A double-spiral maze and hi-resolution tracking pipeline to study dispersal by groups of minute insects

Abstract

Minute insects such as parasitic micro-wasps have high basic and applied importance for their widespread use as biocontrol agents. Their dispersal is a phenotype of particular interest. Classically, it is evaluated using field releases, but those are time consuming, costly, and their results highly variable, preventing high-throughput and repeatability. Alternatively, dispersal can be studied using small-scale assays, but those neglect important higher-scale processes. Consequently, proper evaluation of dispersal is often complicated or lacking in academic studies and biocontrol breeding programs. Here we introduce a new method, the double-spiral maze, that allows the study of spatial propagation of groups of micro-wasps at relevant scales (several hours and meters), retaining high throughput and experimental power. The method records the location of every individual at every time, enabling accurate estimates of diffusion coefficients or other dispersal metrics. We describe this affordable, scalable, and easy-to-implement method, and illustrate its application with a species of agricultural interest.

Space use of invertebrates in terrestrial habitats: Phylogenetic, functional and environmental drivers of interspecific variations

“…The development of innovative tracking methods should improve the spectrum of animals whose movements might be studied in future years (see e.g. Cointe et al, 2023). For the tiniest invertebrates however, the contribution of active movements to overall displacements is likely to strongly decrease compared to the contribution of passive phoretic movements, especially for dispersal.…”

MoveR: an R package for easy processing and analysis of animal video-tracking data

“…Accordingly, improving our understanding of how animals move and behave in various contexts may help to tackle critical conservation aims [17,18], including the need to stabilize or increase the numbers of small or declining populations [19,20], ensure the dispersal of biocontrol agents under various conditions [21,22] and control invasive or pest species [23,24]. For instance, a recent study has shown that combining biopesticides (i.e., essential oils) and biocontrol agents ( Trichogramma evanescens ) to mitigate pest species in agricultural fields may be counter-productive by altering biocontrol agents’ fitness and behavior and hence their efficiency [21].…”