Modeling Climatic Influences on Three Parasitoids of Low-Density Spruce Budworm Populations. Part 2: Meteorus trachynotus (Hymenoptera: Braconidae)

Jacques Régnière,Rémi Saint-Amant,Véronique Martel,Pierre Therrien,Christian Hébert,Jean-Claude Thireau

doi:10.3390/f12020155

Abstract

This is the second article of a series of three where we develop temperature-driven models to describe the seasonal interactions between parasitoids and their hosts which we use to explore the impact of climate on their spatiotemporal biology. Here, we model the biology of Meteorus trachynotus (Hymenoptera: Braconidae) with an individual-based model of its daily interactions with two host species. This model predicts the performance of the parasitoid in response to temperature affecting its seasonal development and that of the two hosts. We compare model output with an extensive set of field observations from natural host populations. The predicted activity of the first adult parasitoid generation closely matches the seasonal pattern of attack on the spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae) within the limitations of available data. The model predicts 1–4 full generations of M. trachynotus per year in eastern North America, with generations well synchronized with larvae of a known overwintering host, the obliquebanded leafroller Choristoneura rosaceana. The model predicts the observed density dependence of parasitism on spruce budworm. Predicted performance exhibits spatial variation caused by complex life-history interactions, especially synchrony with the overwintering host. This leads to a better performance in warm but not hot environments at middle latitudes and elevations. The model’s predicted spatial patterns correspond closely to our field observations on the frequency of parasitism on spruce budworm. Under climate change, the model predicts that the performance of M. trachynotus populations will improve in the northern portion of its range.

Highlights

The spruce budworm (SBW), Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), is an eruptive tortricid that undergoes spectacular population cycles that last about35–40 years [1] and is an important periodic source of perturbation in boreal forests [2].Many factors interact to cause SBW outbreak cycles [3,4]
We report on the development of an individual-based simulation model of the seasonal biology of M. trachynotus and of its interaction with two of its hosts, SBW and obliquebanded leafroller (OBL), which is based on data from Reference [25] on the relationships between temperature and development, and the existing seasonality models for SBW [32] and OBL [14]
Our objective is to study the impact of climate on M. trachynotus at the seasonal level, through its effect on development, reproduction and synchrony with the larval stages of two well-known tortricid hosts of the parasitoid

Summary

Introduction

35–40 years [1] and is an important periodic source of perturbation in boreal forests [2]. Many factors interact to cause SBW outbreak cycles [3,4]. Parasitoids are important mortality factors in insect populations [5]. The parasitoids of SBW are numerous, diverse, and inscribed in a complex and dynamic food web [6]. The impact of parasitoids on the dynamics of its populations is difficult to quantify and put in perspective with respect to that of other sources of mortality [1,4]. We know that parasitoids play a key role in the decline of outbreaks [3,4,7] and during the prolonged period between outbreaks [8,9,10]

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Conclusion