Detecting the influence of rare stressors on rare species in Yosemite National Park using a novel stratified permutation test

Scientific Reports
By: , and 

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Abstract

Statistical models often use observational data to predict phenomena; however, interpreting model terms to understand their influence can be problematic. This issue poses a challenge in species conservation where setting priorities requires estimating influences of potential stressors using observational data. We present a novel approach for inferring influence of a rare stressor on a rare species by blending predictive models with nonparametric permutation tests. We illustrate the approach with two case studies involving rare amphibians in Yosemite National Park, USA. The endangered frog, Rana sierrae, is known to be negatively impacted by non-native fish, while the threatened toad, Anaxyrus canorus, is potentially affected by packstock. Both stressors and amphibians are rare, occurring in ~10% of potential habitat patches. We first predict amphibian occupancy with a statistical model that includes all predictors but the stressor to stratify potential habitat by predicted suitability. A stratified permutation test then evaluates the association between stressor and amphibian, all else equal. Our approach confirms the known negative relationship between fish and R. sierrae, but finds no evidence of a negative relationship between current packstock use and A. canorus breeding. Our statistical approach has potential broad application for deriving understanding (not just prediction) from observational data.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Detecting the influence of rare stressors on rare species in Yosemite National Park using a novel stratified permutation test
Series title Scientific Reports
DOI 10.1038/srep10702
Volume 5
Year Published 2015
Language English
Publisher Nature Publishing Group
Contributing office(s) Western Ecological Research Center
Description 12 p.; Article number: 10702
Country United States
State California
Other Geospatial Yosemite National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N