Hieracium Pilosella Research Articles

Typification ofHieracium pilosellaL. (Asteraceae)

Typification of the name Hieracium pilosella L. (homotypic synonym: Pilosella officinarum F.W. Schultz & Sch. Bip.) (Asteraceae) is discussed. Designation of the type is based on consultation of Linnaeus's original material and the literature cited in the respective protologue. Original material conserved in the Linnaean Herbarium at LINN is designated as the lectotype.

Species-specific effects of the invasive Hieracium pilosella in Magellanic steppe grasslands are driven by nitrogen cycle changes

The principal objective was to evaluate the interference by the invasive species, H. pilosella, on native grassland species at the physiological performance level. We hypothesised that the invasive species is able to alter the nitrogen uptake of native plant species, and can modify community functioning. This study was performed under field conditions in the Magellanic Steppe (Argentina). We compared stable isotope signatures, nutrient content and several functional physiological traits in four grassland species with and without H. pilosella interference. We found significant interference effects from the invasive species on native species, mostly through changes in nitrogen uptake. The variation in the natural abundance of foliar δ15N suggests that the native plants switched nitrogen sources due to interference with the exotic species. A linear relationship between chlorophyll and proline content that disappears when species are under H. pilosella interference, suggests major changes in the N allocation of native species. Grassland species under interference with exotic species exhibit lower photochemical efficiency and higher water use efficiency. Canonical discriminant analysis evidenced the existence of a different set of functional traits between invasive and native plants, and also among native species with and without H. pilosella interference. Our results support the hypothesis that H. pilosella exerts intense interference with native species through shifting the N sources available for native species, a lower leaf N content, and increasing water stress.

Role of mycorrhization and nutrient availability in competitive interactions between the grassland species Plantago lanceolata and Hieracium pilosella

Arbuscular mycorrhizal fungi (AMF) may serve as an effective substitute for root surface. As mycorrhizal benefits are related to nutrient availability, the trade-off between carbon investments into AMF versus roots may drive competitive interactions. We studied competitive interactions between mycorrhizal and non-mycorrhizal individuals of Hieracium pilosella L. and Plantago lanceolata L., species differing in both mycotrophic degree and carbon allocation to roots. Three fertilization treatments were used to simulate nutritional differences over the course of succession. Species-specific differences in mycotrophy were reflected in markedly larger root/shoot allocation in P. lanceolata and higher mycorrhizal growth dependency in H. pilosella. P. lanceolata dominated competition in all fertilizer treatments, enabled by its comparatively larger root biomass allocation. In contrast, under intermediate and high fertilization, H. pilosella exhibited large investments into clonal shoot growth rather than in roots. Unexpectedly, the competitive imbalance between both species was amplified by the presence of AMF. The poor competitive strength of H. pilosella indicates that AMF-dominated foraging can be less effective than root-dominated foraging in competitive interactions, particularly under high nutrient availabilities. However, the competitive imbalance was reduced in favor of H. pilosella under nutrient deficiency. Our results lend support to the idea of differing competitive success of mycorrhizal- versus root-based foraging strategy over a nutritional gradient, which may play a role in the natural distribution of species over the course of succession.

Should I stay or should I go? Roots segregate in response to competition intensity

Root segregation has been observed in a variety of species. Though it is usually attributed to a plant’s attempt to avoid below ground competition, a direct correlation of root distribution with the intensity of competition has never been shown. The test species Hieracium pilosella L. was exposed to a gradient of competitive pressure using the closely related species Arabidopsis petraea (L.) V.I.DOROF., Arabidopsis thaliana (L.) Heynh ., Capsella rubella Reut . and Cardamine hirsuta L. as neighbouring plants. Horizontal root distribution was quantified using a soil monolith method. The neighbour species could be ranked according to their competitive effect on the test species, identifying two weak (A. thaliana and A. petraea) and two strong competitors (C. hirsuta and C. rubella). The degree of root segregation correlated negatively with the competitive effect caused by the various neighbour species. We conclude that root segregation is indeed a response to competitive pressure. Further factors such as root symbiotic relationships or root exuded allelochemicals are supposedly involved in the outcome of root interactions. We propose the use of screening experiments on root responses to various neighbours in order to quantify each factor’s relative influence on rooting patterns.

