Mate‐guarding success depends on male investment in a butterfly

Abstract

Males of many insects, including butterflies, produce mate‐guarding devices, such as mating plugs, to prolong guarding and prevent future female matings in the male's absence. In a few butterflies, large external mate‐guarding devices, that is, sphragides, occur. Gór et al. (Behaviour, 160, 2023 and 515−557) found conspicuously large size and morphological variation of mate‐guarding devices within a single population of the potentially polyandrous Clouded Apollo (Parnassius mnemosyne, L.) butterfly. They termed the externally visible male‐produced devices as Copulatory opening APpendices (CAP) consisting of small devices, termed small CAPs and the much larger shield (i.e. sphragis). Our aim was to reveal CAP replacement dynamics within females during their lifetime and to understand how male investment into small CAPs or shields was (i) related to CAP persistence on the female, that is securing paternity, (ii) associated with female quality, measured as size and (iii) with actual adult sex ratio. We investigated a univoltine Clouded Apollo population to estimate CAP replacement risks, using multistate survival models, in an extensive observational study through 6 years based on mark‐recapture. Shields were the most frequent mate‐guarding devices and were more persistent than small CAPs, often lasting for life, excluding future matings. Thus, most females bearing a shield were deprived of postcopulatory female choice, and the genetic variance in their offspring could be reduced compared to those bearing small CAPs, thus mating more often. The ratio of shields to all CAPs gradually decreased towards the end of the flight period. Males were more prone to produce a shield when mating females with wider thoraces and when the ratio of males (i.e. competition) was higher in the population. To our best knowledge, this is the first quantitative study to investigate potential factors on which male investment in mate‐guarding devices may depend, and how the variation in these devices impacts CAP persistence on females.

The reduction of nuptial gifts in sclerosomatid Opiliones coincides with increased behavioural sexual conflict

“…Sperm competition and cryptic female choice are distinct possibilities in leiobunine harvesters – all females have a sperm-storing spermatheca, while some species have a complex, multi-chambered spermatheca potentially affording the female control over sperm fate (Karachiwalla et al 2020). These potential confounding factors would only further incentivize males to guard females and prevent remating, as suggested by both models and experimental evidence (Bateman et al 2001; Del Matto et al 2021; Gór et al 2023; Harts & Kokko 2013). Many male Opiliones, including Leiobunum species, engage in extended mate guarding which typically lasts until oviposition (Fowler-Finn et al 2014, 2018, 2019; Machado & Burns 2023, Macías-Ordóñez 1997; Wijnhoven 2011; Zatz et al 2011).…”

“…Mate guarding is another strong indicator of sexual conflict commonly found in arthropods (Alcock 1994;Arnqvist & Rowe 2005;Simmons 2002). Mate guarding may allow males additional control over female mating decisions by discouraging remating, preventing sperm removal by rival males, and reducing sperm competitionall factors which might alternatively (or additionally) be influenced by nuptial gifts (Alcock 1994;Arnqvist & Rowe 2005;Elias et al 2014;Frankino & Sakaluk 1994;Gór et al 2023;Hagg et al 2024;Lewis & South 2012;Machado & Burns 2023;Sakaluk 1991;Simmons 2002). Sperm competition and cryptic female choice are distinct possibilities in leiobunine harvestersall females have a sperm-storing spermatheca, while some species have a complex, multi-chambered spermatheca potentially affording the female control over sperm fate (Karachiwalla et al 2020).…”

Taxonomic Structure and Wing Pattern Evolution in the Parnassius mnemosyne Species Complex (Lepidoptera, Papilionidae)

“…Within the genus Parnassius, sphragides are extremely diverse in size and shape [5]. Despite significant individual variation [6,7], the sphragides are species-specific and represent a reliable character for species identification [2,5].…”