Effective species conservation requires an understanding of 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 small populations from local extinction. The effect of dispersal on metapopulation dynamics is especially pronounced when the habitat patch network undergoes its own dynamics. For example, when habitat patches are individual host plants of an insect, then seed dispersal will promote new patches in the metapopulation, while mortality of the host plant removes patches (potentially because of insect consumption). The overall effect of this turnover is a dynamic patch network and an increased reliance on dispersal for the species to track a moving target of habitat patches.
This studentship will focus 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, the beetle was recently rediscovered in two East Anglian fenland sites where it had been considered extinct. Because of its geographical restriction and vulnerability to major flooding, the tansy beetle is listed as endangered in the British Red Data Book and prioritised for conservation as a UK Biodiversity Action Plan species with the support of a dedicated conservation partnership – the Tansy Beetle Action Group (TBAG).
The main focus of the PhD will be on the beetle’s metapopulation dynamics in a dynamic patch network of tansy plants around York. Building on our previous work on patch occupancy and dispersal and an unprecedented >10-year TBAG survey dataset mapping thousands of tansy patches over 45 km of riverbank, the student will investigate questions such as:
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 metapopulation extinction and how might this be minimised?
A second focus will be on better understanding the re-discovered fenland populations to inform conservation, based on knowledge gaps identified by TBAG. Depending on their interest, the student will investigate questions such as:
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.