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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.

Crivellaro, A., A. Piermattei, J. Dolezal, P. Dupree, and U. Büntgen. 2022. Biogeographic implication of temperature-induced plant cell wall lignification. Communications Biology 5. https://doi.org/10.1038/s42003-022-03732-y

More than 200 years after von Humboldt’s pioneering work on the treeline, our understanding of the cold distribution limit of upright plant growth is still incomplete. Here, we use wood anatomical techniques to estimate the degree of stem cell wall lignification in 1770 plant species from six continents. Contrary to the frequent belief that small plants are less lignified, we show that cell wall lignification in ‘woody’ herbs varies considerably. Although trees and shrubs always exhibit lignified cell walls in their upright stems, small plants above the treeline may contain less lignin. Our findings suggest that extremely cold growing season temperatures can reduce the ability of plants to lignify their secondary cell walls. Corroborating experimental and observational evidence, this study proposes to revisit existing theories about the thermal distribution limit of upright plant growth and to consider biochemical and biomechanical factors for explaining the global treeline position. A global survey of lignin content in plant cell walls corroborates suggestions that cold temperature limits upright tree growth.

Xue, T., S. R. Gadagkar, T. P. Albright, X. Yang, J. Li, C. Xia, J. Wu, and S. Yu. 2021. Prioritizing conservation of biodiversity in an alpine region: Distribution pattern and conservation status of seed plants in the Qinghai-Tibetan Plateau. Global Ecology and Conservation 32: e01885. https://doi.org/10.1016/j.gecco.2021.e01885

The Qinghai-Tibetan Plateau (QTP) harbors abundant and diverse plant life owing to its high habitat heterogeneity. However, the distribution pattern of biodiversity hotspots and their conservation status remain unclear. Based on 148,283 high-resolution occurrence coordinates of 13,450 seed plants, w…

Favre, A., J. Paule, and J. Ebersbach. 2021. Incongruences between nuclear and plastid phylogenies challenge the identification of correlates of diversification in Gentiana in the European Alpine System. Alpine Botany 132: 29–50. https://doi.org/10.1007/s00035-021-00267-6

Mountains are reservoirs for a tremendous biodiversity which was fostered by a suite of factors acting in concert throughout evolutionary times. These factors can be climatic, geological, or biotic, but the way they combine through time to generate diversity remains unknown. Here, we investigate the…

Bontrager, M., T. Usui, J. A. Lee‐Yaw, D. N. Anstett, H. A. Branch, A. L. Hargreaves, C. D. Muir, and A. L. Angert. 2021. Adaptation across geographic ranges is consistent with strong selection in marginal climates and legacies of range expansion. Evolution 75: 1316–1333. https://doi.org/10.1111/evo.14231

Every species experiences limits to its geographic distribution. Some evolutionary models predict that populations at range edges are less well‐adapted to their local environments due to drift, expansion load, or swamping gene flow from the range interior. Alternatively, populations near range edges…

Zhang, Y., J. Chen, and H. Sun. 2021. Alpine speciation and morphological innovations: revelations from a species-rich genus in the northern hemisphere N. Rajakaruna [ed.],. AoB PLANTS 13. https://doi.org/10.1093/aobpla/plab018

Background and Aims A large number of studies have attempted to determine the mechanisms driving plant diversity and distribution on a global scale, but the diverse and endemic alpine herbs found in harsh environments, showing adaptive evolution, require more studies. Methods Here, we selected 466 s…

Rincón‐Barrado, M., S. Olsson, T. Villaverde, B. Moncalvillo, L. Pokorny, A. Forrest, R. Riina, and I. Sanmartín. 2021. Ecological and geological processes impacting speciation modes drive the formation of wide‐range disjunctions within tribe Putorieae (Rubiaceae). Journal of Systematics and Evolution 59: 915–934. https://doi.org/10.1111/jse.12747

Wide‐range geographically discontinuous distributions have long intrigued scientists. We explore the role of ecology, geology, and dispersal in the formation of these large‐scale disjunctions, using the angiosperm tribe Putorieae (Rubiaceae) as a case study. From DNA sequences of nuclear ITS and six…

Shaw, E. C., R. Fowler, S. Ohadi, M. J. Bayly, R. A. Barrett, J. Tibbits, A. Strand, et al. 2020. Explaining the worldwide distributions of two highly mobile species: Cakile edentula and Cakile maritima. Journal of Biogeography 48: 603–615. https://doi.org/10.1111/jbi.14024

Aim: If we are able to determine the geographic origin of an invasion, as well as its known area of introduction, we can better appreciate the innate environmental tolerance of a species and the strength of selection for adaptation that colonizing populations have undergone. It also enables us to ma…

Ebersbach, J., N. Tkach, M. Röser, and A. Favre. 2020. The Role of Hybridisation in the Making of the Species-Rich Arctic-Alpine Genus Saxifraga (Saxifragaceae). Diversity 12: 440. https://doi.org/10.3390/d12110440

Evolutionary processes fuelling rapid species diversification are not yet fully understood, although their major contribution to overall patterns of plant biodiversity is well established. Hybridisation is among the least understood of these processes, despite its multifaceted role in speciation pro…

van Treuren, R., R. Hoekstra, R. Wehrens, and T. van Hintum. 2020. Effects of climate change on the distribution of crop wild relatives in the Netherlands in relation to conservation status and ecotope variation. Global Ecology and Conservation 23: e01054. https://doi.org/10.1016/j.gecco.2020.e01054

Crop wild relatives (CWR) are wild plant taxa that are genetically related to a cultivated species and are considered rich sources of useful traits for crop improvement. CWR are generally underrepresented in genebanks, while their survival in nature is not guaranteed. Inventories and risk analyses a…