Theory predicts that the mechanism of genetic sex determination can substantially influence the evolution of sexually selected traits. For example, female heterogamety (ZZ/ZW) can favour the evolution of extreme male traits under Fisher's runaway model of sexual selection. We empirically test whether the genetic system of sex determination has played a role in the evolution of exaggerated male ornaments in actinopterygiian fishes, a clade in which both female-heterogametic and male-heterogametic systems of sex determination have evolved multiple times. Using comparative methods both uncorrected and corrected for phylogenetic non-independence, we detected no significant correlation between sex-chromosome systems and sexually selected traits in males. Results suggest that sex-determination mechanism is at best a relatively minor factor affecting the outcomes of sexual selection in ray-finned fishes. © 2005 The Royal Society.

We report susceptibility experiments in magnetic fields up to 60 T and show conclusively that the de Haas-van Alphen oscillations originate from a single spin Fermi surface. New observed frequencies present in magnetic breakdown and quantum interference oscillations indicate that the Fermi-surface topology changes as a function of the applied field while maintaining a constant volume. These results are not expected from the Anderson lattice model. © 1998 The American Physical Society.