Female-biased sexual size dimorphism: ontogeny, seasonality, and fecundity of the cliff chipmunk (<i>Tamias dorsalis</i>)

Kilanowski, Allyssa L.; Koprowski, John L.

doi:10.1093/jmammal/gyw172

Cited by 7 publications

(9 citation statements)

References 29 publications

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“…The number and variety of displays potentially act as signals to communicate male fitness, which could influence S. plangon female choice. Other investigations have shown that larger females generally have higher fecundity and produce larger offspring in mammals (Kilanowski and Koprowski, 2016), insects, and arthropods (Honěk, 1993;Fox and Czesak, 2000;Stillwell et al, 2010). Additionally, intersexual selection may drive the evolution of small male size in S. plangon, for example, small body size could be beneficial to males that show dynamic or acrobatic courtship (Székely et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Dynamic Courtship Signals and Mate Preferences in Sepia plangon

2020

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Communication in cuttlefish includes rapid changes in skin coloration and texture, body posture and movements, and potentially polarized signals. The dynamic displays are fundamental for mate choice and agonistic behavior. We analyzed the reproductive behavior of the mourning cuttlefish Sepia plangon in the laboratory. Mate preference was analyzed via choice assays ( n = 33) under three sex ratios, 1 male (M): 1 female (F), 2M:1F, and 1M:2F. We evaluated the effect of modifying polarized light from the arms stripes and ambient light with polarized and unpolarized barriers between the cuttlefish. Additionally, to assess whether a particular trait was a determinant for mating, we used 3D printed cuttlefish dummies. The dummies had different sets of visual signals: two sizes (60 or 90 mm mantle length), raised or dropped arms, high or low contrast body coloration, and polarized or unpolarized filters to simulate the arms stripes. Frequency and duration (s) of courtship displays, mating, and agonistic behaviors were analyzed with GLM and ANOVAs. The behaviors, body patterns, and their components were integrated into an ethogram to describe the reproductive behavior of S. plangon . We identified 18 body patterns, 57 body patterns components, and three reproductive behaviors (mating, courtship, and mate guarding). Only sex ratio had a significant effect on courtship frequency, and the male courtship success rate was 80%. Five small (ML < 80 mm) males showed the dual-lateral display to access mates while avoiding fights with large males; this behavior is characteristic of male “sneaker” cuttlefish. Winner males showed up to 17 body patterns and 33 components, whereas loser males only showed 12 patterns and 24 components. We identified 32 combinations of body patterns and components that tended to occur in a specific order and were relevant for mating success in males. Cuttlefish were visually aware of the 3D-printed dummies; however, they did not start mating or agonistic behavior toward the dummies. Our findings suggest that in S. plangon , the dynamic courtship displays with specific sequences of visual signals, and the sex ratio are critical for mate choice and mating success.

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Section: Discussionmentioning

confidence: 99%

Dynamic Courtship Signals and Mate Preferences in Sepia plangon

2020

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“…Sex differences in body size are a conspicuous feature of mammals and vary widely in magnitude and direction between species. For example, in southern elephant seals Mirounga leonina, males can reach a body mass of 3000kg, some 5-6 times that of females (Wilson and Mittermeier 2014), whilst in other mammals, such as chipmunks and spotted hyenas Crocuta crocuta, it is the females that are the larger sex (Ralls 1976, Schulte-Hostedde 2007, Swanson et al 2013, Kilanowski and Koprowski 2017. The developmental processes that lead the sexes to differ in size can take various forms.…”

Section: Introductionmentioning

confidence: 99%

A unified-models analysis of the development of sexual size dimorphism in Damaraland mole-rats, Fukomys damarensis

Thorley

Clutton‐Brock

2019

Journal of Mammalogy

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Individual variation in growth rates often generates variation in fitness. However, the ability to draw meaningful inferences from growth data depends on the use of growth models that allow for direct comparisons of growth between the sexes, between populations, and between species. Unlike traditional sigmoid functions, a recently parameterized family of unified growth models provides a reliable basis for comparisons since each parameter affects a single curve characteristic and parameters are directly comparable across the unified family. Here, we use the unified-models approach to examine the development of sexual size dimorphism in Damaraland mole-rats (Fukomys damarensis), where breeding males are larger than breeding females. Using skeletal measurements, we show here that the larger size of male Damaraland mole-rats arises from an increased growth rate across the entire period of development, rather than through sex differences in the duration or timing of growth. Male-biased skeletal size dimorphism is not unusual among rodents, and our measures of sex differences in size in captive mole-rats are close to sexual size differences in the wild, where size dimorphism = 1.04 (male:female). We hope our study will encourage the wide use of unified growth models by mammalogists.

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“…Male-biased SSD (MBSSD) can be seen in most mammalian species and lizards, where males have larger body size than females (Hudson & Fu, 2013;Kinahan, Bennett, O'Riain, Hart, & Bateman, 2007). Conversely, female-biased SSD (FBSSD) pattern can be seen in invertebrates, ectothermic vertebrates, and some mammalian species, where females are larger than males (Chelini & Hebets, 2017;Kilanowski & Koprowski, 2017). Despite extensive research on this topic, a critical question remains unanswered: Why do males and females manifest different body sizes, although they possess the same genes of growth and development?…”

Section: Introductionmentioning

confidence: 99%

Function‐related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

Hegab

et al. 2018

Ecology and Evolution

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Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.

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Female-biased sexual size dimorphism: ontogeny, seasonality, and fecundity of the cliff chipmunk (Tamias dorsalis)

Cited by 7 publications

References 29 publications

Dynamic Courtship Signals and Mate Preferences in Sepia plangon

Dynamic Courtship Signals and Mate Preferences in Sepia plangon

A unified-models analysis of the development of sexual size dimorphism in Damaraland mole-rats, Fukomys damarensis

Function‐related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

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