Does sexual selection accelerate adaptation in the wild?

Our aim is to understand how sexual selection (variation among males in their ability to gain fertilisations) affects how populations evolve in response to change. This is a very broad question with implications for understanding how all sexually reproducing populations will respond to the challenges of environmental change.

Although sexual selection was originally conceived to explain traits that appeared to reduce survival, it also has the potential to accelerate adaptation. If males that are well adapted to the environment have increased mating success, then genes that contribute to this adaptation will proliferate, both through their naturally selected contributions to survival (because well adapted males live longer and can perform better) and through their sexually selected contributions to reproduction (for instance because the males that are better adapted to the environment also mate at a higher rate). There have been laboratory based studies that address the question of whether sexual selection will tend to accelerate or retard adaption, but they give conflicting results. What is lacking is an experimental study that retains the natural context: it is this context that imposes the true costs and benefits of sexual selection.

Understanding the interactions between natural and sexual selection in the process of ecological adaptation is not only a fundamentally important issue in evolutionary biology, but also has implications for understanding how populations will adapt to changing environments. For example, if sexual selection accelerates adaptation this suggests that populations should be managed to allow sexual selection to occur.

We will conduct experiments on a natural population of crickets, utilising our 'WildCrickets' project - a long term study of a meadow in Spain. This project has the unique capacity to provide detailed information about the lives of every individual in the population through a network of 160 digital video cameras and annual DNA fingerprinting.

We will replace all the males in the population with males bred from other populations so that half come from populations that are similar to our meadow and half come from high altitude where conditions are very different. For sexual selection on males to reinforce natural selection, it is a requirement that less well adapted males have reduced expression of male sexually selected traits and mating rate. This is a very simple assumption and many biologists probably regard it as uncontroversial, but in reality, it has only been tested in a very limited way in either the field or the lab. Fundamentally, we lack a clear test of this assumption and the arising major prediction that sexual selection increases adaptation. A strong test requires an experiment that directly compares well adapted and less well adapted males over the entire adult lifespan. We will make the comparison, measuring the expression of sexually selected traits, the realised reproductive success of males and the naturally selected success of their offspring. We will do this by using our video cameras to monitor the entire adult lives of the introduced crickets and the females left in the meadow and then coming back the next season and doing the same with their offspring. By using DNA fingerprinting we will know which offspring come from which males. Only males with some success in gaining fertilisations will leave any offspring, but there will still be variation in success amongst fathers, allowing us to compare the longevity and activity of individuals whose fathers were successful in sexual selection with offspring of males that were less successful.

This project investigates fundamental questions about how new adaptations are established in natural populations. With environmental change occurring very rapidly, it is essential that we understand the factors that may facilitate or constrain the capacity of populations to thrive. If sexual selection accelerates adaptation this suggests that populations should be managed to allow sexual selection to occur; for instance culling regimes in managed animal populations often target the largest males, which may slow down the rate at which the population can adapt. Alternatively, if sexual selection retards adaptation, then management regimes in which a majority of males are removed from the breeding pool, or even where the most attractive males are selectively removed may be better in terms of allowing adaptive evolution to occur. We do not anticipate being able to make specific recommendations at the end of this grant, but it is clear that our findings will have implications for wildlife managers and policy makers in the near future, and we will work hard to publicise them as widely as possible.

The general public, particularly school pupils and teachers will benefit from this research as a result of our planned impact activities: Our study will generate very high quality video recordings of the cricket population studied, and we intend to exploit this resource for the purposes of wider user engagement, with the purpose of providing a high quality learning resource. We have developed a website aimed at the general public which explains the motivations and findings of our project (www.wildcrickets.org). We will develop this site and associated materials in collaboration with digitalexporer.com to produce a package of materials for teachers. Our study will be used to help students learn about natural and sexual selection, and how they affect the capacity of organisms to adapt to changes in the environment. We will add live video feeds from the meadow, with multiple camera feeds available during the breeding season.

We have developed a website which allows the general public to take part in our research: cricket-tales.exeter.ac.uk allows the public to assist in our task of analysing field cricket behaviour. Using technology to involve people in the research in this way disseminates knowledge about animals and habitats, strengthens understanding of the scientific process and engages people in a deeper way. We will further develop this site with a particular aim of engaging older people in our research.

Our study utilises novel video-based monitoring technology which has many and varied applications and commercial value. By pioneering new applications of this technology this work will be of direct benefit to the CCTV Industry including both hardware manufacturers and software developers. We have been collaborating with i-code systems (www.icode.co.uk/), who have used our input to substantially develop their software and have sold systems to other academic users in the US and NZ as a direct result of the impact of our work on the development of their product. If our impact pathway is funded we will work with i-code to add audio recording to their product, which will contribute to the economic performance of the UK in this potentially major export market.

We can demonstrate a strong commitment to bringing our work to as wide an audience as possible (e.g. Google "Chivalrous Crickets"). Our work has been included in BBC and Discovery Channel broadcasts, national newspapers etc. and we will continue to ensure that we use these avenues to promote our NERC-funded science with support from the university's Press Office.

The Researcher-CI on this project will benefit from acquiring a broad range of skills, including deploying monitoring systems, database design, data analysis etc. We will ensure that he has the opportunity to develop his awareness and skills in knowledge exchange.