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Moore IT, Vernasco BJ, Escallón C, Small TW, Ryder TB, Horton BM. Tales of testosterone: Advancing our understanding of environmental endocrinology through studies of neotropical birds. Gen Comp Endocrinol 2019; 273:184-191. [PMID: 29990493 DOI: 10.1016/j.ygcen.2018.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 06/21/2018] [Accepted: 07/06/2018] [Indexed: 01/29/2023]
Abstract
Studies of birds have greatly advanced our understanding of how testosterone modulates complex phenotypes, specifically its role in mediating male reproductive and associated behaviors. Yet most of the foundational studies have been limited to northern latitude breeding species despite the fact that they represent only a small fraction of worldwide avian diversity. In contrast, phylogenetic, life-history, and mating system diversity all reach their apex in neotropical avifauna and yet these birds, along with more southern latitude species, remain very poorly understood from an endocrine perspective. Despite the relatively limited previous work on taxa breeding in Central and South America, empirical findings have had a disproportionately large impact on our understanding of testosterone's role in everything from geographic variation to behavioral roles and neuroplasticity. Here, we synthesize how studies of neotropical breeding avifauna have advanced our understanding of how testosterone's actions can and are associated with the broad patterns of phenotypic diversity that we see in birds. In addition, we outline how these studies can be used individually or in a comparative context to address fundamental questions about the environmental endocrinology of testosterone and to understand the diversity of roles that testosterone plays in mediating behavioral variation, reproductive strategies, and associated life-history trade-offs.
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Affiliation(s)
- I T Moore
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
| | - B J Vernasco
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - C Escallón
- Departamento de Ciencias Básicas, Universidad de la Salle, Cra 2 No. 10-70, Bogotá, Colombia
| | - T W Small
- Department of Biology, University of Memphis, Memphis, TN 38152, USA
| | - T B Ryder
- Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, PO Box 37012, MRC 5503, Washington DC 20013, USA
| | - B M Horton
- Department of Biology, Millersville University of Pennsylvania, Millersville, PA 17551, USA
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2
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Maldonado K, Newsome SD, Razeto‐Barry P, Ríos JM, Piriz G, Sabat P. Individual diet specialisation in sparrows is driven by phenotypic plasticity in traits related to trade‐offs in animal performance. Ecol Lett 2018; 22:128-137. [DOI: 10.1111/ele.13174] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 06/29/2018] [Accepted: 09/17/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Karin Maldonado
- Departamento de Ciencias Facultad de Artes Liberales Universidad Adolfo Ibáñez Diagonal Las Torres 2640 SantiagoChile
- Departamento de Ciencias Ecológicas Facultad de Ciencias Universidad de Chile Casilla 653 SantiagoChile
| | - Seth D. Newsome
- Department of Biology University of New Mexico Albuquerque NM87131USA
| | - Pablo Razeto‐Barry
- Instituto de Filosofía y Ciencias de la Complejidad IFICC Los Alerces3024 SantiagoChile
- Vicerrectoría académica Universidad Diego Portales Manuel Rodríguez Sur 415 SantiagoChile
| | - Juan Manuel Ríos
- Laboratorio de Química Ambiental Instituto Argentino de Nivología Glaciología y Ciencias Ambientales (IANIGLA, CCT‐CONICET) Mendoza5500Argentina
| | - Gabriela Piriz
- Departamento de Ciencias Ecológicas Facultad de Ciencias Universidad de Chile Casilla 653 SantiagoChile
| | - Pablo Sabat
- Departamento de Ciencias Ecológicas Facultad de Ciencias Universidad de Chile Casilla 653 SantiagoChile
- Departamento de Ecología Center of Applied Ecology & Sustainability (CAPES) Facultad de Ciencias Biológicas Pontificia Universidad Católica de Chile Santiago6513677 Chile
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3
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Intraspecific variation in exploratory behavior and elevational affinity in a widely distributed songbird. Oecologia 2018; 186:931-938. [PMID: 29388024 DOI: 10.1007/s00442-018-4076-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 01/16/2018] [Indexed: 10/18/2022]
Abstract
Populations of the same species can vary substantially in their behavioral and morphometric traits when they are subject to different environmental pressures, which may lead to the development of different adaptive strategies. We quantified variation in exploratory behavior and morphometric traits among two rufous-collared sparrow populations that occur at low and high elevations in central Chile. Moreover, we used census and δ2H values of feather and blood to evaluate migration. We found that individual sparrows inhabiting high elevations were larger and showed more intense exploratory behavior in comparison with those that were captured at lower elevation. Moreover, we observed a steady decline in sparrow abundance during the winter and similar δ2H values for blood collected in the winter and summer at this site, which were significantly lower than blood δ2H values observed at low elevation. This pattern suggests that individuals do not move long distances during winter, and likely they remain at similar elevations in refuge habitats. As predicted, our results support the existent of different adaptive strategies among populations of the same species, and suggest that the combination of behavioral, morphometric, and stable isotope data is a novel and robust integrative approach to assess differences in adaptation across environmental gradients.
