Abstract
This article is the third and last of a series of models developed to investigate the impact of climate on the spatiotemporal biology of parasitoids. After two earlier papers investigating Tranosema rostrale and Meteorus trachynotus, this last article concerns the tachinid fly Actia interrupta (Diptera: Tachinidae). An individual-based model of the seasonal biology of A. interrupta was developed to determine the impact of climate on its interactions with two of its hosts, the spruce budworm Choristoneura fumiferana (Lepidoptera: Tortricidae) and the obliquebanded leafroller C. rosaceana in eastern North America. The model is based on the developmental responses of ‘the parasitoid’s successive life stages and the ovipositional response of adult females to temperature. It was found that the number of generations this parasitoid undergoes each year varies geographically from two to four, and that its potential growth rate, as dictated by synchrony with larvae of its overwintering host C. rosaceana, is highly patterned geographically and topographically as a result of phenological matching with larvae of obliquebanded leafroller entering diapause in late summer.
Highlights
We developed the general approach using the ichneumonid larval parasitoid Tranosema rostrale (Brischke) (Hymenoptera: Ichneumonidae) in interaction with two main host tortricids, the spruce budworm, C. fumiferana and the obliquebanded leafroller (OBL), C. rosaceana (Harris) [19]
It should be noted that development at the lower end of the temperature range was not measured precisely and the value of the lower threshold temperature was set at Tb = 0 for the larval stages developing afterdiapause in OBL larvae
To better understand the seasonal biology of Actia interrupta, in particular as it pertains to synchrony between the adult fly and larvae of two of its major hosts in eastern conifer forests, the SBW and the OBL, we modeled the developmental responses to temperature of the parasitoid’s three life stages: maggots inside the host, pupae and adults
Summary
Changes in the distribution and demographic behavior of herbivorous insect populations are feared [2]. Many biotic and abiotic factors influence the development and spread of outbreaks, and complex interactions are at play. Insect development is directly influenced by daily temperature fluctuations, and their distribution is influenced by local climate and by climate change [5]. While it is relatively easy to quantify the direct impact of temperature on the different life stages of insects in the laboratory [6,7,8], temperature is not the only important factor. Ecological interactions with other organisms (host trees, natural enemies, competitors) play an important role [9,10]. The influence of climate on predator−prey interactions is profound, and can affect the ability of natural enemies to regulate their prey populations [11,12].
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