Scientific background and motivation:

Polar terrestrial habitats are ‘island like’, isolated on various geographical scales. Even though most, but not all, probably became exposed from ice during post-Pleistocene glacial retreat, it is clear that successful dispersal events are not unusual, at least on short distance scales. However, the very strong biological regionalisation recently recognised in Antarctica also argues for strong dispersal limitation, resulting in large-scale area isolation. Biological dispersal processes in the polar regions have yet to be placed in the context of physical (atmospheric) mechanisms and their possible future change. Further, risks in particular to the Antarctic biome of new colonisation events are of increasing concern. Combining atmospheric modelling, Earth observation, and ecophysiology, this proposal will provide an integrated understanding of dispersal opportunities and routes in this rapidly changing region.

Aims and objectives of the PhD project:

Passive aerial dispersal provides one of the most frequently postulated mechanisms of distribution in the polar regions for the dominant terrestrial biological groups (microbes, bryophytes, lichens, invertebrates), all of which are small, very often with (near)-microscopic spores or other propagules, and capable of being carried in the air column. This project, through integrating Lagrangian modelling of air mass transport between different locations and regions within Antarctica, and with lower latitude islands and continental landmasses, with known ecophysiological characteristics of different biological groups, will provide the first robust assessment of potential colonisation routes and frequencies within and between the polar regions and their associated lower latitudes. Further integration with leading climate modelling approaches will allow predictions of how these biological linkages may change in future to be generated.

Methodology:

The precise structure of the project will depend in part on the background of the student appointed, as the core questions can be approached from both biological and physical science perspectives, though we are aiming for a cross-disciplinary combination of approaches. Source-receptor relationships between different Antarctic regions, and remote source regions will be quantified using the FLEXPART Lagrangian air mass transport dispersion model (flexpart.eu), available in Leeds. Simulations will be forced using meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses – ERA5 dataset. The student will use multispectral bands of satellite Landsat or Sentinel-2 to identify different vegetation/habitat types, and use them to choose potentially good source locations to use in the dispersal model. The student may receive appropriate training in acquiring spectral reflectance data from accessible locations in e.g. the Cairngorms or elsewhere in Northern Europe, and we will investigate separate funding sources (e.g. CASS) to support direct Antarctic, Arctic or southern South American fieldwork. In addition, an Earth System Model (UKESM) will be used to simulate emitted organisms from different habitat types to Antarctica. The student will need to use existing ecophysiological data as well as the above identified habitat types map to parameterise the emission fluxes of specific types of organism as input to the 3D model. These estimates will be refined by inclusion of boundary conditions derived from published and possibly experimental and field studies of ecophysiological survival limits and durations of the different terrestrial biological groups, and also of selected currently non-resident groups thought to pose a high risk of invasion in the future. The student will receive full training in running the FLEXPART model from the CEMAC group at Leeds, and for the UKESM-UKCA model, e.g. by attending the week-long in-person NACS workshop at University of Cambridge.

References:

Contador T, Gañan M, Bizama G, Fuentes-Jaque G, Morales L, Rendoll J, Simoes F, Kennedy J, Rozzi R, Convey P. Assessing distribution shifts and ecophysiological characteristics of the only Antarctic winged midge under climate change scenarios. Sci Rep. 2020 Jun 3;10(1):9087. doi: 10.1038/s41598-020-65571-3. PMID: 32493944; PMCID: PMC7270094.

Pertierra, Luis R., Bartlett, Jesamine C., Duffy, Grant A., Vega, Greta C., Hughes, Kevin , Hayward, Scott A. L., Convey, Peter , Olalla-Tarraga, Miguel A., Aragón, P.. (2020) Combining correlative and mechanistic niche models with human activity data to elucidate the invasive potential of a sub‐Antarctic insect.. Journal of Biogeography, 47. 658-673. 10.1111/jbi.13780.

Biersma, Elisabeth M. , Jackson, Jennifer A. , Bracegirdle, Thomas J. , Griffiths, Howard, Linse, Katrin , Convey, Peter . (2018) Low genetic variation between South American and Antarctic populations of the bank-forming moss Chorisodontium aciphyllum (Dicranaceae). Polar Biology, 41. 599-610. 10.1007/s00300-017-2221-1.

Please be aware that due to immigration requirements this project is only available to applicants from the UK or who have settled or pre-settled status in the UK  (i.e. a home fees student)