A three-year grant from the Australian Research Council (ARC) will allow CGB researchers Dustin Marshall and Craig White (Monash University) and Tim Coulson (The University of Oxford) to investigate how evolutionary shifts in body size alter biological processes at three levels of biological organisation: individuals, populations and communities.  This project will help us understand the biological consequences of ongoing worldwide declines in body size in animals.

How will they do this?

Researchers will use two model marine species (a tube worm and a sea squirt) that have short generation times to experimentally evolve individuals of different body size in the lab.  For each generation they will select the largest and smallest individuals which will result in an evolutionary shift in body size.

After every six generations researchers will measure 15 different traits that encompass vital rates (e.g. metabolic rate), life history traits (e.g. egg size) and fitness components (e.g. survival) in order to investigate the consequences of changes in body size.  Measuring such a comprehensive suite of traits has been made possible by the high throughput phenotyping facilities available within the School of Biological Sciences at Monash University.

A major advantage of using the model species chosen for this study is that experimentally evolved individuals can be transplanted into the field – an approach that has been very rarely used with animals.  It will allow researchers to assess the consequences of changing body size and population densities on traits in a natural environment.  Similarly whole communities will be allowed to develop around the experimentally evolved model species which means that researchers can determine how differences in evolved body size affect community assembly and community function.

Why are they doing this?

Once the researchers have collected this data they aim to produce formal models that will allow them to predict the long term consequences of evolutionary shifts in body size for populations and communities.  These models will then be used to progress studies on less tractable but more commercially relevant marine species and provide benefits such as:

• environmental managers can predict the impact of body size on species important for services and food (e.g. fisheries)
• conservation efforts can be targeted with greater certainty about the impacts of body size and the consequences of actions that may affect body size.