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1. Within the host range of herbivorous insects, performance hierarchies are often correlated with relatedness to a primary host plant, as plant traits are phylogenetically conserved. Therefore, it was hypothesised that differences in herbivore performance on closely related plant species are due to resistance traits that vary in magnitude, rather than in the nature of the traits. 2. This hypothesis was tested by manipulating putative resistance traits of three congeneric thistle species (Cirsium arvense, Cirsium palustre, and Cirsium vulgare) and assessing the performance of the oligophagous, leaf-feeding beetle, Cassida rubiginosa. Measurements were done of survival, weight gain, and development time of the beetle on its primary host, C. arvense, and two alternative hosts under low and high nutrient availability, and on shaved and unshaved leaves. 3. Survival of C. rubiginosa was strongly dependent on plant species with final mean survival rates of 47%, 16%, and 8% on C. arvense, C. palustre, and C. vulgare, respectively. Survival was primarily explained by leaf trichome densities, and to a lesser extent by specific leaf area. Leaf flavonoid concentrations did not explain differences in beetle survival, and there were no differences in beetle weight gain or development time of individuals that survived to adulthood. 4. No beetles survived on unshaved (hairy) C. vulgare plants, but manipulating leaf trichome densities of the thistle species by shaving the leaves moderated the plant-specific resistance, and equalised the survival rates. Survival of C. rubiginosa on alternative congeneric hosts was explained by a common physical resistance trait that varied in magnitude.

This study examined a non-soil seed bank deposited inside the tussock cores of Carex cespitosa, a perennial plant with a tussock growth form. Based on the vertical structure of the seed bank in 20 tussock cores, the history of changes in plant species composition during succession in an unmowed grassland in the Bialowieza National Park was reconstructed. Three horizontal layers were distinguished in each tussock core: upper (corresponding to the initial forest stage), middle (transitory stage—forb and swamp communities) and bottom (early successional stage—grassland). The results showed that seeds of both the parental species and other species were stored inside the C. cespitosa tussock cores. More than 50,000 seedlings were found, representing 42 vascular plant species. The highest number of seedlings was recorded in the middle layer. Seedlings of swamp species were dominant in the upper layer, whereas seedlings of grassland species were dominant in the other layers. The highest number of C. cespitosa seedlings was observed in the upper layer. The most common seedlings in the middle layer belonged to the species Epilobium palustre, Lythrum salicaria and Cirsium palustre. In the bottom layer, the most common species of seedlings were grassland species, e.g. Lychnis flos-cuculi and Ranunculus repens. The protected seed bank inside this tussock species reflected recorded changes in species composition of these grasslands through time. Seed banks in this and other tussock-forming species represent a potentially useful tool for reconstructing recent developmental history of plant communities.

The objective of the study was to describe the life-history pattern of the biennial species Cirsium palustre. It has been demonstrated that under optimum conditions in the greenhouse individuals live 1.5 to 2 years, in a mown meadow 2 to 3 years, and during the plant succession in abandoned meadows they prolong their life to several years. This is accompanied by a gradual decrease of C. palustre population size. A relationship between the life-history pattern differences during a plant succession and the population abundance dynamics has been found. Reproductive-phase age is correlated with the rosette size. In spite of the occurrence of many limiting factors during a succession (closed plant cover, shading by macroforbs, willows) C. palustre survives until the formation of forest communities. Its persistence is favoured by: protracted life history, attainment the reproductive phase at different ages (not only in the second year), formation of a permanent seed bank, air-borne seeds and the emergence and survival of seedlings under the canopy of several-year old rosettes during a strong competition. The arresting of juvenile individuals under the rosettes for several years has been termed the "rosette mechanism". Cirsium palustre can be included among facultative biennials. In every conditions a proportion of individuals in a population attain the flowering phase in life year 2. During a succession the proportions of "triennial" and "quadriennial" forms, and at the terminal stage - of perennial monocarpic forms increase.

Whether or not a host plant is incorporated into a phytophagous insect's diet depends on both the insect's ability to colonize the novel host and the host plant's susceptibility to the insect. The latter, again, will be influenced by the genetic structure of the host plant. Cirsium palustre (marsh thistle) is heavily infested by the tephritid fly Tephritis conura in northern Britain, whereas infestation is not only absent in southern England, but also absent on the European continent where T. conura is common on other Cirsium. To understand why regional infestation patterns evolve, we studied how genetic structure and phylogeographic ancestry of C. palustre are related to the probability of infestation in Britain. The probability of infestation in Britain was related neither to phylogeographic lineage (two lineages were observed in Europe), nor to introgressive hybridization with the original host of T. conura, C. heterophyllum. However, infested British C. palustre were strongly genetically deprived. British C. palustre showed continuous loss of genetic variability towards the northern range edge. The loss was explained best by genetic drift during geographic range expansion, rather than by genetic drift in isolated patches or mating system change from predominately outcrossing to selfing. The phylogeographic pattern of C. palustre strongly suggests Scotland as the geographic origin of a recent host-plant expansion of T. conura. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 221–232.

