and disappearing climates by 2100 AD

Key risks associated with projected climate trends for the 21st century include the prospects of future climate states with no current analog and the disappearance of some extant climates. Because climate is a primary control on species distributions and ecosystem processes, novel 21st-century climates may promote formation of novel species associations and other ecological surprises, whereas the disappearance of some extant climates increases risk of extinction for species with narrow geographic or climatic distributions and disruption of existing communities. Here we analyze multimodel ensembles for the A2 and B1 emission scenarios produced for the fourth assessment report of the Intergovernmental Panel on Climate Change, with the goal of identifying regions projected to experience (i) high magnitudes of local climate change, (ii) development of novel 21st-century climates, and/or (iii) the disappearance of extant climates. Novel climates are projected to develop primarily in the tropics and subtropics, whereas disappearing climates are concentrated in tropical montane regions and the poleward portions of continents. Under the high-end A2 scenario, 12–39% and 10–48% of the Earth's terrestrial surface may respectively experience novel and disappearing climates by 2100 AD. Corresponding projections for the low-end B1 scenario are 4–20% and 4–20%. Dispersal limitations increase the risk that species will experience the loss of extant climates or the occurrence of novel climates. There is a close correspondence between regions with globally disappearing climates and previously identified biodiversity hotspots; for these regions, standard conservation solutions (e.g., assisted migration and networked reserves) may be insufficient to preserve biodiversity