Conference season

Conference season is in full swing and members from the Centre for Geometric Biology will be presenting their research over the next few weeks in Portland and Hawaii.  For those of us who can’t make it overseas we can hear research updates at the CGB mini-symposium on the 22 August from 1 pm to 5pm at Monash University.

Dustin Marshall and Diego Barneche will be at the XIth International Larval Biology Symposium in Honolulu, Hawaii. Dustin will be giving a plenary talk on the topic of offspring size in relation to temperature and global change. He will be presenting a new theory on why offspring size often declines with temperature and also presenting evidence that offspring sizes are declining globally in marine invertebrates.

Not only is offspring size getting smaller, we also know that animals are getting smaller but surprisingly we don’t yet know how reproductive output scales with body mass – both issues with profound implications for fisheries management. Life history theory and mechanistic models assume that reproductive output of fish scales on a 1:1 ratio with female size (isometric scaling). However fisheries management is often based around the assumption that larger mothers have a disproportionately greater reproductive output (hyper-allometricscaling). Diego Barneche has compiled raw data on female size, fecundity and egg size of marine fish from over a century of research to start addressing the lack of formal assessments of scaling relationships between reproductive output and female body mass across differentspecies.

While her colleagues are immersed in larval biology research, Giulia Ghedini will be attending the Ecological Society of America Annual Meeting in Portland, Oregon, USA. Giulia will be talking about her research into the relationship between population densities and the ‘scope for growth’ of an individual within that population. She has measured both the foraging rates (energy intake) and metabolism (energy expenditure) in a model system using sessile invertebrates to determine how the growth of an individual is affected by changing densities of other individuals of the same species’.  Giulia found that feeding and metabolism weredensity-dependent, but energy intake through feeding decreased faster than energy expenditure through metabolism, reducing the ‘scope for growth’ of individuals. These results demonstrate that density-dependent growth occurs because of differential rates of change in energy gains and losses with increasing densities. These effects of population density on individual energy budgets have important implications for predicting the dynamics of populations and their responses to environmental change.