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ENV East Doctoral Training Partnership

 

Applications to the EnvEast Doctoral Training Partnership are now closed.

Below you can browse some of the PhD projects we have previously funded; if you would like to be informed when applications open, or if you have any questions about EnvEast and our application process, please email us.

Projects previously funded by EnvEast

GAGE_U14EE

Does male-specific infertility explain butterfly range shifts under climate warming?

Project description

Could heat stress damage the fertility of male insects so that their populations become depleted or even non-viable? We have known for decades that male fertility in ‘warm-blooded’ animals is specifically fragile to increases in temperature that organisms often experience in the natural environment under heatwaves. This thermosensitivity of male fertility is now recognised in ‘cold-blooded’ poikilotherms, whose physiology is also much more directly affected by environmental thermal change. In Drosophila fruitflies, for example, it is the specific thermal sensitivity of male fertility that makes populations non-viable above 30oC, as this is the threshold where males (but not females) become sterile. Apart from a handful of species, most of whom show this characteristic male sensitivity, we know very little about the causes, effects and generality of this potentially important phenomenon for cold-blooded species, despite the fact that these make up the vast majority of biodiversity, and our climate’s thermal environment is changing.

We therefore need to know what reproductive traits in males are damaged by heat, whether they can acclimate or ‘harden’ and recover, if local adaptation has evolved, and ultimately the consequences for population viability. This PhD project will therefore address these questions in a group showing good evidence for local extinction under climate warming: butterflies. We will measure form, function and number of eupyrene and apyrene sperm after thermal treatments at different life stages, in parallel with male behaviour, fertility and sperm competitiveness following experimental matings. Male reproductive effects will be measured in parallel with female effects (which for most species so far examined show much reduced sensitivity to equivalent heat stress). Once controlled experiments have isolated the details of hyperthermia on male reproductive function in the lab, we will take this information to the field, and measure natural fertility across spatial and temporal thermal ranges within species. At the project conclusion, we aim to have identified in an important taxon: (i) which fertility phenotypes are damaged by heat stress, (ii) how they are damaged, (iii) the developmental plasticity and ability of these phenotypes to recover, and ultimately (iv) whether this specifically sensitive individual male trait could explain why some butterfly populations have disappeared from their southern ranges.

Techniques applied will include butterfly rearing, mating and behaviour assays (in UEA’s new Constant Environment Facility), microdissection, microscopy and image analysis (in UEA’s excellent Bio-imaging suite), experimental design, fieldwork, project management and statistical analysis, as well as all the core skills demanded by an exciting multidisciplinary PhD project.
  • Start date 1 January 2015