Jaw morphology and fighting forces in stag beetles

Goyens, Jana; Dirckx, Joris J.J.; Aerts, Peter

doi:10.1242/jeb.141614

Cited by 24 publications

(24 citation statements)

References 44 publications

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“…These determine the shape of the head because a long input lever means that the anterior end of the head must be wider, and the attachment for the jaw closer muscles is at the rear of the head, so larger muscles will be associated with the posterior of the head being enlarged. This relationship between mandible size and head size is also supported by an interspecific comparison which found that species with large heads also have relatively large mandibles 37 . Given this, the clear difference found between morphs of the tri- and tetramorphic species in the geometric morphometric analyses makes sense.…”

Section: Discussionmentioning

confidence: 58%

Diverse and complex male polymorphisms in Odontolabis stag beetles (Coleoptera: Lucanidae)

Matsumoto

Knell

2017

Sci Rep

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When male animals engage in intrasexual contests then any alternative tactics they use can be associated with dimorphisms in the expression of weapons. Some species have recently been found to exhibit trimorphism in their weaponry, suggesting that the processes leading to their evolution and maintenance of these polymorphisms can be more complex than previously thought. Here, we describe the extraordinary diversity of polymorphism within the genus Odontolabis: there are dimorphic species (O. siva and O. platynota), trimorphic species (O. cuvera, as previously described, and O. sommeri s.stricto) and, uniquely, tetramorphic species, with males of O. sommeri lowei and O. brookeana showing four clearly differentiated male morphs: small “Gammas”, “Alphas” which express large, long mandibles, “Betas” which have long mandibles with different morphology and “Boltcutters”, with short, wide mandibles. Such polymorphisms are usually thought of as being maintained as a status-dependent conditional strategy, but we found only one size threshold: in most cases males develop into Gamma males below a certain size but there is no relationship between morph and body size amongst the larger, ‘weaponised’ morphs. We suggest that the complex polymorphisms in these animals are probably maintained by a combination of a conditional strategy and a genetic polymorphism.

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Section: Discussionmentioning

confidence: 58%

Diverse and complex male polymorphisms in Odontolabis stag beetles (Coleoptera: Lucanidae)

Matsumoto

Knell

2017

Sci Rep

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“…The mandible length (ML), head width (HW) and elytra length (EL) of the beetles were measured to the nearest of 0.01 mm using a digital calliper (99MAD027M1, Mitutoyo, Kanagawa, Japan). Mandible length was the average linear distance between the distal tip of the mandible and the axis of the mandibular joint of the two mandibles [7,8,29]; HW was the linear distance between the tips of the protrusions anterior to the eyes; EL was the linear distance between the posterior ends of the scutellum and the elytra. These three measurements were obtained on the day on which the beetles were collected in the field or the 21st day after the eclosion of the beetles reared in the laboratory.…”

Section: Morphological Measurementsmentioning

confidence: 99%

Allometry and Fighting Behaviour of a Dimorphic Stag Beetle Cyclommatus mniszechi (Coleoptera: Lucanidae)

Chen

Hsu

Lin

2020

Insects

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Male stag beetles (Coleoptera: Lucanidae) use their mandibles as weapons to compete for resources and reproduction. Mandible size in stag beetles can be associated with different behaviours and the outcome of male contests. We investigated the allometric relationship between mandible and body size in males of the stag beetle Cyclommatus mniszechi to uncover distinct morphs. The results divided male C. mniszechi into majors and minors with the switch point of mandible length at 14.01 mm. The allometric slope of mandibles was positive for both morphs but was steeper for the minors. We also characterised the fighting behaviour of the different morphs in size-matched contests using sequential analyses. Males matched each other’s behaviour in contests with many physical contacts, no injury and a progression from low towards high aggression and rare de-escalation. Major and minor males employed the same behavioural elements in contests, but major males were more likely to escalate directly into more aggressive phases and minor males tended to stay within phases. This finding suggests that major males may compete more aggressively than minor males in contests.

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“…This trade-off is common in nature and often affects the intricate balance between survival and reproductive prowess, such as fecundity 2 – 4 and male weaponry and ornaments. These latter traits are large, extravagant structures that are energetically costly to develop 5 , 6 but increase males’ reproductive success by enhancing their fighting abilities and/or appeal to female mate choice 7 , 8 . Males of the stag beetle Cyclommatus metallifer , for example, are well known to express extremely large and conspicuous weapons that improve mating success, but come at costs in terms of wing size and flight muscles 9 .…”

Section: Introductionmentioning

confidence: 99%

Condition-Dependent Trade-Off Between Weapon Size and Immunity in Males of the European Earwig

Körner¹,

Vogelweith²,

Foitzik³

et al. 2017

Sci Rep

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Investigating the expression of trade-offs between key life-history functions is central to our understanding of how these functions evolved and are maintained. However, detecting trade-offs can be challenging due to variation in resource availability, which masks trade-offs at the population level. Here, we investigated in the European earwig Forficula auricularia whether (1) weapon size trades off with three key immune parameters – hemocyte concentration, phenoloxidase and prophenoloxidase activity - and whether (2) expression and strength of these trade-offs depend on male body condition (body size) and/or change after an immune challenge. Our results partially confirmed condition dependent trade-offs between weapon size and immunity in male earwigs. Specifically, we found that after an immune challenge, weapon size trades off with hemocyte concentrations in low-condition, but not in good-condition males. Contrastingly, weapon size was independent of pre-challenge hemocyte concentration. We also found no trade-off between weapon size and phenoloxidase activity, independent of body condition and immune challenge. Overall, our study reveals that trade-offs with sexual traits may weaken or disappear in good-condition individuals. Given the importance of weapon size for male reproductive success, our results highlight how low-condition individuals may employ alternative life-history investment strategies to cope with resource limitation.

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Jaw morphology and fighting forces in stag beetles

Cited by 24 publications

References 44 publications

Diverse and complex male polymorphisms in Odontolabis stag beetles (Coleoptera: Lucanidae)

Diverse and complex male polymorphisms in Odontolabis stag beetles (Coleoptera: Lucanidae)

Allometry and Fighting Behaviour of a Dimorphic Stag Beetle Cyclommatus mniszechi (Coleoptera: Lucanidae)

Condition-Dependent Trade-Off Between Weapon Size and Immunity in Males of the European Earwig

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