Experimental Analysis of an Early Life-History Stage: Selection on Size of Hatchling Turtles

Janzen, Fredric J.; Tucker, John K.; Paukstis, Gary L.

doi:10.2307/177115

Cited by 69 publications

(141 citation statements)

References 28 publications

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“…Overall, stabilizing selection was more than twice as plausible as directional selection (AIC weights ratio, 0.709 : 0.291), whereas the naive analysis incorrectly selected the reverse pattern, that is, suggesting directional selection was about twice as plausible as stabilizing selection (AIC weights ratio, 0.664 : 0.336). This discrepancy between the naive and the MR analyses suggests that the curvilinear relationship between survival and body mass may be masked either by a direct correlation between body mass and detection probability (e.g., Janzen et al 2000; but additional analyses did not provide such evidence) or by an indirect relation of both parameters with a third life-history trait, such as age or body size. The observed pattern of stabilizing selection probably results from a trade-off between the risks of starvation at low body mass and predation at high body mass (Covas et al 2002).…”

Section: Natural Selection On Body Mass Of Sociable Weaversmentioning

confidence: 84%

“…Monitoring individuals in multiple sites (so-called multistate MR models; Lebreton and Pradel 2002) can solve this problem by estimating phenotype-dependent movement among sites. Bias may also arise in the calculated strength and form of selection due to covariation between detection probability and the trait under selection (e.g., Janzen et al 2000). MR models can cope with this issue by relating the detection probabilities to the phenotypic trait values (Kingsolver and Smith 1995).…”

Section: Discussionmentioning

confidence: 99%

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The Risk of Flawed Inference in Evolutionary Studies When Detectability Is Less than One

Giménez¹,

Viallefont²,

Charmantier³

et al. 2008

The American Naturalist

100

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Section: Natural Selection On Body Mass Of Sociable Weaversmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

The Risk of Flawed Inference in Evolutionary Studies When Detectability Is Less than One

Giménez¹,

Viallefont²,

Charmantier³

et al. 2008

The American Naturalist

100

View full text Add to dashboard Cite

“…A vantagem adaptativa de produzir filhotes maiores ainda não está muito clara. Para filhotes de Trachemys scripta elegans (Wied, 1839) (Emydidae) a predação de filhotes foi dependente do tamanho dos filhotes, sendo que os maiores apresentaram uma redução da exposição à predação (Janzen et al, 2000). A premissa que filhotes maiores têm melhores condições de sobreviver, denominada de hipótese do "maior é melhor" (bigger is better), é defendida por inúmeros autores (Janzen 1993a,b;haskell et al, 1996;Janzen et al, 2000).…”

Section: Resultsunclassified

“…Para filhotes de Trachemys scripta elegans (Wied, 1839) (Emydidae) a predação de filhotes foi dependente do tamanho dos filhotes, sendo que os maiores apresentaram uma redução da exposição à predação (Janzen et al, 2000). A premissa que filhotes maiores têm melhores condições de sobreviver, denominada de hipótese do "maior é melhor" (bigger is better), é defendida por inúmeros autores (Janzen 1993a,b;haskell et al, 1996;Janzen et al, 2000). Em estudos com Chelydra serpentina (Linnaeus, 1758) (Chelydridae) em cativeiro, entretanto, bobyn & brooks (1994) mostraram que filhotes de tamanhos intermediários, com grandes reservas de vitelo, sobrevivem mais tempo e crescem mais rápido.…”

Section: Resultsunclassified

Alometria reprodutiva de Podocnemis unifilis (Testudines: Podocnemididae) na várzea do baixo rio Amazonas, Santarém, Pará, Brasil

Pignati

Pezzuti

2012

Iheringia, Sér. Zool.

