 Evidence of epistasis from hybridization studies is more scarce. |
| Thus mating of females was strictly along the lines of paternal song. |
| The independent role of morphology in mate choice is revealed by the rare instances where the usual association between song and morphology is disrupted. |
| The theory of founder effects does not explain how novel features like plumage traits arise. |
| We observe closely related species in sympatry and infer how they evolved from a common ancestor. |
| Almost nothing is known from hybridization studies about the inheritance of courtship behavior of females, or of their responsiveness to particular male signals. |
| Males transmit signals in courtship through behavioral displays. |
| To summarize, the particular song a male sings, and the behavioral responses of females to song and morphological signals, are not genetically inherited in a fixed manner but are determined by learning early in life. |
| Exchange of breeding individuals between two populations tends to homogenize their gene pools. |
| Species can be recognized by their morphological characteristics and songs. |
| Closely related species of birds are also chromosomally similar. |
| Islands are known to differ in the food supply available to ground finches, mainly seeds. |
| The process of speciation is completed with the cessation of genetic exchange. |
| Thus the genetic basis to the origin of bird species is to be sought in the inheritance of adult traits that are subject to natural and sexual selection. |
| Plumage features constitute a major component of courtship signals. |
| The divergence of songs in the new population away from those in the progenitor population would only be prevented if these processes were balanced by repeated immigration and subsequent breeding: song flow. |
| Genes that underlie the capacity to receive, use and transmit information are the evolving properties. |
