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Evidence of the effects of alien plant colonisation on plant communities is often hindered by the fact that similar patterns in community composition can arise through a variety of processes. The objective of this study is to determine whether changes in species composition in coastal dune communities depend on the colonisation of a neophyte plant, Oenothera stucchii, or on concurrent processes that favour its colonisation. We hypothesised two scenarios: 1) a direct impact of O. stucchii on colonised communities, leading to displacement of native species; or 2) no direct impact of O. stucchii, i.e. the species colonises plant communities by exploiting disturbances that lead to the rearrangement of plant communities. We used the species-habitat network approach to identify potential drivers of changes in species composition, assuming that changes in the structure of the species-habitat network depend on the nature of the driving process. We demonstrated that changes in species composition in plant communities were due to species rearrangement, with colonised communities characterised by more homogeneous composition of species. We suggest that changes in plant communities may not depend on colonisation by O. stucchii per se, but on concomitant processes that affect coastal dune communities while promoting colonisation by O. stucchii. [ABSTRACT FROM AUTHOR]

Background and Aims The structure of plant communities, which is based on species abundance ratios, is closely linked to ecosystem functionality. Seed germination niche plays a major role in shaping plant communities, although it has often been neglected when explaining species coexistence. The aim of this work is to link the seed germination niche to community ecology, investigating how functional seed traits contribute to species coexistence. Methods Species selection was based on a database of 504 vegetation surveys from the Veneto coast (Italy). Through cluster analysis we identified the foredune community and selected all of its 19 plant species. By using the 'Phi coefficient' and frequency values, species were pooled in different categories (foundation species, accidental species of the semi-fixed dune and aliens), then the 19 species were grouped according to their germination responses to temperature and photoperiod through cluster analyses. For each germination cluster, we investigated germination trends against temperature and photoperiod by using generalized linear mixed models. Key Results We identified four germination strategies: (1) high germination under all tested conditions ('high-germinating'); (2) high germination at warm temperatures in the dark ('dark warm-cued'); (3) high germination at warm temperatures in the light ('light warm-cued'); and (4) low germination, regardless of conditions ('low-germinating'). Foredune foundation species showed a narrow germination niche, being 'low-germinating' or 'dark warm-cued'. Annual species of semi-fixed dunes were 'high-germinating', while alien species were the only members of the 'light warm-cued' cluster. Conclusions Our research suggests that different categories of species have dissimilar seed germination niches, which contributes to explaining their coexistence. Climatic events, such as rising temperature, could alter germination patterns, favouring seed regeneration of certain categories (i.e. alien and semi-fixed dune species) at the expense of others (i.e. foundation species, pivotal to ecosystem functioning), and hence potentially altering the plant community structure. [ABSTRACT FROM AUTHOR]

Aims: The early phases in the life cycle of a plant are the bottleneck for successful species establishment thereby affecting population dynamics and distribution. In coastal environments, the spatial pattern of plant communities (i.e. vegetation zonation) follows the ecological gradient of abiotic stress changing with the distance from the sea. This pattern has been mainly explained based on the adaptation and tolerance to the abiotic stress of adult plants. However, the adult niche may considerably differ from the germination niche of a plant species. The aim of this work was to investigate to what extent abiotic factors (specifically salinity, temperature, nitrogen and their interactions) constrain seed germination along the sea–inland gradient. Location: Latium coast (Central Italy). Methods: Germination tests were performed on seeds of focal species of three different plant communities which establish at increasing distances from the coastline: Cakile maritima subsp. maritima, Elymus farctus, Crucianella maritima. We tested increasing concentrations of NaCl (one of the main abiotic factors which decrease across the sea–inland gradient), and their interactions with temperature and KNO3, to consider other factors which drive germination processes. Results: The tolerance to salinity significantly decreased in relation to the position of species along the coastal zonation. Crucianella maritima was shown to be the least tolerant species, having a decrease in germination >80% across all conditions. KNO3 significantly (although slightly) increased the germination percentage in Cakile maritima subsp. maritima and Elymus farctus. When combined with NaCl, KNO3 alleviated the negative effects of salinity only in Cakile maritima subsp. maritima. Conclusions: The germination responses to the interaction among the tested factors suggest that the germination niche may explain vegetation zonation filtering species at their early stages. Quantifying environmental niches in different phases of the life cycle of plants may provide important insights into community assembly processes. [ABSTRACT FROM AUTHOR]

