Study reveals trait-driven ecological adaptation and rapid radiation in a global phylogeny of Phlomoides
2026-06-11
The Arid Zone Biological Resources Conservation Team from the Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences (XIEG, CAS), in collaboration with the researchers from the Kunming Institute of Botany, CAS, and other institutions, has established the most comprehensive phylogenetic framework for Phlomoides covering the majority of known species globally.
The study was published in Plant Diversity on June 3, 2026.
Phlomoides Moench, the second largest genus in the subfamily Lamioideae (Lamiaceae), comprises approximately 180 species widely distributed across Eurasia, with major diversity hotspots in Central Asia, the Iranian Plateau, the Hengduan Mountains, and the Himalayas in south-western China.
The genus occupies diverse habitats ranging from forest understories and alpine meadows to arid steppes and deserts, exhibiting remarkable morphological and ecological diversity (Fig. 1), making it an important model group for studying floristic formation, environmental adaptation, and species diversification in Eurasia.
The infrageneric classification of Phlomoides has long been controversial. Recent phylogenetic studies have expanded the generic boundary to incorporate seven traditionally distinct genera and one section of Phlomis (Phlomis sect. Phlomoides). However, insufficient taxon sampling and incomplete geographical coverage have hindered the establishment of a stable classification, while the genus’s evolutionary origin, dispersal routes, and adaptive mechanisms remain unclear.
Fig. 1. Habitat and morphological diversity of Phlomoides. (Image by XIEG)
The researchers analyzed 132 species (73% of known species), constructed a dataset of 206 chloroplast genomes (154 newly sequenced), combined with nuclear ribosomal ETS and ITS sequences, to reconstruct the global phylogeny of Phlomoides (Fig. 2).
The results support the broadly circumscribed generic concept of Phlomoides and indicate that the traditional infrageneric classification based on Phlomis and Eremostachys is untenable. Phylogenetic analyses show that Phlomoides is divided into six major clades, each exhibiting potential morphological synapomorphies, laying a foundation for establishing a new infrageneric classification.
Fig. 2. Phylogenetic tree of Phlomoides based on chloroplast genomes. (Image by XIEG)
Divergence time estimation and ancestral range reconstruction based on chloroplast genome data suggest that Phlomoides originated in the Hengduan Mountains or Central Asia during the Middle Miocene Climatic Optimum (ca. 17.72 Ma) (Fig. 3). Driven by Mid-Miocene global cooling around 14.94 Ma, the genus diverged into two main lineages. Clades I–II originated and evolved mainly in the Hengduan Mountains or the Himalayas, whereas Clades III–VI dispersed to Central and West Asia, and diversified in arid and semi-arid regions.
Fig. 3. Chronogram and ancestral area reconstruction of Phlomoides based on complete chloroplast genomes. (Image by XIEG)
The study further revealed significant ecological niche differentiation among the different lineages of Phlomoides. Annual precipitation and temperature annual range are the primary environmental factors driving lineage divergence. Compared to Clades I–II, Clades III–VI are adapted to drier environments with broader seasonal temperature variation.
Diversification analyses detected a significant rapid radiation within a subclade of Clade VI beginning around 4.42 Ma. This subclade is characterized by possessing pinnately divided basal leaves, suggesting that leaf shape innovation may have facilitated adaptation to open, arid habitats and promoted rapid species diversification.
Ancestral state reconstruction identified that basal leaf morphology, mericarp indumentum, and root type are key traits shaping Phlomoides’secological adaptation. The evolution of traits such as pinnately dissected basal leaves, densely hairy mericarps, and robust tuberous roots enabled Phlomoides to expand from early shaded, humid forest understory habitats into extreme environments including alpine meadows, steppes and deserts. These morphological innovations enhanced tolerance to drought, cold, and high irradiance, facilitating the widespread dispersal and ecological niche differentiation of different lineages across Eurasia.
The study provides a basis for a new infrageneric classification, clarifies the genus’s origin, dispersal, and diversification history, and reveals the co-evolution between key morphological innovations and ecological adaptation. These findings advance the understanding of the formation and evolution of the Eurasian flora and provide new evidence for the historical floristic linkages between the Qinghai-Xizang Plateau-Himalaya-Hengduan Mountains and Central-West Asia.
Read the full article: https://doi.org/10.1016/j.pld.2026.05.006
Contact
LI Wenjun
Xinjiang Institute of Ecology and Geography
E-mail: liwenjunao@ms.xjb.ac.cn