Sexual size dimorphism and male reproductive traits vary across populations of a tropical rainforest dung beetle species (<i>Onthophagus babirussa</i>)

Toh, Kai Xin; Yap, Sean; Goh, Thary Gazi; Puniamoorthy, Nalini

doi:10.1002/ece3.9279

Cited by 3 publications

(1 citation statement)

References 120 publications

(159 reference statements)

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“…Whereas the relationship between male-biased SSD and testes size shifts from positive to negative across taxa with an increasing prevalence of female monopolization [ 2 ], paternal care and the expression of sexual weaponry have been positively associated within some taxa (e.g. anurans [ 63 ], fishes [ 64 ], insects [ 65 ]). Hence, we also tested if testes size, paternal care and humeral spine in glassfrogs were associated with SSD, another trait often responding to pre-mating sexual selection.…”

Section: Resultsmentioning

confidence: 99%

Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs

Valencia-Aguilar,

Ringler,

Lüpold

et al. 2024

Proc. R. Soc. B.

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In males, large testes size signifies high sperm production and is commonly linked to heightened sperm competition levels. It may also evolve as a response to an elevated risk of sperm depletion due to multiple mating or large clutch sizes. Conversely, weapons, mate or clutch guarding may allow individuals to monopolize mating events and preclude sperm competition, thereby reducing the selection of large testes. Herein, we examined how paternal care, sexual size dimorphism (SSD), weaponry and female fecundity are linked to testes size in glassfrogs. We found that paternal care was associated with a reduction in relative testes size, suggesting an evolutionary trade-off between testes size and parenting. Although females were slightly larger than males and species with paternal care tended to have larger clutches, there was no significant relationship between SSD, clutch size and relative testes size. These findings suggest that the evolution of testes size in glassfrogs is influenced by sperm competition risk, rather than sperm depletion risk. We infer that clutch guarding precludes the risk of fertilization by other males and consequently diminishes selective pressure for larger testes. Our study highlights the prominent role of paternal care in the evolution of testes size in species with external fertilization.

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Section: Resultsmentioning

confidence: 99%

Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs

Valencia-Aguilar,

Ringler,

Lüpold

et al. 2024

Proc. R. Soc. B.

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Male Reproductive Traits Display Increased Phenotypic Variation in Response to Resource Quality and Parental Provisioning in a Tropical Rainforest Dung Beetle, Onthophagus c.f. babirussa

Yap,

Toh,

Puniamoorthy

2024

Ecology and Evolution

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Reproductive traits that mediate differential fitness associated with mate acquisition and fertilisation success are often strongly linked to the overall condition. We investigated the effects of resource quality and parental provisioning in the phenotypic expression of sexual and non‐sexual traits in a rainforest dung beetle, Onthophagus c.f. babirussa (Eschscholtz, 1822) from Singapore. F1 individuals were reared from wild‐caught beetles and paired up to produce offspring (F2), and F2 larvae from the same F1 parents were reared on two dung substrates (herbivore and omnivore) in a full‐sib design. Sexual traits displayed greater phenotypic variation in response to dung resource quality, with the precopulatory trait (horn length) responding more than the postcopulatory trait (testes weight). Notably, genotype‐by‐environment interactions between parental lines (genotype) and dung type (environment) affected male body size and horn length only, suggesting sex‐specific variance in plasticity associated with sexually selected precopulatory traits. Dung type had significant effects on all measured traits. Offspring that were provisioned higher quality resource (omnivore dung) had larger absolute and relative trait values. Parental lines only significantly affected female body size but none of the male traits, suggesting an important role of environment and resource partitioning in determining precopulatory success of male offspring. Parental provisioning of larval resource varied with resource quality and brood sequence. Parents provisioned more dung when herbivore dung was presented than when they were given omnivore dung and provisioned more dung for their earlier broods when using herbivore dung but not omnivore dung. This suggests a trade‐off between early offspring fitness and resource quality. We tested directly for genotype‐by‐environment (G × E) interactions in the expression of several morphological traits relevant to dung beetle fitness and documented that offspring with similar phenotypes may result from completely different parental resource allocation strategies. We discuss the importance of studying parental investment on trait variation and its implications on dung beetle ecology.

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Are weapon allometries steeper in major or minor males? A meta-analysis

Kochensparger,

Painting,

Buzatto

et al. 2024

Behavioral Ecology

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Competition for mates can drive the evolution of exaggerated weaponry and male dimorphism associated with alternative reproductive tactics. In terrestrial arthropods, male dimorphism is often detected as non-linear allometries, where the scaling relationship between weapon size and body size differs in intercept and/or slope between morphs. Understanding the patterns of non-linear allometries is important as it can provide insights into threshold evolution and the strength of selection experienced by each morph. Numerous studies in male-dimorphic arthropods have reported that allometric slopes of weapons are shallower in large “major” males compared to small “minor” males. Because this pattern is common among beetles that undergo complete metamorphosis (holometabolous), researchers have hypothesized that the slope change reflects resource depletion during pupal development. However, no comprehensive survey has examined the generality of this trend. We systematically searched the literature for reports of weapon allometries in male dimorphic species and conducted a phylogenetically controlled meta-analysis to explore the factors influencing the difference in slopes between morphs. Our search identified 59 effect sizes from 19 studies, 50 species, and 5 orders of terrestrial arthropods. We found strong evidence that metamorphosis type influences the patterns of weapon allometries. Slopes were significantly steeper in minor males compared to major males in holometabolous species, but there was no difference in slopes between morphs in hemimetabolous species (i.e. those that undergo incomplete or no metamorphosis). These results support the hypothesis that holometabolous species face a resource ceiling during pupal development that limits the exaggeration of weapon size.

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Sexual size dimorphism and male reproductive traits vary across populations of a tropical rainforest dung beetle species (Onthophagus babirussa)

Cited by 3 publications

References 120 publications

Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs

Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs

Male Reproductive Traits Display Increased Phenotypic Variation in Response to Resource Quality and Parental Provisioning in a Tropical Rainforest Dung Beetle, Onthophagus c.f. babirussa

Are weapon allometries steeper in major or minor males? A meta-analysis

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