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Condition Dependence (condition + dependence)
Selected AbstractsSEXUAL SELECTION, GENETIC ARCHITECTURE, AND THE CONDITION DEPENDENCE OF BODY SHAPE IN THE SEXUALLY DIMORPHIC FLY PROCHYLIZA XANTHOSTOMA (PIOPHILIDAE)EVOLUTION, Issue 1 2005Russell Bonduriansky Abstract The hypothesis that sexual selection drives the evolution of condition dependence is not firmly supported by empirical evidence, and the process remains poorly understood. First, even though sexual competition typically involves multiple traits, studies usually compare a single sexual trait with a single "control" trait, ignoring variation among sexual traits and raising the possibility of sampling bias. Second, few studies have addressed the genetic basis of condition dependence. Third, even though condition dependence is thought to result from a form of sex-specific epistasis, the evolution of condition dependence has never been considered in relation to intralocus sexual conflict. We argue that condition dependence may weaken intersexual genetic correlations and facilitate the evolution of sexual dimorphism. To address these questions, we manipulated an environmental factor affecting condition (larval diet) and examined its effects on four sexual and four nonsexual traits in Prochyliza xanthostoma adults. As predicted by theory, the strength of condition dependence increased with degree of exaggeration among male traits. Body shape was more condition dependent in males than in females and, perhaps as a result, genetic and environmental effects on body shape were congruent in males, but not in females. However, of the four male sexual traits, only head length was significantly larger in high-condition males after controlling for body size. Strong condition dependence was associated with reduced intersexual genetic correlation. However, homologous male and female traits exhibited correlated responses to condition, suggesting an intersexual genetic correlation for condition dependence itself. Our findings support the role of sexual selection in the evolution of condition dependence, but reveal considerable variation in condition dependence among sexual traits. It is not clear whether the evolution of condition dependence has mitigated or exacerbated intralocus sexual conflict in this species. [source] CONDITION DEPENDENCE OF SEXUAL ORNAMENT SIZE AND VARIATION IN THE STALK-EYED FLY CYRTODIOPSIS DALMANNI (DIPTERA: DIOPSIDAE)EVOLUTION, Issue 5 2004Samuel Cotton Abstract We used the stalk-eyed fly Cyrtodiopsis dalmanni to examine predictions made by condition-dependent handicap models of sexual selection. Condition was experimentally varied by manipulation of larval food availability. Cyrtodiopsis dalmanni is a highly dimorphic species exhibiting strong sexual selection, and the male sexual ornament (exaggerated eyespan) showed strong condition-dependent expression relative to the homologous trait in females and nonsexual traits. Male eyespan also showed a great increase in standardized variance under stress, unlike nonsexual traits. The inflated variance of the male ornament was primarily attributable to condition-dependent (but body-size-independent) increase in variance. Thus, evaluation of male eyespan allows females to gain additional information about male condition over and above that given by body size. These findings accord well with condition-dependent handicap models of sexual selection. [source] Informed dispersal, heterogeneity in animal dispersal syndromes and the dynamics of spatially structured populationsECOLOGY LETTERS, Issue 3 2009Jean Clobert Abstract There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation. [source] SEXUAL SELECTION, GENETIC ARCHITECTURE, AND THE CONDITION DEPENDENCE OF BODY SHAPE IN THE SEXUALLY DIMORPHIC FLY PROCHYLIZA XANTHOSTOMA (PIOPHILIDAE)EVOLUTION, Issue 1 2005Russell Bonduriansky Abstract The hypothesis that sexual selection drives the evolution of condition dependence is not firmly supported by empirical evidence, and the process remains poorly understood. First, even though sexual competition typically involves multiple traits, studies usually compare a single sexual trait with a single "control" trait, ignoring variation among sexual traits and raising the possibility of sampling bias. Second, few studies have addressed the genetic basis of condition dependence. Third, even though condition dependence is thought to result from a form of sex-specific epistasis, the evolution of condition dependence has never been considered in relation to intralocus sexual conflict. We argue that condition dependence may weaken intersexual genetic correlations and facilitate the evolution of sexual dimorphism. To address these questions, we manipulated an environmental factor affecting condition (larval diet) and examined its effects on four sexual and four nonsexual traits in Prochyliza xanthostoma adults. As predicted by theory, the strength of condition dependence increased with degree of exaggeration among male traits. Body shape was more condition dependent in males than in females and, perhaps as a result, genetic and environmental effects on body shape were congruent in males, but not in females. However, of the four male sexual traits, only head length was significantly larger in high-condition males after controlling for body size. Strong condition dependence was associated with reduced intersexual genetic correlation. However, homologous male and female traits exhibited correlated responses to condition, suggesting an intersexual genetic correlation for condition dependence itself. Our findings support the role of sexual selection in the evolution of condition dependence, but reveal considerable variation in condition dependence among sexual traits. It is not clear whether the evolution of condition dependence has mitigated or exacerbated intralocus sexual conflict in this species. [source] MULTIVARIATE QUANTITATIVE GENETICS AND THE LEK PARADOX: GENETIC VARIANCE IN MALE SEXUALLY SELECTED TRAITS OF DROSOPHILA SERRATA UNDER FIELD CONDITIONSEVOLUTION, Issue 12 2004Emma Hine Abstract Single male sexually selected traits have been found to exhibit substantial genetic variance, even though natural and sexual selection are predicted to deplete genetic variance in these traits. We tested whether genetic variance in multiple male display traits of Drosophila serrata was maintained under field conditions. A breeding design involving 300 field-reared males and their laboratory-reared offspring allowed the estimation of the genetic variance-covariance matrix for six male cuticular hydrocarbons (CHCs) under field conditions. Despite individual CHCs displaying substantial genetic variance under field conditions, the vast majority of genetic variance in CHCs was not closely associated with the direction of sexual selection