Abstract
Mangrove is an ecosystem subjected to tide, salinity and nutrient variations. These conditions are stressful to most plants, except to mangrove plants that are well-adapted. However, many mangrove areas have extremely stressful conditions, such as salt marshes, and the plants nearby usually present morphological alterations. In Sepetiba Bay, two species of mangrove plants, Avicennia schaueriana and Laguncularia racemosa, have poor development near a salt marsh (SM) compared to plants at the riverside (RS), which is considered a favorable habitat in mangroves. The level of genetic diversity and its possible correlation with the morphological divergence of SM and RS plants of both species were assessed by AFLP molecular markers. We found moderate genetic differentiation between A. schaueriana plants from SM and RS areas and depleted genetic diversity on SM plants. On the other hand, Laguncularia racemosa plants had no genetic differentiation between areas. It is possible that a limited gene flow among the studied areas might be acting more intensely on A. schaueriana plants, resulting in the observed genetic differentiation. The populations of Laguncularia racemosa appear to be well connected, as genetic differentiation was not significant between the SM and RS populations. Gene flow and genetic drift are acting on neutral genetic diversity of these two mangrove species in the studied areas, and the observed genetic differentiation of A. schaueriana plants might be correlated with its morphological variation. For L. racemosa, morphological alterations could be related to epigenetic phenomena or adaptive loci polymorphism that should be further investigated.
Highlights
Plants are exposed to various stress factors at the same time or at different times of their lives.plant plasticity is essential to overcome such stresses and to establish acclimation mechanisms that allow plants to respond to reiterated stresses [1]
Our results indicate that the mangrove species studied here, A. schaueriana and L. racemosa, have different genetic distribution of the variation, based on the species history and evolutionary forces
The genetic differentiation found between RS and salt marsh (SM) plants of A. schaueriana might be correlated with morphological alterations observed at SM area, we cannot discard the effects of drift
Summary
Plants are exposed to various stress factors at the same time or at different times of their lives.plant plasticity is essential to overcome such stresses and to establish acclimation mechanisms that allow plants to respond to reiterated stresses [1]. The ability of the plants to respond and adapt to recurring biotic and abiotic stresses is essential for their survival because of their sessile nature. The ability to survive is linked to population fitness and this is positively correlated to heterozygosity, population size, and quantitative genetic variation [2]. The study of links between genetic diversity and phenotypic changes that result from habitat-mediated adaptation gives insight into how the mosaic of the natural landscape shapes the genomes of the organisms distributed across its vastness [3]. Plants from different taxonomic groups have developed mechanisms to survive exclusively in the mangrove ecosystem. The three most important adaptive traits found in mangrove plants are vivipary, salt exclusion, and aerial roots [6]. Each mangrove species has its own physiological mechanism of achieving these traits
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