Cotula coronopifolia is a short-lived plant that originates from South Africa and Namibia. It has been present in Europe since the 18th century. This study includes a monitoring inventory of two C. coronopifolia populations on Öland, Sweden, which has taken place continuously four consecutive years (2018-2021). It also includes a climate suitability model projected over Europe.  The monitoring inventory gives a picture of the population’s yearly dynamic in terms of spread, expansion and densities. The population density has decreased during these four years and the expansion speed has shifted from over 370 m/year between 2018 and 2019 to a contraction of -20 m/year thereafter. The decreasing densities seem to be due to lower grazing intensities in the last two years. It is also possible that C. coronopifolia have occupied most of the possible habitat available at these two locations.  The model was made to visualize the potential geographic range of C. coronopifolia based on contemporary climate variables such as temperature and precipitation. Predicted suitable habitat was extensive in the coastal regions of western Europe but surprisingly low in the eastern parts of Europe. The most important variable in the model turned out to be “the annual range between maximum temperature and minimum temperature” and that range is generally smaller in coastal climates. That, together with the fact that most of the occurrence records comes from the western parts of Europe (which may reflect the introduction history of the species rather than the climate and/or a geographic reporting bias), should be considered as alternative explanations for the difference in suitability between eastern and western Europe. However, the model seems to give a plausible picture over the contemporary potential distribution range in Sweden where the reporting effort is generally high. This study shows that C. coronopifolia is a species suitable for modelling. Future, refined models should include dispersal mechanisms, propagule pressure and future climate scenarios to predict plausible population spread.

No description available.

Alien invasive plants are of concern in the world because of their potential to spread into the natural environment. Invasion patterns observed in plant species can be attributed among other things to favourable environmental conditions. Understanding invasion dynamics of alien invasive plants can help in timely intervention initiatives. In Mpumalanga, Lilium formosanum (Liliaceae) appears to be an emerging plant invader and is spreading in the natural environment. The study investigated the invasion extent and predictor variables which could explain abundance patterns of L. formosanum in the invasive range in Mpumalanga province in South Africa and further predict regions of the world that could be climatically suitable. Lilium formosanum was surveyed along 11 major routes leading into the towns of Sabie and Graskop in Mpumalanga from a slow moving vehicle. A total of 241 kilometres was surveyed. Lilium formosanum was found to be invasive from the towns of Sabie and Graskop. Climatically suitable areas were predicted using DIVA-GIS and climate data was obtained from WORLDCLIM database while occurrence records were obtained from the Southern African Plant Invaders Atlas, Australia’s virtual herbarium and the Global Biodiversity Information Facility. In conclusion, distance, altitude and route were found to have an influence on the abundance of L. formosanum in Mpumalanga Province. Climatically suitable areas included the eastern coastal belt, northern provinces and the interior parts of South Africa including major parts of Limpopo and Mpumalanga. / Dissertation (MSc)--University of Pretoria, 2014. / Plant Production and Soil Science / MSc / Unrestricted

No description available.

The disruption of mutualisms by invasive species has consequences for biodiversity loss and ecosystem function. Although invasive plant effects on the pollination of individual native species has been the subject of much study, their impacts on entire plant–pollinator communities are less understood. Community-level studies on plant invasion have mainly focused on two fronts: understanding the mechanisms that mediate their integration; and their effects on plant–pollinator network structure. Here we briefly review current knowledge and propose a more unified framework for evaluating invasive species integration and their effects on plant–pollinator communities. We further outline gaps in our understanding and propose ways to advance knowledge in this field. Specifically, modeling approaches have so far yielded important predictions regarding the outcome and drivers of invasive species effects on plant communities. However, experimental studies that test these predictions in the field are lacking. We further emphasize the need to understand the link between invasive plant effects on pollination network structure and their consequences for native plant population dynamics (population growth). Integrating demographic studies with those on pollination networks is thus key in order to achieve a more predictive understanding of pollinator-mediated effects of invasive species on the persistence of native plant biodiversity.

Premise: Invasive plant species can integrate into native plant–pollinator communities, but the underlying mechanisms are poorly understood. Competitive interactions between invasive and native plants via heterospecific pollen (HP) and differential invasive HP effects depending on HP arrival time to the stigma may mediate invasion success, but these have been little studied. Methods: We evaluated patterns and effects of HP receipt on pollen tube growth in two native and one invasive species in the field. We also used hand-pollination experiments to evaluate the effect of invasive HP pollen and its arrival time on native reproductive success. Results: Native species receive smaller and less-diverse HP loads (5–7 species) compared to invasive species (10 species). The load size of HP had a negative effect on the proportion of pollen tubes in both native species but not in the invasive, suggesting higher HP tolerance in the latter. Invasive HP arrival time differentially affected pollen tube success in native species. Conclusions: Our results highlight the need to study reciprocal HP effects between invasive and native species and the factors that determine differential responses to HP receipt to fully understand the mechanisms facilitating invasive species integration into native plant–pollinator communities.

Background: Coastal ecosystems in Mexico remain understudied in spite of their ecological, economic and conservation value and are being impacted by human activities along the coast. Knowledge on spatial patterns of plant species distribution that helps preserve these fragile ecosystems is crucial. Aims: We evaluated differences in species richness, species diversity and species dominance patterns in 16 plant communities as well as the degree to which differences were driven by climatic conditions in sandy dunes in Yucatán. We evaluated the importance of invasive species in mediating patterns of species diversity and species dominance patterns. Results: We found wide variation in plant species richness, species diversity and species dominance patterns among communities that stems from broad climatic differences along dune systems. Invasive plants represent almost one-third of total species richness and seem to be drastically changing the species dominance patterns in these communities. Conclusions: Regional climatic differences along the Yucatán north coast seems to be a major driver of plant diversity and species composition. Our findings suggest that invasive plants have successfully colonised and spread along the coast over the past 30 years. Even though invasive species do not alter spatial patterns of species diversity, they are becoming more dominant with potential detrimental consequences for native plants.