Experiencias de largo plazo para el manejo de una hierba invasora de pastizales: El caso de Hieracium pilosella L. en la Estepa Fueguina

Ecología Austral 24:135-144 (2014)Long-term experiences are generally rare in studies on management of invasive species, and they are the key to understand the effectiveness of controls. In this work, we revisited a field experiment set seven years ago to evaluate the effects of four control measures (pasture sown + fertilizer, fertilizer and selective/non-selective herbicide applications) under two different grazing conditions (grazed and ungrazed) in rangelands from northern grasslands of Tierra del Fuego Island in Southern Patagonia (Argentina) invaded by the exotic weed Hieracium pilosella L. (mouse-ear hawkweed, Asteraceae). To evaluate the effects of the treatments applied seven years ago, we measured the cover of the invasive species, the dominant growth forms, and bare soil. The effects of fertilization depended on the grazing conditions; H. pilosella cover decreased by more than 82% and it was replaced by naturalized herbs with high forage value in the ungrazed-fertilized plots, while it exhibited no decrease in the grazed-fertilized plots after seven years since the application. Both herbicides (selective and non-selective) reduced H. pilosella cover by ca. 90% independently of grazing. However, the non-selective herbicide application resulted in an increase in bare soil cover (15%) independently of grazing. In contrast, the selective broadleaf herbicide application increased the graminoids cover up to a 60% and the bare soil cover was below the 2%. According with the results, we suggest a control strategy based on the local application of selective herbicides and/or fertilizers in conjunction with a transient ban on sheep grazing because it is able to reduce the invader’s cover at midterm and local scale.

Local and intermediated-intensity soil disturbances increase the colonization and expansion dynamics of an invasive plant in Southern Patagonian rangelands

Disturbances are important drivers in natural ecosystems, affecting the vegetation structure and functioning. Invasions of exotic plant species are often associated to disturbances in a complex manner, because they depend on the type, intensity, spatial and temporal arrangement of disturbances, and the particular abiotic and biotic context. Field studies that evaluate the dynamics of plant invasions under different disturbance regimes have a great importance for the understanding of the disturbance effects on invasion spread. In this work we evaluated, through a field manipulative experiment, the early colonization and expansion dynamics of an aggressive invader of grasslands, Hieracium pilosella L., under two disturbance types. We used a split-plot experiment by crossing three levels for a local, sporadic, of increasing intensity disturbance [i.e., 1- undisturbed, 2- vegetation mowing, and 3- ploughing], within two levels for an extensive and chronic disturbance (i.e., grazed and ungrazed). In the range of intensities of disturbance evaluated, the intermediate intensity (i.e., mowing) accelerated the colonization when it is grazed and the expansion of H. pilosella in ungrazed condition. In contrast, lower and higher intensity disturbances, such as ungrazed and ploughing treatments decelerated both invasion processes. Changes in resource availability, interspecific competition and particular characteristics of the invader, i.e., high light requirements, prostrate growth and the presence of stolons, could explain these early invasion patterns.

Sexual Hieracium pilosella plants are better inter-specific, while apomictic plants are better intra-specific competitors

Apomixis, asexual reproduction through seeds, occurs in over 40 plant families. This widespread phenomenon can lead to the fixation of successful genotypes, resulting in a fitness advantage. On the other hand, apomicts are expected to lose their fitness advantage if the environment changes because of their limited evolutionary potential, which is due to low genetic variability and the potential accumulation of deleterious somatic mutations. Nonetheless, some apomicts have been extremely successful, for example certain apomictic accessions of Hieracium pilosella L. from New Zealand, where the plant is invasive. Here, we investigate whether the success of these apomictic accessions could be due to a fitness advantage by comparing the vegetative competitiveness of apomictic H. pilosella from New Zealand with sexual accessions of H. pilosella from Europe. Sexual and apomictic plants were grown either (A) alone (no competition), (B) in competition with the other type (intra-specific competition), (C) in competition with the grass Bromus erectus (inter-specific competition), and (D) in competition with the other type and the grass B. erectus (intra- and inter-specific competition). To distinguish effects of apomixis and the region of origin, different H. pilosella lineages were compared. Furthermore, experiments were carried out to investigate effects of the ploidy level. We show that sexual plants are better inter-specific competitors than apomicts in terms of vegetative reproduction (number of stolons) and vegetative spread (stolon length), while apomicts do better than sexuals in intra-specific competition. The magnitude of the effect was in some cases dependent on the ploidy levels of the plants. Furthermore, apomicts always produced more stolons than sexuals, suggesting potential displacement of sexuals by apomicts where they co-occur.

