The consequences of photoperiodism for organisms in new climates

A change in climate is known to affect seasonal timing (phenology) of the life stages of poikilothermic organisms whose development depends on temperature. Less understood is the potential for even greater disruption to the life cycle when a phenology shift exposes photoperiod-sensitive life stages to new day lengths. We present a conceptual framework and model to investigate the ways that photoperiod-cued diapause can interact with a change in climate or latitude to influence voltinism in poikilothermic organisms. Our degree-day phenology model combines detailed spatial climate data, latitude- and date-specific photoperiods, and development and photoperiod response parameters. As an example, we model the biological control beetle Galerucella calmariensis and map the number of generations expected following its introduction into diverse climates throughout the continental United States. Incorporation of photoperiodism results in a complex geography of voltinism that differs markedly from predictions of traditional phenology models. Facultative multivoltine species will be prone to univoltism when transported to either warmer or southern climates due to exposure of the sensitive stage to shorter day lengths. When moved to more northern locations, they may attempt too many generations for the season duration thereby exposing vulnerable life stages to harsh weather in the fall. We further show that even small changes in temperature can result in large and unexpected shifts in voltinism. Analogous effects may be expected for organisms from wide variety of taxa that use photoperiod as a seasonal cue during some stage of their life cycle. Our approach is useful for understanding the performance and impacts of introduced pests and beneficial organisms as well as for predicting responses of resident species to climate change and climate variability.This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecapKeywords: seasonal asynchrony, climate change, biological control, introduced species, model, seasonal adaptation, invasive pests, phenology, diapause, voltinism, phenological mismatch, photoperiodKeywords: seasonal asynchrony, climate change, biological control, introduced species, model, seasonal adaptation, invasive pests, phenology, diapause, voltinism, phenological mismatch, photoperio

Data used in: The Consequences of Photoperiodism for Organisms in New Climates.

The data represent 48-state USA weather and climate data (both site and gridded), biological phenology (developmental) models, combined with photoperiod response (diapause inducing sensitivity to short daylengths). The example data sets are specific to a single insect biological control organism (a leaf beetle introduced to control purple loosestrife, an invasive weed), but the methods and ideas are relevant to many, or perhaps most, insects as well as many plants and other invertebrates. A metadata file is included to describe how the data was developed and used for the publication they are associated with

Appendix A. Method detail: phenological event and voltinism mapping.

Method detail: phenological event and voltinism mapping