Duration of Incubation of Sceloporus undulatus Eggs at Constant Temperature

Sexton, Owen J.; Marion, Ken R.

doi:10.1086/physzool.47.2.30155626

Cited by 51 publications

(35 citation statements)

References 9 publications

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“…Unlike other lizards in which residual yolk can contribute to posthatching growth rate (Troyer, 1983(Troyer, , 1987, all the hatchlings in this experiment had an insignificant amount ofyolk present at hatching. Thus, incubation differences among populations are due not only to differences in yolk volume,but also to unexplained differences in incubation attributable to other factors, such as the degree of egg retention by females (Sexton and Marion, 1974) or differences in the rate of embryonic development. The experimental manipulation ofeggsize by yolk reduction also provides a basis for interpreting the difference between the allometric slope for egg and hatchling size among populations and the allometric slope within populations.…”

Section: Discussionmentioning

confidence: 99%

The Evolution of Maternal Investment in Lizards: An Experimental and Comparative Analysis of Egg Size and Its Effects on Offspring Performance

1990

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Abstract.-I used comparative and experimental analysis of egg size in a Sceloporus lizard to examine a fundamental tenet of life-history theory: the presumed trade-offs among offspring number, offspring size, and performance traits related to offspring size that are likely to influence fitness. I analyzed latitudinal and elevational patterns ofegg life-history characteristics among populations and experimentally manipulated egg size and hatchling size by removing yolk from the eggs to examine the causal bases of population differences in offspring traits.Mean clutch size among populations increased to the north (seven vs. 12 eggs/clutch, California vs. Washington), whereas eggsize decreased (0.65 g vs. 0.40 g). The elevational patterns in southern California paralleled the latitudinal trends. Several offspring life-history traits that are correlated with egg size also varied geographically; these traits included incubation time, hatchling size, growth rate, and hatchling sprint performance.Hatchling viability of experimentally reduced eggs was remarkably high (-70%), even when up to 50% of the yolk was removed. The experimentally reduced eggs and hatchlings demonstrated the degree to which size influences each of the offspring life-history traits considered. Northern eggshatched sooner, in part because oftheir small size. Though growth rate is allometrically related to size within each population (i.e., smaller hatchlings grow faster on a mass-specific basis), population differences in growth rate, as measured in the laboratory, are likely to reflect genetic differentiation in the underlying physiology of growth. Moreover, smaller juveniles, because of experimental reduction, had slower sprint speeds than larger juveniles. The slower sprint speed of hatchlings from Washington compared to hatchlings from California is thus largely due to the fact that eggs are smaller in the Washington population.These results provide a basis for interpreting the evolutionary divergence of the suite of traits involved in the evolution ofmaternal investment per offspring in lizards. For example, evolutionary divergence in some offspringtraits functionally related to size (e.g., sprint speed) may be constrained, relative to traits that are determined by other aspects of development or physiology (e.g., growth). I also discuss issues relating to the evolution of maternal investment that could be tested in laboratory and natural populations using experimentally reduced offspring.

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Section: Discussionmentioning

confidence: 99%

The Evolution of Maternal Investment in Lizards: An Experimental and Comparative Analysis of Egg Size and Its Effects on Offspring Performance

1990

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“…Eggs of S. undulatus fail to hatch when incubated at a constant temperature of 20°C (Sexton and Marion 1974). Eggs of Sceloporus virgatus (a member of the undulatus species group), however, hatched when temperatures fluctuated around a mean of 20°C (Andrews et al 1997).…”

Section: Experimental Designmentioning

confidence: 99%

Incubation temperature and phenotypic traits of Sceloporus undulatus: implications for the northern limits of distribution

Parker

Andrews

2006

Oecologia

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Cold environmental temperature is detrimental to reproduction by oviparous squamate reptiles by prolonging incubation period, negatively affecting embryonic developmental processes, and by killing embryos in eggs directly. Because low soil temperature may prevent successful development of embryos in eggs in nests, the geographic distributions of oviparous species may be influenced by the thermal requirements of embryos. In the present study, we tested the hypothesis that low incubation temperature determines the northern distributional limit of the oviparous lizard Sceloporus undulatus. To compare the effects of incubation temperature on incubation length, egg and hatchling survival, and hatchling phenotypic traits, we incubated eggs of S. undulatus under temperature treatments that simulated the thermal environment that eggs would experience if located in nests within their geographic range at 37 degrees N and north of the species' present geographic range at latitudes of 44 and 42 degrees N. After hatching, snout-vent length (SVL), mass, tail length, body condition (SVL relative to mass), locomotor performance, and growth rate were measured for each hatchling. Hatchlings were released at a field site to evaluate growth and survival under natural conditions. Incubation at temperatures simulating those of nests at 44 degrees N prolonged incubation and resulted in hatchlings with shorter SVL relative to mass, shorter tails, shorter hind limb span, slower growth, and lower survival than hatchlings from eggs incubated at temperatures simulating those of nests at 37 and 42 degrees N. We also evaluated the association between environmental temperature and the northern distribution of S. undulatus. We predicted that the northernmost distributional limit of S. undulatus would be associated with locations that provide the minimum heat sum (approximately 495 degree-days) required to complete embryonic development. Based on air and soil temperatures, the predicted northern latitudinal limit of S. undulatus would lie at approximately 40.5-41.5 degrees N. Our predicted value closely corresponds to the observed latitudinal limit in the eastern United States of approximately 40 degrees N. Our results suggest that soil temperatures at northern latitudes are not warm enough for a sufficient length of time to permit successful incubation of S. undulatus embryos. These results are consistent with the hypothesis that incubation temperature is an important factor limiting the geographic distributions of oviparous reptile species at high latitudes and elevations.

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“…When incubated at constant temperatures, embryos hatch successfully in the range of 23-34 8C [23][24][25]. Relatively high temperatures reduce the duration of incubation without affecting the body size at hatching [24,25], but survival is poor if the temperature is too high [23,25].…”

Section: Behavioral Adaptation: Selection Of Nesting Sitesmentioning

confidence: 99%

Thermal adaptation of maternal and embryonic phenotypes in a geographically widespread ectotherm

Angilletta

Oufiero

Sears

2004

International Congress Series

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Duration of Incubation of Sceloporus undulatus Eggs at Constant Temperature

Cited by 51 publications

References 9 publications

The Evolution of Maternal Investment in Lizards: An Experimental and Comparative Analysis of Egg Size and Its Effects on Offspring Performance

The Evolution of Maternal Investment in Lizards: An Experimental and Comparative Analysis of Egg Size and Its Effects on Offspring Performance

Incubation temperature and phenotypic traits of Sceloporus undulatus: implications for the northern limits of distribution

Thermal adaptation of maternal and embryonic phenotypes in a geographically widespread ectotherm

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