The LOSS OF APOMEIOSIS (LOA) locus in Hieracium praealtum can function independently of the associated large‐scale repetitive chromosomal structure

Apomixis or asexual seed formation in Hieracium praealtum (Asteraceae) is controlled by two independent dominant loci. One of these, the LOSS OF APOMEIOSIS (LOA) locus, controls apomixis initiation, mitotic embryo sac formation (apospory) and suppression of the sexual pathway. The LOA locus is found near the end of a hemizygous chromosome surrounded by extensive repeats extending along the chromosome arm. Similar apomixis-carrying chromosome structures have been found in some apomictic grasses, suggesting that the extensive repetitive sequences may be functionally relevant to apomixis. Fluorescence in situ hybridization (FISH) was used to examine chromosomes of apomeiosis deletion mutants and rare recombinants in the critical LOA region arising from a cross between sexual Hieracium pilosella and apomictic H.praealtum. The combined analyses of aposporous and nonaposporous recombinant progeny and chromosomal karyotypes were used to determine that the functional LOA locus can be genetically separated from the very extensive repeat regions found on the LOA-carrying chromosome. The large-scale repetitive sequences associated with the LOA locus in H.praealtum are not essential for apospory or suppression of sexual megasporogenesis (female meiosis).

Local performance of six clonal alien species differs between native and invasive regions in Germany and New Zealand

Exotic plant invasions are widely observed to have strong biogeographic patterns with invasive species occurring at higher abundances in their introduced range when compared with their native range. However, only few field studies have validated this assumption by comparing plant populations of multiple species in their native and introduced ranges and have evaluated to what extent changes in sexual and clonal reproduction potentially have contributed to the success of plant invasions. Here, we present the results of a comparative field study in both the native (Germany) and the introduced (New Zealand, NZ) ranges of six clonal plant species with different invasive status: Achillea millefolium L., Pilosella officinarum Vaill., Hypericum perforatum L., Prunella vulgaris L., Leucanthemum vulgare Lam. and Lotus pedunculatus Cav. We hypothesized that all six species show better performance in introduced NZ than in native German populations and tested if population structures investigated at different scales provide a useful tool to identify differences between native and introduced occurrences. In 10 populations per species and country we assessed plant density and flowering proportion at the population scale and around individual plants, thereby identifying the ‘crowdedness’ of the populations. Furthermore, we collected individual plants and determined the number of attached clonal organs and plant biomass. For all six species crowdedness in NZ populations was higher than in German populations. Additionally, overall population density of four species and the production of clonal organs (expressed as total number or per biomass ratio) of three species were higher in NZ than in Germany. When measured around individual plants, the flowering proportion was higher in native German populations of Pilosella officinarum, Hypericum perforatum and Leucanthemum vulgare. Although the study species differed in their invasive status, our findings show that for all six species performance was better in introduced than in native populations. Furthermore, this study emphasizes that multiple measures of plant performance, different spatial scales and differences among species should be taken into account when trying to identify biogeographic differences in the performance of weed species.

Interspecific competition in Arabidopsis thaliana: root hairs are important for competitive effect, but not for competitive response

The role of root hairs in intraspecific competition for Phosporus (P) is well examined, but their importance during interaction with other plant species is unknown, as is the differential meaning for competitive effect and response. This study aims to fill this gap of knowledge. Competitive abilities of Arabidopsis thaliana wildtype and mutants with aberrant root hair phynotypes (root hair deficient, rhd2-1 or excessive root hair density, prc1-1) were examined in a pot-experiment with P-deficient sand. Competitive effects on a phytometer (Hieracium pilosella) or on A. thaliana itself were assessed as well as competitive responses to species mixtures. In intraspecific interaction, the competitive effect of wildtype was superior to that of rhd2-1 or prc1-1. This was much less pronounced in interspecific interaction. Competitive response was entirely uniform between Arabidopsis root phenotypes. The notion that root hairs are important for competition for P should be differentiated. With A. thaliana root hairs less important in inter- than in intraspecific interaction and with root hairs entirely unimportant for competitive response, functional mechanisms of competition for P appear quite complex. Such differential importance of root traits in different facets of competition might well be more common than previously thought.

