Population Genetic Structure and Biodiversity Conservation of a Relict and Medicinal Subshrub Capparis spinosa in Arid Central Asia

Qian Wang,Hong-Xiang Zhang

doi:10.3390/d14020146

Abstract

As a Tertiary Tethyan relict, Capparis spinosa is a typical wind-preventing and sand-fixing deciduous subshrub in arid central Asia. Due to its medicinal and energy value, this species is at risk of potential threat from human overexploitation, habitat destruction and resource depletion. In this study, our purpose was to evaluate the conservation strategies of C. spinosa according to its genetic structure characteristics and genetic diversity pattern among 37 natural distributional populations. Based on genomic SNP data generated from dd-RAD sequencing, genetic diversity analysis, principal component analysis, maximum likelihood phylogenetic trees and ADMIXTURE clustering, the significant population structure and differentiation were explored. The results showed the following: (1) Six distinct lineages were identified corresponding to geographic locations, and various levels of genetic diversity existed among the lineages for the natural habitat heterogeneity or human interferences; (2) The lineage divergences were influenced by isolation by distances, vicariance and restricted gene flow under complex topographic and climatic conditions. Finally, for the preservation of the genetic integrity of C. spinosa, we suggest that conservation units should be established corresponding to different geographic groups, and that attention should be paid to isolated and peripheral populations that are experiencing biodiversity loss. Simultaneously, monitoring and reducing anthropogenic disturbances in addition to rationally and sustainably utilizing wild resources would be beneficial to guarantee population resilience and evolutionary potential of this xerophyte in response to future environmental changes.

Highlights

Arid central Asia is deemed to be the largest arid region in the temperate zones of the northern hemisphere and even the world [1]
Similar disjunctive or fragmented population structure patterns have been reported in other Tethyan relicts that occur in this area, such as Gymnocarpos przewalskii, Amygdalus mongolica and Ammopiptanthus, owing to the influence of long-term aridification [9,10,11]
Populations at high altitudes of the western Himalayas have been experiencing a gradual decline in genetic diversity and effective scales as a result of inbreeding depression by isolation by distance (IBD) and habitat isolation

Summary

Introduction

Arid central Asia is deemed to be the largest arid region in the temperate zones of the northern hemisphere and even the world [1]. The floristic compositions here are mostly descended from Tethyan xerophytic vegetation flora and have been phenoecological plant taxa shaped by the long-term continental–arid desert climate [2,3]. Oceans have been blocked and intercepted, and the amount of precipitation is low and unevenly distributed, which has constituted the complexity of the extreme geographic and climatic conditions, forming a very fragile ecological environment [1]. It is speculated that the formation of this pattern is the result of intense orogeny during the geological period, coupled with extensive Quaternary glaciation, as well as the long-term process of aridification in central Asia [5,6,7]. Scientists and departments of environmental protection have paid increasing attention to studying and persisting the complex and unique community structure characteristics, as well as the vegetation diversification pattern in arid central

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Discussion

Conclusion