Project description:Background and aimsFour species of Pinus subsection Australes occur in the Caribbean Basin: P. caribaea, P. cubensis, P. maestrensis and P. occidentalis. This study analyses the phylogeography of these species to assess possible colonization events from Central America to the islands and subsequent population expansions during glacial periods driven by both drier climate and larger emerged land areas.MethodsAllele size data were obtained for plastid microsatellites for 314 individuals from 24 populations, covering the distribution range of subsection Australes in the Caribbean Basin.Key resultsIn total, 113 plastid haplotypes were identified. The highest genetic diversity was found in populations of P. caribaea. Overall, Caribbean Basin populations fit the isolation by distance model. Significant phylogeographical structure was found (R(ST) = 0·671 > permuted R(ST) = 0·101; P < 0·0001). The haplotype network and a Bayesian analysis of population structure (BAPS) indicated different Central American origins for P. caribaea var. bahamensis and P. caribaea var. caribaea plastids, with Central America populations in northern and south-eastern groups. Sudden expansion times for BAPS clusters were close to three glacial maxima.ConclusionsCentral America contains ancestral plastid haplotypes. Population expansion has played a major role in the distribution of genetic diversity in P. caribaea var. hondurensis. Two colonization events gave rise to the P. caribaea var. bahamensis and P. caribaea var. caribaea lineages. Plastid variation in the eastern species (P. cubensis, P. maestrensis and P. occidentalis) evolved independently from that in P. caribaea var. caribaea. Incomplete lineage sorting between P. cubensis and P. maestrensis is apparent. Inferred expansion times for P. caribaea var. bahamensis and for the eastern lineages correspond to glacial maxima, whereas those for P. caribaea var. hondurensis correspond to the beginning of the temperature decrease that led to Marine Isotope Stage 8.
Project description:We describe a model for the conditional dependence of a spatial process measured at one or more remote locations given extreme values of the process at a conditioning location, motivated by the conditional extremes methodology of Heffernan and Tawn. Compared to alternative descriptions in terms of max-stable spatial processes, the model is advantageous because it is conceptually straightforward and admits different forms of extremal dependence (including asymptotic dependence and asymptotic independence). We use the model within a Bayesian framework to estimate the extremal dependence of ocean storm severity (quantified using significant wave height, H S ) for locations on spatial transects with approximate east-west (E-W) and north-south (N-S) orientations in the northern North Sea (NNS) and central North Sea (CNS). For H S on the standard Laplace marginal scale, the conditional extremes "linear slope" parameter α decays approximately exponentially with distance for all transects. Furthermore, the decay of mean dependence with distance is found to be faster in CNS than NNS. The persistence of mean dependence is greatest for the E-W transect in NNS, potentially because this transect is approximately aligned with the direction of propagation of the most severe storms in the region.
Project description:Bats provide key ecosystem services such as crop pest regulation, pollination, seed dispersal, and soil fertilization. Bats are also major hosts for biological agents responsible for zoonoses, such as coronaviruses (CoVs). The islands of the Western Indian Ocean are identified as a major biodiversity hotspot, with more than 50 bat species. In this study, we tested 1,013 bats belonging to 36 species from Mozambique, Madagascar, Mauritius, Mayotte, Reunion Island and Seychelles, based on molecular screening and partial sequencing of the RNA-dependent RNA polymerase gene. In total, 88 bats (8.7%) tested positive for coronaviruses, with higher prevalence in Mozambican bats (20.5% ± 4.9%) as compared to those sampled on islands (4.5% ± 1.5%). Phylogenetic analyses revealed a large diversity of α- and β-CoVs and a strong signal of co-evolution between CoVs and their bat host species, with limited evidence for host-switching, except for bat species sharing day roost sites. These results highlight that strong variation between islands does exist and is associated with the composition of the bat species community on each island. Future studies should investigate whether CoVs detected in these bats have a potential for spillover in other hosts.