Pale by comparison: competitive interactions between signaling female glow-worms

Borshagovski, Anna‐Maria; Baudry, Gautier; Hopkins, Juhani; Kaitala, Arja

doi:10.1093/beheco/ary161

Cited by 11 publications

(16 citation statements)

References 31 publications

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“…Our finding of low mate attraction success under artificial light aligns with earlier studies that found streetlights hamper mate attraction [ 27 , 28 ]. Females can respond to light, as they move away from green LED lights imitating conspecific females [ 38 ], but bright artificial light from streetlights is stronger and of different wavelength than the glow of females, which may explain the different responses. During the day, females seldom move more than a few centimetres, as they spend the time in refuges [ 18 , 27 , 33 , 39 ], and relocation, therefore, depends on movement during the night.…”

Section: Discussionmentioning

confidence: 99%

Reproduction under light pollution: maladaptive response to spatial variation in artificial light in a glow-worm

et al. 2020

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The amount of artificial light at night is growing worldwide, impacting the behaviour of nocturnal organisms. Yet, we know little about the consequences of these behavioural responses for individual fitness and population viability. We investigated if females of the common glow-worm Lampyris noctiluca —which glow in the night to attract males—mitigate negative effects of artificial light on mate attraction by adjusting the timing and location of glowing to spatial variation in light conditions. We found females do not move away from light when exposed to a gradient of artificial light, but delay or even refrain from glowing. Further, we demonstrate that this response is maladaptive, as our field study showed that staying still when exposed to artificial light from a simulated streetlight decreases mate attraction success, while moving only a short distance from the light source can markedly improve mate attraction. These results indicate that glow-worms are unable to respond to spatial variation in artificial light, which may be a factor in their global decline. Consequently, our results support the hypothesis that animals often lack adaptive behavioural responses to anthropogenic environmental changes and underlines the importance of considering behavioural responses when investigating the effects of human activities on wildlife.

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Section: Discussionmentioning

confidence: 99%

Reproduction under light pollution: maladaptive response to spatial variation in artificial light in a glow-worm

et al. 2020

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“…Here, particularly female larvae close to the pupation stage were found to disperse by moving from their more forested hunting grounds, presumably towards drier and more open habitats, where adult females were often found performing their nightly glow displays. The suitability of a given site for the displays of an adult female may be affected by at least behavioural interactions among females, population size (driving competitive interactions), visibility to ensure effective mate attraction and egg-laying opportunities nearby (Hopkins 2018;Borshagovski et al 2019;Elgert et al 2020Elgert et al , 2021Lehtonen and Kaitala 2020). Additionally, a female's egg-laying site should not be located too far from where the newly hatched offspring can find their first meal after hatching later in the season.…”

Section: Discussionmentioning

confidence: 99%

“…If the habitat types differ with regard to the distance from which females arrive to their glowing spots along the road, the observed female numbers might bias towards that specific habitat. Fourth, mate attraction success of displaying females is known to be negatively affected by the proximity of rivals (Hopkins 2018;Lehtonen and Kaitala 2020), which may also be driving females to disperse farther away from each other before or after pupation (see Borshagovski et al 2019), resulting in increased dispersal away from habitats with high larva densities (even in the absence of a specific target habitat type). More generally, our results are compatible with the idea that dispersal, even in females, can be driven by density-dependent factors, such as competition for breeding opportunities (Dobson and Jones 1985;Matthysen 2005;Arlt and Pärt 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Aside from buildings belonging to the research station at the end of the road, there is a low number (< 10) of houses along the road, and only a short stretch of it has streetlights (~100 m, on one side). The study site was selected due to the logistic convenience of it being close to the research station and because previous studies had showed that glow-worms inhabit the area (Borshagovski et al 2019(Borshagovski et al , 2020Elgert et al 2020Elgert et al , 2021Lehtonen and Kaitala 2020). More generally, the European glow-worm has a wide range from Iran (N32°) to central Finland (N64°) (Samin et al 2018;Borshagovski et al 2020), with the species being on the decline across Europe, as are many other Lampyrid species globally (Lewis et al 2020).…”

Section: Methodsmentioning

confidence: 99%

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High road mortality during female-biased larval dispersal in an iconic beetle

