Research fellow position: Adaptive Dynamics Modeller

  • Level A, research-only academic
  • $64,450 to $87,471 pa + 9.5% superannuation
  • Full-time, starting late 2017
  • Two-year, fixed-term
  • Monash University Clayton campus

The Centre for Geometric Biology is currently seeking to recruit an experienced theoretical biologist experienced in adaptive dynamics modelling.

As the postdoctoral researcher, you will use adaptive dynamics modelling approaches to explore the drivers and consequences of body size evolution. Working with other researchers in the Centre for Geometric Biology, you will parameterise models based on empirical findings and provide advice of key tests of model predictions.

You will further be expected to maintain consistently high research output in the form of quality publications, supervision of students, development and submission of grant proposals to external funding agencies, contribute more generally to communicating the research activities of the group, and participation in appropriate career development activities.

Key selection criteria

  1. A degree in a relevant area, utilising adaptive dynamics approaches, from a recognised university with subsequent relevant work experience, or an equivalent combination of experience and training.
  2. Demonstrated experience in developing theoretical models in fundamental ecology or empirical research using cutting-edge quantitative approaches.
  3. Demonstrated ability to undertake outstanding research; with a high quality research publication record in recognised journals.
  4. Ability to solve problems by using discretion, innovation and the exercise of high level diagnostic skills within areas of functional responsibility or professional expertise.
  5. Excellent written communication and verbal communication skills with proven ability to effectively analyse information and produce clear, succinct reports and documents which requires interaction with others.
  6. Demonstrated planning and organisational skills, with the ability to prioritise multiple tasks and set and meet deadlines.
  7. Demonstrated awareness of the principles of confidentiality, privacy and information handling.
  8. Demonstrated ability to effectively work independently and in a multidisciplinary team to make a contribution to research and scholarship.
  9. Experience of, or willingness to work on, marine systems.
  10. A demonstrated understanding of questions in fundamental ecology and/or evolution.

Enquiries to Professor Dustin Marshall on +61 3 9902 4449

For more information, or to apply, refer to the Monash University website

Research fellow position: Life History Empiricist

  • Level A, research-only academic
  • $64,450 to $87,471 pa + 9.5% superannuation
  • Full-time, starting late 2017
  • Two-year, fixed-term
  • Monash University Clayton campus

The Centre for Geometric Biology is currently seeking to recruit an experienced zooplankton biologist.

You will further be expected to maintain consistently high research output in the form of quality publications, supervision of students, development and submission of grant proposals to external funding agencies, contribute more generally to communicating the research activities of the group, and participation in appropriate career development activities.

 

Key selection criteria

  1. A PhD on zooplankton or a relevant area, from a recognised university with subsequent relevant work experience, or an equivalent combination of experience and training.
  2. Demonstrated experience in developing theoretical models in fundamental ecology or empirical research using cutting-edge quantitative approaches.
  3. Demonstrated ability to undertake outstanding research; with a high quality research publication record in recognised journals.
  4. Ability to solve problems by using discretion, innovation and the exercise of high level diagnostic skills within areas of functional responsibility or professional expertise.
  5. Excellent written communication and verbal communication skills with proven ability to effectively analyse information and produce clear, succinct reports and documents which requires interaction with others.
  6. Demonstrated planning and organisational skills, with the ability to prioritise multiple tasks and set and meet deadlines.
  7. Demonstrated awareness of the principles of confidentiality, privacy and information handling.
  8. Demonstrated ability to effectively work independently and in a multidisciplinary team to make a contribution to research and scholarship.
  9. Experience of, or willingness to work on, marine systems.
  10. A demonstrated understanding of questions in fundamental ecology and/or evolution.

