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 ◽  
...  

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.

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

2020 ◽  
Vol 13 (3) ◽  
pp. 149-161
Author(s):  
Raisa A Sukhodolskaya ◽  
Anatoly A Saveliev ◽  
Nadezhda L Ukhova ◽  
Iraida G Vorobyova ◽  
Igor A Solodovnikov ◽  
...  

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.


Author(s):  
Raisa Sukhodolskaya ◽  
Anatoliy Saveliev ◽  
Nadezhda Ukhova ◽  
Iraida Vorobyova ◽  
Igor Solodovnikov ◽  
...  

Concretizing 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. Investigating regions covered territory, extending to 3 degrees latitude and 19 degrees longitude. We measured six traits in every of 3294 caught individual. ANOVA showed that latitude, 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.


Biologia ◽  
2015 ◽  
Vol 70 (9) ◽  
pp. 1228-1233 ◽  
Author(s):  
Ehsan Sanaei ◽  
Marjan Seiedy ◽  
Farzaneh Momtazi

Abstract Body size dimorphism between genders is a commonly observed phenomenon in insects, usually manifested in larger female body size. Sexual Size Dimorphism (SSD) varies from species to species, the degree and direction influenced by certain evolutionary pressures. Intraspecific variation in SSD may also occur between populations. The Hypera postica (Gyllenhal, 1813) is a well-known alfalfa plant pest that shows a degree of morphological divergence in its populations. The female alfalfa weevils are very fecund and have a larger body size compared to males. To improve our knowledge on magnitude and direction of SSD in alfalfa weevil, we studied 200 specimens of H. postica from four Iranian populations (Karaj1, Karaj2, Tuyserkan and Jovein). 10 morphological variables from three external anatomic parts (pronotum, elytra and rostrum) and 45 ratio characters were statistically analyzed in order to determine the amount of SSD in Iranian populations. In addition we investigated for morphological divergence pattern in mentioned populations. The results of this study show that a low degree of morphological divergence occurs in Iranian populations. Measured variables indicate that the SSD pattern of H. postica is compatible with the Rensch’s rule, and is related to high fecundity of females and a lack of strong sexual selection. Also it is mentioned that the larger rostrum in females may correspond to its unique role in egg laying.


2007 ◽  
Vol 73 (6) ◽  
pp. 987-997 ◽  
Author(s):  
M.A. Serrano-Meneses ◽  
A. Córdoba-Aguilar ◽  
V. Méndez ◽  
S.J. Layen ◽  
T. Székely

2016 ◽  
Vol 188 (2) ◽  
pp. 264-271 ◽  
Author(s):  
Laura K. Weir ◽  
Holly K. Kindsvater ◽  
Kyle A. Young ◽  
John D. Reynolds

1985 ◽  
Vol 63 (9) ◽  
pp. 2187-2193 ◽  
Author(s):  
Kevin M. O'Neill

Female digger wasps invest substantially in each of their offspring, laying relatively few, large eggs and providing the young with the insect prey on which they depend for food. In a study of six species in the genera Philanthus, Bembecinus, and Bembix, it was found that within each species, there is a positive correlation between female body size and both the size of their ovarial eggs and the size of the prey they provision. In five of the six species, females were larger than males on average. It is suggested that the apparent association between body size and certain aspects of parental investment by females may provide the directional selection pressure that results in the evolution of sexual size dimorphism in digger wasps. In one species, males and females have the same mean size, probably because, in this species, selection pressure on male size is similar to that on females.


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