Population sizes of aquatic insects are hugely variable in time and space. Why is that? Questions like that one have often been put into the too-hard basket, yet answering big, difficult questions is fundamental to scientific progress. We cannot hope to advance our understanding of what promotes or maintains biological diversity without tackling such thorny questions – nor can we hope to understand how to arrest the current extinction crisis.
In this talk, I set out the challenges presented by animals that have complex life cycles (i.e. many different life stages) and - in the case of aquatic insects - live and disperse in both the aquatic and terrestrial environments. Populations of such species may be regulated or limited at any life stage and in either or both environments; that’s the challenge. I set out some of the theory that has been erected to address this kind of complexity and review briefly its success in progressing knowledge. I will then highlight some progress that has been made for riverine fauna but also the many, significant knowledge gaps that remain. Filling some of those gaps is fundamental - both for understanding what drives variability in numbers in space and time, but also the steps we might take to halt or reverse declines in biological diversity. Many of these gaps can be addressed by projects of a length that make them highly suitable as topics for PhD students or grant applications, all of which can be warranted by standing on a solid theoretical foundation for why such research matters.
Along the way, I will note some things I’ve learned that have come from asking scientific questions for some 40+ years, which I hope may be of particular assistance to those who are just starting or still early in their careers.