Genetic diversity and population structure of endemic mushroom Leucocalocybe mongolica in Mongolian Plateau uncovered by EST-SSR markers

Leucocalocybe mongolica (S. Imai) X.D. Yu &Y.J. Yao is an endemic mushroom with a distribution in Mongolian Plateau. It is an important edible and medicinal mushroom which is often collected unscrupulously. Wild L. mongolica is facing an unprecedented threat and is in a critically endangered state. Exploration of the genetic diversity and population structure of L. mongolica is important for conservation biology. The main distribution areas were investigated. In total, 402 alleles of 223 individuals from 17 wild geographical populations were obtained based on the eight simple sequence repeat loci. The total number of alleles from each population ranged from 11 to 31 with an average of 24 per population. The average observed heterozygosity (HO) and expected heterozygosity (HE) ranged from 0.300 to 0.875 and from 0.188 to 0.621, respectively. Analysis of molecular variance (AMOVA) indicated that 14.19% of the total molecular variance could be attributed to differences between populations (p <.001), whereas 85.81% to differences within populations. The mean genetic distance (FST) value of 0.171 suggested low genetic differentiation among populations. The UPGMA dendrogram generated from the SSR data suggested that the 17 populations separated into three main sister clusters on the Nei's genetic identity coefficient 0.8. The 223 L. mongolica individuals were divided into three groups by STRUCTURE analysis. Keeping and enriching the population diversity is crucial for the conservation of L. mongolica. The data about the population structure and genetic diversity obtained in this study will facilitate the establishment of conservation measures. Abbreviations AMOVA: analysis of molecular variance; Dest: estimator of actual differentiation; EST-SSR: Expressed sequence tag- simple sequence repeats; Fis: Inbreeding coefficient; Fit: total inbreeding coefficient; Fst: fixation index; GST coefficient of gene differentiation; G’ST: standardized measure of genetic differentiation; HE: expected Heterozygosity; H0: observed heterozygosity; HS: mean genetic diversity within populations; HT: total genetic diversity for species; I: Shannon’s diversity index; km: kilometer; L. mongolica: Leucocalocybe mongolica; N: sample size; NA: number of average alleles; NE: number of effective alleles; Nm: gene flow; NP: number of private alleles; NR: allelic richness; NT: number of total alleles; PCoA: principal coordinate analysis; PIC: polymorphism information content; PPB: Percentage of polymorphic loci; TP-M13-SSR: tailed primer M13; UHE: unbiased expected Heterozygosity