Reproduction in a warming world – investigating climate change and fertility in important insects

The problem

We are starting to see the devastating impacts of climate change, including accelerating biodiversity loss. However, most biological predictions of how climate change will impact species’ ranges and population persistence are based on the lethal temperatures. We’ve recently learnt that many species can become entirely sterile at temperatures well below those that kill them. This means the effects of climate change have been underestimated. We urgently need to understand what makes species vulnerable to fertility loss at high temperatures (Walsh et al 2019 Trends in Ecology and Evolution).

Temperature has profound effects on biochemical processes governing the behaviour, physiology and therefore distribution of many species. Our recent study found that, in ~42% of fruit fly species, males become entirely sterile at temperatures lower than those that kill them (Parratt et al 2021 Nature Climate Change). Additionally, using the thermal fertility limit was a better match to species ranges than lethal temperatures alone. This shows that even though fertility was measured in a lab setting it is important for species in nature.

The project

However, there are many open questions that need addressing. What is the role of female reproductive fitness in responding to temperature stress? Are different life stages are more sensitive to heat waves? Can we measure signatures of heat waves from natural populations? How does temperature interact with other climate stressors, such as humidity or resource availability (Mugabo et al. 2019 Journal of Animal Ecology)? What do effects on individual reproduction mean for populations? To tackle these questions we will use a range of insect species to conduct reproductive assessments in the lab, in animals from the wild, or in semi-natural mesocosms. There is also the possibility you could be involved in a meta-analysis project to analyse published data and to model population-level effects.

The importance

Most current climate predictions are based on biological estimates of survival limits, neglecting that if species cannot reproduce then they cannot persist. This is fundamental to understanding how biodiversity will change under climate warming. Given humans also suffer temperature-related infertility, it also speaks to fundamental biology underlying climate and health. Likewise, as insects are both critical pollinators, pest and pest controllers, this feeds into understanding of food security and sustainability.

Who you’ll be working with

You would be working with the Bretman and Sait groups in Leeds who are studying temperature effects on life histories. Currently our labs have projects funded by the NERC and BBSRC on understanding the molecular mechanisms that make sperm vulnerable to high temperature, and how climate change will affect multi-trophic systems using a host-parasitoid model. You would also be part of an international network of researchers studying this topic across species and populations using a wide range of techniques, funded by the European Society for Evolutionary Biology, co-led by Bretman.