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Threshold Indicator Taxa ANalysis

Matthew Baker, Department of Geography and Environmental Systems, UMBC
Ryan King, Department of Biology, Baylor University


Threshold Indicator Taxa ANalysis (TITAN) is a straight-forward and objective method of identifying and interpreting ecological community thresholds along an environmental gradient. TITAN is based on indicator species analysis (IndVal), a widely accepted method for identifying indicator taxa among levels of a categorical variable. In TITAN, we extend principles of IndVal to identify the value of a continuous variable, x, resulting in the optimal partitioning of sample units based on normalized indicator values (z) for individual taxa and additive response of all indicator z-scores (sum(z)) at the community level. Resampling procedures are used to estimate reliability of indicators and uncertainty surrounding thresholds and this can be computationally intensive with large datasets. We are exploring the ground-breaking insight provided by TITAN in a variety of large community datasets from across the US.