aquifer microbial community assembly: do neutral processes dominate? presenter: michael strack...
TRANSCRIPT
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Aquifer microbial community assembly:do neutral processes dominate?
Presenter: Michael Strack (@mixtrak)
MQ SupervisorsGrant HoseAdam StowDavid Nipperess
UTS supervisorJohn Ellis
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Structure1. Background – Groundwater & community ecology
2. Project overview
3. Evidence for dispersal limitation
4. Evidence for environmental selection
5. Conclusions & current work
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Chand Baori, Rajasthan
Chennai, Tamil NaduWe rely on groundwater
Global liquid freshwater(Shiklomanov, 1998)
Groundwater Everything else
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Wetlands rely on groundwater
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Microbes regulate water quality
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Processes structuring communities?
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Theory of Community Ecology (TOCE)(Vellend, 2010)
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Sampling design
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Water chemistry & flora
ArchaeaBacteriaFungiEukarya generally
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Dispersal limitation
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Sampling design
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Hypothesis• More DOC, higher richnessApproachMultiple linear regression (MLR): richness vs.• Total organic carbon (TOC)• Inorganic carbon (IC)• Nitrate (NO3)• Dissolved oxygen (DO)• Salinity (conductivity, “cond”)• Depth to water table (water.table)
If not dispersal, what about selection? (sensu Vellend)
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Environmental structuring – richness MLRn = 36
Taxon Model p Adjusted R2Predictor variablesp < 0.05 (*), p < 0.01 (**), p < 0.001 (***)
Archaea < 0.001 0.5665 +NO3***, +cond**, -water.table***
Bacteria 0.001 0.2755 -IC**
Fungi 0.013 0.2016 -TOC**
Eukarya n.s. n.s. n.s.
Aggregate 0.016 0.1412 -TOC*
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Compositional similarityHypothesis• More similar environments = more similar communities
Approach• Distance-based redundancy analysis• Multivariate extension of linear regression• How much variation in response variables is explained by predictors?• Response = matrix of Jaccard distances of communities (i.e. dissimilarity
matrix)• Predictors = environmental variables + region (factor) + richness• Constrained (canonical) ordination – significance testing etc.
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Archaeap = 0.006R2 = 0.05
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Bacteriap = 0.001R2 = 0.12
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Fungip = 0.001R2 = 0.14
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Eukaryap = 0.001R2 = 0.15
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Summary
• Richness• Catchment
Taxon IC TOC NO3 Conductivity
Archaea + ++ +
Bacteria ++ +
Fungi ++ + +
Eukarya ++
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Conclusions• Models significant (p < 0.01) BUT low R2 (< 0.16)• Experimental power? N = 36
OR
Selection & dispersal limitation weak forces in GW?• Oligotrophic - selection slow relative to other processes• Functional redundancy (i.e. small fitness differences)• Sparse populations & limited selective interactions• Resilience: metabolic flexibility, dormancy, resistant structures• Environmental stability, niche construction, refugia, micro-habitats Neutral ecosystem?
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Current work
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Thank you
Acknowledgements• Supervisors: Grant Hose, Adam Stow, David Nipperess, John Ellis• WRS: Martin Anderson, Peter Graham• Funding: ARC/MQ• Mentoring & molbio: Paulsen & Emma V labs
@mixtrak