Plant traits correlated with generation time directly affect inbreeding depression and mating system and indirectly genetic structure

<p>Abstract</p> <p>Background</p> <p>Understanding the mechanisms that control species genetic structure has always been a major objective in evolutionary studies. The association between genetic structure and species attributes has received special attention. As species attributes are highly taxonomically constrained, phylogenetically controlled methods are necessary to infer causal relationships. In plants, a previous study controlling for phylogenetic signal has demonstrated that Wright's <it>F</it>_ST, a measure of genetic differentiation among populations, is best predicted by the mating system (outcrossing, mixed-mating or selfing) and that plant traits such as perenniality and growth form have only an indirect influence on <it>F</it>_STvia their association with the mating system. The objective of this study is to further outline the determinants of plant genetic structure by distinguishing the effects of mating system on gene flow and on genetic drift. The association of biparental inbreeding and inbreeding depression with population genetic structure, mating system and plant traits are also investigated.</p> <p>Results</p> <p>Based on data from 263 plant species for which estimates of <it>F</it>_ST, inbreeding (<it>F</it>_IS) and outcrossing rate (<it>t</it>_m) are available, we confirm that mating system is the main influencing factor of <it>F</it>_ST. Moreover, using an alternative measure of <it>F</it>_STunaffected by the impact of inbreeding on effective population size, we show that the influence of <it>t</it>_mon <it>F</it>_STis due to its impact on gene flow (reduced pollen flow under selfing) and on genetic drift (higher drift under selfing due to inbreeding). Plant traits, in particular perenniality, influence <it>F</it>_STmostly via their effect on the mating system but also via their association with the magnitude of selection against inbred individuals: the mean inbreeding depression increases from short-lived herbaceous to long-lived herbaceous and then to woody species. The influence of perenniality on mating system does not seem to be related to differences in stature, as proposed earlier, but rather to differences in generation time.</p> <p>Conclusion</p> <p>Plant traits correlated with generation time affect both inbreeding depression and mating system. These in turn modify genetic drift and gene flow and ultimately genetic structure.</p

spacodiR: structuring of phylogenetic diversity in ecological communities

Motivation: spacodiR is a cross-platform package, written for the R environment, for studying partitioning of diversity among natural communities in space and time. Complementing and extending existing software, spacodiR allows for hypothesis testing and parameter estimation in studying spatial structuring of species-, phylogenetic- and trait diversities. Availability: Integrated with other software in the R environment and with well documented and demonstrated functions, spacodiR is an open-source package and available at http://cran.r-project.org. Contact: [email protected]; [email protected]

On a species complex, Afzelia, in African forests of economic and ecological interest. A review

The purpose of this review is to provide a knowledge update and a comprehensive literature review of the genus Afzelia, a complex of sister species exploited for their timber in Central Africa. The distribution of Afzelia species in Africa suggests that the tree has made various adaptations due to ecological factors. However, on the basis of only vegetative criteria, it is difficult to distinguish species in forest inventory, and this could compromise the sustainable management approach promoted by the populations of Central African countries. We show that the genus remains generally understudied, although some of its species are considered by the IUCN as being under threat. Therefore, the ecological and genetic aspects of our investigations should prove relevant to the future cultivation of Afzelia

Lifshitz critical point in the cuprate superconductor YBa2Cu3Oy from high-field Hall effect measurements

The Hall coefficient R_H of the cuprate superconductor YBa2Cu3Oy was measured in magnetic fields up to 60 T for a hole concentration p from 0.078 to 0.152, in the underdoped regime. In fields large enough to suppress superconductivity, R_H(T) is seen to go from positive at high temperature to negative at low temperature, for p > 0.08. This change of sign is attributed to the emergence of an electron pocket in the Fermi surface at low temperature. At p < 0.08, the normal-state R_H(T) remains positive at all temperatures, increasing monotonically as T \to 0. We attribute the change of behaviour across p = 0.08 to a Lifshitz transition, namely a change in Fermi-surface topology occurring at a critical concentration p_L = 0.08, where the electron pocket vanishes. The loss of the high-mobility electron pocket across p_L coincides with a ten-fold drop in the conductivity at low temperature, revealed in measurements of the electrical resistivity $\rho$ at high fields, showing that the so-called metal-insulator crossover of cuprates is in fact driven by a Lifshitz transition. It also coincides with a jump in the in-plane anisotropy of $\rho$, showing that without its electron pocket the Fermi surface must have strong two-fold in-plane anisotropy. These findings are consistent with a Fermi-surface reconstruction caused by a unidirectional spin-density wave or stripe order.Comment: 16 pages, 13 figures, see associated Viewpoint: M. Vojta, Physics 4, 12 (2011