Behaviour before beauty: Signal weighting during mate selection in the butterfly Papilio polytes

Abstract

Mating displays often contain multiple signals. Different combinations of these signals may be equally successful at attracting a mate, as environment and signal combination may influence relative signal weighting by choosy individuals. This variation in signal weighting among choosy individuals may facilitate the maintenance of polymorphic displays and signalling behaviour. One group of animals known for their polymorphic patterning are Batesian mimetic butterflies, where the interaction of sexual selection and predation pressures is hypothesized to influence the maintenance of polymorphic wing patterning and behaviour. Males in the female‐limited polymorphic Batesian mimetic butterfly Papilio polytes use female wing pattern and female activity levels when determining whom to court. They court stationary females with mimetic wing patterns more often than stationary females with non‐mimetic, male‐like wing patterns and active females more often than inactive females. It is unclear whether females modify their behaviour to increase (or decrease) their likelihood of receiving male courtship, or whether non‐mimetic females spend more time in cryptic environments than mimetic females, to compensate for their lack of mimicry‐driven predation protection (at the cost of decreased visibility to males). In addition, relative signal weighting of female wing pattern and activity to male mate selection is unknown. To address these questions, we conducted a series of observational studies of a polymorphic P. polytes population in a large butterfly enclosure. We found that males exclusively courted active females, irrespective of female wing pattern. However, males did court active non‐mimetic females significantly more often than expected given their relative abundance in the population. Females exhibited similar activity levels, and selected similar resting environments, irrespective of wing pattern. Our results suggest that male preference for non‐mimetic females may play an active role in the maintenance of the non‐mimetic female form in natural populations, where males are likely to be in the presence of active, as well as inactive, mimetic and non‐mimetic females.

Quantifying the effects of species traits on predation risk in nature: A comparative study of butterfly wing damage

“…In species in which females appeared to forage less than males, the proportion of symmetrical wing surface loss was higher in females, suggesting that less active butterflies are more frequently attacked while at rest. However, it is questionable to what extent foraging activity is measured by traps catches represents overall activity which also includes mate finding behaviour and oviposition behaviour (Westerman et al, ). One may argue that foraging provides the fuel for flight and thus that more foraging behaviour is correlated with more flight, but this remains to be tested.…”

“…Further insight into how butterfly traits such as activity, flight speed and aposematism (e.g. Westerman et al, ) are correlated with each other would also contribute to understanding links between butterfly traits and wing damage patterns. We also note that our results illustrate that it is especially important to use a phylogenetic approach.…”

“…In addition to differences among species, there are intraspecific differences between the sexes in activity, body size and allometry, coloration, wing shape and anti‐predator tactics in many butterfly species (e.g. Fermon, Waltert, & Mühlenberg, ; Ide, ; Ohsaki, ; Owen & Smith, ; Wallace, ; Westerman et al, ). For example, flight morphology can be in part shaped by mate locating behaviour and may therefore differ between the sexes (Wickman, ).…”

Mimicry genes reduce pre‐adult survival rate in Papilio polytes: A possible new mechanism for maintaining female‐limited polymorphism in Batesian mimicry

“…Since mimicry has obvious survival benefits, the above phenomenon raises the question of how nonmimetic individuals are maintained in populations without being completely replaced by mimetic individuals. This problem has been the focus of many researchers since Darwin's era (e.g., Bates, 1862; Komata, Lin, Iijima, Fujiwara, & Sota, 2016; Kunte, 2009b; Ohsaki, 1995, 2005; Ruxton et al, 2004; Turner, 1978; Wallace, 1867; Westerman et al., 2018, 2019; Wickler, 1968; Zhang, Westerman, Nitzany, Palmer, & Kronforst, 2017).…”

“…Interestingly, mimetic and nonmimetic females co‐occur in almost all populations of P. polytes throughout the distribution range (Sekimura, Fujihashi, & Takeuchi, 2014; Tsurui‐Sato et al, 2019; Westerman et al., 2019); this is in marked contrast to the cases of Papilio ambrax and Papilio phestus in which all females are mimetic (Zhang et al., 2017). On Miyako Island, the establishment of a population of P. aristolochiae, which previously did not exist on the island, resulted in a rapid increase in the proportion of mimetic females of P. polytes in the field.…”