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1. Exotic plant invasions can alter fire regimes in plant communities. Invaders often possess traits that differ from native plants in the community, resulting in increases or declines in community-level flammability, changing fire regimes and potentially causing long-term modifications to plant community composition. Although considering traits of multiple invaders and native species together is useful to better understand how invasions change community-level flammability, few studies have done this. 2. We measured morphological and flammability traits of 51 native and exotic plant species common in tussock grasslands in New Zealand's south-eastern South Island to examine relationships between morphology and whole-plant and shoot-level flammability. Plant community data from 103 permanent transects in this region measured over a 25-year period (c. 1982-2007) were used to determine how flammability changed with increasing levels of plant invasion. 3. Invasion by exotic plants has led to reduced community-level flammability due to shifts from native tussock grasses with high flammability and high fuel loads to mat-forming exotic forbs with low flammability and little fuel. These changes will likely lead to considerable alterations to the fire regime, resulting in lower intensity fires that burn more patchily and for shorter amounts of time, potentially causing further changes in floristic composition. We found considerable differences in flammability across the wide range of species and growth forms that we studied, emphasising the importance of quantifying species-level flammability and the need to avoid treating grasslands as homogenous in terms of their flammability. Total biomass, leaf length and leaf area were the traits most positively correlated with flammability in these tussock grasslands. 4. Synthesis. We show how plant invasions over decadal time-scales have reduced the community-level flammability of tussock grasslands and, for the first time, demonstrate how this can be driven by exotic forbs. The total biomass of constituent species is a useful surrogate for community flammability across a wide range of species and growth forms in both temperate grasslands and savanna ecosystems and should be used in dynamic global vegetation models to assess how flammability varies under various global change scenarios.

The repetitive content of the plant genome (repeatome) often represents its largest fraction and is frequently correlated with its size. Transposable elements (TEs), the main component of the repeatome, are an important driver in the genome diversification due to their fast-evolving nature. Hybridization and polyploidization events are hypothesized to induce massive bursts of TEs resulting, among other effects, in an increase of copy number and genome size. Little is known about the repeatome dynamics following hybridization and polyploidization in plants that reproduce by apomixis (asexual reproduction via seeds). To address this, we analyzed the repeatomes of two diploid parental species, and (sexual), their diploid F1 synthetic and their natural triploid hybrids ( and , apomictic). Using low-coverage next-generation sequencing (NGS) and a graph-based clustering approach, we detected high overall similarity across all major repeatome categories between the parental species, despite their large phylogenetic distance. Medium and highly abundant repetitive elements comprise ∼70% of genomes; most prevalent were Ty3/Gypsy chromovirus Tekay and Ty1/Copia Maximus-SIRE elements. No TE bursts were detected, neither in synthetic nor in natural hybrids, as TE abundance generally followed theoretical expectations based on parental genome dosage. Slight over- and under-representation of TE cluster abundances reflected individual differences in genome size. However, in comparative analyses, apomicts displayed an overabundance of pararetrovirus clusters not observed in synthetic hybrids. Substantial deviations were detected in rDNAs and satellite repeats, but these patterns were sample specific. rDNA and satellite repeats (three of them were newly developed as cytogenetic markers) were localized on chromosomes by fluorescence hybridization (FISH). In a few cases, low-abundant repeats (5S rDNA and certain satellites) showed some discrepancy between NGS data and FISH results, which is due partly to the bias of low-coverage sequencing and partly to low amounts of the satellite repeats or their sequence divergence. Overall, satellite DNA (including rDNA) was markedly affected by hybridization, but independent of the ploidy or reproductive mode of the progeny, whereas bursts of TEs did not play an important role in the evolutionary history of .

Biological invasions are a key component of global change. Thousands of exotic plant species are distributed worldwide, potentially disrupting ecosystem functioning. There is a particular need to investigate invasive species at high latitudes, especially in the Southern Hemisphere, where research is limited. We conducted a study to evaluate the niche shifts of Hieracium pilosella , a species native to Eurasia and invasive in high-latitude rangelands in North America, Oceania, and South America. We assessed niche conservatism across different regions using niche modeling techniques. Our findings reveal niche shifts between native and invasive populations of H. pilosella . In all invaded ranges, there is both niche expansion into environments not occupied in the native range and unfilling of habitats that belong to the native niche. The overlap of the native niche with the invasive niches varies between invaded regions but is generally lesser than expected by chance. The potential range of H. pilosella may increase considerably in some regions if it colonizes unfilling habitats. Therefore, it is crucial to maintain ongoing observation and monitoring methods to control this troublesome species. Understanding spatial niche dynamics in problematic invasive species that invade high-latitude ecosystems offers valuable insights for the global investigation and management of invasions. This is especially relevant in the context of climate change, where such invasions may expand toward higher latitudes soon.

