Scientists Clarified the Phylogeographical History and Conservation Units of the Endangered Wild Apple Tree

Long-term aridification had been undergone in Central Asia during the Cenozoic. The aridification was related to the retreat of Tethys, global cooling and the Quaternary climatic changes. Arid climate was profoundly influenced the distribution, origin and evolution of plants. Malus sieversii is an edificator species of the relict broad-leaved forest in the Central Asian Mountains region and an ancient progenitor of the domesticated apple. It is also an endangered species in the "China Plant Red Data Book". However, it is unclear that the reason shaped the fragmented distribution of the wild apple tree. Phylogenetic relationships of the populations were also still unreported among different countries.

To address these questions, researchers from the State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, sampled and sequenced the genome-wide SNPs of 173 M. sieversii individuals from 15 populations from China, Kazakhstan, Kyrgyzstan, and Tajikistan using the SLAF-seq approach.

The 15 populations were divided into three groups: the eastern group of western Junggar Mountains in China; the central group of the Ili Valley, the Talas Alatau Mountains in Kazakhstan and Kyrgyzstan; and the western group of Tajikistan and the Dzungarian Alatau in Kazakhstan. Central populations had higher genetic diversity and effective population size than eastern and western populations.

The three groups split at the late Miocene and subsequently experienced extensive admixture. Long-term aridification promoted distribution fragmentation and plant lineage divergence of relict broad-leaved forests in Central Asian Mountains. Both geographical isolation and environmental heterogeneity shaped spatial patterns in genetic variation among M. sieversii populations. To maintain genetic integrity, we propose the establishment of an international network for the conservation of this endangered wild apple tree.

The research results were published in the Journal of Biogeography, entitled "Insights into the aridification history of Central Asian Mountains and international conservation strategy from the endangered wild apple tree".

Article link: https://onlinelibrary.wiley.com/doi/10.1111/jbi.13999 

Figure 1 Population sites of the 15 sampled Malus sieversii populations and their genetic lineages (The yellow shaded area indicates the full distribution range of this species)