Clarifying Recent Adaptive Diversification of the Chrysanthemum-Group on the Basis of an Updated Multilocus Phylogeny of Subtribe Artemisiinae (Asteraceae: Anthemideae)

Abstract

Understanding the roles played by geography and ecology in driving species diversification and in the maintenance of species cohesion is the central objective of evolutionary and ecological studies. The multi-phased orogenesis of Qinghai-Tibetan Plateau (QTP) and global climate changes over late-Miocene has profoundly influenced the environments and evolution of organisms in this region and the vast areas of Asia. In this study, we investigate the lineage diversification of Chrysanthemum-group in subtribe Artemisiinae (tribe Anthemideae, Asteraceae) likely under the effects of climate changes during this period. Using DNA sequences of seven low-copy nuclear loci and nrITS and the coalescent analytical methods, a time-calibrated phylogeny of subtribe Artemisiinae was reconstructed with emphasis on Chrysanthemum-group. The monophyletic Chrysanthemum-group was well resolved into two major clades corresponding to Chrysanthemum and Ajania, two genera which can be well identified by capitulum morphology but have been intermingled in previous plastid and ITS trees. Within Chrysanthemum, a later divergence between Ch. indicum-complex and Ch. zawadskii-complex can be recognized. The time frames of these sequential divergences coincide with the late Cenozoic uplift of the Northern QTP and the concomitant climatic heterogeneity between eastern and inland Asia. Reconstruction of historical biogeography suggested the origin of Chrysanthemum-group in Central Asia, followed by eastward migration of Chrysanthemum and in situ diversification of Ajania. Within Chrysanthemum, Ch. indicum-complex and Ch. zawadskii-complex exhibited contemporary distributional division, the former in more southern and the latter in more northern regions. The geographic structure of the three lineages in Chrysanthemum-group have been associated with the niche differentiation, and environmental heterogenization in Asia interior.

The genus Chrysanthemum: Phylogeny, biodiversity, phytometabolites, and chemodiversity

“…It was found that the affinity between Chrysanthemum and Ajania is very close, and the resolving power of CDS and cpDNA markers were not enough. When eight nuclear sequences were used (Shen et al, 2021), Chrysanthemum and Ajania were well separated with only a few exceptions (Figure 2), which agrees with traditional taxonomy mainly based on capitulum morphology. In Chrysanthemum, two Chinese endemic species with white ray flowers, C. rhombifolium and C. vestitum, are sister to C. indicum complex with yellow/white ray flowers (Figure 2).…”

“…The number after the taxon name represents the ploidy level. This schematic is compiled mainly based on Shen et al, 2021 , as the phylogenetic topology inferred from low-copy nuclear genes and nrITS could be more convincing than those inferred from cp sequences ( Liu et al, 2012 ; Lu et al, 2022a ). It should be noted that it is challenging to distinguish taxa from each other within C. indicum complex and C. zawadskii complex, respectively.…”

“…The geography and ecology play a key role in driving species diversification of Anthemideae and in shaping genotype/phenotype of species. The multi-phased orogenesis of Qinghai-Tibetan Plateau (QTP) and global climate changes over late-Miocene has profoundly influenced the environments and evolution of Anthemideae plants in QTP and adjacent regions ( Shen et al, 2021 ). The DNA sequences of seven low-copy nuclear genes and nrITS were combined to reconstruct a time-calibrated phylogeny of subtribe Artemisiinae ( Figure 2 ).…”

“…Anthemideae is a taxonomically controversial Asteraceae (Compositae) tribe, in which phylogenetic relationships are still not settled ( Criado Ruiz et al, 2021 ). In Anthemideae, Artemisiinae and Matricariinae are the two most widely distributed subtribes ( Watson et al, 2002 ; Shen et al, 2021 ). Artemisiinae ( Figure 1 ) includes 1/3 species of tribe Anthemideae, consisting of more than 600 species of 18–19 genera, which are mainly in the northern hemisphere, especially in Central Asia and East Asia.…”

The complete sequence of the chloroplast genome of Chrysanthemum rupestre, a diploid disciform capitula species of Chrysanthemum

“…Furthermore, on the basis of phylogenetic analysis using nuclear-encoded genes, Shen et al. ( 2021 ) revealed that C. pacificum, Chrysanthemum shiwogiku Kitam., 1935 (syn. Ajania shiwogiku (Kitam.)…”