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Phenotypic Trade-offs (phenotypic + trade-off)
Selected AbstractsIntraclutch egg-size variation in acanthosomatid bugs: adaptive allocation of maternal investment?OIKOS, Issue 2 2001Shin-ichi Kudo If there are differences in predation risk among the offspring within a clutch, parents may allocate less resources to the offspring facing higher risk. I examined parental investment in terms of egg size within clutches in five species of stink bugs (Heteroptera, Acanthosomatidae). In subsocial Elasmucha and Sastragala species, the female guards her eggs and first-instar nymphs against invertebrate predators by covering her clutch with her body. Large differences in survival from predation between offspring at the centre and offspring at the periphery of the clutch have been reported in such subsocial insects. I found that Elasmucha and Sastragala females laid significantly smaller eggs in the peripheral (and thus more vulnerable) part of the clutch. Phenotypic trade-offs between egg size and clutch size were detected in these subsocial species. Egg size was positively correlated with hatched first-instar nymph size: smaller nymphs hatched from smaller peripheral eggs. In asocial Elasmostethus humeralis, however, no significant difference in size was detected between the eggs at the centre of and those at the periphery of the clutch. Thus, in subsocial acanthosomatid bugs, females seem to allocate their resources according to the different predation risks faced by the offspring within the clutch. [source] Effects of size and morphology on swimming performance in juvenile brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 4 2003A. F. Ojanguren Abstract,,, Our study assesses swimming capacity (speed and stamina) and possible morphometric determinants of locomotor performance of juvenile brown trout (Salmo trutta L.). We addressed these issues at the individual level to have an approach of the functional significance of intraspecific variation in morphological design. Both swimming speed and endurance time showed significant positive relationships with fish length. Size-corrected values of speed and endurance time were negatively correlated suggesting a phenotypic trade-off between burst and prolonged swimming. Size was also highly correlated with all the morphological variables measured. Therefore, we used the residuals of the regressions of those variables on fish length to remove the effect of body size. A principal components analysis (PCA) summarised the 12 morphological variables into two factors, which accounted for 44.3% of the variance. PC1 combined several measures of body depth and width, whereas PC2 represented mainly postanal length relative to abdomen length. Relationships between the scores of the two factors and size-corrected values of maximum swimming speed and endurance time were weak. PC2 showed a significant positive relationship with endurance time; that is, individuals with longer caudal regions were able to swim against water flow for longer periods of time. Stoutness (PC1) showed a marginally significant negative correlation with endurance time. The lack of stronger relationships could be because of the low morphometric variability among the test individuals, all proceeding from the same population, reared in a common environment, and measured at the same ontogenetic stage. [source] Temperature dependent larval resource allocation shaping adult body size in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2003Z. Bochdanovits Abstract Geographical variation in Drosophila melanogaster body size is a long-standing problem of life-history evolution. Adaptation to a cold climate invariably produces large individuals, whereas evolution in tropical regions result in small individuals. The proximate mechanism was suggested to involve thermal evolution of resource processing by the developing larvae. In this study an attempt is made to merge proximate explanations, featuring temperature sensitivity of larval resource processing, and ultimate approaches focusing on adult and pre-adult life-history traits. To address the issue of temperature dependent resource allocation to adult size vs. larval survival, feeding was stopped at several stages during the larval development. Under these conditions of food deprivation, two temperate and two tropical populations reared at high and low temperatures produced different adult body sizes coinciding with different probabilities to reach the adult stage. In all cases a phenotypic trade-off between larval survival and adult size was observed. However, the underlying pattern of larval resource allocation differed between the geographical populations. In the temperate populations larval age but not weight predicted survival. Temperate larvae did not invest accumulated resources in survival, instead they preserved larval biomass to benefit adult weight. In other words, larvae from temperate populations failed to re-allocate accumulated resources to facilitate their survival. A low percentage of the larvae survived to adulthood but produced relatively large flies. Conversely, in tropical populations larval weight but not age determined the probability to reach adulthood. Tropical larvae did not invest in adult size, but facilitated their own survival. Most larvae succeeded in pupating but then produced small adults. The underlying physiological mechanism seemed to be an evolved difference in the accessibility of glycogen reserves as a result of thermal adaptation. At low rearing temperatures and in the temperate populations, glycogen levels tended to correlate positively with adult size but negatively with pupation probability. The data presented here offer an explanation of geographical variation in body size by showing that thermal evolution of resource allocation, specifically the ability to access glycogen storage, is the proximate mechanism responsible for the life-history trade-off between larval survival and adult size. [source] The heritability of inducible defenses in tadpolesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2005R. A. RELYEA Abstract The evolution of plastic traits requires phenotypic trade-offs and heritable traits, yet the latter requirement has received little attention, especially for predator-induced traits. Using a half-sib design, I examined the narrow-sense heritability of predator-induced behaviour, morphology, and life history in larval wood frogs (Rana sylvatica). Many of the traits had significant additive genetic variation in predator (caged Anax longipes) and no-predator environments. Whereas most traits had moderate to high heritability across environments, tail depth exhibited high heritability with predators but low heritability without predators. In addition, several traits had significant heritability for plasticity, suggesting a potential for selection to act on plasticity per se. Genetic correlations confirmed known phenotypic relationships across environments and identified novel relationships within each environment. This appears to be the first investigation of narrow-sense heritabilities for predator-induced traits and confirms that inducible traits previously shown to be under selection also have a genetic basis and should be capable of exhibiting evolutionary responses. [source] Consequence of herbivory for the fitness cost of herbicide resistance: photosynthetic variation in the context of plant,herbivore interactionsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2005A. J. Gassmann Abstract The cost of adaptations may depend on environmental conditions. We consider how the fitness cost of resistance to the herbicide triazine in Amaranthus hybridus interacts with folivory from the beetle Disonycha glabrata. Triazine-resistant (TR) genotypes suffer a fitness cost because of a pleiotropic reduction in the light reaction of photosynthesis, which in turn often leads to a reduction in photosynthetic rate. We found that the fitness cost of triazine resistance was 360% greater in the presence than absence of D. glabrata. This resulted from multiple phenotypic trade-offs, with TR plants suffering greater herbivory and displaying a diminished tolerance of damage. Our work highlights the importance of incorporating appropriate ecological variation into the assessment of fitness trade-offs. The results of this study also illustrate the potential for herbivores to impose selection on photosynthetic variation, and for variation in resource acquisition to obscure fitness costs. [source] Fitness, developmental instability, and the ontogeny of fluctuating asymmetry in Daphnia magnaBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2006LEIF CHRISTIAN STIGE Fluctuating asymmetry (FA) is the most commonly used measure of developmental instability. The relation between FA and individual fitness remains controversial, partly due to limited knowledge on the mechanisms behind variation in FA. To address this, we investigated the associations between FA, growth and reproduction as well as the ontogeny of FA in a clonal population of Daphnia magna. FA was not correlated with growth and reproduction, either at the between- or the within-individual level, in a high (N = 48 individuals) or in a low (N = 52 individuals) food-quantity regime. There were therefore no indications of functional effects of FA or of phenotypic trade-offs between developmental stability, growth and reproduction. Individual asymmetries varied randomly in sign and magnitude between subsequent molts (N = 19 individuals, 9,11 instars), but the levels of FA were generally lowest at intermediate ages. No feedback between right and left sides was detected. This suggests that FA only reflects the most recent growth history, that developmental instability may increase in old age, and that FA depends on processes operating on each side of the body independently. The results also suggest that FA differences within and among individual Daphnia are largely random, with limited biological significance. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 179,192. [source] | ||||||||||||||||||||||