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.

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.

Determining how to cost‐effectively allocate resources for managing invasive species is a notoriously difficult problem. Invasive species control problems are always spatiotemporal, but much of the current theory about control strategies is either spatial or temporal. This article uses a deterministic spatiotemporal model of invasive species dynamics and identifies the optimal management strategy across a range of situations. The optimal solution points a principle of targeting the source of the population, which in many cases is the region of the landscape where the invader is most abundant. The analysis presented here is the first capable of solving for optimal strategies for invasive species over large and irregular environments. Thus, it is an important step forward for both the understanding of control strategies and the application to management scenarios.

Competition exerted by native plant communities is an important component of biotic resistance against the spread and impact of non-indigenous plant species in novel habitats. However, how the role of biotic resistance varies along environmental gradients to delay invasions is less clear. We conducted two field experiments to determine how competition from native communities affects colonization of a recognized invader of grasslands, Hieracium pilosella L., in the Fuegian steppe along different environmental gradients at regional and landscape scale. We assessed the role of competition on invader survival and growth along a climate gradient at regional scale (4.7–6.6 °C and 270–450 mm year⁻¹), and across four major plant communities (i.e. meadows, grasslands, scrublands, and heathlands) along a topographic catena. At regional scale, the climate gradient showed a 33% reduction in H. pilosella survival at the coldest and wettest extreme, while reduced its biomass in 41% at the warmest and driest site, in the opposite extreme of the gradient. Competition caused a 34% decrease of the invader biomass, similarly along the climate gradient. At landscape scale, the topographic gradient had a stronger effect on invader survival reaching a 67% reduction in lowland meadows due to flooding events, while competition reduced in 29–39% the invader biomass only in grasslands or scrublands with negligible effects on low-resource heathlands. These results suggest that biotic resistance plays a significant and similar role along the climate gradient to delay invasion at regional scale, but at landscape scale is only determinant for rich-resource communities in absence of abiotic stresses.

Recent studies suggest that plant detection is not perfect, even for large, highly visible plants. However, this is often not taken into account during plant surveys where failing to detect a plant when present can result in poor management and biodiversity outcomes. Including knowledge of imperfect detectability into survey design and evaluation is hampered by the paucity of empirical data, and in particular, how detectability will change with search effort, plant size and abundance, the surrounding vegetation, or observer experience. We carried out a search experiment to measure the detection-–effort curve for the invasive species orange hawkweed ( Hieracium aurantiacum ) in Victoria, Australia. The probability that hawkweed was detected increased with increasing search effort and the number of plants at the location. While detection probability varied between observers, experience appeared to have little effect. Accounting for imperfect detectability in plant surveys holds much promise for improved survey design and biodiversity outcomes, and we encourage other researchers to undertake similar experiments to further our understanding of plant detectability.

Within the agamic Pilosella complex, apomixis (asexual reproduction through seed) involves apospory, parthenogenesis, and autonomous endosperm development. Observations of reproductive biology in P. brzovecensis throughout four growing seasons in the garden have shown that both tetraploid and pentaploid plants of this species do not produce viable seeds and reproduce exclusively vegetatively by underground stolons. The reasons for the seed development failure were unknown, therefore our research focused on the analysis of reproductive events in the ovules of this taxon. We found that apospory was initiated in the ovules of both cytotypes. Multiple aposporous initial (AI) cells differentiated in close proximity to the megaspore mother cell (MMC) and suppressed megasporogenesis at the stage of early prophase I. However, none of the AI cells was able to further develop into a multi-nucleate aposporous embryo sac (AES) due to the inhibition of mitotic divisions. It was unusual that callose was accumulated in the walls of AI cells and its synthesis was most likely associated with a response to the dysfunction of these cells. Callose is regarded as the isolating factor and its surprising deposition in the ovules of P. brzovecensis may signal disruption of reproductive processes that cause premature termination of the aposporous development pathway and ultimately lead to ovule sterility. The results of our embryological analysis may be the basis for undertaking advanced molecular studies aimed at fully understanding of the causes of female sterility in P. brzovecensis.

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.