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Genetic diversity increases population productivity in a sessile marine invertebrate

Authors: J David Aguirre and Dustin J Marshall

Published in: Ecology, volume 93, issue 5, doi: 10.1890/11-1448.1

Abstract

Reductions in genetic diversity can have widespread ecological consequences: populations with higher genetic diversity are more stable, productive and resistant to disturbance or disease than populations with lower genetic diversity.

These ecological effects of genetic diversity differ from the more familiar evolutionary consequences of depleting genetic diversity, because ecological effects manifest within a single generation.

If common, genetic diversity effects have the potential to change the way we view and manage populations, but our understanding of these effects is far from complete, and the role of genetic diversity in sexually reproducing animals remains unclear.

Here, we examined the effects of genetic diversity in a sexually reproducing marine invertebrate in the field. We manipulated the genetic diversity of experimental populations and then measured individual survival, growth, and fecundity, as well as the size of offspring produced by individuals in high and low genetic diversity populations.

Overall, we found greater genetic diversity increased performance across all metrics, and that complementarity effects drove the increased productivity of our high-diversity populations.

Our results show that differences in genetic diversity among populations can have pervasive effects on population productivity within remarkably short periods of time.

Full paper

Aguirre JD, Marshall DJ (2012) Genetic diversity increases population productivity in a sessile marine invertebrate. Ecology 93: 1134–1142 PDFPDF 1.3 MB doi: 10.1890/11-1448.1

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Advantages and disadvantages of interference-competitive ability and resource-use efficiency when invading established communities

Authors: Simon P Hart and Dustin J Marshall

Published in: Oikos, volume 121, issue 3, doi: 10.1111/j.1600-0706.2011.19557.x

Abstract

Invaders into established communities must overcome low resource availability. To establish, invaders must either appropriate resources from existing individuals through interference competition or efficiently use the small amount of resource that remains. Although both strategies may be important, they are rarely considered together and, in particular, resource-use efficiency is often ignored in systems dominated by interference competition.

To identify the traits that confer invasion success, we experimentally invaded resource patches in established communities with multiple species from two functional groups that differ in interference competitive ability and resource-use efficiency.

In contrast to previous assessments, we show that resource-use efficiency can facilitate invasion in systems dominated by interference competition. Furthermore, large resource requirements can be a liability when establishing because interference competition is inherently costly and so cannot fully compensate for limitations in the primary resource.However, we also show that there is a tradeoff in performance among functional groups between small and large resource gaps.

Our results suggest we modify the way we view and manage species invasion in systems dominated by interference competition.

Full paper

Hart SJ, Marshal DJ (2012) Advantages and disadvantages of interference-competitive ability and resource-use efficiency when invading established communities. Oikos, 121: 396–402 PDFPDF 132 KB doi: 10.1111/j.1600-0706.2011.19557.x

dustinmeeg

Does genetic diversity reduce sibling competition?

Authors: J. David Aguirre and Dustin J. Marshall

Published in: Evolution, volume 6, issue 1, doi: 10.1111/j.1558-5646.2011.01413.x

Abstract

An enduring hypothesis for the proximal benefits of sex is that recombination increases the genetic variation among offspring and that this genetic variation increases offspring performance. A corollary of this hypothesis is that mothers that mate multiply increase genetic variation within a clutch and gain benefits due to genetic diversity alone.

Many studies have demonstrated that multiple mating can increase offspring performance, but most attribute this increase to sexual selection and the role of genetic diversity has received less attention. Here, we used a breeding design to generate populations of full-siblings, half-siblings, and unrelated individuals of the solitary ascidian Ciona intestinalis. Importantly, we preclude the potentially confounding influences of maternal effects and sexual selection.

We found that individuals in populations with greater genetic diversity had greater performance (metamorphic success, postmetamorphic survival, and postmetamorphic size) than individuals in populations with lower genetic diversity. Furthermore, we show that by mating with multiple males and thereby increasing genetic variation within a single clutch of offspring, females gain indirect fitness benefits in the absence of mate-choice.

Our results show that when siblings are likely to interact, genetic variation among individuals can decrease competition for resources and generate substantial fitness benefits within a single generation.

Full paper

Aguirre JD, Marshall DJ (2012) Does genetic diversity reduce sibling competition? Evolution, 66-1: 94–102 PDFPDF 688 KB doi: 10.1111/j.1558-5646.2011.01413.x

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PhD positions available: the evolutionary ecology and/or quantative genetics of marine invertebrates

Two fully-funded PhD stipends are available to students interested in working on the evolutionary ecology of marine invertebrates in Dr Dustin Marshall’s group.

The stipends include all course fees plus ~$25,000 AUD per annum tax-free (the equivalent of  approx. $33,000 before tax) with no teaching requirements.

I can guarantee funding of project costs including the costs of attending at least one conference per year.

Project start dates can be any time in 2012.

Interested students should send their CVs, a brief statement of their interests and the contact details of two referees.

To be eligible, applicants must have completed at least one year of post-graduate research and ideally a masters degree.

Preference will be given to those with strong quantitative skills.