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Zhao, Z., X. Feng, Y. Zhang, Y. Wang, and Z. Zhou. 2023. Species richness, endemism, and conservation of wild Rhododendron in China. Global Ecology and Conservation 41: e02375. https://doi.org/10.1016/j.gecco.2023.e02375

This study aimed to identify the main factors driving species richness and endemism patterns of Chinese wild Rhododendron as well as to assess the hotspots of species diversity and their conservation status. We initially mapped the species richness and endemism (expressed by weighted endemism) patterns of 546 wild Rhododendron in China in 100 × 100 km grids using 13,969 occurrence records. Subsequently, the effects of environmental variables on species richness and endemism patterns were assessed using regression models, and hotspots were identified based on the areas overlapping in 10% of the grids with the highest species richness and endemism. Finally, the conservation status of the hotspots was evaluated via gap analysis. The key environmental variables affecting species richness and endemism patterns differed. Species richness patterns were significantly influenced by moisture index, whereas endemism patterns were significantly influenced by elevation range. Moreover, the following five species diversity hotspots were identified: southern Xizang, Hengduan Mountains, south-central Sichuan, eastern Yungui Plateau, and central Gansu; however, these hotspots are not fully covered by the existing nature reserves. Our results indicate that the establishment of nature reserves should be actively promoted to effectively protect wild Rhododendron in hotspots with a conservation gap.

Vieira, M., R. Zetter, F. Grímsson, and T. Denk. 2023. Niche evolution versus niche conservatism and habitat loss determine persistence and extirpation in late Neogene European Fagaceae. Quaternary Science Reviews 300: 107896. https://doi.org/10.1016/j.quascirev.2022.107896

An increasing body of palaeobotanical data demonstrates a series of Pliocene and Pleistocene extirpations and extinctions of plant lineages in western Eurasia, which are believed to have been determined by the climatic properties of their related East Asian and North American sister lineages. We investigated the diversity of a widespread northern hemispheric plant family, Fagaceae, during the Late Pliocene of Portugal. We found a high diversity of Fagaceae comprising extant and extinct lineages. Dispersed pollen of Castanopsis and Quercus sect. Cyclobalanopsis represent the youngest records of these Himalayan-Southeast Asian groups in western Eurasia. Likewise, fossil-species of Quercus sect. Lobatae and the North American clade of sect. Quercus are the youngest records of these modern New World groups in western Eurasia. For the extinct Trigonobalanopsis, the pollen record of Portugal is the youngest known of this genus. Climate data of modern representatives demonstrate that a deterministic model can explain only a part of the Pliocene and Pleistocene extirpations. Modern cold month mean temperatures of Castanopsis and Quercus sect. Cyclobalanopsis and their last occurrences in western Eurasia in the Pliocene fit with a deterministic model (niche conservatism). In contrast, survival or extirpation of groups with high cold tolerance appear to have been more complex. Here, niche evolution, abundance and diversity of a lineage during pre-Pleistocene times, and habitat availability/loss determined the fate of Fagaceae lineages in western Eurasia.

Fan, Z., B. Zhou, C. Ma, C. Gao, D. Han, and Y. Chai. 2022. Impacts of climate change on species distribution patterns of Polyspora sweet in China. Ecology and Evolution 12. https://doi.org/10.1002/ece3.9516

