Landscape barriers to pollen and seed flow in the dioecious tropical tree Astronium fraxinifolium in Brazilian savannah

Abstract

Gene flow studies provide information on gene exchange between populations, which is essential for developing genetic conservation strategies. Such analyses enable a better understanding of the life history and seed and pollen dispersal mechanisms of plant species. In this study, we investigate pollen and seed flow in a regenerant population of the pioneer species Astronium fraxinifolium in an area degraded during the construction of a hydroelectric dam. We mapped, sampled, sexed, and genotyped 386 individuals in the regenerant population (RP), as well as 128 adult trees located along two highways adjacent to the degraded area; one in Mato Grosso do Sul State (MS) and other in São Paulo State (SP). Parentage analyses was carried out for 370 individuals of the RP population, using as putative parents 348 individuals from RP and all 128 individuals sampled in MS and SP. Based on parentage analysis and eight microsatellite loci, our analyses revealed that for individuals of the RP with an identified father (pollen donor), 1.1% of the pollen was dispersed up to 532 m, while for those with an identified mother (seed donor), 0.5% of seeds were dispersed up to 4,782 m. However, a large proportion of pollen (76.5%) and seeds (57%) immigrated from trees outside the sampled populations. Pollen and seeds were dispersed through a pattern of isolation by distance. Genetic diversity was significantly similar between adults of both highway populations and individuals from RP, with significant levels of inbreeding detected only in RP. Our results demonstrate that the nearest trees contributed pollen and seeds for the recovery of the degraded area, indicating reproductive spatial isolation among the sampled populations due to the damming of the river. Such results help to understand the process of regeneration for A. fraxinifolium in regenerant populations to inform strategies for conservation and environmental recovery with this species.

Microsatellites are important for forest genetic resources conservation in Brazilian biomes

“…Pollen and seed flow for Astronium fraxinifolium, investigated through parentage analysis and microsatellite loci, revealed that a large proportion of pollen (76.5 %) and seeds (57 %) immigrated from trees outside the sampled populations and the dispersion followed a pattern of isolation by distance (Manoel et al 2021).…”

Spatial genetic structure and mating system in forest tree populations from seasonally dry tropical forests: a review

“…All of these species develop fruits that are attractive to dispersers such as drupes and fleshy appendages and show seed dispersal mediated by birds. In Copaifera langsdorffii populations from Central Brazil, also dispersed by birds, saplings recruited within a fragmented population were all assigned to mothers located within the same population (Sebbenn et al 2011), suggesting restricted seed dispersal, whereas gene dispersal among patches was attributed to far-ranging pollen dispersal (Manoel et al 2012(Manoel et al , 2021. Genetic studies in other Neotropical trees are in agreement with a pattern of narrow-ranging seed dispersal vs. far-ranging pollen dispersal, e.g., species with seed dispersal mediated by gravity and zoochory such as Bertholletia excelsa, Genipa americana, Hymenaea stigonocarpa, and Ilex paraguariensis (Baldoni et al 2020;de Vasconcelos Melo et al 2021;Moreno et al 2021;Seoane et al 2019), and others with seed dispersal mediated by anemochory such as Swietenia macrophylla (Silva de Oliveira et al 2020).…”

Características morfométricas, reproductivas y germinativas del germoplasma de Swietenia humilis Zucc. en Guerrero

“…Sin embargo, dado que los otros sitios, principalmente Zacapalco y Santa Fe, tuvieron frutos con producción alta de semillas desarrolladas y con alta capacidad germinativa, se recomienda que la hipótesis del efecto en la capacidad reproductiva se compruebe con estudios a nivel genético, con un enfoque experimental similar al de los estudios deWhite et al (2002),Moraes et al (2018),Garcia et al (2019) yManoel et al (2021) porque, además, en varias especies tropicales no se ha observado una reducción de su diversidad genética a pesar de que sus poblaciones naturales estén fragmentadas.…”