Abstract
ABSTRACT Rhizophora mangle L. (Rhizophoraceae) grows on aerial roots, which emerge above the water level, giving stands of this tree the characteristic “mangrove” appearance. To produce in situ and ex situ information for genetic conservation programs for this species, we investigated the genetic diversity and mating system of one R. mangle population. We sampled 30 adult trees and a total of 349 seeds in Northern Brazil. We genotyped all adult trees and seeds with four microsatellite loci. The average fixation index was -0.222 for adult trees and 0.030 for seeds. The multilocus outcrossing rate (t m =0.921) was significantly lower than unity (1.0). There was no substantial evidence of null alleles nor genotypic disequilibrium among the loci. The combined power to exclude the first parent probability was 0.921. The average coancestry coefficient (=0.180) was similar to that expected for half-sib progenies (=0.125). Thus, the number of adult trees necessary for seed collection to obtain progeny arrays with an effective size of 150 was estimated to be 62. In conclusion, this study produced important information for the management and conservation of R. mangle and will contribute to conservation and management programs for this species.
Highlights
The Rhizophora genus dominates many tropical mangrove forests worldwide and plays pivotal roles in mangrove ecosystems (Duke & Allen, 2006)
The number of alleles obtained in this study was lower than that obtained by Pil et al (2011) for the same species from the Brazilian coast, those authors used a different set of loci and number of individuals across 10 populations
Despite the small number of microsatellite loci studied in this population, we found an increase in the endogamy of the studied seed generation, even with the observation of high outcrossing rates
Summary
The Rhizophora genus dominates many tropical mangrove forests worldwide and plays pivotal roles in mangrove ecosystems (Duke & Allen, 2006). Mangroves, which are heterogeneous habitats with an uncommon variety of animals and plants adapted to conditions of high salinity, frequent flooding and muddy anaerobic soil, cover approximately 137,700 km worldwide (Giri et al, 2011). These mangrove trees have morphological characteristics and adaptations, including aerial roots and a fast-growing canopy, that contribute to efficient nutrient retention mechanisms, water retention and balance sheet carbon estimates (Ezcurra et al, 2016). Rhizophora species are mainly pollinated by the wind, as they have considerably more pollen grains than ovaries per flower (Tomlinson, 1986). R. mangle is one of the main representative species of this ecosystem in Brazil
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