Factors influencing abundance of invasive hawkweeds, Hieracium species, in tall tussock grasslands in the Canterbury high country

Hawkweed (Hieracium species) invasion in the tussock grasslands of South Island, New Zealand, has been well documented. Distribution of these species ranges from montane to alpine grasslands, from Hawkes Bay to Southland. This study quantifies the distribution of three Hieracium species in a high country tall (snow) tussock grassland along the Upper Cass River. Hieracium pilosella and Hieracium praealtum are widespread throughout the study site, whereas Hieracium lepidulum is rare. Major factors influencing the abundance of H. pilosella and H. praealtum are altitude and dense vegetation cover such as tall tussocks, large herbs and sub-shrubs. Both H. pilosella and H. praealtum are present at high altitude,>1800 m above sea level. Differences in the invasion stages of Hieracium species are evident. Mean abundance of H. pilosella ranged from 0.5% cover at altitudes > 1800 m above sea level, to 60% cover at altitudes < 1200 m above sea level. Hieracium praealtum averaged 0.5% cover at all altitudes.

Belowground neighbor perception in Arabidopsis thaliana studied by transcriptome analysis: roots of Hieracium pilosella cause biotic stress.

Root-root interactions are much more sophisticated than previously thought, yet the mechanisms of belowground neighbor perception remain largely obscure. Genome-wide transcriptome analyses allow detailed insight into plant reactions to environmental cues. A root interaction trial was set up to explore both morphological and whole genome transcriptional responses in roots of Arabidopsis thaliana in the presence or absence of an inferior competitor, Hieracium pilosella. Neighbor perception was indicated by Arabidopsis roots predominantly growing away from the neighbor (segregation), while solitary plants placed more roots toward the middle of the pot. Total biomass remained unaffected. Database comparisons in transcriptome analysis revealed considerable similarity between Arabidopsis root reactions to neighbors and reactions to pathogens. Detailed analyses of the functional category “biotic stress” using MapMan tools found the sub-category “pathogenesis-related proteins” highly significantly induced. A comparison to a study on intraspecific competition brought forward a core of genes consistently involved in reactions to neighbor roots. We conclude that beyond resource depletion roots perceive neighboring roots or their associated microorganisms by a relatively uniform mechanism that involves the strong induction of pathogenesis-related proteins. In an ecological context the findings reveal that belowground neighbor detection may occur independently of resource depletion, allowing for a time advantage for the root to prepare for potential interactions.

Biotic and abiotic constraints to a plant invasion in vegetation communities of Tierra del Fuego

AbstractThe biotic resistance theory relates invader success to species richness, and predicts that, as species richness increases, invasibility decreases. The relationship between invader success and richness, however, seems to be positive at large scales of analysis, determined by abiotic constraints, and it is to be expected that it is negative at small scales, because of biotic interactions. Moreover, the negative relationship at small scales would be stronger within species of the same functional group, because of having similar resource exploitation mechanisms. We studied the relationship between the cover of a worldwide invader of grasslands, Hieracium pilosella L., and species richness, species diversity and the cover of different growth forms at two different levels of analysis in 128 sites during the initial invasion process in the Fuegian steppe, Southern Patagonia, Argentina. At regional level, the invader was positively correlated to total (r = 0.28, P = 0.003), exotic (r = 0.273, P = 0.004), and native species richness (r = 0.210, P = 0.026), and to species diversity (r = 0.193, P = 0.041). At community level, we found only a weak negative correlation between H. pilosella and total richness (r = −0.426, P = 0.079) and diversity (r = −0.658, P = 0.063). The relationship between the invader and other species of the same growth form was positive both at regional (r = 0.484, P &lt; 0.001) and community (r = 0.593, P = 0.012) levels. Consequently, in the period of establishment and initial expansion of this exotic species, our results support the idea that invader success is related to abiotic factors at large scales of analysis. Also, we observed a possible sign of biotic constraint at community level, although this was not related to the abundance of species of the same growth form.

DEVELOPMENT AND VALIDATION OF TLC METHOD FOR THE IDENTIFICATION OF EUCALYPTUS LEAVES

say; the extract prepared from the roots of P. hoppeana subsp. testimonialis was found to be the most active one with iC 50 values of 0,231 M. The MdA level of this sample was found as 3.91 nmol/ml. Phytochemical screening of the tested extracts was performed by RP-hPlC using some flavonoids and phenolic acids as standards.

