Abstract
ABSTRACT The continuing fragmentation of forests has been a threat to the maintenance of genetic resources. Genetic diversity is fundamental to the survival of species in natural environments in the long term, as well as being the basis for genetic improvement. The objective of this study was to evaluate the genetic diversity in natural populations of Hancornia speciosa and to contribute to the development of conservation strategies. We sampled 105 individuals of H. speciosa, distributed in seven populations. The ISSR (Inter-Simple Sequence Repeat) markers provided 70 loci, of which 81% were polymorphic. The mean genetic diversity of Nei (h) was 0.19, and the Shannon index (I) was 0.27. The h and I diversity indices ranged respectively from 0.16 to 0.24 in the PAD (Parque das Dunas) population and from 0.21 to 0.29 in MAC (Macaíba) population. Resulting from a Bayesian analysis, the genotypes were divided into four groups (K = 4). The allelic diversity patterns observed indicated the occurrence of the genetic bottleneck in all populations, according to the stepwise mutation model (SMM). The infinite allele model (IAM) revealed an imbalance between mutation and genetic drift only in the PAD population. Genetic conservation strategies for H. speciosa should cover each genetic group that was differentially structured. We recommend in situ conservation and the creation of germplasm banks, especially with the PAD population which demonstrated the lower genetic diversity and decreased effective population size according to the two mutational models.
Highlights
A contínua fragmentação das florestas tem sido uma ameaça à manutenção dos recursos genéticos
The average value obtained for the effective number of alleles was 1.345, the average genetic diversity of Nei (h) was 0.19, and the average Shannon index (I) was 0.27 (Table 3)
The number of polymorphic loci of the sampled populations was low, ranging from 29 (41%) in COT to 33 (47%) in MAC. This low index is indicative of low genetic diversity
Summary
A contínua fragmentação das florestas tem sido uma ameaça à manutenção dos recursos genéticos. In the north east region of Brazil, towards the mid-west and the north, H. speciosa var. North east Brazil is the region that produces the most fruit, as known as mangaba, and the collection is a predominantly extractive activity (IBGE, 2016). In the north east of Brazil, real estate speculation and the establishment of monocultures such as coconut, sugar cane, extensive livestock breeding, and various extractive activities are constant threats to the genetic integrity of the natural populations of H. speciosa. Genetic diversity is represented by distinct alleles and genotypes found within and among the populations This variability is reflected in physiological and morphological characteristics, being the basis of the evolutionary potential of the species in response to human disturbances (Mimura et al, 2017). Further research is needed to provide a broad overview of the geographic distribution of genetic diversity (Almeida et al, 2016), with implications for genetic conservation and breeding
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