Can your behaviour blow you away? Contextual and phenotypic precursors to passive aerial dispersal in the wheat curl mite

Authors: LASKA, ALICIA - Adam Mickiewicz University; Rector, Brian; SKORACKA, ANNA - Adam Mickiewicz University; KUCZYNSKI, LECHOSLAW - Adam Mickiewicz University

Submitted to: Journal of Animal Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2019
Publication Date: 8/10/2019
Citation: Laska, A., Skoracka, A., Rector, B.G., Kuczynski, L. 2019. Can your behaviour blow you away? Contextual and phenotypic precursors to passive aerial dispersal in the wheat curl mite. Journal of Animal Behavior. 155(2019):141-151.

Interpretive Summary: Many eriophyoid mite species, like the wheat curl mite (WCM), are important agricultural pests, while some are beneficial weed biocontrol agents. However, much is still unknown about their dispersal potential and efficacy, as they are microscopic and disperse passively on wind currents. The purpose of this study was to gain a better understanding of possible predictors, including behavioral, morphological, and environmental, of eriophyoid mite dispersal, using WCM as the study subject. Mites were observed and measured in a wind tunnel under a range of wind speeds. Chain-forming behavior among groups of mites was found to increase the likelihood of dispersal, with mites that formed chains being more elongate than the average mite, particularly at moderate wind speeds. By contrast, mites standing upright on their hind-quarters did not disperse, contrary to what had been predicted from prior observations. The results provide important insight into passive mite dispersal and are relevant to both pest managers and biocontrol practitioners.

Technical Abstract: Dispersal involves many behavioural impications, which if ineffective or incorrect would be costly with serious fitness consequences. Those costs are particularly high for passively dispersing organisms for which direction of movement is determined by external forces. In this study, we investigate whether environment and morphology influence dispersal behaviours and decisions of a passive, aerially dispersing organism, using the eriophyoid wheat curl mite, Aceria tosichella, MT-1 genotype (WCM MT-1) as study system. We used a wind tunnel to generate stable wind speeds at intervals between 0.2 – 5.7 m/s,. We analyzed mite behaviour, morphology and dispersal rate during five-minute intervals for each wind speed treatment. We showed that dispersal is phenotype- and context-dependent with an important behavioural component. Chain-formation among individuals significantly increased the likelihood of lift-off and mites dispersing in chains were significantly more elongated compared to controls. This difference in shape significantly interacted with wind speed but diminished at wind speeds above 4 m/s. We demonstrated a significant interaction between body shape of mites standing upright and environmental context - wind speed. In the lowest wind speed (below 2 m/s) upright individuals were rounder. However, we found that the upright position was not related to the likelihood of being blown away. The results indicate that WCM MT-1 dispersal is influenced by the interaction of behaviour, morphology and environment. Our study represents a substantial step toward explaining WCM MT-1 dispersal and its colonization potential, with implications for passively dispersing organisms in general and other eriophyoid species of economic import in particular.