Sexual differences rather than flight performance underlie movement and exploration in a tropical butterfly

Abstract

1. Individual movement behaviour governs several routine processes, and may scale up to important ecological processes, including dispersal. However, movement is affected by a wealth of factors, including abiotic conditions, flight performance, and behavioural traits. Although it has been historically assumed that insect flight is in the first place ruled by physiology and morphology, researchers have only recently begun to understand the potentially important role of behavioural traits.2. This study aims to disentangle the relative importance of thermal conditions during development, and especially flight performance (capacity), versus behaviour (intrinsic motivation) in relation to movement attributes (i.e. time until take-off, number of positions visited) under controlled laboratory conditions in the tropical butterfly Bicyclus anynana.3. As predicted, links were found between flight performance (forced flight) and morphological traits (body size). However, this link was less pronounced for movement and exploratory behaviour, suggesting a more pronounced role of intrinsic motivation on the actual decision to move, or not. Thus, flight performance and movement may not be intimately associated.4. Flight behaviour was mainly determined by sexual differences, with males showing better flight performance, higher mobility, and enhanced exploration than females.5. Lower developmental temperatures increased thorax-abdomen ratio, thorax mass, and exploratory behaviour, and decreased wing loading. This may potentially aid flight capacity under thermally challenging conditions. 6. This study adds to the growing evidence that behavioural traits should not be neglected when investigating movement and dispersal, as they may well play a crucially important role.

Silencing of the phosphofructokinase gene impairs glycolysis and causes abnormal locomotion in the subterranean termite Reticulitermes chinensis Snyder

“…2B, C). Similar behaviour was shown by males of the tropical butterfly Bicyclus anynana, which exhibited the higher mobility than female butterflies (Reim et al, 2019). A previous study also revealed a sexually dimorphic response to stress (mechanical perturbation and adult crowding) in Drosophila females, which exhibited reduced motivation towards the exploration of novel habitats (Lall et al, 2019).…”

The importance of including habitat-specific behaviour in models of butterfly movement

“…A limitation of this approach is that it ignores, or simplifies, activity budgets so that time spent stationary or duration of flights are only very roughly approximated. This may limit our understanding of the effects of motivation, activity or resources density on movement rates as they may differ between substantially between habitats and sexes (Reim et al 2019). The effects of changing behaviour in movement models can have strong effects on their predictions (Lima and Zollner 1996;Morales and Ellner 2002;Pauli et al 2013) and habitatdependent changes in movement rates have been quantified for only a small minority of species (Zalucki and Kitching 1982;Odendaal et al 1989;Roland et al 2000;Fownes and Roland 2002;Schtickzelle et al 2007;Ovaskainen et al 2008b;Schultz et al 2019).…”

Heat stress reduced survival but sped up development in Heliconius erato butterflies

“…Greater wing loading may translate into reduced flight performance and dispersal ability as shown in experiments with Monarch butterflies (Soule et al, 2020), potentially leading to lower fitness and reproductive success despite the enhanced growth rate under warmer temperatures. This has been found in the tropical B. anynana butterflies as well, where under increased developmental temperature, male butterflies tend to show better flight performance and higher mobility and stronger intrinsic motivation for movement and exploratory behaviour than females (Reim et al, 2019). Similar results to the temperature‐wing loading relationship are also found in Drosophila (Fallen) (Diptera: Drosophilidae) (Fraimout et al, 2018).…”

“…Females often have a higher body mass due to a positive correlation between body size and fecundity, whereas males are typically selected for larger wings, which increases their mating opportunities (Blanckenhorn et al, 2007;Deinert et al, 1994;Gotthard et al, 1994;Honěk, 1993;Montejo-Kovacevich et al, 2019). This sexual difference in adult body mass has been seen in other butterfly species, including the copper butterfly (Fischer & Fiedler, 2000) and the B. anynana butterflies (Reim et al, 2019). Although this can be explained by fecundity selection, where female reproductive success is determined by adult body mass (Blanckenhorn et al, 2007;Gotthard, 2008), this effect might be more subtle in Heliconius butterflies as they feed on pollen to boost both lifespan and egg production.…”