Age-Dependent Developmental Response to Temperature: An Examination of the Rarely Tested Phenomenon in Two Species (Gypsy Moth (Lymantria dispar) and Winter Moth (Operophtera brumata)).

David Gray

doi:10.3390/insects9020041

Abstract

The pervading paradigm in insect phenology models is that the response to a given temperature does not vary within a life stage. The developmental rate functions that have been developed for general use, or for specific insects, have for the most part been temperature-dependent but not age-dependent, except where age is an ordinal variable designating the larval instar. Age dependence, where age is a continuous variable, is not often reported (or investigated), and is rarely included in phenology models. I provide a short review of the seldom-investigated phenomenon of age dependence in developmental response to temperature, and compare the derivation of the winter moth egg phenology model by Salis et al. to the derivation of another egg phenology model with age-dependent responses to temperature I discuss some probable reasons for the discrepancies (acknowledged by Salis et al.) between modelled and observed developmental rates of the winter moth, and discuss the contribution that geographically robust phenology models can make to estimates of species distributions.

Highlights

IntroductionPhenological studies remained principally limited to observations of phenological events until Réaumur [2] observed that differences between locations in phenological events could be explained by differences in the sum of daily temperatures between some arbitrary starting date to the date of the event
The history of phenological observations dates to at least the 11th C BCE [1]
To incorporate age-dependent developmental rates—which Salis et al [10] detected from their experimental observations of developmental duration—into their phenology model, the authors

Summary

Introduction

Phenological studies remained principally limited to observations of phenological events until Réaumur [2] observed that differences between locations in phenological events could be explained by differences in the sum of daily temperatures between some arbitrary starting date to the date of the event. The developmental responses of organisms to temperature have been of interest since. Insect phenology models have been built as components of integrated pest management (IPM) programs [3] for more efficacious applications of pesticides and for optimizing biological control tactics [4]. Phenology models have been used in investigations of biological ranges of invading insects under current [5] and future [6]. Phenology models provide valuable insight into the potential disruption of the important synchrony between insect herbivores and their hosts under future climates [9]

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