Climate change is an important driver of species distribution and biodiversity. Understanding the response of plants to climate change is helpful to understand species differentiation and formulate conservation strategies. The genus Polyspora (Theaceae) has an ancient origin and is widely distributed in subtropical evergreen broad‐leaved forests. Studies on the impacts of climate change on species geographical distribution of Chinese Polyspora can provide an important reference for exploring the responses of plant groups in subtropical evergreen broad‐leaved forests with geological events and climate change in China. Based on the environmental variables, distribution records, and chloroplast genomes, we modeled the potential distribution of Chinese Polyspora in the Last Glacial Maximum, middle Holocene, current, and future by using MaxEnt‐ArcGIS model and molecular phylogenetic method. The changes in the species distribution area, centroid shift, and ecological niche in each periods were analyzed to speculate the response modes of Chinese Polyspora to climate change in different periods. The most important environmental factor affecting the distribution of Polyspora was the precipitation of the driest month, ranging from 13 to 25 mm for the highly suitable habitats. At present, highly suitable distribution areas of Polyspora were mainly located in the south of 25°N, and had species‐specificity. The main glacial refugia of the Chinese Polyspora might be located in the Ailao, Gaoligong, and Dawei Mountains of Yunnan Province. Jinping County, Pingbian County, and the Maguan County at the border of China and Vietnam might be the species differentiation center of the Chinese Polyspora. Moderate climate warming in the future would be beneficial to the survival of P. axillaris, P. chrysandra, and P. speciosa. However, climate warming under different shared socio‐economic pathways would reduce the suitable habitats of P. hainanensis and P. longicarpa.

Zhang, X., X. Ci, J. Hu, Y. Bai, A. H. Thornhill, J. G. Conran, and J. Li. 2022. Riparian areas as a conservation priority under climate change. Science of The Total Environment: 159879. https://doi.org/10.1016/j.scitotenv.2022.159879

Identifying climatic refugia is important for long-term conservation planning under climate change. Riparian areas have the potential to provide climatic refugia for wildlife, but literature remains limited, especially for plants. This study was conducted with the purpose of identifying climatic refugia of plant biodiversity in the portion of the Mekong River Basin located in Xishuangbanna, China. We first predicted the current and future (2050s and 2070s) potential distribution of 50 threatened woody species in Xishuangbanna by using an ensemble of small models, then stacked the predictions for individual species to derive spatial biodiversity patterns within each 10 × 10 km grid cell. We then identified the top 17 % of the areas for spatial biodiversity patterns as biodiversity hotspots, with climatic refugia defined as areas that remained as biodiversity hotspots over time. Stepwise regression and linear correlation were applied to analyze the environmental correlations with spatial biodiversity patterns and the relationships between climatic refugia and river distribution, respectively. Our results showed potential upward and northward shifts in threatened woody species, with range contractions and expansions predicted. The spatial biodiversity patterns shift from southeast to northwest, and were influenced by temperature, precipitation, and elevation heterogeneity. Climatic refugia under climate change were related closely to river distribution in Xishuangbanna, with riparian areas identified that could provide climatic refugia. These refugial zones are recommended as priority conservation areas for mitigating the impacts of climate change on biodiversity. Our study confirmed that riparian areas could act as climatic refugia for plants and emphasizes the conservation prioritization of riparian areas within river basins for protecting biodiversity under climate change.

Yu, J., Y. Niu, Y. You, C. J. Cox, R. L. Barrett, A. Trias‐Blasi, J. Guo, et al. 2022. Integrated phylogenomic analyses unveil reticulate evolution in Parthenocissus (Vitaceae), highlighting speciation dynamics in the Himalayan‐Hengduan Mountains. New Phytologist. https://doi.org/10.1111/nph.18580

Hybridization caused by frequent environmental changes can lead to both species diversification (speciation) and 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 focussed 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 hotspots 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.

Fu, P., A. Favre, R. Wang, Y. Huang, and S. Sun. 2022. Between allopatry and secondary contact: differentiation and hybridization among three sympatric Gentiana species in the Qinghai-Tibet Plateau. BMC Plant Biology 22. https://doi.org/10.1186/s12870-022-03879-0

