ACB Talkfest 2008 Winners

1st prize winner at the 2008 ACB Talkfest

John Morrongiello, Dr Bob Wong, Dr David Crook and Dr Nick Bond

john.morrongiello@sci.monash.edu.au
Faculty of Science, Department of Biological Sciences

Environmental quality and predictability influence egg size and egg number in Southern pygmy perch

Life-history theory proposes that mothers allocate finite resources to offspring via a trade-off between size and number. Optimality models assuming stable environmental conditions predict egg size will be optimised to reflect trade-off between maternal (many eggs) and offspring (large eggs) fitness. Many environments, however, vary in quality and predictability. Likewise, offspring
size can vary considerably. In unpredictable environments, it has been proposed that mothers may adopt a bet-hedging approach whereby resources are unevenly spread amongst offspring or offspring size is increased above the theorised optimum for a given environment. The hydrology of freshwater systems in SE Australia is characterised by high levels of spatial and temporal variability and unpredictability. We used Southern pygmy perch, (Nannoperca australis), as a model species in which to explore the trade-off between egg size and egg number, including egg size variation, across gradients of environmental quality (mean flow) and predictability (flow CV). Nine populations were each sampled twice during the breeding season. Egg size and fecundity varied significantly through space and time with evidence of a trade-off. Early season females in
higher flow environments had smaller and more eggs than those in low flow environments but this pattern was reversed later in the season.

2nd Prize winner at the 2008 ACB Talkfest

Giselle Perdomo, Dr Paul Sunnucks, Dr Ross Thompson and Dr Tim Cavagnaro

giselle.perdomo@sci.monash.edu.au
Faculty of Science, Department of Biological Sciences

Biodiversity and ecosystem function in a changing world: insights from a mossmicroarthropod ecosystem

As human impacts on natural habitats increase and as more pressure is put on ameliorating the effects and speed of global climate change, the need to understand how we can best restore degraded habitats and the services they provide has become greater and more urgent. Natural microecosystems (small, contained ecological systems that are naturally populated by minute organisms) can be used as models in this context because they vary on small temporal and
spatial scales (making them experimentally tractable) whilst sharing with large-scale ecosystems, features such as intricate food webs and complex interactions between organisms. In particular, microarthropod communities associated with moss comprise a wide range of functional groups, modes of dispersal and body sizes. I will use this micro-ecosystem to test the role of dispersal distance, climate conditions and primary-producer biodiversity on community assembly and ecosystem function. Large ‘mainland’ areas of moss will be used as source populations for surrounding defaunated moss patches; community composition and ecosystem function over time will be studied. Variants to the central design will be used to assess the effects of each the three factors. Results of these experiments are expected to provide insight into the niche/neutral theory debate and are intended to inform on restoration ecology practices in the face of climate
change.

3rd Prize winner at the 2008 ACB talkfest

Susie Ho, Dr Ross Thompson and Dr Nick Bond

susie.ho@sci.monash.edu.au
Faculty of Science, Department of Biological Sciences

Food web consequences of an invasive fish in floodplain wetlands

The food web consequences of invasion are rarely examined due to the potential complexity of outcomes and the difficulty of studying whole communities. While indirect effects can have major impacts on biodiversity values and ecosystem structure and function, they are difficult to disentangle from temporal and spatial environmental variability. Gambusia holbrooki is an invasive poeciliid fish which is widespread throughout the waterways of mainland Australia. Little is known about its food web effects, particularly in the context of the seasonal and hydrological variability within the wetlands which it frequently inhabits. Here we describe a study examining G. holbrooki’s trophic impacts under dynamic environmental conditions, with a particular focus on its coexistence with sympatric species. While previous studies and anecdotal reports have
suggested that G. holbrooki dominates many invaded habitats, we found evidence for coexistence with several small-bodied native fish and predatory macroinvertebrate species. Whilst G. holbrooki may dominate specific habitats for limited periods, interactions with native fish fauna appear much more complex than initially thought.