Search Results (7)

A review of the known diploid species in Hieracium L. s.s. (Asteraceae, Cichorieae) is presented. This article aims to summarize the current knowledge of the taxa with the basic ploidy level in the genus (2n = 2x = 18), as these entities are supposed to have originated the outstanding diversity observed nowadays, which is largely ascribable to polyploid microspecies. The study of extant diploid species is crucial for the understanding of the speciation dynamics that occurred in hawkweeds. All available cytological data in the literature, pertinent to Europe and adjacent countries, are included to have an overview of the obligately sexual species in this genus and highlight gaps and uncertainties. In order to preliminarily investigate the geographical distribution, all records are georeferenced and projected on a map to highlight the hotspots of Hieracium diversity. A brief account of each taxon is included, with some additional considerations and remarks on doubtful records. Full article

The taxonomic history, nomenclature and application of the oldest species names available for the common hybrids between Pilosella caespitosa and P. lactucella are reviewed. Elias Fries created a nomenclatural and bibliographical collision when he replaced a printed label of his exsiccata Herbarium normale with its second version, distributed at a later date, in which the protologue of Hieracium suecicum had appeared. In this protologue, the new species name was validly published with a mere reference to the original description of H. auricula var. majus, thus being based on the type of the latter. In a later fascicle of the same exsiccata, Fries excluded this synonym and distributed a different morphotype of H. suecicum, which caused taxonomic confusion and re-description of the same taxon under the name H. fennicum. The surviving original material of H. auricula var. majus is rejected, and its neotype is designated, making H. suecicum the correct name for the hybrids strictly intermediate between P. lactucella and P. caespitosa. Such hybrids constitute the most common hybridogenous taxon of Pilosella in Scandinavia, Finland and neighbouring Russia, with many synonyms described from this area and partly typified here. Another hybridogenous taxon of the same origin, more similar to P. lactucella and previously known as P. cochlearis, is correctly named P. stipitiflora comb. nov. The nomenclatural value and bibliographic complexity of exsiccata, a commonly underestimated kind of grey literature in taxonomic botany, are further highlighted. Full article

Hawkweeds (Pilosella spp.) have become a severe and rapidly invading weed in pasture lands and forest meadows of New Zealand. Detection of hawkweed infestations is essential for eradication and resource management at private and government levels. This study explores the potential of machine learning (ML) algorithms for detecting mouse-ear hawkweed (Pilosella officinarum) foliage and flowers from Unmanned Aerial Vehicle (UAV)-acquired multispectral (MS) images at various spatial resolutions. The performances of different ML algorithms, namely eXtreme Gradient Boosting (XGB), Support Vector Machine (SVM), Random Forest (RF), and K-nearest neighbours (KNN), were analysed in their capacity to detect hawkweed foliage and flowers using MS imagery. The imagery was obtained at numerous spatial resolutions from a highly infested study site located in the McKenzie Region of the South Island of New Zealand in January 2021. The spatial resolution of 0.65 cm/pixel (acquired at a flying height of 15 m above ground level) produced the highest overall testing and validation accuracy of 100% using the RF, KNN, and XGB models for detecting hawkweed flowers. In hawkweed foliage detection at the same resolution, the RF and XGB models achieved highest testing accuracy of 97%, while other models (KNN and SVM) achieved an overall model testing accuracy of 96% and 72%, respectively. The XGB model achieved the highest overall validation accuracy of 98%, while the other models (RF, KNN, and SVM) produced validation accuracies of 97%, 97%, and 80%, respectively. This proposed methodology may facilitate non-invasive detection efforts of mouse-ear hawkweed flowers and foliage in other naturalised areas, enabling land managers to optimise the use of UAV remote sensing technologies for better resource allocation. Full article