The cold water of Antarctica has a unique endemic fauna, where durophagous predators are rare or absent. Due to climate change the water is heating up and the predators have begun to return to the Southern Ocean, which could bring a lot of changes to the food web. There is a high risk it will lead to losses in the unique marine fauna of Antarctica. The aim of this study is therefore to examine the potential effect these invasive species has on the food web structure in the Weddell Sea. To study this, several general network metrics were used (connectance, number of interactions, vulnerability and generality, trait distributions), as well as a number of centrality metrics (betweenness, closeness, PageRank). The analyses showed that none of the invasive species become important in the Weddell Sea food web. Nor do they significantly change the food web structure in any way which impact the importance of the native species. Their great opportunism regarding their prey species, and thereby their connectedness and thus their position in the network, are probably the main reason why theses invasive species did not become important in this food web. The lack of changes in the food web structure due to the presence of these invasive species are probably also a result of not including factors such as abundances and network dynamics in the analyses, which seem to be the driving forces when it comes to changes in food web structure caused by invasion of species.

Studies were conducted to determine the effectiveness of using targeted grazing and prescribed burning as tools to reduce fire hazards and cheatgrass (Bromus tectorum) dominance on rangelands in the northern Great Basin. A field study, with four grazing-burning treatments (graze and no-burn, graze and burn, no-graze and burn, and no-graze and no-burn), was conducted on a B. tectorum-dominated site near McDermitt, Nevada from 2005-2007. Cattle removed 80-90% of standing biomass in grazed plots in May 2005 and 2006 when B. tectorum was in the boot (phenological) stage. Grazed and ungrazed plots were burned in October 2005 and 2006. Targeted grazing in May 2005 reduced B. tectorum biomass and cover, which resulted in reductions in flame length and rate of spread when plots were burned in October 2005. When grazing treatments were repeated on the same plots in May 2006, B. tectorum biomass and cover were reduced to the point that fires did not carry in grazed plots in October 2006. Fuel characteristics of the October 2005 burns were used to parameterize dry climate grass models in BehavePlus 3.0, and simulation modeling indicated that grazing in spring (May) would reduce the potential for catastrophic fires during the peak fire season (July-August). The graze-and-burn treatment was more effective than grazing alone (graze and no-burn treatment) and burning alone (no-graze and burn treatment) in reducing B. tectorum cover, biomass, plant density, and seed density, and in shifting species composition from a community dominated by B. tectorum to one composed of a suite of species [including tumble mustard (Sisymbrium altissimum), clasping pepperweed (Lepidium perfoliatum), and Sandberg bluegrass (Poa secunda)], with B. tectorum as a component rather than a dominant. A simulation study was designed to compare the cost-effectiveness of using cattle grazing and herbicide to create fuel breaks on B. tectorum-dominated landscapes in the northern Great Basin. Fuel characteristics from this targeted grazing study and from a Plateau® (Imazapic) herbicide study near Kuna, Idaho were used to parameterize fire behavior models and simulate flame lengths and rates of spread for the two fuel reduction treatments under peak fire conditions using BEHAVE Plus. Targeted grazing and Plateau® had similar reductions in flame length and rate of spread. Cattle grazing had high fixed costs (primarily fencing), and was more cost-effective than applications of Plateau® under five fuel loading scenarios except for three consecutive years of low fuel loads.

Goatsrue is an introduced perennial plant that has proven to have great invasive potential, leading to its classification as a noxious weed in many states and at the federal level. This research focused on seed biology, herbicide control, and toxic dynamics of goatsrue. Physical dormancy of mature goatsrue seed was tested through scarification using sulfuric acid with exposures of up to 60 minutes resulting in 100% germination. Comparison of dormancy for 26-year-old and 6-month-old goatsrue seed indicated aged seeds had reduced dormancy levels compared to newly harvested seeds, but had similar viability. Goatsrue seedling emergence was inversely related to burial depth; emergence was greatest at 0.5 cm soil depth (93%), and no emergence occurred from 12 and 14 cm. Goatsrue seed density ranged from 14,832 seeds m-2 to 74,609 seeds m-2 in the soil seed bank of five goatsrue-infested areas. Viability and dormancy of seeds recovered from the soil seed bank survey ranged from 91 to 100% and 80 to 93%, respectively. Goatsrue was most sensitive to the ALS inhibitor herbicides chlorsulfuron and imazapyr in greenhouse trials. Field studies showed that plots treated with dicamba, chlorsulfuron, metsulfuron, aminopyralid, triclopyr, and picloram provided at least 93% control of goatsrue 12 months after treatment at two field sites and increased perennial grass cover at one site. All treatments at one site decreased seedling goatsrue cover 11 months after treatment. The concentration and pools (dry weight x concentration) of the toxin galegine, found in goatsrue, vary over plant tissues and phenological growth stages. Galegine concentration is significantly different among plant tissues; reproductive tissues have the highest levels of galegine (7 mg/g), followed by leaf (4 mg/g), and then stem (1 mg/g) tissues. Galegine pools or the total amount of galegine per stalk was lowest at the vegetative growth stage and increased until reaching a maximum at the immature pod stage, but decreased nearly in half at the mature seed stage. Average galegine concentration also peaked at the immature pod stage and decreased by half at the mature seed stage. Thus, goatsrue is most toxic in its phenological development at the immature pod stage.