Enquiries to Professor Dustin Marshall on +61 3 9902 4449

For more information, or to apply, refer to the Monash University website

Ocean sunfish as indicators for the ‘rise of slime’

Authors: David Grémillet, Craig R White, Matthieu Authier, Ghislain Dorémus, Vincent Ridoux, and Emeline Pettex

Published in: Current Biology

Summary

Overfishing and ocean warming are drastically altering the community composition and size structure of marine ecosystems, eliminating large bodied species. Against a backdrop of such environmental change, the heaviest of all bony fish, the ocean sunfish (Mola mola), seems an improbable survivor. Indeed this indolent giant is killed globally as bycatch, and is listed as ‘Vulnerable’.

Sunfish are so named because they engage in extensive sunbathing at the water surface making them far easier to monitor than jellyfish. Image credit: Mike Baird via Flickr.

We undertook the most extensive aerial surveys of sunfish ever conducted and found surprisingly high abundances off the Atlantic and Mediterranean coasts of Western Europe. With up to 475 individuals per 100 square kilometres, these figures are one order of magnitude higher than abundance estimates for other areas. Using bioenergetic modelling, we estimate that each sunfish requires 71 kilograms per day of jellyfish, a biomass intake more than an order of magnitude greater than predicted for a similarly sized teleost. Scaled up to the population level, this equates to a remarkable 20,774 tonnes per day of predated jellyfish across our study area in summer.

Sunfish abundance may be facilitated by overfishing and ocean warming, which together cause reduced predation of sunfish by sharks and elevated jellyfish biomass. Our combined survey and bioenergetic data provide the first-ever estimate of spatialized ocean sunfish daily food requirements, and stress the importance of this species as a global indicator for the ‘rise of slime’.

This hypothesis posits that, in an overfished world ocean exposed to global warming, gelatinous zooplankton should flourish, to the detriment of other mesotrophic species such as small pelagic fish, causing irreversible trophic cascades as well as a series of other environmental and economic issues.

Grémillet D, White CR, Authier M, Dorémus G, Ridoux V, Pettex E (2017) Ocean sunfish as indicators for the ‘rise of slime’, Current Biology, PDF DOI 

It’s life, but not as we know it

The deserts of Antarctica are one of the most extreme environments on earth. While it was once believed that the harsh conditions precluded life, we now know that terrestrial Antarctica hosts a surprising diversity of microbial taxa.

Chris Greening from the Centre for Geometric Biology  and colleagues (Sean Bay, Thomas Lines and John Beardall) from the School of Biological Sciences have been working with researchers from a range of institutions to investigate how microbes can exist despite freezing temperatures, strong UV radiation, frequent freeze-thaw cycles and limited carbon, nitrogen and water availability.

Soil samples from three arid Antarctic sites were found to have low concentrations of organic carbon, nitrogen and moisture content and a low proportion of phototrophs (organisms able to use light to create energy)  – findings incompatible with observed bacterial diversity.

Adams Flat: one of the arid, Antactic sampling sites with surprisingly high microbial diversity.

The researchers used a range of techniques to help them understand the possible alternative energy sources that microbial communities are using to support their maintenance energy and carbon needs.

Shotgun DNA sequencing identified a large number of taxa and also genes that suggested that the Antarctic microbial communities are able to scavenge H2/CO2 and CO from the atmosphere to use as energy and carbon sources. These findings were followed up by further experimental work to test the hypothesis that microbial communities are, in fact, using atmospheric trace gases for carbon and energy sources.

In laboratory microcosms, the research team found that soil communities aerobically oxidised atmospheric H2 and CO.  What’s more, when 14C-labelled CO2 was added to microcosms, H2 addition caused a significant increase in CO2 fixation in the dark but not the light.  These findings are consistent with the hypothesis that energy needs are being met via chemosynthetic and not photosynthetic CO2 fixation.

The arid and nutrient starved surface soils from Antarctica are the first ecosystem described to date that appears to use atmospheric trace gases to drive primary production.  But it may not be the last; possibly this process also dominates other arid desert systems and provides a mechanism to explain high microbial diversity in nutrient starved environments as well as opening the door to the possibility that atmospheric gases could support life on other planets.

Metabolic theory: how does the cost of development scale allometrically with offspring size?

