Testing environment filters as mechanisms of ecosystem resilience to non-native species invasion

Primary supervisor: 

Supervisory team: 

  • Professor David Bilton (UoP (SoBMS)) 
  • Dr Louise Firth (UoP (SoBMS)) 
  • Dr Tiago Silva (Centre for Environment, Fisheries and Aquatic Sciences (CEFAS)) 
  • Dr Louisa Wood - Centre for Environment, Fisheries and Aquatic Sciences (CEFAS), Weymouth. Dr Wood coordinates the Invasive Species Team at CEFAS and will supervise the outreach/policy inteface aspects of the proposed work. 

Project description: 

In the midst of Earth’s sixth mass extinction event, non-native species (NNS) are driving declines in imperilled species’ and ecosystem services. In the US alone, NNS put at risk 49% of native species (Wilcove et al. 1998) and cost industry in excess of $128 billion annually (Pimentel et al. 2005). Knowledge of the factors that contribute to the successful dispersal/establishment of NNS is fundamental to understanding their spread, and how this may change under global environmental change. Rising sea temperatures, and changes to ocean currents and community structure may all facilitate NNS expansion by altering dispersal pathways and/or habitat suitability. Simultaneously, however, the environment may act as a barrier that selectively blocks NNS range expansion – a process referred to as 'environmental filtering'. To inform management strategies, identification of invasion-risk locations, and to predict biogeographical changes under rapid environmental change, a fundamental understanding of the mechanisms of invasion and natural resilience of ecosystems is urgently required. 

This interdisciplinary studentship will explore how environmental filtering may affect invasion success, using the non-native Pacific oyster (Magallana gigas) as a model species; an ecologically problematic yet important aquaculture species across the north-east Atlantic. Previously, four filtering mechanisms have been proposed, relating to development (dispersal limitation), species identity (competitive exclusion), habitat suitability and heterogeneity (Fig. 1). The project will use a combination of hydrodynamic modelling and manipulative experiments to explore the effect of these filtering mechanisms on the dispersal, establishment and performance of NNS across local and landscape scales. With support from experts at CEFAS and Natural England, the student's research will help inform and shape policy and management of invasive species into the future. 

Based at the UoP with a 4-month secondment at CEFAS, the student will carry out both hydrodynamic modelling and manipulative experimental research. Training in numerical methods, experimental design, and statistics will be provided by the host institutions in addition to training programmes available through the ARIES DTP. 

Person specification 

Honours or masters degree (e.g. 2:1 or above) in marine biology, oceanography, environmental science or related discipline. Desirable skills include numeracy, programming and statistics (e.g. R, Matlab).

Supplementary information: 

Anthropogenic activity is changing marine ecosystems worldwide, with grave consequences for their functioning1 and significant socio-economic costs2,3. The spread of non-native species (NNS) is facilitated by a range of human-induced factors, including climate change and, given their impact, NNSs are at the heart of global (CBD) and national (GB-NNS Strategy) environmental policy. Biosecurity options to constrain NNS spread in marine systems are limited, and a key question is can ecosystems ‘protect themselves’ by selectively filtering out NNSs? Our existing data suggest a combination of larval behaviour4, dispersal capacity4, community structure5 and environment (e.g. local adaptation under thermal selection, see6) all play important roles in regulating NNS establishment by filtering traits and/or phenotypes that favour persistence across environmental gradients (e.g. temperature). Our limited understanding of the relative importance of these mechanisms severely restricts policy and management of NNSs. The student will work to provide better understanding of the relationships between environmental, biodiversity and NNSs establishment, and the potential to offset invasion, using a non-native oyster as a model. 

Objective 1: Dispersal limitation. The student will adapt a hydrodynamic model (General Individuals Transport Model, GITM) and couple recent larval behavioural insights4 to generate better predictions of NNS dispersal including network models of local/regional connectivity across the seascape. CEFAS will provide the GITM and provide training during secondment to Lowestoft. 

Objective 2: Environmental filtering. Pacific oysters will be collected from locations across a temperature gradient throughout its NE Atlantic range (Norway-Portugal) and experimentally challenged with a combination of temperature and anoxia to assess change in performance (clearance rate, respiration). Data will determine the extent to which adults are abiotically limited, and whether there is evidence of local adaptation of physiological traits. 

Objective 3: Competitive exclusion. The student will use a series of manipulative transplant experiments (described in7) to test the ability of the NNS to colonise space in the presence/absence of native competitors in a variety of environmental contexts (i.e. within/outside their ecological range8) and include results from Objective 2. 

Objective 4: Heterogeneity promotes coexistence. Habitat heterogeneity can be critical to invasion, NNS spread, and changes in biodiversity. Small-scale heterogeneity (e.g. rugosity/substrate type) facilitates niche partitioning that may promote invasion success by reducing competition with native species, and hence coexistence9. 

The student will experimentally test if differences in habitat complexity10 alters NNS recruitment success. The student will acquire highly sought-after technical and academics skills in ecological experiments and modelling. The supervisory team brings a track-record of high-quality training and PhD mentoring. The student will join a vibrant community of marine biology staff (22) and PhD students (45) at the UoP and can choose from a range of UoP and ARIES training courses for continuing professional development. They'll present their work at international conferences and alongside the Research Impact Advisor, develop outreach/science communication skills. This project draws on the supervisors’ strong track records in developing/running innovative research in the areas outlined. The collaboration draws together this experience within a holistic, multidisciplinary framework to tackle questions at the heart of sustainable marine management.


1. Firth, L.B. et al. Predicting impacts of climate-induced range expansion: an experimental framework and a test involoving key grazers on temperate rocky shores. Global Change Biology 15, 1413-1422 (2009).

2. Jupe L.L., Bilton D.T. and A.M. Knights (Accepted) Do differences in developmental mode shape the potential for local adaptation? Ecology.

3. James M., Polton J., Brereton A., Howell K., Nimmo-Smith A. and A.M. Knights (2019) Reverse engineering field-derived vertical distribution profiles to infer larval swimming behaviors. PNAS (IF = 9.5) www.pnas.org/cgi/doi/10.1073/pnas.1900238116

4. Calosi P., Bilton DT and JI Spicer. (2008) Thermal tolerance, acclimatory capacity and vulnerability to global climate change. Biology Letters 4.1: 99-102.

5. Kraft N.J.B. et al. (2015) Community assembly, coexistence and the environmental filter metaphor. Functional Ecology 29: 592-599.