Background Mountains of the world host a significant portion of all terrestrial biodiversity, and the region of the Qinghai-Tibet Plateau (QTP) stands as one of the most remarkable mountain regions on Earth.  Because many explosive radiations occurred there, the QTP is a natural laboratory which is ideal to investigate patterns and processes linked to speciation and diversification. Indeed, understanding how closely related and sympatric species diverged is vital to explore drivers fostering speciation, a topic only rarely investigated in the QTP. By combining genomic and environmental data, we explored the speciation process among three closely related and sympatric species, Gentiana hexaphylla , G. lawrencei and G. veitchiorum in the QTP region. Results Combining genome sizes and cytological data, our results showed that G. hexaphylla and G. veitchiorum are diploid, whereas G. lawrencei is tetraploid. Genetic clustering and phylogenetic reconstruction based on genomic SNPs indicated a clear divergence among the three species. Bayesian clustering, migrant, and D -statistic analyses all showed an obvious signature of hybridization among the three species, in particular between G. lawrencei and both G. hexaphylla and G. veitchiorum in almost all populations. Environmental variables related to precipitation and particularly temperature showed significant differences among the three gentians, and in fact a redundancy analysis confirmed that temperature and precipitation were the major climatic factors explaining the genetic differentiation among the three species. Conclusion Our study suggested that ancient hybridization, polyploidization, geological isolation and the evolution of different climatic preferences were all likely to be involved in the divergence of the three Gentiana species, as may be the case for many other taxa in the QTP region.

Aguirre‐Liguori, J. A., A. Morales‐Cruz, and B. S. Gaut. 2022. Evaluating the persistence and utility of five wild Vitis species in the context of climate change. Molecular Ecology. https://doi.org/10.1111/mec.16715

Crop wild relatives (CWRs) have the capacity to contribute novel traits to agriculture. Given climate change, these contributions may be especially vital for the persistence of perennial crops, because perennials are often clonally propagated and consequently do not evolve rapidly. By studying the landscape genomics of samples from five Vitis CWRs (V. arizonica, V. mustangensis, V. riparia, V. berlandieri and V. girdiana) in the context of projected climate change, we addressed two goals. The first was to assess the relative potential of different CWR accessions to persist in the face of climate change. By integrating species distribution models with adaptive genetic variation, additional genetic features such as genomic load and a phenotype (resistance to Pierce’s Disease), we predicted that accessions from one species (V. mustangensis) are particularly well‐suited to persist in future climates. The second goal was to identify which CWR accessions may contribute to bioclimatic adaptation for grapevine (V. vinifera) cultivation. To do so, we evaluated whether CWR accessions have the allelic capacity to persist if moved to locations where grapevines (V. vinifera) are cultivated in the United States. We identified six candidates from V. mustangensis and hypothesized that they may prove useful for contributing alleles that can mitigate climate impacts on viticulture. By identifying candidate germplasm, this work takes a conceptual step toward assessing the genomic and bioclimatic characteristics of CWRs.

Shen, Y., Z. Tu, Y. Zhang, W. Zhong, H. Xia, Z. Hao, C. Zhang, and H. Li. 2022. Predicting the impact of climate change on the distribution of two relict Liriodendron species by coupling the MaxEnt model and actual physiological indicators in relation to stress tolerance. Journal of Environmental Management 322: 116024. https://doi.org/10.1016/j.jenvman.2022.116024

Climate change has a crucial impact on the distributions of plants, especially relict species. Hence, predicting the potential impact of climate change on the distributions of relict plants is critical for their future conservation. Liriodendron plants are relict trees, and only two natural species have survived: L. chinense and L. tulipifera. However, the extent of the impact of future climate change on the distributions of these two Liriodendron species remains unclear. Therefore, we predicted the suitable habitat distributions of two Liriodendron species under present and future climate scenarios using MaxEnt modeling. The results showed that the area of suitable habitats for two Liriodendron species would significantly decrease. However, the two relict species presented different habitat shift patterns, with a local contraction of suitable habitat for L. chinense and a northward shift in suitable habitat for L. tulipifera, indicating that changes in environmental factors will affect the distributions of these species. Among the environmental factors assessed, May precipitation induced the largest impact on the L. chinense distribution, while L. tulipifera was significantly affected by precipitation in the driest quarter. Furthermore, to explore the relationship between habitat suitability and Liriodendron stress tolerance, we analyzed six physiological indicators of stress tolerance by sampling twelve provenances of L. chinense and five provenances of L. tulipifera. The composite index of six physiological indicators was significantly negatively correlated with the habitat suitability of the species. The stress tolerance of Liriodendron plants in highly suitable areas was lower than that in areas with moderate or low suitability. Overall, these findings improve our understanding of the ecological impacts of climate change, informing future conservation efforts for Liriodendron species.