One of the most fundamental patterns studied in life-history theory is how offspring size links to performance of an individual. Within species, larger offspring generally have higher survival, reproductive output and growth, and lower risk of predation and starvation. One key question that remains is why larger offspring outperform smaller offspring.

The Centre’s Amanda Pettersen and colleagues Craig White, Robert Bryson-Richardson and Dustin Marshall explored one potentially widespread mechanism: how the costs of development scale with offspring size, using metabolic theory. Metabolic theory proposes that there is an allometric relationship between energy use (metabolic rate) and body size, where on a log-log scale, the slope of this relationship is less than one.

Amanda and colleagues sought to explore whether the same pattern (i.e allometric scaling) occurs with offspring size, in order to understand how size affects the relative use of energy reserves throughout a critical life period. They measured embryo mass and metabolic rate throughout development, from fertilisation to hatching, in the freshwater fish, Danio rerio.

3-hour old embryos of the tropical freshwater zebrafish, Danio rerio.

The team found an allometric relationship between embryo mass and metabolic rate – while larger offspring use absolutely more energy, they also use relatively less energy to reach the end of development, than smaller offspring. Larger offspring use proportionally less of their supplied energy to reach the end of development than smaller offspring. These findings are supported by the observation that hatchlings from larger embryos are both disproportionately heavier and retain relatively more of their initial energy reserves than smaller embryos. These findings mean that the same allometric scaling relationships that are found for adult body size also apply for offspring size. But they also may explain a fundamental pattern in life-history theory: allometric scaling with offspring size may serve as a widely applicable explanation for why larger offspring often perform better than smaller offspring.

This research in published in the journal Functional Ecology.

What happens in 60,000 generations of evolution?

Mike McDonald, working with colleagues from the United States, has found that long-term adaptation to a constant environment can be a more complex and dynamic process than is often assumed.

The team were able to observe this process directly by using frozen samples of E. coli from the ongoing experimental evolution study led by Richard Lenski, now in its 30th year. This is over 67,000 generations for each of the 12 replicate populations.

This figure shows the trajectories of different mutations in different populations. A mutation may become ‘fixed’ where 100% of all alleles have that mutation, others may reach substantial frequencies before becoming extinct. What was most striking however was when neither fixation or extinction occurred, with 9 of the 12 populations maintaining 2 or more stable “subpopulations”, within the culture. This indicates that one way the populations can continue to adapt for so long is by diversifying and evolving niche specific subpopulations.

Previous studies have shown that the populations have not yet reached the expected ‘fitness peak’ despite tens of thousands of generations in the same environment.  While the competitive fitness of each generation continues to increase, the rate of improvement has slowed. Through analysing genome sequences every 500 generations, Mike and the research team have been able to analyse when, and in what order, successful mutations occur, the dynamics by which they spread through a population and what other competing mutations have arisen.

Their data revealed a complex adaptive process with competition between lineages arising from different beneficial mutations important, but genetic drift and eco-evolutionary feedback also playing significant roles. In the latter instance the evolving E. coli change the environment they are growing in, which can, in turn, influence the evolutionary trajectories of the different populations.

The combination of such processes can help explain why the rate of molecular evolution in E. coli populations remains so high through 60,000 generations.

These results help us understand the complex population genetic processes that take place in the long term adaptation to a fixed environment and are in stark contrast to the ‘evolutionary desert’ expected near a fitness peak.

This research has been published in the journal Nature.

Evolving smaller body sizes improves the ability to persist when resources are limited, but at a cost

We know that the growth and reproduction of an organism are dependent on both energy acquisition and energy use – net energy flux –  but few studies look at both these simultaneously.  Recent reductions in body size across a range of taxa worldwide, has focused attention on increasing our understanding about the role size plays in determining net energy flux.

Martino Malerba and co-authors Dustin Marshall and Craig White used a technique called artificial selection to genetically evolve small and large populations of a single-celled marine alga Dunaliella tertriolecta that differed in size by 500%. They then assessed some physiological and ecological consequences of this size shift.

