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Mischaracterising density dependence biases estimated effects of coloured covariates on population dynamics

In English

Författare

  • Andreas Linden
  • Mike S. Fowler
  • Niclas Jonzén

Summary, in English

Environmental effects on population growth are often quantified by coupling environmental covariates with population time series, using statistical models that make particular assumptions about the shape of density dependence. We hypothesized that faulty assumptions about the shape of density dependence can bias estimated effect sizes of temporally autocorrelated covariates. We investigated the presence of bias using Monte Carlo simulations based on three common per capita growth functions with distinct density dependent forms (theta-Ricker, Ricker and Gompertz), autocorrelated (coloured) 'known' environmental covariates and uncorrelated (white) 'unknown' noise. Faulty assumptions about the shape of density dependence, combined with overcompensatory intrinsic population dynamics, can lead to strongly biased estimated effects of coloured covariates, associated with lower confidence interval coverage. Effects of negatively autocorrelated (blue) environmental covariates are overestimated, while those of positively autocorrelated (red) covariates can be underestimated, generally to a lesser extent. Prewhitening the focal environmental covariate effectively reduces the bias, at the expense of the estimate precision. Fitting models with flexible shapes of density dependence can also reduce bias, but increases model complexity and potentially introduces other problems of parameter identifiability. Model selection is a good option if an appropriate model is included in the set of candidate models. Under the specific and identifiable circumstances with high risk of bias, we recommend prewhitening or careful modelling of the shape of density dependence.

Publiceringsår

2013

Språk

Engelska

Sidor

183-192

Publikation/Tidskrift/Serie

Population Ecology

Volym

55

Issue

1

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Biological Sciences

Nyckelord

  • Autoregressive models
  • Environmental forcing
  • Prewhitening
  • Statistical
  • inference
  • Theta-Ricker model
  • Time series

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1438-390X