Home About us Contact
|
Home About us Contact | ||
|
|
||
Artificial Selection Experiments (artificial + selection_experiment)
Selected AbstractsSelection experiments and the study of phenotypic plasticity,JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2002S. M. Scheiner Abstract Laboratory selection experiments are powerful tools for establishing evolutionary potentials. Such experiments provide two types of information, knowledge about genetic architecture and insight into evolutionary dynamics. They can be roughly classified into two types: (1) artificial selection in which the experimenter selects on a focal trait or trait index, and (2) quasi-natural selection in which the experimenter establishes a set of environmental conditions and then allows the population to evolve. Both approaches have been used in the study of phenotypic plasticity. Artificial selection experiments have taken various forms including: selection directly on a reaction norm, selection on a trait in multiple environments, and selection on a trait in a single environment. In the latter experiments, evolution of phenotypic plasticity is investigated as a correlated response. Quasi-natural selection experiments have examined the effects of both spatial and temporal variation. I describe how to carry out such experiments, summarize past efforts, and suggest further avenues of research. [source] Genetic independence of female signal form and male receiver design in the almond moth, Cadra cautellaJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2008J. D. ALLISON Abstract Efficient signalling requires coordination of signal form and receiver design. To maintain signal function, parallel changes in signaller and receiver traits are required. Genetic correlation and co-evolution among signal and response traits have been proposed to preserve signal function (i.e. coordination) during the evolution of mate recognition systems. Empirical studies have provided support for both mechanisms; however, there is debate regarding the interpretation of some of these studies. Tests for a genetic correlation typically hybridize divergent signalling systems and look at hybrid signal form and receiver design, or impose artificial selection on signal form and look for an indirect response to selection in receiver design. Some of the hybridization studies did not achieve reassortment of genes from the parental types, whereas some of the artificial selection studies incorporated random mating in their designs. As a result of these limitations, the hybridization studies cannot discriminate between genetic correlation and co-evolution with primarily additive genetic effects underlying signal and response traits. Similarly, the artificial selection experiments cannot discriminate between genetic correlation because of linkage disequilibrium and co-evolution. This study examined the mating preferences of male almond moths, Cadra cautella, before and after female moths were artificially selected (using a design incorporating assortative mating) for novel pheromone blend ratios. Our results demonstrate the absence of a genetic correlation between signal and response traits in the almond moth. [source] The evolution of trade-offs: where are we?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007D. A. ROFF Abstract Trade-offs are a core component of many evolutionary models, particularly those dealing with the evolution of life histories. In the present paper, we identify four topics of key importance for studies of the evolutionary biology of trade-offs. First, we consider the underlying concept of ,constraint'. We conclude that this term is typically used too vaguely and suggest that ,constraint' in the sense of a bias should be clearly distinguished from ,constraint' in the sense of proscribed combinations of traits or evolutionary trajectories. Secondly, we address the utility of the acquisition,allocation model (the ,Y-model'). We find that, whereas this model and its derivatives have provided new insights, a misunderstanding of the pivotal equation has led to incorrect predictions and faulty tests. Thirdly, we ask how trade-offs are expected to evolve under directional selection. A quantitative genetic model predicts that, under weak or short-term selection, the intercept will change but the slope will remain constant. Two empirical tests support this prediction but these are based on comparisons of geographic populations: more direct tests will come from artificial selection experiments. Finally, we discuss what maintains variation in trade-offs noting that at present little attention has been given to this question. We distinguish between phenotypic and genetic variation and suggest that the latter is most in need of explanation. We suggest that four factors deserving investigation are mutation-selection balance, antagonistic pleiotropy, correlational selection and spatio-temporal variation, but as in the other areas of research on trade-offs, empirical generalizations are impeded by lack of data. Although this lack is discouraging, we suggest that it provides a rich ground for further study and the integration of many disciplines, including the emerging field of genomics. [source] The sexually-selected sperm hypothesis: sexbiased inheritance and sexual antagonismBIOLOGICAL REVIEWS, Issue 2 2002T. PIZZARI ABSTRACT When females are inseminated by more than one male (polyandry) sexual selection continues after insemination in the form of sperm competition and cryptic female choice. The sexually-selected sperm hypothesis proposes that, under the risk of sperm competition, additive variation in male traits determining fertilising effciency will select for female propensity to be polyandrous in order to increase the probability of producing sons with superior fertilising effciency. Two factors complicate this prediction: sex-biased transmission of male fertilising effciency traits and sexual antagonism of sex-limited traits, fostered by sexbiased inheritance. Here, we (i) review the evidence that male traits contributing towards fertilising effciency are heritable through sex-biased mechanisms, and (ii) explore the evolutionary implications for male and female reproductive strategies caused by both sex-biased transmission and sexual antagonism of fertilising effciency traits. Many male fertilising effciency traits are heritable through sex-biased mechanisms and may not necessarily increase female fitness. The predictions of the sexually-selected sperm hypothesis change dramatically under these different mechanisms of inheritance of fertilising effciency traits, and different fitness pay-offs derived by females from the expression of such traits. Both sex-biased control of fertilising effciency and sexual antagonism may also be important in explaining the maintenance of the genetic variance and selection potential of fertilising effciency. We propose that a useful approach to test the sexually-selected sperm hypothesis is to combine studies which identify behavioural and physiological mechanisms explaining variation in reproductive success with artificial selection experiments to infer the underlying evolutionary patterns. [source] | ||||||||||