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Offspring Traits (offspring + trait)
Selected AbstractsTHE ADAPTIVE SIGNIFICANCE OF TEMPERATURE-DEPENDENT SEX DETERMINATION: EXPERIMENTAL TESTS WITH A SHORT-LIVED LIZARDEVOLUTION, Issue 10 2005Daniel A. Warner 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. [source] Fitness consequences of temperature-mediated egg size plasticity in a butterflyFUNCTIONAL ECOLOGY, Issue 6 2003K. Fischer Summary 1By randomly dividing adult females of the butterfly Bicyclus anynana, reared in a common environment, among high and low temperatures, it is demonstrated that oviposition temperature induces a plastic response in egg size. Females kept at a lower temperature laid significantly larger eggs than those ovipositing at a higher temperature. 2Cross-transferring the experimentally manipulated eggs between temperatures and investigating hatching success showed that a lower rearing temperature is more detrimental for the smaller eggs produced at a higher temperature than for the larger eggs produced at a lower temperature, supporting an adaptive explanation. 3However, when examining two potential mechanisms for an increased fitness of larger offspring (higher desiccation resistance of larger eggs and higher starvation resistance of larger hatchlings), no direct link between egg size and offspring fitness was found. Throughout, i.e. even under benign conditions, larger offspring had a higher fitness. 4Therefore, egg size should be viewed as a conveniently measurable proxy for the plastic responses induced by temperature, but caution is needed before implying that egg size per se is causal in influencing offspring traits. [source] Body size, locomotor speed and antipredator behaviour in a tropical snake (Tropidonophis mairii, Colubridae): the influence of incubation environments and genetic factorsFUNCTIONAL ECOLOGY, Issue 5 2001J. K. Webb Summary 1,The physical conditions experienced by reptile embryos inside natural nests can influence the size, shape and behaviour of the resultant hatchlings. Although most reptiles are tropical, the effects of incubation temperatures on offspring phenotypes have received little attention in tropical species. 2,The consequences of differences in thermal variance during incubation on offspring were studied in a tropical natricine snake (the Keelback Tropidonophismairii), which lays eggs in soil cracks of varying depths. Some 253 eggs from 19 clutches were incubated under two thermal regimes with identical mean temperatures (25·6 °C), but temperatures in the ,variable' treatment fluctuated more (21·8,29·6 °C) than those in the ,constant' temperature treatment (25·2,26·5 °C). These thermal regimes were similar to those of shallow (20 cm deep) and deep (40 cm deep) soil cracks, respectively, and represent thermal conditions inside natural nests and potential nest sites. 3,Incubation temperatures affected body size, shape and antipredator behaviour of hatchling snakes. Snakes from constant temperature incubation were longer and thinner than snakes from high variance incubation. Clutch effects influenced all offspring traits, with significant interactions between clutch of origin and incubation treatment for body size, but not swimming speed or behaviour. 4,There was a significant interaction between incubation treatment and offspring sex on neonate swimming speed. Incubation under cycling thermal regimes significantly increased swimming speeds of females, but had little effect on males. Such sex differences in phenotypic responses of hatchling snakes support a major assumption of the Charnov,Bull hypothesis for the evolution of temperature-dependent sex determination. [source] Cohort variation in offspring growth and survival: prenatal and postnatal factors in a late-maturing viviparous snakeJOURNAL OF ANIMAL ECOLOGY, Issue 3 2010Jean-Pierre Baron Summary 1. Recruitment to adulthood plays an important role in the population dynamics of late-maturing organisms as it is usually variable. Compared to birds and mammals, few studies assessing the contributions to this variation of environmental factors, offspring traits and maternal traits have been carried out for late-maturing snakes. 2. Cohort variation in recruitment through offspring growth and survival in the meadow viper (Vipera ursinii ursinii) was evaluated from 13 years of mark,recapture data collected at Mont Ventoux, France. In this species, females are mature at the age of 4,6 years and adult survival and fecundity rates are high and constant over time. 3. Offspring were difficult to catch during the first 3 years of their lives, but their mean annual probability of survival was reasonably high (0·48 ± 0·11 SE). Mass and body condition at birth (mass residuals) varied significantly between years, decreased with litter size, and increased with maternal length. 4. Cohorts of offspring in better condition at birth grew faster, but offspring growth was not affected by sex, habitat or maternal traits. 5. Survival varied considerably between birth cohorts, some cohorts having a high-survival rate and others having essentially no survivors. No difference in mass or body condition at birth was found between cohorts with ,no survival' and ,good survival'. However, offspring survival in cohorts with good survival was positively correlated with mass at birth and negatively correlated with body condition at birth. 6. Thus, variation in offspring performance was influenced by direct environmental effects on survival and indirect environmental effects on growth, mediated by body condition at birth. Effects of maternal traits were entirely channelled through offspring traits. [source] Maternal and paternal condition effects on offspring phenotype in Telostylinus angusticollis (Diptera: Neriidae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2007R. BONDURIANSKY Abstract It is widely recognized that maternal phenotype can have important effects on offspring, but paternal phenotype is generally assumed to have no influence in animals lacking paternal care. Nonetheless, selection may favour the transfer of environmentally acquired condition to offspring from both parents. Using a split-brood, cross-generational laboratory design, we manipulated a key environmental determinant of condition , larval diet quality , of parents and their offspring in the fly Telostylinus angusticollis, in which there is no evidence of paternal provisioning. Parental diet did not affect offspring survival, but high-condition mothers produced larger eggs, and their offspring developed more rapidly when on a poor larval diet. Maternal condition had no effect on adult body size of offspring. By contrast, large, high-condition fathers produced larger offspring, and follow-up assays showed that this paternal effect can be sufficient to increase mating success of male offspring and fecundity of female offspring. Our findings suggest that both mothers and fathers transfer their condition to offspring, but with effects on different offspring traits. Moreover, our results suggest that paternal effects can be important even in species lacking conventional forms of paternal care. In such species, the transfer of paternal condition to offspring could contribute to indirect selection on female mate preferences. [source] Contribution of direct and maternal genetic effects to life-history evolutionNEW PHYTOLOGIST, Issue 3 2009Laura F. Galloway Summary ,,Maternal effects are ubiquitous in nature. In plants, most work has focused on the effects of maternal environments on offspring trait expression. Less is known about the prevalence of genetic maternal effects and how they influence adaptive evolution. Here, we used multivariate genetic models to estimate the contributions of maternal and direct genetic (co)variance, the cross-generation direct-maternal covariance, and M, the matrix of maternal effect coefficients, for life-history traits in Campanulastrum americanum, a monocarpic herb. ,,Following a three-generation breeding design, we grew paternal half-sib families with full-sib relatives of each parent and measured juvenile and adult traits. ,,Seed size was influenced exclusively by maternal environmental effects, whereas maternal genetic effects influenced traits throughout the life cycle, including strong direct and maternal additive genetic correlations within and between generations for phenological and size traits. Examination of M suggested that both juvenile and adult traits in maternal plants influenced the expression of offspring traits. ,,This study reveals substantial potential for genetic maternal effects to contribute to adaptive evolution including cross-generation direct-maternal correlations that may slow selection response, maternal effects on phenology that reinforce genetic correlations, and within- and between-generation genetic correlations that may influence life-history polymorphism. [source] | ||||||||||