Native American hawkweeds are mainly mountainous species that are distributed all over the New World. They are severely understudied with respect to their origin, colonization of the vast distribution area, and species relationships. Here, we attempt to reconstruct the evolutionary history of the group by applying seven molecular markers (plastid, nuclear ribosomal and low-copy genes). Phylogenetic analyses revealed that Chionoracium is a subgenus of the mainly Eurasian genus Hieracium, which originated from eastern European hawkweeds about 1.58–2.24 million years ago. Plastid DNA suggested a single origin of all Chionoracium species. They colonized the New World via Beringia and formed several distinct lineages in North America. Via one Central American lineage, the group colonized South America and radiated into more than a hundred species within about 0.8 million years, long after the closure of the Isthmus of Panama and the most recent uplift of the Andes. Despite some incongruences shown by different markers, most of them revealed the same crown groups of closely related taxa, which were, however, largely in conflict with traditional sectional classifications. We provide a basic framework for further elucidation of speciation patterns. A thorough taxonomic revision of Hieracium subgen. Chionoracium is recommended. Full article

The gall wasp Aulacidea hieracii L., 1758 (Hymenoptera: Cynipidae) forms a stem gall on the hawkweed Hieracium × robustum Fries, 1848 (Asteraceae), a weedy herb that grows in the steppe biotopes of Eurasia. In its turn, gall former serves as food for a large number of parasitoids and predators, which also live and develop inside and outside the gall. Moreover, the inhabitants of the galls are consumed by birds. In addition, a specific microbiota develops inside the gall, which includes representatives of Gram-negative bacteria Pseudomonas rhizosphaerae, Curtobacterium flaccumfaciens, Pantoea agglomerans and fungi Alternaria alternata. The authors found out the composition of parasitoids, predators, inquilines and microorganisms for a gall on the hawkweed. For the first time, studies were carried out on the development of the moth caterpillars Oxyptilus chrysodactyla (Denis & Schiffermüller, 1775) on the hawkweed H. robustum. We found that the caterpillars of the moths cohabit on their fodder plant on the surface of the gall together with the larvae of gall wasps. Notably, the gall wasp larvae are the first to inhabit the plant. Thus, gall on the plant is a complex ecosystem, which balances and increases diversity of living organisms. Full article

This study examined the use of hyperspectral profiles for identifying three selected weed species in the alpine region of New South Wales, Australia. The targeted weeds included Orange Hawkweed, Mouse-ear Hawkweed and Ox-eye daisy, which have caused a great concern to regional biodiversity and health of the environment in Kosciuszko National Park. Field surveys using a spectroradiometer were undertaken to measure the hyperspectral profiles of leaves and flowers of the selected weeds and companion native plants. Random Forest (RF) classification was then applied to distinguish which spectral bands would differentiate the weeds from the native plants. Our results showed that an accuracy of 95% was achieved if the spectral profiles of the distinct flowers of the weeds were considered, and an accuracy of 80% was achieved if only the profiles of the leaves were considered. Emulation of the spectral profiles of two multispectral sensors (Sentinel-2 and Parrot Sequoia) was then conducted to investigate whether classification accuracy could potentially be achieved using wider spectral bands. Full article

The main aim of this study was to compare the cytological difference between ovular mucilage cells in two Asteraceae species—Pilosella officinarum and Taraxacum officinale—in order to determine whether pectic epitopes, arabinogalactan proteins, or extensins are present. The immunocytochemical technique was used. Both the Taracacum and Pilosella genera have been used recently as models for understanding the mechanisms of apomixis. Knowledge of the presence of signal molecules (pectic epitopes, arabinogalactan proteins, and extensins) can help better understand the developmental processes in these plants during seed growth. The results showed that in Pilosella officinarum, there was an accumulation of pectins in the mucilage, including both weakly and highly esterified pectins, which was in contrast to the mucilage of Taraxacum officinale, which had low amounts of these pectins. However, Taraxacum protoplasts of mucilage cells were rich in weakly methyl-esterified pectins. While the mucilage contained arabinogalactan proteins in both of the studied species, the types of arabinogalactan proteins were different. In both of the studied species, extensins were recorded in the transmitting tissues. Arabinogalactan proteins as well as weakly and highly esterified pectins and extensins occurred in close proximity to calcium oxalate crystals in both Taraxacum and Pilosella cells. Full article