Biological invasions by alien species are regarded as one of the top five direct drivers (together with habitat destruction, over-exploitation, climate change and pollution) of recent global biodiversity loss, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. The impacts of alien species are linked to the declining conservation status of threatened species, and their accelerated spread into protected and biodiverse habitats are a major global concern. Riparian habitats are one of the richest and most complex habitats globally. However, encroachment and establishment of invasive alien species pose additional challenges to the unique flora and fauna, as well as ecosystem function, of these freshwater habitats.
Impatiens glandulifera, Himalayan balsam, is an annual plant native to the western Himalayas, prolific along waterways. It is listed under Schedule 9 of the Wildlife and Countryside Act 1981, therefore it is an offence to plant or otherwise cause this species to grow in the wild. Himalayan balsam, by forming tall, dense colonies, shades out and results in the extirpation of native vegetation. This species is notoriously difficult to manage, particularly if an adjacent water way provides a constant input of viable seeds. In 2014, a biological control agent, rust fungus Puccinia komarovii var. glanduliferae var. nov, was approved for release in the EU. The rust fungus was deployed at various sites from 2015 to better manage I. glandulifera in the UK by the Centre for Agriculture and Bioscience International (CABI).
CABI found that results from inoculated populations of I. glandulifera were variable, with low levels of infection observed in the field. Subsequent inoculation experiments conducted under controlled conditions, revealed significant variation in the susceptibility of plant populations to the rust, with some showing immunity (no infection observed). Further study by CABI showed that I. glandulifera had been introduced into the British Isles on more than one occasion, from multiple locations within the native range and therefore different variants of the rust fungus are needed. Further studies have shown an indication of overwintering of the fungus in suitable conditions. However, more information is needed to identify which factors are most suitable for the rust fungus in the field (rather than in controlled environments). Although there is also an indication that the rust fungus may spread naturally from the initial release site, little is known of the timing and efficacy of natural spread.
The aim of this project is to assess the in-situ drivers of rust fungus infection success of I. glandulifera and develop a modelling and monitoring framework to determine the natural dispersal efficacy of the rust fungus to other invaded sites.
Specifically, the project objectives are to:
1) Determine the key environmental variables that impact the efficacy of rust fungus infection and survival in-situ.
2) Undertake an assessment of the impact of the rust fungus on I. glandulifera seed production as a determinant of biological control success in managing invaded areas.
3) Determine the efficacy of drone imagery in assessing reduction in population size of infected I. glandulifera populations and determining infection status of I. glandulifera populations.
4) Assess the natural dispersal capabilities of the rust fungus using a spatial modelling approach