Male sex pheromone release and female mate choice in a butterfly

Abstract

SUMMARY In butterflies female mate choice is influenced by both visual and olfactory cues, the latter of which are important at close range. Males of the green-veined butterfly, Pieris napi, are known to release citral(mixture of geranial and neral, 1:1), but its role(s) and conditions of release are not known. Here, we show that male P. napi release citral when interacting with conspecific males, conspecific females, heterospecific males and also when alone. The amount of citral released correlated strongly with male flight activity, which explained more than 70% of the variation. This suggests that males do not exercise control over turning release on or off, but rather that citral is emitted as a passive physical process during flight. Electroantennogram experiments showed that female antennal response was ten times more sensitive to citral than male response. Females expressed acceptance behavior when exposed to models made with freshly excised male wings or those treated with citral following chemical extraction, but not to ones with extracted wings only. Hence, these behavioral and electrophysiological tests provide strong evidence that citral is a signal from the male directed to the female during courtship, and that it functions as a male sex pheromone.

Co-option of a motor-to-sensory histaminergic circuit correlates with insect flight biomechanics

“…While the distribution of turning angles in moths is either bimodal or normal [45], the distribution in butterflies is uniform across all angles [46] and butterflies have been shown to prioritize flower colour over scent [47]. Furthermore, although male and female butterflies produce pheromones, they are used as short-range cues (1-2 m) to determine mate quality after a potential mate has been located visually [27,48], whereas male moths locate female moths via pheromones over distances of several tens of meters [49]. Although the path of the wing tip during each wing stroke is similar between D. melanogaster and moths [50], the wing-beat frequency of D. melanogaster is approximately 190-230 Hz [51], much higher than the approximately 27-28 Hz wing-beat frequency of M. sexta [21] and much higher than the upper limit of what antennal responses in D. melanogaster can track [52].…”

Selection on male sex pheromone composition contributes to butterfly reproductive isolation

“…This first selection still resulted in more compounds than known from data obtained using GC-EAD and behavioural assays in B. anynana, in which the MSP components are the top third of the most abundant compounds [25 -27]. Moreover, MSP components that experience directional sexual selection are usually more abundant than other compounds (see [30] and examples in Lepidoptera [31,32], Hymenoptera [33], lizards [34] or elephants [35]). Thus, from the first selection, we kept the top third most abundant compounds for each Bicyclus species, forming the dataset of pMSP components used in all subsequent analyses (electronic supplementary material, table S1).…”

Estimating the Mating Success of Male Butterflies in the Field

“…In butterflies, many laboratory experiments have demonstrated the occurrence of female preference for particular male traits, including wing coloration (Krebs and West 1988;Robertson and Monteiro 2005;Andersson et al 2007). However, the conclusions of these studies have rarely been validated against data obtained in more natural field-based settings (Kemp and Rutowski 2011).…”