High Genetic Diversity and Low Differentiation in Michelia shiluensis, an Endangered Magnolia Species in South China

Yanwen Deng,Youhai Shi,Tingting Liu,Zicai Xie,Yuqing Xie,Xiaomei Deng,Yaqing Wei

doi:10.3390/f11040469

Abstract

Research Highlights: This study is the first to examine the genetic diversity of Michelia shiluensis (Magnoliaceae). High genetic diversity and low differentiation were detected in this species. Based on these results, we discuss feasible protection measures to provide a basis for the conservation and utilization of M. shiluensis. Background and Objectives: Michelia shiluensis is distributed in Hainan and Guangdong province, China. Due to human disturbance, the population has decreased sharply, and there is thus an urgent need to evaluate genetic variation within this species in order to identify an optimal conservation strategy. Materials and Methods: In this study, we used eight nuclear single sequence repeat (nSSR) markers and two chloroplast DNA (cpDNA) markers to assess the genetic diversity, population structure, and dynamics of 78 samples collected from six populations. Results: The results showed that the average observed heterozygosity (Ho), expected heterozygosity (He), and percentage of polymorphic loci (PPL) from nSSR markers in each population of M. shiluensis were 0.686, 0.718, and 97.92%, respectively. For cpDNA markers, the overall haplotype diversity (Hd) was 0.674, and the nucleotide diversity was 0.220. Analysis of markers showed that the genetic variation between populations was much lower based on nSSR than on cpDNA (10.18% and 77.56%, respectively, based on an analysis of molecular variance (AMOVA)). Analysis of the population structure based on the two markers shows that one of the populations (DL) is very different from the other five. Conclusions: High genetic diversity and low population differentiation of M. shiluensis might be the result of rich ancestral genetic variation. The current decline in population may therefore be due to human disturbance rather than to inbreeding or genetic drift. Management and conservation strategies should focus on maintaining the genetic diversity in situ, and on the cultivation of seedlings ex-situ for transplanting back to their original habitat.

Highlights

Habitat destruction and environmental pollution caused by human disturbance [1] have limited the distribution and promoted the spatial isolation of many wildlife species, threatening theirForests 2020, 11, 469; doi:10.3390/f11040469 www.mdpi.com/journal/forestsForests 2020, 11, 469 reproduction and development [2,3]
Michelia shiluensis (Magnoliaceae) is an evergreen tree that has been placed on the Red List of Magnoliaceae, which identifies magnolia species that are at risk of extinction throughout the world [18]
The results show that all 78 individuals comprised two clusters (Figure 2), which separate individuals from DL from the other populations; there was evidence of minor genetic mixing between DL and other populations

Summary

Introduction

Habitat destruction and environmental pollution caused by human disturbance [1] have limited the distribution and promoted the spatial isolation of many wildlife species, threatening theirForests 2020, 11, 469; doi:10.3390/f11040469 www.mdpi.com/journal/forestsForests 2020, 11, 469 reproduction and development [2,3]. Michelia shiluensis (Magnoliaceae) is an evergreen tree that has been placed on the Red List of Magnoliaceae, which identifies magnolia species that are at risk of extinction throughout the world [18]. This tree is scattered throughout Hainan [19] and southern Guangdong provinces [20], and is characterized by a straight tree shape, bright leaves, elegant and aromatic flowers, and dense wood structure [21,22]. There is an urgent need to understand the genetic diversity and population structure of M. shiluensis in order to plan conservation actions on its behalf

Objectives

Methods

Results