scholarly journals Smaller beetles are better scramble competitors at cooler temperatures

2007 ◽  
Vol 3 (5) ◽  
pp. 475-478 ◽  
Author(s):  
Jordi Moya-Laraño ◽  
Maysaa El Tigani El-Sayyid ◽  
Charles W Fox
Keyword(s):  
Body Size ◽  
Scramble Competition ◽  
Small Male ◽  
Male Body ◽  
Ecological Processes ◽  
Male Body Size ◽  
Small Seed ◽  
Stator Limbatus ◽  
Seed Beetles

The role of temperature is central to both organic evolution and ecological processes. However, how temperature affects selection on body size is unknown. We tested whether small seed beetles ( Stator limbatus ) have an advantage over large beetles during scramble competition for mates, and whether this advantage varies with temperature. Within lines of beetles artificially selected to be large versus small, small males have a significant advantage over large males in scramble competition for females because the former takeoff more quickly and thus reach females before larger males. Selection favouring small male body size is significantly (and substantially) more intense at cooler temperatures. The adaptive significance of small male body size thus depends on ambient temperature.

Small male body size in garter snake depends on testes

1985 ◽  
Vol 249 (1) ◽  
pp. R62-R66 ◽  
Author(s):  
D. Crews ◽  
M. A. Diamond ◽  
J. Whittier ◽  
R. Mason
Keyword(s):  
Body Size ◽  
Garter Snake ◽  
Thamnophis Sirtalis ◽  
Sham Operation ◽  
Small Male ◽  
Male Body ◽  
Adult Males ◽  
Thamnophis Sirtalis Parietalis ◽  
Circulating Levels

In the red-sided garter snake (Thamnophis sirtalis parietalis) adult females are larger than adult males; this difference is apparent within 3 wk of birth, a time coinciding with high circulating levels of androgens. To study the ontogeny and regulation of this sexual dimorphism, male neonates were either castrated, castrated and given Silastic capsules containing testosterone or estradiol, or given a sham operation at 8, 9, or 10 wk of age. Female neonates were either given a Silastic capsule containing testosterone or dihydrotestosterone or given a sham operation at 8, 9, 10, or 14 wk of age. The sex difference in body size and growth rate in neonates was abolished by castration; the pattern of growth of castrated males was similar to sham-operated females. Androgens in the amounts administered failed to reverse the effects of castration, because castrated male and female neonates receiving exogenous androgens grew at the same rate as did sham-operated females. Males castrated as adults grow larger than adult males given a sham operation, indicating the inhibitory role of the testes on body size exists after sexual maturity. Treatment of adult males with testosterone, however, prevented the increase in body size after castration, suggesting that the mechanism regulating weight gain in the garter snake depends on gonadal androgen.

Effects of body size and mass on running speed of male yellow-pine chipmunks (Tamias amoenus)

2002 ◽  
Vol 80 (9) ◽  
pp. 1584-1587 ◽  
Author(s):  
Albrecht I Schulte-Hostedde ◽  
John S Millar
Keyword(s):  
Body Size ◽  
Mating Success ◽  
Sexual Size Dimorphism ◽  
Small Male ◽  
Male Body ◽  
Running Speed ◽  
Size Dimorphism ◽  
Male Body Size ◽  
Tamias Amoenus ◽  
Yellow Pine

Male-biased sexual size dimorphism in mammals is usually attributed to the success of large males in intrasexual combat for mates. However, mating success may be determined by contests that are not combative. In the mating chase of the yellow-pine chipmunk (Tamias amoenus), a mammalian species with female-biased sexual size dimorphism, fast males may have an advantage in acquiring matings with estrous females. However, the effects of intraspecific variation in body size on running speed are not obvious; heavy individuals may run more slowly than light individuals because excess mass can be a hindrance to locomotion, but individuals that are structurally large may run faster than small individuals because of longer stride length. We examined the effects of both body mass and structural size on running speed in male yellow-pine chipmunks using manipulated runs in which male chipmunks were chased over a known distance. Structurally large male chipmunks had faster running speeds than small males, potentially giving large males an advantage when chasing estrous females. However, small male chipmunks are known to be aggressively dominant over large males. This leads to a potential trade-off in male body size between two behavioural components of mating success (running speed and dominance) that may constrain the evolution of male body size, ultimately leading to female-biased sexual size dimorphism.

Intra- and intersexual selection on male body size in the annual killifish Austrolebias charrua

2013 ◽  
Vol 96 ◽  
pp. 20-26 ◽  
Author(s):  
Carlos Passos ◽  
Bettina Tassino ◽  
Marcelo Loureiro ◽  
Gil G. Rosenthal
Keyword(s):  
Body Size ◽  
Male Body ◽  
Male Body Size ◽  
Annual Killifish

Sexual size dimorphism in the American rubyspot: male body size predicts male competition and mating success

2007 ◽  
Vol 73 (6) ◽  
pp. 987-997 ◽  
Author(s):  
M.A. Serrano-Meneses ◽  
A. Córdoba-Aguilar ◽  
V. Méndez ◽  
S.J. Layen ◽  
T. Székely
Keyword(s):  
Body Size ◽  
Mating Success ◽  
Sexual Size Dimorphism ◽  
Male Competition ◽  
Male Body ◽  
Size Dimorphism ◽  
Male Body Size

scholarly journals A new species of Kurixalus from western Yunnan, China (Anura, Rhacophoridae)

ZooKeys ◽  
2018 ◽  
Vol 770 ◽  
pp. 211-226 ◽  
Author(s):  
Guohua Yu ◽  
Hong Hui ◽  
Dingqi Rao ◽  
Junxing Yang
Keyword(s):  
New Species ◽  
Body Size ◽  
Outer Edge ◽  
Male Body ◽  
Male Body Size ◽  
Western Yunnan ◽  
A New Species

A new species of the genus Kurixalus (Anura: Rhacophoridae) is described from western Yunnan, China. Genetically the new species, Kurixalusyangi sp. n., is closer to Kurixalusnaso than to other known congeners. Morphologically the new species is distinguished from all other known congeners by a combination of the following characters: smaller ratios of head, snout, limbs, IND, and UEW to body size; male body size larger than 30 mm; curved canthus rostralis; weak nuptial pad; brown dorsal color; absence of large dark spots on surface of upper-middle abdomen; presence of vomerine teeth; gold brown iris; single internal vocal sac; serrated dermal fringes along outer edge of limbs; granular throat and chest; rudimentary web between fingers; and presence of supernumerary tubercles and outer metacarpal tubercle.

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