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Dryad

Multiple origins of the desert shrub Reaumuria songarica in northern Xinjiang involving homoploid and tetraploid hybrids

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Aug 14, 2024 version files 1.26 MB

Abstract

Reaumuria songarica is a constructive shrub widely distributed in temperate deserts of arid Central Asia. Previous studies inferred that the populations of R. songarica in the Gurbantunggut Desert (GuD) originated from homoploid hybridizations between its eastern and western lineages and may have evolved into an incipient species. To further reveal the genetic composition of different hybrid populations and determine the species boundary of this independent hybrid lineage, we hereby investigated the overall phylogeographic structure of R. songarica based on variation patterns of five cpDNA sequences and one nrITS sequence in 32 populations. Phylogenetic analyses demonstrated that in the GuD lineage, the Wuerhe population evolved directly from the ancestors, whereas the others were derived from hybrids between the eastern and western lineages. PCoA and genetic barrier analysis strongly supported that the GuD lineage was further divided into two genetic groups: the southern group near the Tianshan Mountains (GuD-S) and the northern group (GuD-N). The populations in GuD-S group had consistent genetic composition and the same ancestral parents, indicating that they belong to the homoploid hybrid lineage. However, the mixed GuD-N group had undergone genetic admixture of the eastern and western lineages on nrITS and cpDNA, and some populations were allopolyploid. Additionally, BEAST analyses revealed that the origins of the GuD-S and GuD-N groups were later than 0.5 Ma.