High Exploration Behavior of Termite Propagules Can Enhance Invasiveness

Louis Pailler,Fanny Ruhland,Pierre-André Eyer,Arthur Matte,Christophe Lucas,Alexis Groseiller

doi:10.3389/fevo.2022.840105

Abstract

Social life is usually associated with enhanced propagule pressure, which increases the chance of introducing several individuals during a single introduction event. Social insects are therefore among the most successful invasive species, benefiting from rapid establishment and increased foundation success in new habitats. In termites, propagule pressure may also be increased by the development of reproductive individuals from a small group of foraging workers. This suggests that enhanced exploration activity may increase propagule pressure through an elevated chance of transporting isolated groups of foragers. Here, we analyzed the exploration behavior of three termite species of the Reticulitermes genus, comparing the invasive species Reticulitermes flavipes (testing both native and introduced populations) to the native species Reticulitermes grassei and Reticulitermes lucifugus. Different features representative of the exploration capacity were measured during 48 h, including: the number of tunnels, the length of tunnels, the number of foragers, and the interindividual distance of foragers in a straight line or through tunnels. Our results show that compared to the native Reticulitermes species, R. flavipes foragers from both populations dug more tunnels with a longer total length, and individuals were more spatially dispersed and covered a larger exploration zone. These findings suggest that the enhanced exploration ability of R. flavipes may have played a role in its invasion success, by increasing its propagule pressure through a higher chance of human-mediated transport. In addition, the absence of differences between the native and introduced populations of R. flavipes suggests that the exploration behaviors facilitating the worldwide invasion of this species originated in its native range.

Highlights

Biological invasions are a serious global environmental threat (Walther et al, 2009) and have economic repercussions due to their impairment of ecosystem services and destruction of human infrastructure (Scanes, 2018)
The invasive success of many termite species is enhanced by the development of neotenic reproductives from nymphs or workers, which can transform a small group of workers into a viable propagule (Eyer and Vargo, 2021)
The number of tunnels at 6 h was higher in the two populations of R. flavipes than in R. grassei and R. lucifugus (Tukey’s multiple comparisons test, all p < 0.024; Figure 1A)

Summary

INTRODUCTION

Biological invasions are a serious global environmental threat (Walther et al, 2009) and have economic repercussions due to their impairment of ecosystem services and destruction of human infrastructure (Scanes, 2018). The invasive success of many termite species is enhanced by the development of neotenic reproductives from nymphs or workers, which can transform a small group of workers into a viable propagule (Eyer and Vargo, 2021) Both of these features increase their propagule pressure, as every transported wood/soil material containing a colony fragment may represent an invasive threat (Evans et al, 2013). Using three species of this genus (R. flavipes, R. grassei, and R. lucifugus), we determined whether small groups of workers display differences in their exploration behaviors These small groups were composed of thirty workers – the initial number of individuals required to form a viable propagule (Pichon et al, 2007). We predicted that the two populations of R. flavipes possess higher exploration efficiency compared to the two native species (R. grassei and R. lucifugus), whereby high foraging activity potentially drives invasive success via enhanced propagule pressure

MATERIALS AND METHODS

RESULTS

DISCUSSION