Genetic Diversity of Andean Tuber Crop Species in the in situ Microcenter of Huanuco, Peru

in Crop Science (2010), (50), 1915-1923

Forest refugia revisited: nSSRs and cpDNA sequences support historical isolation in a wide-spread African tree with high colonization capacity, Milicia excelsa (Moraceae)

in Molecular Ecology (2010)

The impact of the Pleistocene climate oscillations on the structure of biodiversity in tropical regions remains poorly understood. In this study, the forest refuge theory is examined at the molecular ... [more ▼]

The impact of the Pleistocene climate oscillations on the structure of biodiversity in tropical regions remains poorly understood. In this study, the forest refuge theory is examined at the molecular level in Milicia excelsa, a dioecious tree with a continuous range throughout tropical Africa. Eight nuclear microsatellites (nuSSRs) and two sequences and one microsatellite from chloroplast DNA (cpDNA) showed a deep divide between samples from Benin and those from Lower Guinea. This suggests both that these populations were isolated in separate geographical regions, probably for several glacial cycles of the Pleistocene, and a poor mixture of gene pools despite M. excelsa’s wind-pollination syndrome. The divide can also be related to seed dispersal patterns, which should be largely determined by the migration behaviour of M. excelsa's main seed disperser, the frugivorous bat Eidolon helvum. Within Lower Guinea, a north-south divide, observed with both markers despite weak genetic structure (nuSSRs: FST=0.035, cpDNA: GST=0.506), suggested the existence of separate Pleistocene refugia in Cameroon and the Gabon/Congo region. We inferred a pollen-to-seed dispersal distance ratio of 1.76, consistent with wide-ranging gene dispersal by both wind and bats. Simulations in an Approximate Bayesian Computation framework suggested low nuSSR and cpDNA mutation rates but imprecise estimates of other demographic parameters, probably due to a substantial gene flow between the Lower Guinean gene pools. The decline of genetic diversity detected in some Gabonese populations could be a consequence of the relatively recent establishment of a closed canopy forest which may negatively affect M. excelsa's reproductive system. [less ▲]

Spatial genetic structure in Milicia excelsa (Moraceae) indicates extensive gene dispersal in a low-density wind-pollinated tropical tree

in Molecular Ecology (2009), 18

In this study, we analysed spatial genetic structure (SGS) patterns and estimated dispersal distances in Milicia excelsa (Welw.) C.C. Berg (Moraceae), a threatened windpollinated dioecious African tree ... [more ▼]

In this study, we analysed spatial genetic structure (SGS) patterns and estimated dispersal distances in Milicia excelsa (Welw.) C.C. Berg (Moraceae), a threatened windpollinated dioecious African tree, with typically low density ( 10 adults ⁄km2). Eight microsatellite markers were used to type 287 individuals in four Cameroonian populations characterized by different habitats and tree densities. Differentiation among populations was very low. Two populations in more open habitat did not display any correlation between genetic relatedness and spatial distance between individuals, whereas significant SGS was detected in two populations situated under continuous forest cover. SGS was weak with a maximum Sp-statistic of 0.006, a value in the lower quartile of SGS estimates for trees in the literature. Using a stepwise approach with Bayesian clustering methods, we demonstrated that SGS resulted from isolation by distance and not colonization by different gene pools. Indirect estimates of gene dispersal distances ranged from rg = 1 to 7.1 km, one order of magnitude higher than most estimates found in the literature for tropical tree species. This result can largely be explained by life-history traits of the species. Milicia excelsa exhibits a potentially wideranging wind-mediated pollen dispersal mechanism as well as very efficient seed dispersal mediated by large frugivorous bats. Estimations of gene flow suggested no major risk of inbreeding because of reduction in population density by exploitation. Different strategy of seed collection may be required for reforestation programmes among populations with different extent of SGS. [less ▲]

Fitness And Genetic Variation Of Viola Calaminaria, An Endemic Metallophyte: Implications Of Population Structure And History

in Plant Biology (2008), 10(6), 684-693

We investigated variations in genetic diversity and plant fitness in a rare endemic metallophyte of calamine soils, Viola calaminaria, in relation to population size, population connectivity and ... [more ▼]

