Invasive beetles travel further on longer legs

Individuals within a species can vary greatly in their ability to move around and disperse within their environment. This variation in movement ability can often be described by physiological, morphological and behavioural traits that are related to dispersal, but the associations among such traits are not always clear-cut or predictable. Previous studies, including work on the invasive cane toad in Australia, have identified that individuals that are larger and have longer legs relative to their body size are able to move farther and faster than smaller or proportionate individuals.

The Centre For Geometric Biology’s Craig White and colleagues Pieter Arnold and Phillip Cassey used an invasive insect species, the red flour beetle, as a model to investigate how movement characteristics related to morphological and physiological traits.

Individual beetles were run through a maze that simulated a complex environment to assess their movement. The researchers identified that movement ability could be described along an axis; individuals that scored positively on this axis moved at higher speed, travelled longer distances, moved continuously, and reached the edge of the maze quicker. Leg-length relative to body size was strongly correlated to movement ability. That is, beetles with relatively long legs had positive movement ability scores, presumably because longer legs allow for longer stride length and therefore a greater movement ability. Surprisingly, body size and metabolic rate (energy expenditure) were unrelated to movement ability. The results suggests that dispersal may be more strongly related to the muscles and structures that directly affect locomotion, rather than body size overall or energy-related traits.

It will be important for future studies to consider locomotor morphology as a foundation for studying variation in movement and dispersal, especially when investigating the ecology and evolution of traits in invasive or pest species.

This research was published in Functional Ecology.