In the balance: competition and facilitation affected by resource availability

Congratulations to Karin Svanfeldt who recently submitted her PhD and has published some of her research in The Journal of Animal Ecology, with her supervisors, Keyne Monro and Dustin Marshall.

Karin was interested in the balance between the negative effects of increased population density, (when interactions are dominated by competition for resources), versus the positive effects of increased densities which can arise from facilitation. In examples of the latter, increased densities can provide benefits by making the habitat more suitable for other individuals or through increasing the availability of basic resources. Karin particularly wanted to test how manipulating resources affected density-dependent performance in the field.

There have been few field studies that have directly manipulated environmental conditions to test these types of ideas and so Karin and her colleagues designed an experiment where they could influence both food availability and flow rates and measure the performance of an encrusting colonial bryozoan, Watersipora subtorquata.

Watersipora subtorquata, commonly known as the ‘red rust’ bryozoan.
Watersipora growing on artificial substrates.

Watersipora is sessile (non-moving) and filters resources such as food and oxygen from the surrounding water. Reducing flow rates will therefore impact resource availability. Karin was able to manipulate food availability by creating slow releasing food blocks (‘Reef Feed’ mixed with dental plaster) and flow, by boxing in the artificial substrates that were home to different densities of Watersipora colonies. Performance was measured by recording changes in size of Watersipora colonies over 13 weeks as well as the colony survival and the proportion of the colonies that had senesced.

Karin’s PhD research found evidence that resource availability altered the balance between facilitation and competition in the system they were studying. When resources were abundant, facilitation dominated and when resources were scarce, competition dominated. This work adds to existing evidence that both competition and facilitation can be important and explores how the balance between the two affects interactions within and between populations.

PhD positions ×2: the evolutionary ecology of marine heterotrophs

Two fully-funded PhD stipends are available to students interested in working on the evolutionary ecology of marine heterotrophs in the Centre for Geometric Biology.

The stipends include all course fees plus $26,288 AUD per annum tax-free with no teaching requirements for 3.5 years (the length of a PhD in Australia). Students from Australian and New Zealand will be eligible for ‘top-up funding’ to a total stipend of $30,000 AUD.

Guaranteed funding of project costs and research support, including the costs of attending at least one conference per year, is included.

Project start dates to be in the first half of 2017.

Although Professors Dustin Marshall and Craig White are Director and Deputy Director, respectively, project specifics and appropriate supervisors will depend on the interests of the successful students and collaboration between student and supervisor.

To be eligible, applicants must have completed at least one year of post-graduate research in ecology and/or evolution.

Successful applicants will hold a Bachelor of Science with first class honours (or equivalent) or a Masters by research degree. Preference will be given to those with strong quantitative skills and publications in international journals.

Any offers are subject to acceptance by Monash University.

Interested students should send a CV, brief statement of interests and contact details of two referees to Liz Morris, Administrations Manager.

Applications close Sunday 22 January 2017.

Monterey Meeting 2016

This November, researchers from the Centre will be attending the Western Society of Naturalists 100th anniversary meeting in Monterey, California. The work they are presenting reflects the work of the CGB on how size and shape can affect an organism’s ability to acquire and expend energy and how other factors might affect the balance between energy acquisition and energy expenditure and the consequences of this for survival, growth and reproduction.


PhD students Amanda Pettersen and Hayley Cameron will be presenting findings from their research into variation in offspring size. Hayley’s research interests focus in on the variation in offspring size within a brood and what the consequences of this unequal maternal investment are to maternal fitness. Amanda’s research considers the recognised biogeographical patterns in temperature and productivity and that while we know that mothers produce larger offspring in cooler environments, we don’t yet have broadly applicable explanations for why this happens. In contrast the biogeographic relationship between temperature and egg size has not been demonstrated for fish although again observations have noted that colder temperatures often cause egg size in fish to increase.

Post doctoral research fellow Diego Barneche will present his work on the largest dataset of marine fish egg size compiled to date in order to address the knowledge gaps in this area.

We also know that animal body sizes are changing and that these evolutionary shifts in size have been triggered by both direct (e.g. harvesting of large individuals) and indirect anthropogenic pressures (e.g. warming).  Martino Malerba will talk about his research on the consequences of evolutionary shifts in body size on the physiology and ecology of a green algal species when exposed to differing light intensity and duration. Large scale stressors such as warming rarely occur in isolation however and Rolanda Lange will explore how multiple stressors might impact on an organism’s ability to adapt to environmental change.

Dustin Marshall will also be attending the conference and presenting seminars at the University of Toronto and Queens University, Canada.  He will then spend some time working with colleague and CGB member Tim Coulson at the University of Oxford on the demographics of body size.

Visiting academic: André de Roos


The Centre for Geometric Biology will be hosting a visit from André de Roos, Professor of Theoretical Ecology at the University of Amsterdam during November 2016.  André’s research interests focus on the relationship between individual life history, in particular developmental changes that relate to the size and shape of an organism over an individual’s lifespan (ontogenetic development), and the dynamics of populations and communities. Changes during ontogeny result in individuals playing a different ecological role in the different stages of their life history.

The main aspect of ontogenetic development is an increase in body size as every individual at least has to double in size before it can replicate itself. Since this type of growth requires energy, the rate at which individuals increase in size depends in most species on the food conditions these individuals experience.  André’s research is hence about the population and community ecology of ontogenetic development, in particular food-dependent growth. The results of this research were recently synthesized in a Princeton Monograph. See the accompanying webinars for a more detailed overview of André’s research.

André will also be presenting a seminar during his time at the Centre:

What:  When ecological principles break down: exploring the community consequences of ontogeny and energetics

When:  12 noon to 1 pm Friday 18 November 2016

Where:  Sanson Room (22 G01/02), Rainforest Walk, Monash University.

Morning tea and open forum

The Centre for Geometric Biology is hosting a morning tea and open forum to provide the opportunity to hear a brief overview of the intellectual framework and core research questions of the centre. There will be time for informal chat and morning tea.

Research centre staff aim to tackle these core questions through specific studies on body size, metabolic rate, energy acquisition, energy usage and growth in a range of biological model organisms.

When: 10 am to 11 am, Thursday 22 September 2016

Where: Sanson Room (22 G01/02), Rainforest Walk, Monash University.

Enquiries to Liz Morris, Administrations Manager.