Date / 4, August (Mon) 9：00〜13：00
Place/ 'Kinen-koudou' building in Hakozaki campus
Invited speakers
- Interaction between ambient light, visual backgrounds, signaling behavior and vision in setting the direction of sexual selection of color patterns.
John Endler (U.C. Santa Barbara)
The visibility and attractiveness of color pattern signals is influenced by the choice of the light environment in which to display, the visual background against which to display, and the spectral absorption functions of the eye and eye photoreceptors. Knowledge of these factors, knowledge of visual processes, and some new non-parametric statistical tests, allows testing of hypotheses about the direction of sexual selection. Hypothesis testing about the design of bowerbird plumage and bowers will be presented for several species of Australian Bowerbirds.- Condition-dependent signalling in stalk-eyed flies
Andrew Pomiankowski (University College London)
The handicap theory of sexual selection predicts that male sexual ornaments signal information about male quality. This predicts that the development of sexual ornaments should be strongly condition-dependent, both in relation to environmental stress and genetic quality. In addition, theory predicts that sexual ornaments should be highly genetically variable. These hypotheses were tested using a species of stalk-eyed fly, Cyrtodiopsis dalmanni, in which females show strong mating preferences for males with exaggerated eyespan. Experiments used controlled levels of environmental variation to cause larval stress, and compared the response of sexual and non-sexual traits. The experiments were carried out on sibships in order to measure the genetic component of variation. A further comparison was made with a non-sexually selected species, Sphyracephala beccarri, to check whether the differences between male and female traits were limited to species subject to strong sexual selection.- Parallel changes in gene expression after 20,000 generations of evolution in Escherichia coli
Tim F. Cooper, Daniel E. Rozen and Richard, E. Lenski. (Michigan State U)Twelve populations of Escherichia coli derived from a common ancestor were propagated in glucose-limited medium for 20,000 generations. The trajectory of fitness increase was similar for all populations, but the extent to which this response was caused by the same or different adaptations is not known. Here we use gene-array technology to address whether evolution in two of these populations has proceeded in parallel and to gain insight into the mechanisms underlying adaptation. We compared the expression profile of the ancestor to that of clones isolated from both populations after 2,000, 10,000 and 20,000 generations of evolution. Changes to this profile reflect the effect of mutations accumulating during evolution. Therefore, changes in common to both populations suggest the presence of underlying parallelism. A total of 118 genes had changed significantly in both populations. Remarkably, in every case, these ‘in common’ genes had changed in the same direction relative to the common ancestor. In an attempt to elucidate the genetic basis of this expression parallelism we examined genes which had changed in parallel for common regulation effectors. This search revealed that many were members of the cAMP-CRP or ppGpp regulons. Sequencing of genes able to alter the levels of these effectors uncovered a mutation in the spoT gene in one of the populations. Introduction of this mutation into the ancestral background confirmed that it did contribute to adaptation and produced many of the parallel expression changes observed after 20,000 generations. These results indicate that the two populations have adapted in part via parallel mechanisms and demonstrate the utility of gene-arrays in addressing basic evolutionary questions, here suggesting ways in which insight into the effect of beneficial mutations can be obtained.- Experimental molecular evolutions with and without cellular interaction
Tetsuya Yomo (Osaka U)We conducted two experimental evolutions accelerated by random mutagenesis to address the following questions: 1) How much variety in the sequences is needed to prompt the evolution of protein functions from random polypeptides? 2) How does cellular interaction affect the dynamics of molecular evolution to allow genetic diversity in population?The first experimental evolution was carried out on a small library of phage-displayed polypeptides with random sequences of about 140 amino acid residues. With less than twenty cycles of random mutagenesis and some different functional selections, the polypeptides evolved with different protein functions, such as esterase activity, DNA binding activity, and so forth. The experimental results basically mean that the evolution of protein functions can be prompted from a small sequence variety, even from a single arbitrarily chosen random sequence.
To know the role of cellular interaction in molecular evolution, we conducted the second experimental evolution, three serial cycles of random mutagenesis of the glutamine synthetase gene and chemostat culture of the transformed Escherichia coli cells containing the mutated genes. The molecular phylogeny and population dynamics of the experimental evolution show the coexistence of some mutant cells having different level of glutamine synthetase activity at each cycle. The coexistence was proven to be stable and require the cellular interaction via the medium. In addition, the mutant gene once extinct at the earlier generation was found to coexist with the population of the final generation. These results show that cellular interaction brought about the change of the fitness of each mutant, giving a chance to increase and maintain genetic diversity even in a spatially-unbiased environment.