The research team found that under low energy conditions (ie low light intensities or short light durations) the smaller cells showed faster growth rates than control and larger cells and conversely under high energy conditions larger cells displayed faster growth rates. Surprisingly though, the smaller cells reached lower total biovolumes overall regardless of the light regime.

Scanning electron micrographs of artificially selected algae. “If the environment allows you to “acquire much”, be big! Otherwise, better to “desire little” and be little.

Other traits such as swimming speed and distance travelled showed the highest performance in the control cells; perhaps because they maintained an optimal ratio of cell size to length of swimming flagella.

These results emphasise that the costs and benefits of different cells sizes depend on the context.  In low resource environments smaller cells will have a greater ability to persist but will be less productive than larger cells, while in high resource environments larger cells will perform better.

This research, published in the highly regarded journal Ecology Letters, will inform the debate on how natural ecosystems will respond to human impacts. Open oceans are the most productive systems in the world and single celled algal species dominate this production. These results show that reductions in cell size as a result of human activities such as fishing and climate change can severely reduce this rate of carbon fixation by as much as 40%.

Australian Research Council Discovery Projects to begin in 2018

Exciting new projects will begin in the Centre for Geometric Biology in 2018 as part of the Australian Research Council (ARC) Discovery Projects funding scheme.

Professor Dustin Marshall will be investigating how the paternal environment, that is, the environment that developing sperm experience, can influence reproductive and offspring success.  Dustin will use an externally fertilising marine invertebrate as his study organism which will allow him to manipulate the paternal environment without the confounding effect of the maternal environment.

Professor Craig White and Dr Lesley Alton will be tackling the fundamental biological question of why so few biological traits scale proportionally with body size. Craig and Lesley will use artificial selection to engineer animals where biological scaling laws are either ‘broken’ or enhanced. This means that they will create large animals with low metabolic rates and small animals with high metabolic rates and measure the consequences of this for fitness.

Dr Mike McDonald will be collaborating with Dr Kat Holt from the University of Melbourne to investigate the co-evolution of microbes in a long-term evolution experiment.  The bacteria Escherichia coli and the baker’s yeast Saccharomyces cerevisiae will be cultured independently or together in two different environments for 1,000 generations. Mike and Kat will then measure individual growth rates, ecosystem performance, fitness, and sequence the whole genome. They will then look for signals of co-evolution between E.coli and yeast.

Dr Chris Greening will be collaborating with Associate Professor Perran Cook from the School of Chemistry and Ronnie Glud and Damien Callahan (University of Southern Denmark and Deakin University) to investigate the role that hydrogen plays in sandy sediments that are anoxic (depleted of oxygen). This project aims to quantify the respiratory pathways and the importance of hydrogen in the microbial ecology and biogeochemistry in the sandy sediments that dominate our coastline.

Eco-energetic consequences of evolutionary shifts in body size

Authors: Martino E Malerba, Craig R White, and Dustin J Marshall

Published in: Ecology Letters

Abstract

Size imposes physiological and ecological constraints upon all organisms. Theory abounds on how energy flux covaries with body size, yet causal links are often elusive.

As a more direct way to assess the role of size, we used artificial selection to evolve the phytoplankton species Dunaliella tertiolecta towards smaller and larger body sizes.

Within 100 generations (c. 1 year), we generated a fourfold difference in cell volume among selected lineages. Large-selected populations produced four times the energy than small-selected populations of equivalent total biovolume, but at the cost of much higher volume-specific respiration. These differences in energy utilisation between large (more productive) and small (more energy-efficient) individuals were used to successfully predict ecological performance (r and K) across novel resource regimes.

We show that body size determines the performance of a species by mediating its net energy flux, with worrying implications for current trends in size reduction and for global carbon cycles.

Malerba ME, White CR, Marshall DJ (2017) Eco-energetic consequences of evolutionary shifts in body size, Ecology Letters, PDF DOI