Paternity analysis, pollen flow, and spatial genetic structure of a natural population ofEuterpe precatoriain the Brazilian Amazon

Abstract

Euterpe precatoria, known as açaí do Amazonas, is a regionally important palm of the Amazon rainforest for the fruit production through extractive agriculture. Little information is available with regard to genetic diversity, gene flow, and spatial genetic structure (SGS) of açaí populations, which are essential for the use, management, and conservation of genetic resources of the species. This research aimed to assess the genetic diversity, inbreeding level, SGS, and gene flow in four ontogenetic stages of a natural E. precatoria population in the Brazilian Amazon, based on 18 microsatellite loci. The study was carried out in a natural population dispersed in an area of about 10 ha. Leaf tissues of 248 plants were mapped and sampled and classified into four ontogenetic stages: reproductive (59), immature (70), young (60), and seedling (59). Genetic diversity indices were high for all ontogenetic stages. The fixation index (F) for all ontogenetic stages was not significantly different from zero, indicating the absence of inbreeding. A significant SGS was found for all ontogenetic stages (68–110 m), indicating seed dispersal over short distances. Paternity analysis detected pollen immigration of 39.1%, a selfing rate of 4.2%, and a mean pollen dispersal distance within the population of 531 m. The results indicate substantial allele input in the population via pollen immigration, contributing to the maintenance of the genetic diversity of the population. However, within a population, the renewal with new progenies selected from seed plants spaced at least 110 m apart is important to avoid collecting seeds from related plants.

Genetic Structure in Populations of Euterpe precatoria Mart. in the Brazilian Amazon

“…The negative values for the fixation indices (f ) and the observed (H O ) and expected (H E ) heterozygosity coefficients indicate high genetic diversity (Nazareno and Reis, 2014), as confirmed by the excess of heterozygotes in the populations. The low f values and high H O also indicate that the result may be influenced by the reproductive system of the species (Ramos et al, 2011) which is allogamy (Ramos et al, 2018(Ramos et al, , 2019. Similar results were found in other palm species, such as Geonoma schottiana (Silva et al, 2011), Phoenix dactylifera (Arabnezhad et al, 2012) and Oenocarpus bataua (Ottewell et al, 2012), which could indicate a behavior common to plants of the family Arecaceae.…”

“…The populations also showed significant differences when analyzed in pairs (F ST ), also confirming the existence of genetic structure among the sampled populations (Wright, 1951). This result may be strongly influenced by the reproductive characteristics of the species, as well as the dispersion capacity of its genetic material, the degree of isolation of the population, the self-incompatibility system and allelic diversity that it presents (Leducq et al, 2011;Ramos et al, 2018). The genetic structure observed also indicates that the sampled populations would be grouped according to the geographical distances within the hydrographic basins.…”

“…There is a concern about the intensification of fruit collection by extractive exploitation which is driven by the market (Instituto Brasileiro de Geografia e Estatística -IBGE, 2019) as it could be having significant impacts on genetic erosion in the near future, and, consequently, the reduction of fruit availability for frugivorous vertebrates, as well as the reduction of gene flow among populations (Ramos et al, 2018). To address this, restrictions on fruit harvesting should be carried out, such as avoiding fruit collection in years of low productivity and maintaining at least minus 50% of the fruits on mother palms for later consumption of fauna (Novello et al, 2018) and regeneration of new remnants.…”

“…In the process of ecological and dynamic succession of the forest with respect to the species E. precatoria, the plants of the populations may be showing high levels of genetic diversity at different ontogenetic ages (Ramos et al, 2018). The seeds are expected to represent a mixture of half sibs and full sibs (Bittencourt and Sebbenn, 2007).…”

There Is No ‘Rule of Thumb’: Genomic Filter Settings for a Small Plant Population to Obtain Unbiased Gene Flow Estimates

“…With notable reductions in populations, the species has become increasingly rare, with a few remaining small populations. Consequently, both direct measures of dispersal from parentage analyses, as well as indirect estimates of dispersal from fine-scale spatial genetic structure (SGS; i.e., non-random spatial distribution of genotypes within populations), provide useful information for management activities and policies, including seed collection for ex situ conservation, tree breeding, and/or reforestation (e.g., Bittencourt and Sebbenn, 2007 ; Ramos et al, 2018 ; de Oliveira et al, 2020 ).…”