RegulatoRy MechanisMs that undeRlie Phenology, BehavioR, and coPing with enviRonMental PeRtuRBations: an alteRnative look at BiodiveRsity

The Auk, Vol. 129, Number 1, pages 1−7. ISSN 0004-8038, electronic ISSN 1938-4254.  2012 by The American Ornithologists’ Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www.ucpressjournals. com/reprintInfo.asp. DOI: 10.1525/auk.2012.129.1.1 1E-mail: [email protected] Over one hundred years of laboratory research on highly inbred model organisms has greatly advanced our knowledge of how regulatory networks such as the endocrine system work at the cellular and molecular levels. However, an understanding of how these systems play a vital role in mediating the effects of environmental change on morphology, physiology, and behavior must rely on investigations of organisms in their natural environments. To achieve this has meant integrating laboratory and field investigations wherever possible. Field endocrinology, in which free-living birds are captured and sampled for blood, feces, or feathers, has allowed us to assess for the first time how individuals respond to their physical and social environments under natural conditions (Wingfield and Farner 1976, Möstl et al. 2005). Controlled experiments have also made it possible to manipulate hormonal state (Ketterson and Nolan 1999, Ketterson et al. 2009) or social environment (Wingfield et al. 1999) to further expand our understanding of regulatory mechanisms in ecological context. Here, I discuss how regulatory mechanisms, in relation to seasonal events such as breeding, migrations, or environmental perturbations, can have diverse levels of control that we are only beginning to appreciate. Three examples will address territoriality in different seasonal contexts, adrenocortical responses to stress, and thyroid hormone involvement in control of the life cycle. There is now an urgent need to understand regulatory mechanisms, in the face of massive global changes resulting from anthropogenic influences. For example, loss of biodiversity globally is without doubt one of the biggest issues of our time. Yet we are just beginning to understand how knowledge of the interrelationships among phylogeny, gene–environment interactions, and function may help to facilitate the preservation of remaining biodiversity. Within phenotypes, cells respond in diverse ways to changes in the internal and external environment according to time of day, season, social interactions, and, thus, in how they cope with perturbations. In vertebrates these responses involve perception of the environment through sensory mechanisms, neural transduction within the central nervous system, and neuroendocrine and endocrine cascades to regulate morphological, physiological and behavioral responses of target tissues. This “perception–transduction–response” complex (Fig. 1) involves multiple regulatory mechanisms and is key to predicting how organisms will fare in relation to global change, including direct human disturbance. Furthermore, there are diverse ways in which individuals can respond to the same environmental change, indicating multiple mechanisms (diversity) by which the perception–transduction–response complex can be regulated (Wingfield 2008, Wingfield and Mukai 2009). The traditional view is that selection has favored the persistence of conserved molecular, cellular, and physiological mechanisms of the perception–transduction–response axis over a broad range of populations, habitats, life cycles, and phenology. Evidence is building, however, that there are many variations on this conserved framework that allow individuals not only to survive environmental challenges, but also to successfully reproduce, migrate, molt, and endure a wide range of winter conditions (Wingfield 2008; Wingfield et al. 2011a, b). For example, regulatory networks (e.g., Martin et al. 2011, A. A. Cohen et al. PERSPECTIVES IN ORNITHOLOGY The Auk An International Journal of Ornithology