Aims The loss of species that engage in close ecological interactions, such as pollination, has been shown to lead to secondary extinctions, ultimately threatening the overall ecosystem stability and functioning. Pollination studies are currently flourishing at all possible levels of interaction organization (i.e. species, guild, group and network), and different methodological protocols aimed to define the resilience of pollination interactions have been proposed. However, the temporal dimension of the resilience of pollination interactions has been often overlooked. In the light of these considerations, we addressed the following questions: does a temporal approach help to reveal critical moments during the flowering season, when pollination interactions are less resilient to perturbations? Do pollination interactions evaluated at species, guild, group and network level show different patterns when assessed through time? Methods We monitored contacts between plant and pollinator species in dry grassland communities every 15 days during the overall community flowering season (12 surveys). For each survey, we built a quantitative plant–pollinator interaction matrix and we calculated two sets of metrics characterizing, respectively, the diversity and the distribution of interactions across hierarchical levels. To describe the diversity of interactions, we calculated partner diversity (PD) at the species level, vulnerability/generality (V/G) at the guild level, and interaction diversity and evenness at the network level. The distribution of interactions was characterized by calculating selectiveness at the species and the network level, and modularity at the group level. We assessed the temporal variation of PD, V/G at the level of plants and pollinators, and species selectiveness, by means of Linear Mixed Models (LMMs). To investigate the temporal variation of indexes calculated at group and network level, we applied simple linear and quadratic regressions after checking for temporal autocorrelation in residuals. Important Findings When taking into account the temporal dimension of interactions, the diversity of interactions showed different patterns at different levels of organization. At the species level, no relationship was disclosed between PD and time, when assessing the temporal trend of V/G separately for the guild of plants and pollinators we observed an asymmetric structure of interactions. Pollination interactions showed to be asymmetric throughout the flowering season; however, evenness of interactions and network selectiveness showed significant positive relationships with time, revealing a poorer network of interactions during the end of the flowering season. The temporal analysis of pollination interactions revealed a stronger risk of secondary extinctions at the end of the flowering season, due to a lower degree of redundancy and thus of resilience of the overall network of interactions. [ABSTRACT FROM AUTHOR]

The transect method has been widely used to monitor habitat conservation status and has been recently recommended as the best tool to monitor steep ecological gradients, such as those in coastal systems. Despite that, the effectiveness of the transect approach can be limited when considering the sampling effort in terms of time needed for sampling. Our work aimed at evaluating the efficacy of the transect approach in a Mediterranean coastal system. Specifically we aimed at evaluating the sampling effort versus the completeness of datasets obtained by performing belt transects in different ways specifically designed to progressively reduce the sampling effort: (i) sampling plots adjacently ("adjacent-plot transect"); (ii) sampling plots alternately ("alternate-plot transect"); (iii) sampling one plot at each plant community along the vegetation zonation ("zonation-plot transect"). We evaluated method efficiency in terms of number and type of habitats identified, spatial extent, species richness and composition, through multivariate analyses, null models and rarefaction curves. The sampling effort was measured in terms of time needed for sampling. The zonation-plot transect had the lowest sampling effort, but provided only an approximation of the state of the dunal communities. The alternate-plot transect showed the best trade-off between the sampling effort and the completeness of information obtained, and may be considered as a efficient option in very wide coastal systems. Our research provides guidelines that can be used in other coastal systems to choose the most cost-effective monitoring method thereby maximising the efficient use of monitoring resources. [ABSTRACT FROM AUTHOR]

Invasive alien plants are a major threat to biodiversity and they contribute to the unfavourable conservation status of habitats of interest to the European Community. In order to favour implementation of European Union Regulation no. 1143/2014 on invasive alien species, the Italian Society of Vegetation Science carried out a large survey led by a task force of 49 contributors with expertise in vegetation across all the Italian administrative regions. The survey summed up the knowledge on impact mechanisms of invasive alien plants in Italy and their outcomes on plant communities and the EU habitats of Community Interest, in accordance with Directive no. 92/43/EEC. The survey covered 241 alien plant species reported as having deleterious ecological impacts. The data collected illustrate the current state of the art, highlight the main gaps in knowledge, and suggest topics to be further investigated. In particular, the survey underlined competition as being the main mechanism of ecological impact on plant communities and Natura 2000 habitats. Of the 241 species, only Ailanthus altissima was found to exert an ecological impact on plant communities and Natura 2000 habitats in all Italian regions; while a further 20 species impact up to ten out of the 20 Italian administrative regions. Our data indicate that 84 out of 132 Natura 2000 Habitats (64%) are subjected to some degree of impact by invasive alien plants. Freshwater habitats and natural and semi-natural grassland formations were impacted by the highest number of alien species, followed by coastal sand dunes and inland dunes, and forests. Although not exhaustive, this research is the first example of nationwide evaluation of the ecological impacts of invasive alien plants on plant communities and Natura 2000 Habitats. • We surveyed impacts of IAPs on plant communities and Natura 2000 Habitats in Italy. • 241 IAPs are impacting 84 Natura 2000 Habitats, with competition as main impact mechanism. • Information on IAPs impacts is very uneven at the national level. • Few IAPs are well-studied and impacts on Natura 2000 Habitats are scarcely known. • First evaluation of IAPs impacts on Natura 2000 Habitats at the national level. [ABSTRACT FROM AUTHOR]

Phenological relationships among entomophilous species for pollination may play an important role in structuring natural plant communities. The main aim of this work was to test whether in dry grassland communities there is a non-random flowering pattern and if the pattern influences the species richness, and the richness of subordinate and common species. Field sampling was carried out in temperate dry grasslands in NE Italy. Species composition and the flowering phenology were monitored in 45 2 m × 2 m plots randomly placed over dry grasslands. To quantify the degree to which insect-pollinated species overlap in their flowering time we developed a “co-flowering index” (CF-index). The significance of the observed flowering pattern was tested using a null model. A positive correlation was found between the synchronic flowering and the number of subordinate species. Subordinate species showed shorter flowering length than the common species and a mostly specialized pollination system. Our findings suggest that flowering synchrony might be a key characteristic which may contribute to shape dry grassland composition by favouring the long lasting maintenance of rare species populations within the community. The comprehension of such functional relationships between species of different trophic levels is of great importance for the conservation of dry grasslands and the maintenance of the ecosystem services that pollination provides. [ABSTRACT FROM AUTHOR]