Comparative Population Genetic Structures And Local Adaptation Of Two Mutualists

International audienceSimilar patterns of dispersal and gene flow between closelyassociated organisms may promote local adaptation andcoevolutionary processes. We compare the genetic structures of thetwo species of a plant genus (Roridula gorgonias and R. dentata)and their respective obligately associated hemipteran mutualists(Pameridea roridulae and P. marlothi) using allozymes. Inaddition, we determine whether genetic structure is related todifferences in host choice by Pameridea. Allozyme variation wasfound to be very structured among plant populations but less soamong hemipteran populations. Strong genetic structuring amonghemipteran populations was only evident when large distancesisolated the plant populations on which they live. Althoughgenetic distances among plant populations were correlated withgenetic distances among hemipteran populations, genetic distancesof both plants and hemipterans were better correlated withgeographic distance. Because Roridula and Pameridea have differentscales of gene flow, adaptation at the local population level isunlikely. However, the restricted gene flow of both plants andhemipterans could enable adaptation to occur at a regional level.In choice experiments, the hemipteran (Pameridea) has a strongpreference for its carnivorous host plant (Roridula) aboveunrelated host plants. Pameridea also prefers its host species toits closely related sister species. Specialization at the specificlevel is likely to reinforce cospeciation processes in thismutualism. However, Pameridea does not exhibit intraspecificpreferences toward plants from their natal populations aboveplants from isolated, non-natal populations

Relationships between demography and gene flow and their importance for the conservation of tree populations in tropical forests under selective felling regimes

Determining how tropical tree populations subject to selective felling (logging) pressure may be conserved is a crucial issue for forest management and studying this issue requires a comprehensive understanding of the relationships between population demography and gene flow. We used a simulation model, SELVA, to study (1) the relative impact of demographic factors (juvenile mortality, felling regime) and genetic factors (selfing, number and location of fathers, mating success) on long-term genetic diversity; and (2) the impact of different felling regimes on population size versus genetic diversity. Impact was measured by means of model sensitivity analyses. Juvenile mortality had the highest impact on the number of alleles and genotypes, and on the genetic distance between the original and final populations. Selfing had the greatest impact on observed heterozygote frequency and fixation index. Other factors and interactions had only minor effects. Overall, felling had a greater impact on population size than on genetic diversity. Interestingly, populations under relatively low felling pressure even had a somewhat lower fixation index than undisturbed populations (no felling). We conclude that demographic processes such as juvenile mortality should be modelled thoroughly to obtain reliable long-term predictions of genetic diversity. Mortality in selfed and outcrossed progenies should be modelled explicitly by taking inbreeding depression into account. The modelling of selfing based on population rate appeared to be oversimplifying and should account for inter-tree variation. Forest management should pay particular attention to the regeneration capacities of felled species

Relationships between population density, fine-scale genetic structure, mating system and pollen dispersal in a timber tree from African rainforests

Owing to the reduction of population density and/or the environmental changes it induces, selective logging could affect the demography, reproductive biology and evolutionary potential of forest trees. This is particularly relevant in tropical forests where natural population densities can be low and isolated trees may be subject to outcross pollen limitation and/or produce low-quality selfed seeds that exhibit inbreeding depression. Comparing reproductive biology processes and genetic diversity of populations at different densities can provide indirect evidence of the potential impacts of logging. Here, we analysed patterns of genetic diversity, mating system and gene flow in three Central African populations of the self-compatible legume timber species Erythrophleum suaveolens with contrasting densities (0.11, 0.68 and 1.72 adults per ha). The comparison of inbreeding levels among cohorts suggests that selfing is detrimental as inbred individuals are eliminated between seedling and adult stages. Levels of genetic diversity, selfing rates ([sim]16%) and patterns of spatial genetic structure (Sp [sim]0.006) were similar in all three populations. However, the extent of gene dispersal differed markedly among populations: the average distance of pollen dispersal increased with decreasing density (from 200[thinsp]m in the high-density population to 1000[thinsp]m in the low-density one). Overall, our results suggest that the reproductive biology and genetic diversity of the species are not affected by current logging practices. However, further investigations need to be conducted in low-density populations to evaluate (1) whether pollen limitation may reduce seed production and (2) the regeneration potential of the species.SCOPUS: ar.jinfo:eu-repo/semantics/publishe