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Escallón C, Weinstein NM, Tallant JA, Wojtenek W, Rodríguez-Saltos CA, Bonaccorso E, Moore IT. Testosterone and Haemosporidian Parasites Along a Tropical Elevational Gradient in Rufous-Collared Sparrows (Zonotrichia capensis). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL GENETICS AND PHYSIOLOGY 2016; 325:501-510. [PMID: 27527346 DOI: 10.1002/jez.2034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/25/2016] [Accepted: 07/26/2016] [Indexed: 11/09/2022]
Abstract
Elevation has been proposed as a dominant ecological variable shaping life history traits and subsequently their underlying hormonal mechanisms. In an earlier meta-analysis of tropical birds, elevation was positively related to testosterone levels. Furthermore, parasitism by avian haemosporidians should vary with elevation as environmental conditions affect vector abundance, and while testosterone is needed for breeding, it is hypothesized to be immunosuppressive and thus could exacerbate haemosporidian infection. Our objective in this study was to examine the relationships between elevation, testosterone levels, and parasitism by avian haemosporidians. We surveyed breeding male rufous-collared sparrows (Zonotrichia capensis) across a wide elevational range along the equator. We measured baseline testosterone levels, haemosporidian infection at four elevations spanning the species' natural range in the Ecuadorian Andes (600, 1500, 2100, 3300 m). Testosterone levels from breeding males were not related to elevation, but there was high intrapopulation variability. Testosterone levels were not related to the probability of parasitism, but our results from one population suggested that the likelihood of being infected by haemosporidian parasites was greater when in breeding condition. In conclusion, even though there is variation in life history strategies among the studied populations, wider divergence in seasonality and life history traits would probably be needed to detect an effect of elevation on testosterone if one exists. Additionally, our results show that variation in testosterone is not related to infection risk of haemosporidians, thus other factors that take a toll on energetic resources, such as reproduction, should be looked at more closely.
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Affiliation(s)
- Camilo Escallón
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia.
| | - Nicole M Weinstein
- VA-MD Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia
| | - James A Tallant
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia
| | | | | | - Elisa Bonaccorso
- Centro de Investigación de la Biodiversidad y Cambio Climático (BioCamb) e Ingenieriía en Biodiversidad y Recursos Genéticos, Facultad de Ciencias de Medio Ambiente, Universidad Tecnológica Indoamérica, Machala y Sabanilla, Cotocollao, Quito, Ecuador
| | - Ignacio T Moore
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia
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Merrill L, González-Gómez PL, Ellis VA, Levin II, Vásquez RA, Wingfield JC. A blurring of life-history lines: Immune function, molt and reproduction in a highly stable environment. Gen Comp Endocrinol 2015; 213:65-73. [PMID: 25712433 DOI: 10.1016/j.ygcen.2015.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 01/26/2015] [Accepted: 02/14/2015] [Indexed: 10/24/2022]
Abstract
Rufous-collared sparrows (Zonotrichia capensis peruviensis) from valleys in the Atacama Desert of Chile, live in an extremely stable environment, and exhibit overlap in molt and reproduction, with valley-specific differences in the proportion of birds engaged in both. To better understand the mechanistic pathways underlying the timing of life-history transitions, we examined the relationships among baseline and stress-induced levels of corticosterone (CORT), testosterone, and bacteria-killing ability of the blood plasma (BKA), as well as haemosporidian parasite infections and the genetic structure of two groups of sparrows from separate valleys over the course of a year. Birds neither molting nor breeding had the lowest BKA, but there were no differences among the other three categories of molt-reproductive stage. BKA varied over the year, with birds in May/June exhibiting significantly lower levels of BKA than the rest of the year. We also documented differences in the direction of the relationship between CORT and BKA at different times during the year. The direction of these relationships coincides with some trends in molt and reproductive stage, but differs enough to indicate that these birds exhibit individual-level plasticity, or population-level variability, in coordinating hypothalamo-pituitary-adrenal axis activity with life-history stage. We found weak preliminary evidence for genetic differentiation between the two populations, but not enough to indicate genetic isolation. No birds were infected with haemosporidia, which may be indicative of reduced parasite pressure in deserts. The data suggest that these birds may not trade off among different life-history components, but rather are able to invest in multiple life-history components based on their condition.
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Affiliation(s)
- Loren Merrill
- Illinois Natural History Survey, University of Illinois, Urbana-Champaign, IL 61820, USA.
| | | | - Vincenzo A Ellis
- Department of Biology, University of Missouri, St. Louis, MO 63121, USA.
| | - Iris I Levin
- Department of Biology, Grinnell College, Grinnell, IA 50112, USA; Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309, USA(1).
| | - Rodrigo A Vásquez
- Instituto de Ecología y Biodiversidad, IEB, Universidad de Chile, Santiago, Chile.
