Swamped: Is Crassula helmsii a significant threat to wetland biodiversity?

Director of Studies: Professor David Bilton

2nd Supervisor: Dr Andy Foggo

3rd Supervisor: Dr Robert Puschendorf

Applications are invited for a 3.5 years PhD studentship. The studentship will start on 1 October 2025

Biological invasions represent one of the most significant threats to biodiversity. Freshwaters are disproportionately affected by such invasions, and home to a disproportionately large proportion of biodiversity, especially invertebrates. They also provide crucial ecosystem services. Crassula helmsii, a native Australasian plant, has been aggressively invading European freshwaters for over 30 years, with drastic consequences for their floristic diversity. Understanding of Crassula’s impacts on invertebrates, which make up the bulk of freshwater diversity, are more limited. Our work suggests that whilst Crassula invasion changes community composition and function, it does not lead to drastic declines in fully aquatic macroinvertebrate diversity or biomass. Much of the biodiversity in sites invaded by Crassula is not fully aquatic, however, with many specialist wetland invertebrates living in the seasonally flooded margins, which are heavily invaded, alongside open water habitats. The impact of Crassula on this critical component of freshwater ecosystems remains unknown, and there is an urgent need for quantitative data to inform management and policy.

This project will examine the effects of Crassula on wetland invertebrates using both fieldwork and laboratory experiments. Fieldwork will be conducted in established locations, where investigations of aquatic communities has already been undertaken, allowing a holistic picture of Crassula’s ecological impacts.

Training in a range of skills, from freshwater invertebrate biology through experimental design, to advanced univariate and multivariate analyses of ecological data. Will gain experience of fieldwork alongside experienced scientists, develop knowledge of cutting-edge approaches in biostatistics and test fundamental ecological hypotheses about the mechanistic bases for the spread/control of invasives. Will have the opportunity to act as a university demonstrator, disseminate their work and its results via written and oral outputs, and build a library of skills and competences that will elevate their employability to a level commensurate with doctoral status, applicable across a wide range of employment.

You must be numerate and literate with an interest in aquatic ecology and a driving licence valid for UK use is desirable; some demonstrable experience in invertebrate taxonomy and identification is desirable although not essential, as is a training in the fundamentals of biostatistics.

Tasker, S. J. L., Foggo, A., Scheers, K., van, D. L. J., Giordano, S. & Bilton, D. T., (2024) Nuanced impacts of the invasive aquatic plant Crassula helmsii on Northwest European freshwater macroinvertebrate assemblages. Science of the Total Environment 913: 169667.

Tasker, S. J. L., Foggo, A. & Bilton, D. T., (2024) Are impacts of the invasive alien plant Crassula helmsii mediated by detritus? A litter experiment in a temperate pond. Hydrobiologia 851: 4135–4148.

Tasker, S. J. L., Foggo, A. & Bilton, D. T., (2022) Quantifying the ecological impacts of alien aquatic macrophytes: a global meta-analysis of effects on fish, macroinvertebrate and macrophyte assemblages. Freshwater Biology 67: 1847-1860.

Tasker, S. J. L. & Bilton, D. T., (2023) Field evidence of caddisfly larvae (Trichoptera: Limnephilidae, Leptoceridae) using alien Crassula helmsii (Kirk) Cockayne fragments (Saxifragales: Crassulaceae) in case construction. Aquatic Insects 45: 82-86.

Applicants should have a first or upper second class honours degree in Biological or Environmental Science or a relevant Masters qualification.

If your first language is not English, you will need to meet the minimum English requirements for the programme, IELTS Academic score of 6.5 (with no less than 5.5 in each component test area) or equivalent.

Successful candidates who meet UKRI’s eligibility criteria will be awarded a fully-funded ARIES studentship of fees, maintenance stipend (£19,237 p.a. for 2024/25) and research costs.

A limited number of ARIES studentships are available to International applicants. Please note however that ARIES funding does not cover additional costs associated with relocation to, and living in, the UK.

NB: The studentship is supported for 3.5 years of the four-year registration period. The subsequent 6 months of registration is a self-funded ‘writing-up’ period.

ARIES is committed to equality, diversity, widening participation and inclusion in all areas of its operation. We encourage applications from all sections of the community regardless of gender, ethnicity, disability, age, sexual orientation, and transgender status. Projects have been developed with consideration of a safe, inclusive, and appropriate research and fieldwork environment. Academic qualifications are considered alongside non-academic experience, with equal weighting given to experience and potential.

For further information, please visit www.aries-dtp.ac.uk.

If you wish to discuss this project further informally, please contact Professor David Bilton .

Please see our apply for a postgraduate research programme page for a list of supporting documents to upload with your application.

For more information on the admissions process generally, please visit our Apply for a postgraduate research programme page or contact the Doctoral College .

Shortlisted candidates will be invited for interview after the deadline. We regret that we may not be able to respond to all applications. Applicants who have not received a response within six weeks of the closing date should consider their application has been unsuccessful on this occasion.