Within and among population gene flow is a central aspect of the evolutionary history of ecosystems and essential for the potential for adaptive evolution of populations. We employed nuclear microsatellite markers to assess inter- and intra-population gene flow in five natural populations of Luehea divaricata growing in the Pampa biome, in southern Brazil. This species occurs in practically all secondary forests of the Pampa and has recognized ecological significance for these formations. The genetic structuring of the studied populations suggests limited gene dispersal among forest fragments, despite a homogeneous level of migration among populations. Notwithstanding the gene flow among populations, significant SGS is still found in some fragments. Significant spatial genetic structure within population was also found likely as result of limited seed and/or pollen dispersal. The scattered distribution of the populations and their relatively high density seem to limit pollen dispersal. Also seed dispersal by wind is not efficient due to large distances among forest formations. As conservationist actions towards preserving the genetic resources of L. divaricata and the Brazilian Pampa, we suggest the protection of the existing forest formations and the maintenance of the natural expansion of the forests over the grasslands in the biome.

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Highlights• Signatures of genetic bottlenecks and reduction of populations' fitness were observed in populations of Luehea divaricata in southern Brazil.• Lower levels of observed heterozygosity are correlated with populations' fitness, decreasing germination capacity and increasing the proportion of anomalous germinated plantlets.• Promoting the connection among populations is proposed as a key strategy towards conservation of L. divaricata genetic resources in its southernmost distribution range. AbstractExtant populations growing in regions that were refugia during the last glacial period are expected to show higher genetic diversity than populations that moved from these refugia into new areas in higher latitudes. Such new populations likely faced harsher climatic conditions, being established with reduced population size and experiencing the effects of genetic bottlenecks. In this study we employed data from nuclear SSR markers for detecting molecular signatures of genetic bottlenecks, and germination experiments to evaluate reduction of populations' fitness in natural populations of Luehea divaricata Mart. et Zucc., growing in the southern range of the species distribution (around 30°S latitude). Signatures of genetic bottlenecks and reduction of populations' fitness were observed in all populations. Lower levels of observed heterozygosity are correlated with populations' fitness, decreasing germination capacity and increasing the proportion of anomalous germinated plantlets. Promoting the connection among populations is proposed as a key strategy towards conservation of L. divaricata genetic resources in its southernmost distribution range. The offspring from crosses among populations would significantly increase the observed heterozygosity and fitness of multiple populations.

Cinza de casca de arroz como reservatório molecular de água para a produção de soja Rice bark gray as a molecular water reservoir for soy production

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