Sexual Size Dimorphism: Evolution and Perils of Extreme Phenotypes in Spiders

2020 ◽  
Vol 65 (1) ◽  
pp. 57-80 ◽  
Author(s):  
Matjaž Kuntner ◽  
Jonathan A. Coddington
Keyword(s):  
Equilibrium Model ◽  
Sexual Size Dimorphism ◽  
Size Variation ◽  
Sexual Cannibalism ◽  
Size Dimorphism ◽  
Terminal Investment ◽  
Dead End ◽  
Extreme Phenotypes ◽  
Context Specific ◽  
Female Gigantism

Sexual size dimorphism is one of the most striking animal traits, and among terrestrial animals, it is most extreme in certain spider lineages. The most extreme sexual size dimorphism (eSSD) is female biased. eSSD itself is probably an epiphenomenon of gendered evolutionary drivers whose strengths and directions are diverse. We demonstrate that eSSD spider clades are aberrant by sampling randomly across all spiders to establish overall averages for female (6.9 mm) and male (5.6 mm) size. At least 16 spider eSSD clades exist. We explore why the literature does not converge on an overall explanation for eSSD and propose an equilibrium model featuring clade- and context-specific drivers of gender size variation. eSSD affects other traits such as sexual cannibalism, genital damage, emasculation, and monogyny with terminal investment. Coevolution with these extreme sexual phenotypes is termed eSSD mating syndrome. Finally, as costs of female gigantism increase with size, eSSD may represent an evolutionary dead end.

Geographic variation in body size and sexual size dimorphism of North American Ratsnakes (Pantherophis spp. s.l.)

2018 ◽  
Vol 96 (11) ◽  
pp. 1196-1202 ◽  
Author(s):  
Brett A. DeGregorio ◽  
Gabriel Blouin-Demers ◽  
Gerardo L.F. Carfagno ◽  
J. Whitfield Gibbons ◽  
Stephen J. Mullin ◽  
...  
Keyword(s):  
Body Size ◽  
Large Scale ◽  
Sexual Size Dimorphism ◽  
Size Variation ◽  
Sexually Dimorphic ◽  
Male Body ◽  
Complex Species ◽  
Size Dimorphism ◽  
Body Size Variation ◽  
Female Body Size

Because body size affects nearly all facets of an organism’s life history, ecologists have long been interested in large-scale patterns of body-size variation, as well as why those large-scale patterns often differ between sexes. We explored body-size variation across the range of the sexually dimorphic Ratsnake complex (species of the genus Pantherophis Fitzinger, 1843 s.l.; formerly Elaphe obsoleta (Say in James, 1823)) in North America. We specifically explored whether variation in body size followed latitudinal patterns or varied with climatic variables. We found that body size did not conform to a climatic or latitudinal gradient, but instead, some of the populations with the largest snakes occurred near the core of the geographic range and some with the smallest occurred near the northern, western, and southern peripheries of the range. Males averaged 14% larger than females, although the degree of sexual size dimorphism varied between populations (range: 2%–25%). There was a weak trend for male body size to change in relation to temperature, whereas female body size did not. Our results indicate that relationships between climate and an ectotherm’s body size are more complicated than linear latitudinal clines and likely differ for males and females.

scholarly journals Body size variation and sexual size dimorphism across climatic gradients in the widespread treefrogScinax fuscovarius(Anura, Hylidae)

2017 ◽  
Vol 43 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Javier Goldberg ◽  
Darío Cardozo ◽  
Francisco Brusquetti ◽  
Diego Bueno Villafañe ◽  
Andrea Caballero Gini ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Size Variation ◽  
Size Dimorphism ◽  
Body Size Variation

Mate choice and sexual size dimorphism, not personality, explain female aggression and sexual cannibalism in raft spiders

2016 ◽  
Vol 111 ◽  
pp. 49-55 ◽  
Author(s):  
Simona Kralj-Fišer ◽  
Klemen Čandek ◽  
Tjaša Lokovšek ◽  
Tatjana Čelik ◽  
Ren-Chung Cheng ◽  
...  
Keyword(s):  
Mate Choice ◽  
Sexual Size Dimorphism ◽  
Female Aggression ◽  
Sexual Cannibalism ◽  
Size Dimorphism

scholarly journals Modeling sexual differences of body size variation in ground beetles in geographical gradient (The case study in Pterostichus oblongpunctatus Fabricius, 1787)

2020 ◽  
Vol 13 (3) ◽  
pp. 149-161
Author(s):  
Raisa A Sukhodolskaya ◽  
Anatoly A Saveliev ◽  
Nadezhda L Ukhova ◽  
Iraida G Vorobyova ◽  
Igor A Solodovnikov ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Ground Beetle ◽  
Geographical Location ◽  
Size Variation ◽  
Ground Beetles ◽  
Mean Values ◽  
Size Dimorphism ◽  
Body Size Variation

Fleshing out the mechanisms of Bergmann rule, we found saw-tooth pattern in body size variation in ground beetle Pterostichus oblongopunctatus. We sampled beetles in 2010 – 2018 at the forest undisturbed plots on the broad territory in Russia and Belarus. Investigating regions covered territory, extending to 3 degrees latitude and 31 degrees longitude. We measured six traits in every of 3294 caught individuals. ANOVA showed that geographical location and sex affected significantly body size of the species studied. Mean values of each trait changed significantly from one studied region to another in females and males as well. Sexual size dimorphism in species was female-biased. We performed models in R to estimate the steepness of body size variation in both sexes. In overwhelming majority of cases that parameter was equal in both sexes. So the hypothesis, that male′s variation is steeper in latitude gradient was not confirmed.

scholarly journals Population-specific sex and size variation in long-term foraging ecology of belugas and narwhals

2021 ◽  
Vol 8 (2) ◽  
pp. 202226
Author(s):  
Marie Louis ◽  
Mikkel Skovrind ◽  
Eva Garde ◽  
Mads Peter Heide-Jørgensen ◽  
Paul Szpak ◽  
...  
Keyword(s):  
Trophic Level ◽  
Life Histories ◽  
Sexual Size Dimorphism ◽  
Foraging Ecology ◽  
Size Variation ◽  
Maternal Investment ◽  
Bone Collagen ◽  
Size Dimorphism ◽  
West Greenland

Intraspecific variation in resource use by individuals of different age, sex or size may reflect differing energetic requirements and physiological constraints. Males and females often show differences in diet owing to sexual size dimorphism, different life histories and/or habitat use. Here, we investigate how sex and size influence the long-term foraging ecology of belugas and narwhals in Greenland, using stable isotopes of carbon and nitrogen from bone collagen. We show that males have a higher trophic level and a larger ecological niche than females in West Greenland belugas and in East Greenland narwhals. In addition, for these two populations, we find that δ 15 N increases with size, particularly in males. We hypothesize that sexual size dimorphism together with strong maternal investment drive these differences. By contrast, we find no differences in foraging ecology between sexes in West Greenland narwhals and observe no influence of size on trophic level. This may reflect the influence of interspecific competition in West Greenland, where the distributions of belugas and narwhals overlap, and/or geographical resource partitioning among different summer aggregations of narwhals. Our results suggest that sex and size variations in diet are population dependent, and probably the result of varying ecological interactions.

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