Lehtonen

Babic

Piepponen

et al. 2021

Behav Ecol Sociobiol

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Animals often disperse from one habitat to another to access mates or suitable breeding sites. The costs and benefits of such movements depend, in part, on the dispersing individuals’ phenotypes, including their sex and age. Here we investigated dispersal and road-related mortality in larvae of a bioluminescent beetle, the European common glow-worm, Lampyris noctiluca, in relation to habitat, sex and proximity of pupation. We expected these variables to be relevant to larval dispersal because adult females are wingless, whereas adult males fly when searching for glowing females. We found that dispersing glow-worm larvae were almost exclusively females and close to pupation. The larvae were often found on a road, where they were able to move at relatively high speeds, with a tendency to uphill orientation. However, each passing vehicle caused a high mortality risk, and we found large numbers of larvae run over by cars, especially close to covered, forest-like habitat patches. In contrast, adult females in the same area were most often found glowing in more open rocky and grassy habitats. These findings demonstrate an underappreciated ecological strategy, sex-biased dispersal at larval phase, motivated by different habitat needs of larvae and wingless adult females. The results are also consistent with roads being an ecological trap, facilitating dispersal and presumably females’ signal visibility but causing severe larval mortality just before the reproductive stage. Hence, in addition to the previously recognised threats of urbanisation, even low traffic volumes have a high potential to negatively affect especially females of this iconic beetle. Significance statement Animals sometimes need to move from one habitat to another to find mating partners or breeding sites. We found this need to result in strongly female-biased larval dispersal in the European common glow-worm, a beetle known for the glow of wingless females that attract flying males to mate. Female larvae moving between habitats often used a road or trail but perished in high numbers when run over by cars. Hence, roads are likely to be ecological traps for the female glow-worm larvae, attracting them during dispersal, but causing grave mortality. The sex-biased larval dispersal, demonstrated in this study, is a poorly known ecological strategy that was found to be very risky in a human-modified landscape.

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“…gadm.org), version 3.4, in April 2018 were low, and the female glowing capacity may have been challenged. After the glow measurement, we measured the width of the back shield (the pronotum) with a Vernier calliper, as it is a good proxy of female body size (Hopkins et al 2015;Borshagovski et al 2019). We measured each female only once and then returned it to its original spot of collection.…”

Section: Measurementsmentioning

confidence: 99%

When night never falls: female sexual signalling in a nocturnal insect along a latitudinal gradient

Borshagovski

Saari

Lehtonen

et al. 2020

Behav Ecol Sociobiol

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The environment can play an important role in animal communication by affecting signal transmission and detection. Variation in the signalling environment is expected to be especially pronounced in widely distributed species, potentially affecting how their signals are detected. Such environmental variability is presumably relevant for sedentary females of a nocturnal capital breeder, the European common glow-worm (Lampyris noctiluca), which produce green light during the night to attract flying males to mate. Being widely distributed in Europe, glow-worm populations are exposed to both rapidly descending, darker summer nights in the south, and slowly dimming, brighter summer nights further north, with the latter potentially posing challenges to the visibility of the female glow. To test how female signalling is affected by latitude, we sampled glowing females during summer nights along a latitudinal gradient in Finland, Northern Europe, and used a novel apparatus to measure the intensity and peak wavelength (hue/colour) of their glow. Surprisingly, females at higher latitudes, similar to those at lower latitudes, were commonly glowing during the brightest (and hence the shortest) nights of the year. Females also glowed brighter in more northern areas, partly due to their larger body size, whereas the colour of their glow was not associated with latitude. Since females glow even during midsummer, independent of latitude, the increase in glow intensity at higher latitudes presumably serves to maintain signal visibility in brighter signalling conditions. Overall, these findings highlight the influence of environmental conditions on the evolution of sexual signals, especially in the context of species distribution range. Significance statement When environmental conditions impact signal transmission and perception, local conditions can have a crucial role in shaping animal communication and signal evolution. To analyse how dark-dependant common glow-worm females cope with variable nocturnal light environments, we used a novel apparatus, presumably not applied to living animals before, to measure female glow intensity at various latitudes along a latitudinal gradient. Interestingly, females did not avoid signalling during the brightest summer nights, but instead, their glow intensity and body size both increased with latitude. These findings suggest that females can ensure visibility to mate-searching males over a range of local conditions. Our study therefore shows how females can adapt to environmental constraints on signal visibility, and how the expression of sexual signals is shaped not only by social interactions but also by the signalling environment.

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Pale by comparison: competitive interactions between signaling female glow-worms

Cited by 11 publications

References 31 publications

Reproduction under light pollution: maladaptive response to spatial variation in artificial light in a glow-worm

Reproduction under light pollution: maladaptive response to spatial variation in artificial light in a glow-worm

High road mortality during female-biased larval dispersal in an iconic beetle

When night never falls: female sexual signalling in a nocturnal insect along a latitudinal gradient

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