It is not always about body size: evidence of Rensch's rule in a male weapon

Machado, Glauco; Buzatto, Bruno A.; Samia, Diogo S. M.

doi:10.1098/rsbl.2021.0234

Cited by 6 publications

(2 citation statements)

References 38 publications

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“…Due to differences in seasonality, we expected natural and sexual selection to favor smaller body and faster maturation at higher altitudes. Also, despite a smaller body, if sexual selection was stronger at high altitudes, we expected higher levels of sexual size dimorphism bias towards males in traits that are larger in males, and lower levels of sexual size dimorphism in traits that are larger in females (Machado et al, 2021). Moreover, as previous works have detected protandry in S. purpurascens (Cueva del Castillo & Núñez‐Farfán, 1999), we performed a common garden experiment to evaluate possible protandry in grasshoppers from the three sampling sites that were reared under laboratory conditions.…”

Section: Introductionmentioning

confidence: 89%

Seasonality, body size, and maturation time in the neotropical grasshopper Sphenarium histrio across an altitudinal gradient

Ramírez‐Delgado

Castillo

2022

Entomologia Exp Applicata

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In insects, male mating success and female fecundity usually increase with body size. However, natural selection favors faster maturation, reducing the risk of prereproductive death, when the reproductive season is short in habitats located at high altitudes or far from the equator. Also, if males that mature earlier than females under these conditions increase their mating opportunities, protandry may evolve in their populations. Nonetheless, as body size is strongly correlated with maturation time in insects, faster sexual maturation is reached at the expense of having a small body size. We analyzed the differences in adult body size of males and females of the grasshopper Sphenarium histrio Gerstaecker (Orthoptera: Pyrgomorphidae) in three sites across an altitudinal gradient in southern Mexico. We also evaluated the possibility of protandry in these sampling sites using a common garden experiment. Male and female grasshoppers collected from low altitude sites in the field and reared in the laboratory were larger than those from a high altitude, suggesting genetic differentiation. Grasshoppers from a high altitude hatched earlier, had a shorter development time, presented fewer instars, and were smaller than grasshoppers from the other sampling sites. Moreover, development time in the three sampling sites was shorter in males than in females, suggesting protandry. Interestingly, the males from the three sites showed similar growth rates, but the females from low and high altitudes, respectively, had the fastest and slowest growth rates. In general, the adaptive value of the evolution of protandry has been focused on males. However, it may be that the growth rates of females in these sites could modify the degree of protandry as a response to their risk of pre-reproductive death and the potential benefits associated with multiple matings.

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Section: Introductionmentioning

confidence: 89%

Seasonality, body size, and maturation time in the neotropical grasshopper Sphenarium histrio across an altitudinal gradient

Ramírez‐Delgado

Castillo

2022

Entomologia Exp Applicata

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“…2022 ). Intriguingly, recent studies also suggest that Rensch's rule can manifest in traits other than body size, including male ornaments and weapons ( Machado et al. 2021 ; Reyes-Puig et al.…”

Section: Introductionmentioning

confidence: 99%

Sharks Violate Rensch's Rule for Sexual Size Dimorphism

Gayford,

Sternes

2024

Integrative Organismal Biology

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Systematic trends in body size variation exist in a multitude of vertebrate radiations, however their underlying ecological and evolutionary causes remain poorly understood. Rensch's rule describes one such trend – in which the scaling of sexual size dimorphism (SSD) depends on which sex is larger. Where SSD is male-biased, SSD should scale hyperallometrically, as opposed to hypoallometrically where SSD is female-biased. The evidence for Rensch's rule is mixed, and comes from a small subset of total vertebrate diversity. We conducted the first empirical test of Rensch's rule in sharks, seeking to confirm or refute a long-hypothesied trend. We find that sharks violate Rensch's rule, as the magnitude of SSD increases with body size despite sharks predominantly exhibiting female-biased SSD. This adds to a growing literature of vertebrate clades that appear not to follow Rensch's rule, suggesting the absence of a single, conserved scaling trend for SSD amongst vertebrates. It is likely that selection associated with fecundity results in the ‘inverse Rensch's rule’ observed in sharks, although additional studies will be required to fully reveal the factors underlying SSD variation in this clade.

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