The Physiological Regulation of Simultaneously Selected Traits

几乎所有的生物特征都有可能在选择中进化。 然而，有些性状可能不会像预期的那样对选择做出反应，因为它们与其他性状呈负相关。 这种现象产生的权衡是生命史进化的基础。 通常在生活史进化的研究中，一个焦点特征被允许经历选择，它和其他特征之间的相关性被用来估计权衡。 然而，选择倾向于同时作用于多个性状，因此需要研究多个性状的同时选择，而不是与一个焦点性状的相关性。很少有研究探讨了生活史性状的生理或发育机制是如何对焦点性状的选择做出反应的，迄今为止还没有研究探讨了多个生活史性状同时选择的生理调节。本研究将解决这些问题的研究，著名的烟草天蛾，天蛾（鳞翅目：天蛾科）。 这是极少数的物种之一，其中调节两个重要的生活史特征，身体大小和发育时间的生理机制，是已知的，本研究提供了必要的背景。一系列的六个定向选择实验将进行十代。 这些将包括所有四种可能的组合，即同时选择增加和减少发育时间和体型，以及选择增加体型和选择减少发育时间。决定这些性状的三个生理因素（临界重量、PTTH延迟时间和生长速率）将在选择前后进行测量。这将是第一个研究如何调节生理因素，约束或产生，多个生活史性状的进化，以应对同时选择。

Almost all biological traits have the potential to evolve in response to selection. Some traits may not respond to selection as might be expected, however, because they are negatively correlated with other traits. Such phenomena generate the tradeoffs that are the basis of life history evolution. Typically in studies of life history evolution, one focal trait is allowed to experience selection, and correlations between it and other traits are used to estimate the tradeoffs. However, selection tends to act on multiple traits simultaneously, necessitating studies of simultaneous selection on multiple traits rather than on correlations with one focal trait. Few studies have examined how the physiological or developmental mechanisms that underlie life history traits respond to selection on the focal traits and no study to date has examined the physiological regulation of simultaneous selection on multiple life history traits. This study will address these issues with studies of the well-known tobacco hornworm, Manduca sexta (Lepidoptera: Sphingidae). This is one of very few species in which the physiological mechanisms regulating two important life history traits, body size and development time, are known, providing essential background for this study. A series of six directional selection experiments will be run for ten generations. These will include all four possible combinations of simultaneous selection for increased and decreased development time and body size as well as selection to increase body size and selection to decrease development time. The three physiological factors that determine these traits (critical weight, PTTH delay time, and growth rate) will be measured before and after selection. This will be the first study to examine how the regulating physiological factors, constrain or engender, the evolution of multiple life history traits in response to simultaneous selection.