We investigated variations in genetic diversity and plant fitness in a rare endemic metallophyte of calamine soils, Viola calaminaria, in relation to population size, population connectivity and population history in order to evaluate and discuss potential conservation strategies for the species. Mean population genetic diversity (Hs = 0.25) of V. calaminaria was similar to endemic non-metallophyte taxa. Twenty-one per cent of the genetic variation was partitioned among populations and a low (9%) but significant differentiation was found among geographical regions. Our results did not support the hypothesis that the acquisition of metal tolerance may result in reduced genetic diversity, and suggested that strict metallophytes do not exhibit higher inter-population differentiation resulting from scattered habitats. There were no relationships between population genetic diversity and population size. Significant correlations were found between plant fitness and (i) population size and (ii) connectivity index. Recently-founded populations exhibited the same level of genetic diversity as ancient populations and also possessed higher plant fitness. There was no indication of strong founder effects in recently-established populations. The results suggest that the creation of habitats through human activities could provide new opportunities for conservation of this species. [less ▲]

Spatial and temporal variation of reproductive success in an endemic metallophyte, Viola calaminaria: implications for conservation.

Conference (2007)

Hybridization And Morphogenetic Variation In The Invasive Alien Fallopia (Polygonaceae) Complex In Belgium

in American Journal of Botany (2007), 94(11), 1900-1910

The invasive alien knotweeds, Fallopia spp. (Polygonaceae), are some of the most troublesome invasive species in Europe and North America. Invasive success in Fallopia may be enhanced by multiple ... [more ▼]

The invasive alien knotweeds, Fallopia spp. (Polygonaceae), are some of the most troublesome invasive species in Europe and North America. Invasive success in Fallopia may be enhanced by multiple hybridization events. We examined the pattern of hybridization and its evolutionary consequences in Belgium with a concerted analysis of ploidy levels (chromosome counts and flow cytometry), morphological variation, and genetic variation (RAPDs). At least four taxa with different ploidy levels were part of the pattern of invasion in Belgium. Hybrid F.3bohemica with various chromosome numbers restored the genotypic diversity that was lacking in the parental species. Hybrid genotypes were mainly assigned to a specific genetic pool and not to a mixture between the genetic pools of the putative parental species as would be expected for hybrids. Parental species and hexaploid hybrids differed significantly for a set of well-defined morphological characters, enabling future researchers to distinguish these taxa. On the basis of our results, the importance of hybridization has probably been underestimated in large parts of the adventive range of alien Fallopia species, pointing to the need for concerted molecular and morphological analyses in the study of the evolutionary consequences of hybridization. [less ▲]

Influence of human activities on the metallic trace elements status in soils

Conference (2006)

The total concentrations of trace elements in soils results from natural and anthropic factors. Knowledge of natural distribution (e.g. bio-geochemical background) helps assessing the impacts of human ... [more ▼]

The total concentrations of trace elements in soils results from natural and anthropic factors. Knowledge of natural distribution (e.g. bio-geochemical background) helps assessing the impacts of human activities in terms of contaminations. But the processes generated by the modifications of the soil environment may also affect the form of a trace element, that is its distribution through various pools. We investigated the chemical speciation of some metallic trace elements (Cu, Zn, Cr, Ni, Pb, Co, Cd) in soils from various land-use environment: “natural” soils under forest, “typical” cultivated soils, kitchen-garden soils, soils developped on geogenic anomalies and on contaminated areas. The analysis protocol aims at identifying different pools from their reaction to various extraction phases, ordered by increasing intensity in a single sequence. The different fractions are so-called soluble, linked to carbonates, to organic matter, to manganese oxides, to weakly cristallized Fe-Al oxides, to well-cristallized oxides, and residual. The “available” and total fractions have also been measured. The results stress the fact that the comparisons are difficult from one situation to another because each one represents a particular case of human activity without a common logic. The relationships with the classical pedological parameters are therefore difficult to generalize. However some relationships between elements have been found inside the various types of land use, which could be usefull in the risk assesment of transfers from soils to plants. [less ▲]

Within-population genetic structure and clonal diversity of Viola calaminaria, an endemic metallophyte

Poster (2006)

Viola calaminaria: genetic diversity and occurrence in Belgium.

Conference (2006)

The role of heavy-metal stress on plant population genetic variation: the case of Viola calaminaria.

Conference (2005)