Cumulative weather effects can impact across the whole life cycle

Hindle, Bethan J.; Pilkington, Jill G.; Pemberton, Josephine M.; Childs, Dylan Z.

Abstract

Predicting how species will be affected by future climatic change requires the underlying environmental drivers to be identified. As vital rates vary over the lifecycle, structured population models derived from statistical environment-demography relationships are often used to inform such predictions. Environmental drivers are typically identified independently for different vital rates and demographic classes. However, these rates often exhibit positive temporal covariance, suggesting the vital rates respond to common environmental drivers. Additionally, models often only incorporate average weather conditions during a single, a priori chosen time window (e.g. monthly means). Mismatches between these windows and the period when the vital rates are sensitive to variation in climate decrease the predictive performance of such approaches. We used a demographic structural equation model (SEM) to demonstrate that a single axis of environmental variation drives the majority of the (co)variation in survival, reproduction, and twinning across six age-sex classes in a Soay sheep population. This axis provides a simple target for the complex task of identifying the drivers of vital rate variation. We used functional linear models (FLMs) to determine the critical windows of three local climatic drivers, allowing the magnitude and direction of the climate effects to differ over time. Previously unidentified lagged climatic effects were detected in this well-studied population. The FLMs had a better predictive performance than selecting a critical window a priori, but not than a large-scale climate index. Positive covariance amongst vital rates and temporal variation in the effects of environmental drivers are common, suggesting our SEM-FLM approach is a widely applicable tool for exploring the joint responses of vital rates to environmental change.

• Journal Article Type: Article
• Acceptance Date: Jun 13, 2019
• Online Publication Date: Jun 25, 2019
• Publication Date: Oct 1, 2019
• Deposit Date: Jun 25, 2019
• Publicly Available Date: Oct 17, 2019
• Journal: Global Change Biology
• Print ISSN: 1354-1013
• Electronic ISSN: 1365-2486
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 25
• Issue: 10
• Pages: 3282-3293
• DOI: https://doi.org/10.1111/gcb.14742
• Keywords: climate, covariation, density dependence, environmental variation, functional linear model, North Atlantic Oscillation, structural equation model, survival
• Public URL: https://uwe-repository.worktribe.com/output/1492468
• Publisher URL: https://doi.org/10.1111/gcb.14742
• Contract Date: Jun 25, 2019