Threshold Indicator Taxa Analysis (TITAN) – a potential tool for

ecological management?

Ray Biastoch Environmental Monitoring and Data Management TRCA SOSMART Spring Meeting April 10, 2015

Ecological thresholds

What are they? • Transition points (or zones of rapid change) in

biological community in response to small, continuous increases in a stressor

(Baker and King 2010)

Ecological thresholds

Why are they important? • Anthropogenic environmental gradients/stressors

can represent evolutionarily novel physical/chemical conditions

• A biological community may abruptly respond at a critical point along novel gradient

• Ecological management applications

(Baker and King 2010)

Predecessors/Alternatives to TITAN

• Most models

– Are univariate, not multivariate – At ecosystem-scale, not particular biological

community – Assume species respond in a linear fashion – Exclude rare species, but these species may be more

sensitive to stressor

Advantages of TITAN

• Based on individual species response, assesses when there is threshold response in biological communities to an increasing stressor

• Distinguishes the strength and direction of species response

• Identifies when most species respond = community threshold

• Useful: – For species rich communities – If most species occur infrequently

Advantages of TITAN

• Non-parametric • Currently only available in R • No complicated statistical analysis, just interpret

graph! • Not a hypothesis test, no p values • Similar to ordinations, this analysis is exploratory

• 2013 benthic invertebrate data

• OBBN sampling • LPL identification

(genus/species) • 130 sites, 9

watersheds across TRCA jurisdiction

• >XXX taxa

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MI T

axa

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Wallace, A.M. and R.G. Biastoch. 2016.

• 2013 benthic invertebrate data

• OBBN sampling • LPL identification

(genus/species) • 130 sites, 9

watersheds across TRCA jurisdiction

• >XXX taxa • Est. chloride based

on conductivity on sampling date

Sen

sitiv

e B

MI T

axa

Tole

rant

BM

I Tax

a

Wallace, A.M. and R.G. Biastoch. 2016. 120 640

Summary

• TITAN provides a fairly straight-forward yet robust method for identifying ecological community thresholds along an environmental gradient

• Does TITAN results agree with other urban/impervious study results? i.e. <10% imperviousness?

• Ray Biastoch rbiastoch@trca.on.ca or 289.268.3945

Useful References

• Baker, M. and R. King. 2010. A new method for detecting and interpreting biodiversity and ecological community thresholds. Methods in Ecology and Evolution 1:25-37.

• Baker, M. and R. King. 2013. Of TITAN and straw men: an appeal for greater understanding of community data. Freshwater Science 352:489-506.

• King, R. S., M. E. Baker, P. F. Kazyak, and D. E. Weller. 2011. How novel is too novel? Stream community thresholds at exceptionally low levels of catchment urbanization. Ecological Applications 21:1659–1678.

• Porter-Goff, E. R., P. C. Frost, M. A. Xenopoulos. 2013. changes in riverine benthic diatom community structure along a chloride gradient. Ecological Indicators 32:97-106.