Summary 1. Many flowering plant species have a facultative or obligate dependence on insect pollination for reproductive success. Anthropogenic disturbance may alter these species interactions, but the extent to which structural changes to plant-pollinator networks affect plant species mating systems is not well understood. 2. We used long-term livestock grazing of a birch wood ecosystem to test whether disturbance of this semi-natural habitat altered floral resources, the structure of plant–insect visitation networks and the mating system of a focal plant species, Cirsium palustre. 3. Grazed habitat had a higher species richness of floral resources for pollinators. Visitation networks in grazed habitats were larger, more diverse, with an increase in the number of pollinators per plant species. Controlling for sampling effects, however, showed networks in grazed habitats were less nested and revealed a positive correlation between network connectance and floral species richness. 4. Network connectance was negatively related to C. palustre outcrossing rate within grazed and ungrazed sites. However, on average, the effects of grazing, including greater mean connectance, produced higher overall outcrossing rates and more pollen donors compared with ungrazed habitat. The number of different pollen donors, spatial genetic structure and mating among close relatives were all correlated with greater extent of suitable C. palustre habitat in the landscape, consistent with the effects of increasing plant population size but limited seed dispersal. 5. Pre-adaptation of C. palustre to disturbance coupled with a preponderance of highly dispersive flies attracted to the greater food resources in grazed habitat is a likely mechanism underpinning this increased pollen transport. 6. Habitat modification by long-term mammalian grazing fundamentally shifted visitation network structure and the state of a plant mating system, indicating how ecosystem disturbance can cascade across levels of biological organization through altered interspecific interactions. Cirsium palustre retains flexibility to bias reproduction towards selfing where pollen donor diversity is limited; such reproductive flexibility may be an important mechanism structuring plant populations in human-modified landscapes.

Summary 1. Both resources and natural enemies can influence the distribution of a herbivore. The ideal free distribution predicts that herbivores distribute themselves to optimise utilisation of resources. There is also evidence of herbivores seeking out refuges that reduce natural enemy attack (enemy-free space). Which of these theories predominates in a thistle–tephritid Terellia ruficauda (Diptera: Tephritidae)–parasitoid interaction is examined. 2. The plant, Cirsium palustre, had a contagious distribution approximated by the negative binomial distribution. Terellia ruficauda foraged preferentially and oviposited on isolated plants although its larvae gained neither nutritional benefit nor reduced natural enemy pressure from such behaviour. 3. Parasitoids of T. ruficauda foraged and oviposited more frequently on isolated than on crowded T. ruficauda, resulting in inverse density-dependent parasitoid attack at all spatial scales examined. Neither the herbivore nor natural enemies distributed themselves according to the predictions of the ideal free distribution and the herbivore did not oviposit to reduce natural enemy attack. 4. Extrapolating from the theoretical predictions of the ideal free distribution and enemy-free space to the field requires considerable caution. Terellia ruficauda and its parasitoids appear to select their oviposition sites to spread the risk of losses through factors (e.g. mammal herbivory) that may damage dense clusters of C. palustre.

Case studies implementing early detection and rapid response (EDRR) protocols are crucial to our understanding of how to evaluate the threat of a new invasive organism. Most EDRR schematics depict a linear approach to EDRR beginning with detection, then assessment, and concluding with the rapid response. Our case study exemplified the need to adjust this protocol by interlacing all three phases. Our target species is a recent invader to central New York: Cirsium palustre (marsh thistle). We observed 192 populations and reported them on iMapInvasives.org. These locations were used to generate risk maps of neighboring counties. Six test plots evaluated the plant's bienniality and monocarpism. A life-stage analysis allowed us to delineate the invasion front to target control and management solutions where they are most effective for marsh thistle. An adaptive approach to EDRR can expedite response strategies, develop risk maps, and train partners for better control.

Many plant populations have persistent seed banks, which consist of viable seeds that remain dormant in the soil for many years. Seed banks are important for plant population dynamics because they buffer against environmental perturbations and reduce the probability of extinction. Viability of the seeds in the seed bank can depend on the seed’s age, hence it is important to keep track of the age distribution of seeds in the seed bank. In this paper we construct a general density-dependent plant-seed bank model where the seed bank is age-structured. We consider density dependence in both seedling establishment and seed production, since previous work has highlighted that overcrowding can suppress both of these processes. Under certain assumptions on the density dependence, we prove that there is a globally stable equilibrium population vector which is independent of the initial state. We derive an analytical formula for the equilibrium population using methods from feedback control theory. We apply these results to a model for the plant species Cirsium palustre and its seed bank.

