Despite great interest, the integration of in- and extrinsic factors and of past and present condition into the adaptive regulation of the phenotype remains a puzzle. A phenotype consists of a network of traits also including brain morphology. As some of these traits can be developed well before the actual functional examination, one expects long-lasting impacts of developmental conditions on many traits of this network. Conversely, rapid changes of current conditions should lead to adjustments of the integrator network that could counteract long-term effects of previous conditions and result in the modification of phenotypic traits. Because testosterone regulates the expression of many individual traits it has the potential to function as a mediator that integrates different cues into the phenotype. However, such networks have rarely been considered as a whole, and the role of testosterone in mediating and integrating trait development and
expression has never been tested in detail. Therefore, the applicant proposes a 3-year project in 2 model systems: the red-backed fairywren (Malurus melanocephalus) and the brichard’s lamprologus (Neolamprologus brichardi). In both species young males engage in either of three/two distinct breeding phenotypes. Specifically, the project addresses 1) if and how testosterone levels during early adulthood affect not only ornamentation but also subsequent breeding behaviour, song parameters and brain function, and 2) how experimentally-induced rapid changes in social status or in testosterone levels during breeding affect male phenotype and the perception of the resulting altered phenotype by conspecifics. The applicant expects clear differences between male phenotypes and long-lasting impacts of elevated testosterone levels on breeding strategy. Furthermore, she expects a reflection of changes in social status or testosterone levels during breeding on rapid changes in behaviour, brain morphology and the perception by conspecifics.
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