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O tamanho do corpo dos organismos representa um parâmetro importante, podendo gerar consequências na sua ecologia, atividades reprodutivas, evolução e desenvolvimento. Relação alométrica é o estudo do tamanho (ou do crescimento) de uma parte do corpo relacionado com o tamanho (ou crescimento) total do corpo do organismo. Este estudo analisou a relação alométrica entre as fêmeas de Podocnemis unifilis (Troschel, 1848) e seus ovos e filhotes e entre as características dos ninhos e a ninhada em uma área de várzea do baixo rio Amazonas, estado do Pará, Brasil. As ninhadas de P. unifilis foram monitoradas no Tabuleiro da Água Preta durante o período reprodutivo de 2009. As fêmeas encontradas desovando foram medidas e seus respectivos ninhos marcados com estacas numeradas e as características físicas mensuradas. Os ovos e filhotes destes ninhos foram retirados e contados, e tiveram seus dados biométricos tomados. Os parâmetros das fêmeas analisados (comprimento retilíneo da carapaça e massa) correlacionaram-se fortemente às variáveis dos ovos (variável x) e filhotes (variável y), exceto com o comprimento do ovo e com a massa do filhote. Estudos futuros direcionados para melhor compreensão de como as características ambientais influenciam nas ninhadas podem ser aplicados, sendo úteis no manejo da espécie.

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“…A caveat is, however, that our hatchlings experienced a predator-free environment. Relatively large hatchlings (from large eggs) may have had greater survival than small individuals if predators were present (Janzen 1993;Sorci and Clobert 1999;Janzen et al 2000), and this size-versus-survival relationship might differ between the sexes under more natural conditions.…”

Section: Hypothesis A: Different Optimal Egg Sizes For Sons Versus Damentioning

confidence: 99%

The Adaptive Significance of Temperature-Dependent Sex Determination: Experimental Tests With a Short-Lived Lizard

Warner

Shine

2005

Evolution

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Abstract. Why is the sex of many reptiles determined by the temperatures that these animals experience during embryogenesis, rather than by their genes? The Charnov-Bull model suggests that temperature-dependent sex determination (TSD) can enhance maternal fitness relative to genotypic sex determination (GSD) if offspring traits affect fitness differently for sons versus daughters and nest temperatures either determine or predict those offspring traits. Although potential pathways for such effects have attracted much speculation, empirical tests largely have been precluded by logistical constraints (i.e., long life spans and late maturation of most TSD reptiles). We experimentally tested four differential fitness models within the Charnov-Bull framework, using a short-lived, early-maturing Australian lizard (Amphibolurus muricatus) with TSD. Eggs from wild-caught females were incubated at a range of thermal regimes, and the resultant hatchlings raised in large outdoor enclosures. We applied an aromatase inhibitor to half the eggs to override thermal effects on sex determination, thus decoupling sex and incubation temperature. Based on relationships between incubation temperatures, hatching dates, morphology, growth, and survival of hatchlings in their first season, we were able to reject three of the four differential fitness models. First, matching offspring sex to egg size was not plausible because the relationship between egg (offspring) size and fitness was similar in the two sexes. Second, sex differences in optimal incubation temperatures were not evident, because (1) although incubation temperature influenced offspring phenotypes and growth, it did so in similar ways in sons versus daughters, and (2) the relationship between phenotypic traits and fitness was similar in the two sexes, at least during preadult life. We were unable to reject a fourth model, in which TSD enhances offspring fitness by generating seasonal shifts in offspring sex ratio: that is, TSD allows overproduction of daughters (the sex likely to benefit most from early hatching) early in the nesting season. In keeping with this model, hatching early in the season massively enhanced body size at the beginning of the first winter, albeit with a significant decline in probability of survival. Thus, the timing of hatching is likely to influence reproductive success in this short-lived, early maturing species; and this effect may well differ between the sexes.

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Experimental Analysis of an Early Life-History Stage: Selection on Size of Hatchling Turtles

Cited by 69 publications

References 28 publications

The Risk of Flawed Inference in Evolutionary Studies When Detectability Is Less than One

The Risk of Flawed Inference in Evolutionary Studies When Detectability Is Less than One

Alometria reprodutiva de Podocnemis unifilis (Testudines: Podocnemididae) na várzea do baixo rio Amazonas, Santarém, Pará, Brasil

The Adaptive Significance of Temperature-Dependent Sex Determination: Experimental Tests With a Short-Lived Lizard

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