Distinct hybridization modes in wide- and narrow-ranged lineages of Causonis (Vitaceae).

BACKGROUND: Explaining contrasting patterns of distribution between related species is crucial for understanding the dynamics of biodiversity. Despite instances where hybridization and whole genome duplication (WGD) can yield detrimental outcomes, a role in facilitating the expansion of distribution range has been proposed. The Vitaceae genus Causonis exhibits great variations in species' distribution ranges, with most species in the derived lineages having a much wider range than those in the early-diverged lineages. Hybridization and WGD events have been suggested to occur in Causonis based on evidence of phylogenetic discordance. The genus, therefore, provides us with an opportunity to for explore different hybridization and polyploidization modes in lineages with contrasting species' distribution ranges. However, the evolutionary history of Causonis incorporating potential hybridization and WGD events remains to be explored. RESULTS: With plastid and nuclear data from dense sampling, this study resolved the phylogenetic relationships within Causonis and revealed significant cyto-nuclear discordance. Nuclear gene tree conflicts were detected across the genus, especially in the japonica-corniculata clade, which were mainly attributed to gene flow. This study also inferred the allopolyploid origin of the core Causonis species, which promoted the accumulation of stress-related genes. Causonis was estimated to have originated in continental Asia in the early Eocene, and experienced glaciation in the early Oligocene, shortly after the divergence of the early-divergent lineages. The japonica-corniculata clade mainly diversified in the Miocene, followed by temperature declines that may have facilitated secondary contact. Species distribution modeling based on current climate change predicted that the widespread C. japonica tends to be more invasive, while the endemic C. ciliifera may be at risk of extinction. CONCLUSIONS: This study presents Causonis, a genus with complex reticulate evolutionary history, as a model of how hybridization and WGD modes differ in lineages of contrasting species' geographic ranges. It is important to consider specific evolutionary histories and genetic properties of the focal species within conservation strategies.

A chromosome-level genome of Syringa oblata provides new insights into chromosome formation in Oleaceae and evolutionary history of lilacs.

Lilacs (Syringa L.), a group of well-known ornamental and aromatic woody plants, have long been used for gardening, essential oils and medicine purposes in East Asia and Europe. The lack of knowledge about the complete genome of Syringa not only hampers effort to better understand its evolutionary history, but also prevents genome-based functional gene mining that can help in the variety improvement and medicine development. Here, a chromosome-level genome of Syringa oblata is presented, which has a size of 1.12 Gb including 53 944 protein coding genes. Synteny analysis revealed that a recent duplication event and parallel evolution of two subgenomes formed the current karyotype. Evolutionary analysis, transcriptomics and metabolic profiling showed that segment and tandem duplications contributed to scent formation in the woody aromatic species. Moreover, phylogenetic analysis indicated that S. oblata shared a common ancestor with Osmanthus fragrans and Olea europaea approximately 27.61 million years ago (Mya). Biogeographic reconstruction based on a resequenced data set of 26 species suggested that Syringa originated in the northern part of East Asia during the Miocene (approximately 14.73 Mya) and that the five Syringa groups initially formed before the Late Miocene (approximately 9.97 Mya). Furthermore, multidirectional dispersals accompanied by gene introgression among Syringa species from Northern China during the Miocene were detected by biogeographic reconstruction. Taken together, the results showed that complex gene introgression, which occurred during speciation history, greatly contributed to Syringa diversity.

Integrated phylogenomic analyses unveil reticulate evolution in Parthenocissus (Vitaceae), highlighting speciation dynamics in the Himalayan-Hengduan Mountains.

Hybridization caused by frequent environmental changes can lead both to species diversification (speciation) and to speciation reversal (despeciation), but the latter has rarely been demonstrated. Parthenocissus, a genus with its trifoliolate lineage in the Himalayan-Hengduan Mountains (HHM) region showing perplexing phylogenetic relationships, provides an opportunity for investigating speciation dynamics based on integrated evidence. We investigated phylogenetic discordance and reticulate evolution in Parthenocissus based on rigorous analyses of plastome and transcriptome data. We focused on reticulations in the trifoliolate lineage in the HHM region using a population-level genome resequencing dataset, incorporating evidence from morphology, distribution, and elevation. Comprehensive analyses confirmed multiple introgressions within Parthenocissus in a robust temporal-spatial framework. Around the HHM region, at least three hybridization hot spots were identified, one of which showed evidence of ongoing speciation reversal. We present a solid case study using an integrative methodological approach to investigate reticulate evolutionary history and its underlying mechanisms in plants. It demonstrates an example of speciation reversal through frequent hybridizations in the HHM region, which provides new perspectives on speciation dynamics in mountainous areas with strong topographic and environmental heterogeneity.

Transition of survival strategies under global climate shifts in the grape family.

Faced with environmental changes, plants may either move to track their ancestral niches or evolve to adapt to new niches. Vitaceae, the grape family, has evolved diverse adaptive traits facilitating a global expansion in wide-ranging habitats, making it ideal for investigating transition between move and evolve strategies and exploring the underlying mechanisms. Here we inferred the patterns of biogeographic diversification and trait evolution in Vitaceae based on a robust phylogeny with dense sampling including 495 species (~52% of Vitaceae species). Vitaceae probably originated from Asia-the diversity centre of extant genera and the major source of dispersals. Boundaries of the Eocene, Oligocene and Miocene were identified as turning points in shifting strategies. A significant decrease in move strategy was identified during the Oligocene, followed by increases in move and evolve. After the Miocene, evolve began to dominate, during which increased niche opportunities and key trait innovations played important roles.

A comprehensive evaluation of flowering plant diversity and conservation priority for national park planning in China.

Establishment of a national park protection system in China, including the latest target proposed to protect at least 30% of the land area, calls for a comprehensive exploration of conservation priorities incorporating multiple diversity facets. We herein evaluate the spatial distribution of Chinese flowering plants from the perspectives of richness, uniqueness, vulnerability, and evolutionary history, by integrating three mega-phylogenies and comprehensive distribution data. We detect significantly high consistency among hotspots of different diversity measures for Chinese flowering plants, suggesting that multiple facets of evolutionary diversity are concentrically distributed in China. Affording legal protection to these areas is expected to maximize positive conservation outcomes. We propose two integrative diversity indices by incorporating three richness-based and three phylogeny-based measures, respectively. Both methods identify areas with high species richness, but the integrative phylogeny-based index also locates key areas with ancient and unique evolutionary histories (e.g., Ailao-Wuliang Mts, Dabie Mts, Hainan rainforest, Karst area of Yunnan-Guizhou-Guangxi, Nanling Mts, and southeast coastal regions). Of all the diversity indices explored, phylogenetic endemism maximizes the incidental protection of other indices in most cases, emphasizing its significance for conservation planning. Finally, 42 priority areas are identified by combining the 5%-criterion hotspots of two integrative indices and the minimum area to protect all threatened species analyzed. These priorities cover only 13.3% of China's land area, but host 97.1% of species richness (23,394/24,095), 96.5% of endemic species (11,841/12,274), 100% of threatened species (2,613/2,613), and 99.3% of phylogenetic diversity for flowering plants involved in this study. These frameworks provide a solid scientific basis for national park planning in China.