Ploidy levels and reproductive behaviour in invasive Hieracium pilosella in Patagonia

Within a population of invasive Hieracium pilosella in Chilean Patagonia we found two ploidy levels, pentaploid and hexaploid. Each ploidy level was represented by one clone. Their reproductive system was apomictic (and thus replicating the maternal genome), with a low degree of residual sexuality. It is necessary to prevent the evolution of new biotypes via hybridisation with different clones of H. pilosella or other Hieracium species introduced into Patagonia.

Control measures for a recent invasion of Hieracium pilosella in Southern Patagonian rangelands

Cipriotti PA, Rauber RB, Collantes MB, Braun K &amp; Escartín C (2011). Control measures for a recent invasion of Hieracium pilosella in Southern Patagonian rangelands. Weed Research 52, 98–105.SummaryPlant invasions have important ecological impacts on biodiversity, the functioning of ecosystems and economic sustainability. In this study, we evaluated the effects of four control measures (pasture sown + fertiliser, fertiliser and selective/non‐selective herbicide applications) in two different grazing conditions (grazed and ungrazed) during a recent invasion of the exotic herb Hieracium pilosella in northern grasslands of Tierra del Fuego Island in Southern Patagonia, Argentina. As response variables, we measured the cover of the invasive species, the dominant growth forms of other plant species, litter and bare soil at patch scales (m²) during two consecutive growing seasons. The effects of fertilisation depended on the grazing conditions; H. pilosella cover decreased by more than 92% and was replaced by dicotyledonous herbs in the ungrazed/fertilised subplots, while it exhibited no decrease in the grazed/fertilised subplots after the second growing season. Both herbicides (selective and non‐selective) reduced H. pilosella cover by c. 63% compared with the untreated subplots independently of grazing. However, the non‐selective herbicide application resulted in an increase in bare soil and litter cover in the treated grazed and ungrazed subplots respectively. In contrast, such effects were not observed with the selective broad‐leaved herbicide application. A control strategy based on the local application of selective herbicides and/or NP fertilisers, in conjunction with a transient ban on sheep grazing, reduced the invader’s cover in the short term and at a local scale and also reduced the cover of bare soil through the restoration of native vegetation. An economic assessment of this strategy supported the profitability of these control measures.

The role of UV-B radiation in the invasion of Hieracium pilosella—A comparison of German and New Zealand plants

Intensity of ultraviolet-B radiation (UV-B) differs between northern and southern hemispheres. Therefore, exotic plants species that originate from the northern hemisphere provide an opportunity to study the effects of UV-B on plant physiology and growth, and their implications for the role of adaptation and phenotypic plasticity during plant invasion on the southern hemisphere. We conducted a growth-chamber experiment with and without UV-B on Hieracium pilosella plants from Germany, where the species occurs natively and New Zealand (NZ), where it is invasive. We tested the hypothesis that: (i) H. pilosella plants respond to UV-B with high phenotypic plasticity, demonstrating the ability to react to changes in UV-B, and (ii) NZ plants are better adapted to UV-B than German plants as a result of directional selection of well adapted phenotypes. Consistent with our first hypothesis H. pilosella plants reacted plastically to UV-B by producing longer foliar hairs and a higher leaf dry matter content (LDMC) when they were treated with UV-B regardless of their origin. Additionally, irrespective of the treatment, plants from NZ displayed a higher LDMC and grew less but longer leaves than German plants. Plants showed typical stress responses and a reduction in growth caused by the UV-B treatment: below-ground biomass and production of ramets were reduced when plants were treated with UV-B. H. pilosella proved to be particularly well predisposed to grow in areas of high UV-B radiation. Our findings hint at the necessity to consider UV-B radiation in future research on mechanisms of invasions in regions with high UV-B irradiation. Species that provide the ability to respond directly to UV-B might have an advantage to invade these areas. As UV-B intensity is likely to change in the future due to ongoing ozone depletion, research addressing the effects of UV-B during plant invasions is of increasing importance.

Chromosomes carrying meiotic avoidance loci in three apomictic eudicot Hieracium subgenus Pilosella species share structural features with two monocot apomicts.

