Published papers

dustinmeeg

Published paper: Minimal increase in genetic diversity enhances predation resistance

Authors: Kai S Koh, Carsten Matz, Chuan H Tan, Hoang L Le, Scott A Rice, Dustin J Marshall, Peter D Steinberg and Steffan Kjelleberg

Published in: Molecular Ecology, volume 21, issue 7, doi: 10.1111/j.1365-294X.2011.05415.x

Abstract

The importance of species diversity to emergent, ecological properties of communities is increasingly appreciated, but the importance of within-species genetic diversity for analogous emergent properties of populations is only just becoming apparent.

Here, the properties and effects of genetic variation on predation resistance in populations were assessed and the molecular mechanism underlying these emergent effects was investigated.

Using biofilms of the ubiquitous bacterium Serratia marcescens, we tested the importance of genetic diversity in defending biofilms against protozoan grazing, a main source of mortality for bacteria in all natural ecosystems.

S. marcescens biofilms established from wild-type cells produce heritable, stable variants, which when experimentally combined, persist as a diverse assemblage and are significantly more resistant to grazing than either wild type or variant biofilms grown in monoculture.

This diversity effect is biofilm-specific, a result of either facilitation or resource partitioning among variants, with equivalent experiments using planktonic cultures and grazers resulting in dominance by a single resistant strain.

The variants studied are all the result of single nucleotide polymorphisms in one regulatory gene suggesting that the benefits of genetic diversity in clonal biofilms can occur through remarkably minimal genetic change.

The findings presented here provide a new insight on the integration of genetics and population ecology, in which diversity arising through minimal changes in genotype can have major ecological implications for natural populations.

Full paper

Koh KS, Matz C, Tan CH, Le HL, Rice SA, Marshall DJ, Steinberg PP, Kjelleberg S (2012) Minimal increase in genetic diversity enhances predation resistance. Molecular Ecology 21: 1741–1753 PDFPDF 681 KB doi: 10.1111/j.1365-294X.2011.05415.x

dustinmeeg

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

dustinmeeg

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