Genetic diversity and biogeographic determinants of population structure in Araucaria angustifolia (Bert.) O. Ktze

Abstract

Araucaria (Araucaria angustifolia (Bert.) O. Ktze) is a primarily dioecious species threatened with extinction that plays an important social and economic role especially in the southern region of Brazil. The aim of this work is to investigate the diversity and likely determinants of genetic lineages in this species for conservation management. For this, a collection of 30-year-old Araucaria was used. Accessions collected from 12 sites across the species range were analyzed, with ten individuals per site. The SSR genotyping was conducted with 15 loci and the data were analyzed using several complementary approaches. Descriptive statistics among sampling sites were used and diversity was partitioned non-hierarchically to estimate the size and composition of genetic clusters using a Bayesian assignment method. To explore possible biological implications of differences between Niche Models and habitat suitability, a series of statistical procedures were used, and tests were carried out using the software ENM Tools and Maxent. Populations from the southernmost zone showed higher genetic variation and a lower inbreeding coefficient compared to the northernmost zone, which may correlate with their isolation. A positive relation between genetic differentiation and geographic distance was observed. Two genetic groups (southernmost and northernmost zones) were evident. The Niche modelling showed separate ranges for each genetic lineage suggesting that differences in selection pressure may be playing a role in the apparent differentiation and may be adaptive. Finally, an evident correlation was observed between genetic data and habitat suitability. The two distinct groups observed must be considered as independent units for conservation and hybridization in breeding programs.

A 3K Axiom® SNP array from a transcriptome-wide SNP resource sheds new light on the genetic diversity and structure of the iconic subtropical conifer tree Araucaria angustifolia (Bert.) Kuntze

“…The SNP data gathered validate the ample applicability of the Axiom array and casts new light on the overall picture of diversity and structure of A. angustifolia along its extensive natural range. SNPs more accurately showed that southern populations ( H o =0.353) are significantly more genetically diverse that northern populations ( H o = 0.262) (Table 3), consistent with recent indications [31]. When compared to microsatellites, SNPs provided considerably lower estimates of heterozigosity and scant, if any, evidence of trivial inbreeding either positive or negative within-populations, and none at range wide level.…”

“…3), and showing a considerably higher population differentiation due to regional than population within-region difference (Table 4). This genetic cline has been explained by the combined effect of post-glacial migration from different refugia [22, 81] and a north-south isolation most likely due to niche suitability [31]. The possibility of an additional phylogeographic separation of a third genetic group in the northern populations was also suggested earlier based on tenuous evidence from microsatellites [22] and recently confirmed based on sequence data of three intragenic regions in the chloroplast genome (cpDNA) [81].…”

The genetic legacy of fragmentation and overexploitation in the threatened medicinal African pepper-bark tree, Warburgia salutaris

“…The importance of phylogenetic data, genetic diversity, and population structure analyses to characterize the biodiversity of wild species has been well-established in numerous studies (e.g. [35][36][37][38][39] ). Microsatellites (Single Sequence Repeats, SSR) are amongst the most efficient and widely used markers for these studies as they are codominant and highly polymorphic loci 40 .…”

A 3K Axiom SNP array from a transcriptome-wide SNP resource sheds new light on the genetic diversity and structure of the iconic subtropical conifer tree Araucaria angustifolia (Bert.) Kuntze

“…Regarding population differentiation, isozymes, microsatellites and AFLPs provided equally low estimates as our microsatellite dataset. However, a recent study with 15 microsatellites showed a slightly higher estimate based on spatial AMOVA ( F ct = 0.187) [ 31 ], suggesting that if a larger number of microsatellites is used the estimates might eventually converge to those obtained with SNPs. Chloroplast DNA, as expected, provided significantly higher estimates of population differentiation.…”

“…Isozymes allowed the first estimates of genetic diversity, structure and mating system [ 17 – 21 ]. Next, studies were carried out using dominant AFLP markers [ 22 – 24 ], or small sets of five to 15 microsatellites to compare the genetic diversity among natural and planted forest stands or estimate spatial genetic structure, mating system and gene flow [ 22 , 25 – 31 ]. The ultimate goal of these studies has been to provide evidence-based information for supporting conservation strategies.…”