measured on field phenotypes. Relative concentrations of three CHCs correlated positively with body size in the field, but not under laboratory conditions, suggesting condition-dependent expression of CHCs under field conditions. Therefore condition dependence may not maintain genetic variance in preferred combinations of male CHCs under field conditions, suggesting that the large mutational target supplied by the evolution of condition dependence may not provide a solution to the lek paradox in this species. Sustained sexual selection may be adequate to deplete genetic variance in the direction of selection, perhaps as a consequence of the low rate of favorable mutations expected in multiple trait systems. [source] Characterizing the pigment composition of a variable warning signal of Parasemia plantaginis larvaeFUNCTIONAL ECOLOGY, Issue 4 2010Carita Lindstedt Summary 1.,Aposematic animals advertise their defences to predators via warning signals that often are bright colours combined with black patterns. Predation is assumed to select for large pattern elements and conspicuousness of warning signals because this enhances avoidance learning of predators. However, conspicuousness of the colour pattern can vary among individuals of aposematic species, suggesting that warning signal expression may be constrained by opposing selection pressures. If effective warning signals are costly to produce, variation in signal expression may be maintained via physiological trade-offs. To understand the costs of signalling that might underlay both physiological and ecological trade-offs, it is crucial to identify the pigments involved in aposematic traits, how they or their precursors are acquired and how their production and/or deposition interact with other physiological processes. 2.,We characterized the pigments responsible for the genetically and phenotypically variable orange-black warning signal of the hairy larvae of an Arctiid moth, Parasemia plantaginis. We tested orange and black coloured hairs for the presence of six candidate pigment types using high-performance liquid chromatography, spectral and solubility analyses. 3.,After excluding the presence of carotenoids, ommochromes, pterins and pheomelanins in orange hairs, our results suggest that tiger moth larvae produce their orange warning signal by depositing both diet-derived flavonoids and trace levels of synthesized eumelanin in their hairs. The nearby black hairs are coloured by eumelanin. 4.,In light of previous studies, we conclude that although a large orange patch increases the 1larvae's antipredator efficacy, variation in the size of orange patches within a population can be driven by scarcity of flavonoids in diet. However, traces of eumelanin found in the orange hairs of the larvae may also play a significant role in the maintenance of the signal pattern on poor quality diets. 5.,The goal of the future studies will be to test the condition dependence of pigment deposition in aposematic colour patterns by directly manipulating relevant nutritional parameters such as dietary flavonoid or nitrogen content (i.e. amino acid content). [source] Iridescent hindwing patches in the Pipevine Swallowtail: differences in dorsal and ventral surfaces relate to signal function and contextFUNCTIONAL ECOLOGY, Issue 4 2010Ronald L. Rutowski Summary 1.,Iridescent colour signals are directional but, like diffusely reflected colours, vary within and among species in ways that may be adaptations to specific types of receivers in specific light environments. 2.,The hindwings of pipevine swallowtail butterflies exhibit brilliant blue and iridescent colour patches on the ventral surface in both sexes and on the dorsal wing surface in males. Evidence suggests that the ventral iridescent blue is a component of the warning coloration of this distasteful species, while the dorsal blue iridescent wing area is a sexual signal. Given differences in the function and ecological context of signal production, we analysed reflectance spectra from the iridescent blue areas of both field-caught and laboratory-reared animals to test several predictions about the iridescent colour patches on these wing surfaces. 3.,The ventral blue patches in the warning coloration of males and females should be most visible early and late in the day, due to wing orientation relative to sun angle. We therefore predicted that these iridescent colour patches would be brighter and of longer wavelengths than the male dorsal blue patch displayed during midday courtships. The prediction about reflectance intensity was supported but the prediction about hue was not. 4.,We predicted that the sexually selected dorsal hindwing iridescence of males would be more variable among individuals and condition dependent than the naturally selected ventral iridescent colour patches. To assess variation and condition dependence, laboratory-reared and field-captured individuals were compared. The prediction about variation was not supported, but only the dorsal wing surfaces showed evidence of being condition dependent. 5.,We investigated whether development of dorsal and ventral blue iridescence was coupled by determining correlations in colour properties between the wing surfaces. Our finding of positive correlations indicated a potential developmental constraint in the evolution of colour differences between the two wing surfaces. 6.,Results of this study suggest that some properties of iridescent coloration on the hindwing of the pipevine swallowtail (especially intensity) may have been fine-tuned by evolution in response to prevailing ambient light conditions and viewing perspectives that differ among types of signal receivers. [source] Heightened condition dependence is not a general feature of male eyespan in stalk-eyed flies (Diptera: Diopsidae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2004S. Cotton Abstract Stalk-eyed flies are exemplars of sexual selection leading to the evolution of exaggerated male ornaments (eyespan). In Sphyracephala beccarri, there is no evidence for female mate choice for exaggerated male eyespan and only minor sex differences in eyespan. We used S. beccarri to test whether heightened condition dependence only evolves when male eyespan becomes sexually exaggerated. Male eyespan showed heightened condition dependence under food stress compared with a control trait (wing length). However, female eyespan displayed a similar pattern and there was no sex difference in the degree of increased eyespan sensitivity. The finding that eyespan is a sensitive indicator of food stress, even in an unexaggerated state, suggests that this may have acted as a pre-adaptation to the role of eyespan in sexual signalling in other Diopsid species. These results are consistent with handicap theory and Fisher's view of how sexual selection is initiated. [source] | ||||||||||