The extent of within-patch dispersal by a tephritid fly and its four major parasitoids was examined over three field seasons. Hosts and parasitoids were marked using acrylic paint and observed as they oviposited into the flowerheads of marsh thistle, Cirsium palustre. The average recapture rate pooled across all species was 22%. The four parasitoids showed consistently greater rates of movement than the host in all three years. In nearly all comparisons, male dispersal was less than female dispersal. There was no evidence that parasitoids moved longer distances after visiting low quality rather than high quality patches. In the one season it was studied, no correlations between movement and insect size were observed. The relevance of these observations to host-parasitoid population dynamics is discussed.

In the first years after coppicing, Cirsium palustre is abundant in Dutch ash coppice woodlands and in the second year, it flowers abundantly. In later years the species is nearly absent. In contrast to its behaviour in meadow and spring communities, the species typically behaves as a true biennial in this system. Despite fairly high mortality, the plants flowering in their second year produce enough seeds to replenish the seed bank. It is suggested that the persistence of the species in this system depends on Its ability to form a longlived seed bank and on a nutrient availability high enough to enable some rosettes to exploit the high photosynthetic photon flux density (PPFD) in the first year after coppicing and thus to reach the critical size needed for flowering in the second year. Rosettes persisting to the third year generally do not flower and ultimately die because shading by the tree canopy has become too severe.

In European floras Cirsium palustre (L.) Scop. usually is classified as a biennial and monocarpic species. The value of this classification was examined in a population growing in a spring area in Jutland, Denmark. It was possible to describe five ontogenetic states, i.e. life-states, in the population, the seed state excluded. Each Kate normally lasted for one growing season. Therefore the flowering state was generally not reached until in the fifth growing season. Observation on mortality revealed that seedlings were exposed to an extremely high death risk. However, in the other vegetative life states the death risk was rather low and constant.

Extensively managed and flower-rich mountain hay meadows, hotspots of Europe's biodiversity, are subject to environmental and climatic gradients linked to altitude. While the shift of pollinators from bee- to fly-dominated communities with increasing elevation across vegetation zones is well established, the effect of highland altitudinal gradients on the community structure of pollinators within a specific habitat is poorly understood. We assessed wild bee and hoverfly communities, and their pollination service to three plant species common in mountain hay meadows, in eighteen extensively managed yellow oat grasslands (Trisetum flavescens) with an altitudinal gradient spanning approx. 300 m. Species richness and abundance of pollinators increased with elevation, but no shift between hoverflies and wild bees (mainly bumblebees) occurred. Seedset of the woodland cranesbill (Geranium sylvaticum) increased with hoverfly abundance, and seedset of the marsh thistle (Cirsium palustre) increased with wild bee abundance. Black rampion (Phyteuma nigrum) showed no significant response. The assignment of specific pollinator communities, and their response to altitude in highlands, to different plant species underlines the importance of wild bees and hoverflies as pollinators in extensive grassland systems.

(1) Cirsium palustre, Galeobdolon luteum and Sanicula europaea were used in factorial experiments to investigate the effects of two features of vegetational shade: shade density, measured as the percentage transmission of photosynthetically active radiation (PAR), and shade type, measured as the ratio of red to far-red radiation (R/FR ratio). Neutral shade has an unaltered R/FR ratio, filtered shade a low R/FR ratio as under a deciduous tree canopy in summer. (2) The growth of all species was reduced in shade but not proportionately to shade density, partly because of compensatory increases in specific leaf area. Shade type had little or no effect. Plants died under 1 % PAR: Cirsium quickly, Galeobdolon more slowly and Sanicula most slowly of all, but in all cases more rapidly in filtered than in neutral shade. All grew well at 20% PAR and above. (3) Cirsium leaves and Sanicula petioles were longer the less dense the shade and tended to be longer in filtered shade. The lengths of Galeobdolon internodes and petioles were greater in denser shade and in filtered shade. (4) The flowering of Galeobdolon was reduced in filtered shade as well as in dense shade and independently of plant size. The flowering of Sanicula was not affected by shade type but was related to shade density and plant size. (5) Herbaceous woodland plants respond to filtered shade although increased height growth to overtop the shading plants would not be appropriate. Leaf display responses and increases in leaf and petiole lengths help to optimize PAR interception among the ground vegetation.