Temporal variability in sexual selection acting on reproductive tactics and body size in male snakes

Article Abstract:

A population of adders (Vipera berus) in southern Sweden were studied from 1984-90 to determine whether whether there is temporal variability exists in selective forces, and whether alternative reproductive tactics exist as a consequence of variable selective forces. The results showedthat in adders, intensity of sexual selection for dominance over rival males varied considerably in different years, and depended on the number of reproducing males and females in the population. The implications for findings on the effects of sexual selection on the evolution of mating systems and sexual dimorphism based on short-term studies were discussed.

Environmental aspects, Sexual behavior in animals, Animal sexual behavior, Dimorphism (Animals), Dimorphism (Biology)

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Patterns of survival, growth, and maturation in snakes and lizards

Article Abstract:

Growth rates, adult survival rates and ages at sexual maturation of squamate reptiles were surveyed from published data to determine whether they exhibit two patterns observed in other organisms that continue growth after sexual maturity. The two patterns involve correlations between adult instantaneous mortality rate and the von Bertalanffy growth coefficient and between body length at maturity and von Bertalanffy asymptotic body length. The results showed that reptiles exhibit the same patterns, which have been observed in some groups of sea urchins, fish and shrimp.

Physiological aspects, Snakes, Lizards, Life cycles (Biology)

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A new hypothesis for the evolution of viviparity in reptiles

Article Abstract:

A prolonged uterine retention directly improves hatching viability as eggs incubated at maternal body temperatures produce better hatchlings than eggs incubated at normal temperature. This presents a feasible selective advantage for the evolution of viviparity in squamate reptiles and probably in other vertebrates as well as invertebrates. The expression of phenotypic plasticity may have a pivotal role in the adaptive motivation of life-history phenomenon.

Reptiles, Viviparity, Eggs

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