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A Practical Guide to Phylogenetics for Nonexperts
Published on: February 5, 2014
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Correcting for Phylogenetic Autocorrelation in Species Sensitivity Distributions
Dwayne Rj Moore1, Colleen D Priest1, Nika Galic2
1Intrinsik Ltd, New Gloucester, Maine, USA.
Integrated Environmental Assessment and Management
|August 22, 2019
Summary
Species sensitivity distributions (SSDs) often assume independent data, but phylogenetic signals can reduce effective sample size. However, SSDs and hazardous concentrations (HC5s) remain robust even with this dependency.
Area of Science:
- Environmental toxicology
- Ecotoxicology
- Computational biology
Background:
- Species sensitivity distributions (SSDs) are crucial for ecological risk assessment.
- A key assumption in SSD derivation is data independence, which may be violated due to phylogenetic relationships.
- Phylogenetic signal, or the tendency for related species to have similar traits, can introduce autocorrelation in toxicity data.
Purpose of the Study:
- To investigate the impact of phylogenetic signal on the derivation of SSDs.
- To assess whether ignoring phylogenetic relationships affects the accuracy of SSDs and derived metrics like HC5.
- To evaluate the robustness of SSDs to violations of the independence assumption.
Main Methods:
- Case studies using toxicity data for atrazine and chlorpyrifos across various aquatic and avian species.
- Analysis of full and partial data sets to examine varying phylogenetic signal strengths and sample sizes.
- Statistical evaluation of the significance of phylogenetic signal and its effect on effective sample size and SSD fitting.
Main Results:
- Significant phylogenetic signal was detected in some toxicity data sets (e.g., most chlorpyrifos data), but not others (e.g., atrazine data).
- A significant phylogenetic signal reduced the effective sample size, with greater reduction observed for stronger signals.
- Despite reduced effective sample sizes, fitted SSDs and hazardous concentrations for the 5th percentile of species (HC5) showed minimal impact, even in the tails of the distribution.
Conclusions:
- Accounting for phylogenetic signal in SSD derivation is statistically recommended due to potential violations of the independence assumption.
- SSDs and HC5 values demonstrate robustness to deviations from the independence assumption caused by phylogenetic signal.
- The findings suggest that while accounting for phylogeny is good practice, current SSD methods are resilient to its effects in many cases.
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