Marcussen, T., H. E. Ballard, J. Danihelka, A. R. Flores, M. V. Nicola, and J. M. Watson. 2022. A Revised Phylogenetic Classification for Viola (Violaceae). Plants 11: 2224. https://doi.org/10.3390/plants11172224

The genus Viola (Violaceae) is among the 40–50 largest genera among angiosperms, yet its taxonomy has not been revised for nearly a century. In the most recent revision, by Wilhelm Becker in 1925, the then-known 400 species were distributed among 14 sections and numerous unranked groups. Here, we provide an updated, comprehensive classification of the genus, based on data from phylogeny, morphology, chromosome counts, and ploidy, and based on modern principles of monophyly. The revision is presented as an annotated global checklist of accepted species of Viola, an updated multigene phylogenetic network and an ITS phylogeny with denser taxon sampling, a brief summary of the taxonomic changes from Becker’s classification and their justification, a morphological binary key to the accepted subgenera, sections and subsections, and an account of each infrageneric subdivision with justifications for delimitation and rank including a description, a list of apomorphies, molecular phylogenies where possible or relevant, a distribution map, and a list of included species. We distribute the 664 species accepted by us into 2 subgenera, 31 sections, and 20 subsections. We erect one new subgenus of Viola (subg. Neoandinium, a replacement name for the illegitimate subg. Andinium), six new sections (sect. Abyssinium, sect. Himalayum, sect. Melvio, sect. Nematocaulon, sect. Spathulidium, sect. Xanthidium), and seven new subsections (subsect. Australasiaticae, subsect. Bulbosae, subsect. Clausenianae, subsect. Cleistogamae, subsect. Dispares, subsect. Formosanae, subsect. Pseudorupestres). Evolution within the genus is discussed in light of biogeography, the fossil record, morphology, and particular traits. Viola is among very few temperate and widespread genera that originated in South America. The biggest identified knowledge gaps for Viola concern the South American taxa, for which basic knowledge from phylogeny, chromosome counts, and fossil data is virtually absent. Viola has also never been subject to comprehensive anatomical study. Studies into seed anatomy and morphology are required to understand the fossil record of the genus.

Canavan, S., Z. T. Brym, G. Brundu, K. Dehnen-Schmutz, D. Lieurance, T. Petri, W. H. Wadlington, et al. 2022. Cannabis de-domestication and invasion risk. Biological Conservation 274: 109709. https://doi.org/10.1016/j.biocon.2022.109709

Cultivated plants provide food, fiber, and energy but they can escape, de-domesticate, colonize agroecosystems as weeds, and disrupt natural ecosystems as invasive species. Escape and invasion depend on traits of the species, type and rate of domestication, and cultivation context. Understanding this “de-domestication invasion process” is critical for managing conservation efforts to reduce unintended consequences of cultivated species in novel areas. Cannabis (Cannabis sativa L.) is an ideal case study to explore this process because it was one of the earliest plants to co-evolve with humans, has a crop to weed history, and has been introduced and cultivated globally. Moreover, recent liberalization of cannabis cultivation and use policies have raised concerns about invasion risk. Here, we synthesize knowledge on cannabis breeding, cultivation, and processing relevant to invasion risk and outline research and management priorities to help overcome the research deficit on the invasion ecology of the species. Understanding the transition of cannabis through the de-domestication-invasion process will inform policy and minimize agricultural and environmental risks associated with cultivation of domesticated species.