Background
Fire suppression has become the dominant form of shrubland management in much of the Mediterranean Basin. Plant species adapted to recurrent fire regimes are therefore increasingly found in human-disturbed habitats. Research on the carnivorous plant Drosophyllum lusitanicum, a flagship species in fire-adapted Mediterranean heathlands, has shown that under human disturbances, where shrub cover is permanently kept low, seed dormancy in soils is selected against. This maladaptive strategy may lead to continuous seed germination, followed by mass mortality of recruits due to increasingly harsh temperatures. This response can generate an extinction debt, whereby the population structure is skewed towards old individuals that cannot be replaced themselves in the long term. However, despite 13 years of individual-based monitoring of aboveground D. lusitanicum individuals under different disturbance pressures in So. Spain, our knowledge about processes in the seed bank, including seed dormancy, comes largely from greenhouse experiments. Such experimental data generated under controlled conditions overestimate seed and seedling survival, which then may lead to overly optimistic forecasts of population dynamics when critical seed-bank dynamics are integrated into above-ground life-cycle models. General approximations of seed-bank processes occur in the vast majority of plant population models, potentially generating biased population estimates. However, the scale of this problem remains understudied.
Aims of the project
This project aims to understand how much population forecasts can be improved by including variable, field-based estimates of seed-bank processes into plant population models. We will work in fire-disturbed (natural) and permanently disturbed populations of D. lusitanicum to perform various seed burial experiments for at least two years. These experiments will allow us to quantify field-based survival of seeds in and germination from the seed bank. By utilizing seeds from the focal populations as well as ones from populations exposed to different disturbance regimes in the same burial plots, we will also be able to explore (i) whether permanent human pressures have led to genetic adaptations towards a loss of seed-bank dormancy; and (ii) how such adaptations may affect population persistence under climate change.
Methods to be used
The student will use a combination of data collection techniques such as classical permanent plot monitoring, and in situ and greenhouse seed dormancy and viability assays. The data will be integrated within stage-structured population models. The student will develop game theory models to explore optimal strategies under stochastic environments.
Specialised skills required
Competitive candidates will be proficient in R, have fieldwork experience, be capable of carrying out fieldwork in Spain, and possess a valid driver’s license to operate manual gearbox vehicles in Spain.
Please contact Rob Salguero-Gomez on rob.salguero@biology.ox.ac.uk if you are interested in this project. The CASE partner supervisor will be Maria Paniw, Estacion Biological Doñana (EBD) on maria.paniw@ebd.csic.es.
