IAP2-22-435

Conservation in a dynamic landscape: metapopulation ecology of the endangered tansy beetle

Conserving endangered species requires an understanding of their population dynamics in space and time. Many rare species function as metapopulations, in which networks of populations exchange individuals through dispersal, allowing colonisation of empty patches and potentially rescuing populations from local extinction. Turnover in the patch network itself complicates these dynamics, as the species tracks a moving target of habitat patches. Ultimately, better understanding of metapopulation dynamics in dynamic networks will allow better assessment of regional extinction risk, species recovery after disturbance and better targeting of ecological restoration efforts.

This studentship focuses on the tansy beetle (Chrysolina graminis). The beetle has a stronghold (meta)population on the banks of the River Ouse around York, which was thought to be its entire UK population. However, it was recently rediscovered in two East Anglian fenland sites where it had been thought extinct. Because of its geographical restriction and vulnerability (e.g. to major flooding), the tansy beetle is listed as Endangered in the National Red List for England, prioritised for conservation as a Section 41 species in England and was a UK Biodiversity Action Plan species. It has the support of the Species Recovery Trust (SRT, project CASE partner) and a dedicated conservation partnership in the Tansy Beetle Action Group (TBAG).

The first focus of the studentship will be on beetle metapopulation dynamics in a dynamic network of host plant (tansy) patches around York. Building on our previous work on patch occupancy and dispersal and an unprecedented >12-year SRT and TBAG survey dataset mapping thousands of tansy patches over 45 km of riverbank, the student will investigate:
1. How dynamic is the tansy patch network? What determines patch appearance and loss?
2. How does the beetle metapopulation function? What determines colonisation and local extinction?
3. What are the long-term risks of regional extinction and how might this be minimised?

A second focus will be on better understanding the re-discovered fenland populations to inform conservation. The student will investigate:
1. How are beetle distributions structured in the fenland sites? Are they aggregated in particular areas or on particular host plants?
2. How does performance vary on alternative host plants? The fenland populations seem to use the mint family rather than tansy but the effects of host plant choice are not known.

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Image Captions

By Geoff Oxford – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13290111

Methodology

To investigate metapopulation dynamics the student will contribute to ongoing field surveys around York, analyse/model these data and conduct targeted fieldwork to enhance understanding from the survey data. Depending on their interests, the student may work on:
1. Statistical analysis of food plant patch network dynamics, e.g. Generalised Linear Mixed Models (GLMMs) for tansy patch appearances and disappearances using predictors such as patch size, proximity, land use, historical flooding, soil moisture and beetle density.
2. Statistical modelling of beetle occupancy dynamics, e.g. dynamic occupancy models or GLMMs predicting colonisation and local extinction. Targeted fieldwork may supplement the existing data, e.g. to measure soil moisture or egg/larval predation rates.
3. Statistical analysis of spatial synchrony in tansy and beetle dynamics, testing for effects of distance, crossing the river (a dispersal barrier), land use and flooding perturbations.
4. Development of realistic metapopulation models to estimate regional extinction risk and project impacts of future conservation and environmental change scenarios. Simulations could test effects of changes in grazing, patch creation, translocations between riverbanks, and/or climate change scenarios for flooding.

To better understand the ecology of the fenland populations and inform their conservation, the student will:
1. Survey alternative host plant distributions and beetle numbers in the fenland populations, to test for spatial aggregation and local host plant/habitat preferences.
2. Test whether beetle populations differ in growth, survival and fecundity on different host plants. Rearing experiments will be performed at the University of Stirling Controlled Environment Facility.

Project Timeline

Year 1

Literature review on dynamic metapopulations.
GIS analysis of York survey data and preliminary analysis.
Training in statistical methods using R (e.g. GLMM, occupancy models)
Fieldwork: beetle surveys in York and fenland populations.

Year 2

Finalise statistical modelling of patch and beetle dynamics (write up as 1 or 2 chapters/papers).
Fieldwork: beetle surveys and additional fieldwork to supplement data analyses
Perform rearing experiments

Year 3

3-month CASE remote placement at Species Recovery Trust
Development and simulation of metapopulation models (writing up as a paper/chapter).
Analysis of rearing experiment (write up as a paper/chapter)

Year 3.5

Finalise papers and thesis.

Training
& Skills

Quantitative and fieldwork expertise will be developed with the supervisory team and wider training opportunities, including:
1. Endangered species conservation ecology
2. Spatial analysis (e.g. QGIS and R)
3. Advanced modelling in R (e.g. occupancy models, GLMM, metapopulation models) including high performance computing clusters (HPC)
4. Field surveys and experimental design (including insect rearing in Controlled Environment Facilities)
5. Presenting to academics and conservation stakeholders.

References & further reading

Oxford, G. (2021) Biology and Conservation of the Tansy Beetle – 20 years on. British Wildlife 32, 411-418.
Oxford, G. & Oxford, R. (in press) Food and floods: Four observations on aspects of the biology of the endangered tansy beetle, Chrysolina graminis (L.) (Coleoptera: Chrysomelidae) and their implications for conservation. British Journal of Entomology and Natural History.
Chapman et al (2007) Modelling population redistribution in a leaf beetle: an evaluation of alternative dispersal functions. Journal of Animal Ecology 76, 36-44.
Chapman et al (2009) Process from pattern in the distribution of an endangered leaf beetle. Ecography 32, 259-268.
Bullock et al (2020) Human-mediated dispersal and disturbance shape the metapopulation dynamics of a long-lived herb. Ecology 101, e03087

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