The LOSS OF APOMEIOSIS (LOA) locus is one of two dominant loci known to control apomixis in the eudicot Hieracium praealtum. LOA stimulates the differentiation of somatic aposporous initial cells after the initiation of meiosis in ovules. Aposporous initial cells undergo nuclear proliferation close to sexual megaspores, forming unreduced aposporous embryo sacs, and the sexual program ceases. LOA-linked genetic markers were used to isolate 1.2 Mb of LOA-associated DNAs from H. praealtum. Physical mapping defined the genomic region essential for LOA function between two markers, flanking 400 kb of identified sequence and central unknown sequences. Cytogenetic and sequence analyses revealed that the LOA locus is located on a single chromosome near the tip of the long arm and surrounded by extensive, abundant complex repeat and transposon sequences. Chromosomal features and LOA-linked markers are conserved in aposporous Hieracium caespitosum and Hieracium piloselloides but absent in sexual Hieracium pilosella. Their absence in apomictic Hieracium aurantiacum suggests that meiotic avoidance may have evolved independently in aposporous subgenus Pilosella species. The structure of the hemizygous chromosomal region containing the LOA locus in the three Hieracium subgenus Pilosella species resembles that of the hemizygous apospory-specific genomic regions in monocot Pennisetum squamulatum and Cenchrus ciliaris. Analyses of partial DNA sequences at these loci show no obvious conservation, indicating that they are unlikely to share a common ancestral origin. This suggests convergent evolution of repeat-rich hemizygous chromosomal regions containing apospory loci in these monocot and eudicot species, which may be required for the function and maintenance of the trait.

Succession of arbuscular mycorrhizal communities in the foreland of the retreating Morteratsch glacier in the Central Alps

The development of communities of arbuscular mycorrhizal fungi (AMF) was investigated in the subalpine foreland of the glacier Morteratsch located at approx. 1900–2100 m a.s.l. near Pontresina (Engiadin’ Ota, Switzerland). In particular, we asked if the succession of AMF communities follows or precedes the primary plant succession, and we checked the mycorrhizal status of the pioneer plant Epilobium fleischeri. Soil samples were taken at pioneer and dense grassland sites established during the last hundred years representing different periods of glacier retreat: 1875–1900, 1940–1950, 1970–1980 and 1990–2000. Extraradical hyphal length densities and AMF spore populations were analyzed in soil samples. Spore formation and mycorrhizal root colonization were monitored in trap cultures grown on Trifolium pratense, Lolium perenne, Plantago lanceolata and Hieracium pilosella or on E. fleischeri over 14 months. We found that E. fleischeri is strongly arbuscular mycorrhizal, but plants in closest distance to the glacier (glacier retreat in the last 4–6 years before sampling) were non-mycorrhizal. Spore densities and root colonization in trap cultures were generally low in samples from glacier stage 1990–2000. Highest spore density and colonization were found for the sites ice-free since 1970–1980, whilst highest AMF species richness and hyphal length densities were found at the sites ice-free since 1875–1900. Our findings show an establishment of a few AMF pioneer species (e.g. Diversispora versiformis and Acaulospora punctata) within 5–10 years and species rich AMF communities at sites ice-free for 100 years (28 species). Their succession generally follows the succession of the plant communities. We conclude that AMF pioneer species might be mainly distributed by wind transport while other AMF fungi (e.g. Glomus rubiforme and Glomus aureum) rather need a below-ground hyphal network to invade new areas.

Germination responses of three grassland species differ between native and invasive origins

AbstractThe germination stage is critical in plant life‐history and is also a key process during the expansion of species’ ranges into new environments. In this study we investigated the germination patterns of three plant species (Achillea millefolium,Hieracium pilosellaandHypericum perforatum) that are invasive to New Zealand (NZ) and native to Central Europe. We asked whether the species show differences in germination temperature requirements, germination speed and maximum germination rates, and thus, whether they display evidence of adaptation to different conditions in the invasive range. Seeds from three populations per species and region were subjected to three different temperature regimes to compare germination rates among origins and across temperature conditions. ForAchillea millefoliumandHypericum perforatum, germination rates were significantly higher for invasive NZ provenances than for native German ones. Seeds from invasive populations of all three species displayed increased maximum germination at medium temperature conditions when compared to native populations, which indicates altered germination strategies in the invaded range. Changes in temporal development patterns were most conspicuous for invasiveHieracium pilosellaandHypericum perforatumpopulations. These findings imply that adaptation in germination patterns towards different climatic conditions in invasive populations has occurred. Our study emphasises the importance of the germination stage during plant invasion and its role in explaining range expansion of these species.