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Bergeon Burns CM, Rosvall KA, Hahn TP, Demas GE, Ketterson ED. Examining sources of variation in HPG axis function among individuals and populations of the dark-eyed junco. Horm Behav 2014; 65:179-87. [PMID: 24140626 PMCID: PMC3944345 DOI: 10.1016/j.yhbeh.2013.10.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 09/04/2013] [Accepted: 10/09/2013] [Indexed: 11/22/2022]
Abstract
Gonadal steroids are important mediators of traits relevant to fitness, and thus may be targets of selection. However, more knowledge is needed about sources of variation along the endocrine axes that may contribute to functional variation in steroid levels. In a controlled captive environment, we studied males of two closely related subspecies of the dark-eyed junco (Junco hyemalis) that differ in testosterone-related phenotype, asking whether they also differ in testosterone (T), and assessing the contribution of the sequential links of the hypothalamic-pituitary-gonadal axis. When males of both subspecies were challenged with gonadotropin-releasing hormone (GnRH), they were similar in circulating luteinizing hormone (LH) and T responses. When challenged with exogenous LH, they again produced levels of T similar to one another, and to the levels produced in response to GnRH. However, the smaller, less ornamented, and less aggressive subspecies had greater abundance of mRNA for LH receptor in the testes and for androgen receptor in the rostral hypothalamus, suggesting potential differences in regulatory feedback. We suggest that circulating hormone levels may be less prone to evolutionary change than the responsiveness of individual hormone targets. Among individuals, T titers were highly repeatable whether males were challenged with GnRH or with LH, but LH produced in response to GnRH did not covary with T produced in response to LH. Testis mass, but not LH receptor transcript abundance, predicted individual variation in T responses. These data implicate the gonad, but not the pituitary, as an important source of individual variation in T production.
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Affiliation(s)
- Christine M Bergeon Burns
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Kimberly A Rosvall
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Thomas P Hahn
- Department of Neurobiology, Physiology & Behavior, University of California, Davis, CA 95616, USA.
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Ellen D Ketterson
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
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7
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Pradhan DS, Connor KR, Pritchett EM, Grober MS. Contextual modulation of androgen effects on agonistic interactions. Horm Behav 2014; 65:47-56. [PMID: 24315925 DOI: 10.1016/j.yhbeh.2013.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 11/23/2013] [Accepted: 11/25/2013] [Indexed: 12/15/2022]
Abstract
Seasonal changes in steroid hormones are known to have a major impact on social behavior, but often are quite sensitive to environmental context. In the bi-directionally sex changing fish, Lythrypnus dalli, stable haremic groups exhibit baseline levels of interaction. Status instability follows immediately after male removal, causing transiently elevated agonistic interactions and increase in brain and systemic levels of a potent fish androgen, 11-ketotestosterone (KT). Coupling KT implants with a socially inhibitory environment for protogynous sex change induces rapid transition to male morphology, but no significant change in social behavior and status, which could result from systemically administered steroids not effectively penetrating into brain or other tissues. Here, we first determined the degree to which exogenously administered steroids affect the steroid load within tissues. Second, we examined whether coupling a social environment permissive to sex change would influence KT effects on agonistic behavior. We implanted cholesterol (Chol, control) or KT in the dominant individual (alpha) undergoing sex change (on d0) and determined the effects on behavior and the degree to which administered steroids altered the steroid load within tissues. During the period of social instability, there were rapid (within 2 h), but transient effects of KT on agonistic behavior in alphas, and secondary effects on betas. On d3 and d5, all KT, but no Chol, treated females had male typical genital papillae. Despite elevated brain and systemic KT 5 days after implant, overall rates of aggressive behavior remained unaffected. These data highlight the importance of social context in mediating complex hormone-behavior relationships.
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Affiliation(s)
- D S Pradhan
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
| | - K R Connor
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA
| | - E M Pritchett
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA
| | - M S Grober
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA; Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
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Addis EA, Clark AD, Vasquez RA, Wingfield JC. Seasonal modulation of testosterone during breeding of the rufous-collared sparrow (Zonotrichia capensis australis) in Southern Patagonia. Physiol Biochem Zool 2013; 86:782-90. [PMID: 24241074 DOI: 10.1086/673868] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The roles of testosterone (T) during reproduction are often complex and vary among and within vertebrate taxa and locations, making general hypotheses relating T to breeding behavior and success difficult to integrate. In birds, T is thought to influence degrees of territoriality and associated aggression in males to maximize breeding success. Importantly, most work supporting these ideas has been conducted in the Northern Hemisphere. However, accumulating work on tropical species has shown divergent patterns of T in association with breeding behavior. The compilation of work from northern temperate and tropical species suggests that the function of T in relation to breeding behavior varies across latitude and environmental conditions. We investigate the patterns of T in relation to breeding behavior in a subspecies of the rufous-collared sparrow Zonotrichia capensis australis breeding at high latitude in the Southern Hemisphere (55°S). We then compare the T profiles and breeding behaviors of male Z. c. australis to conspecifics breeding in the tropics and congeners in North America to test the hypothesis that environments with breeding seasons of similar lengths will drive similar patterns of T in relation to breeding behavior. We found that Z. c. australis have high levels of T during the early-breeding periods when territories are being established and low levels of T during the parental phase of breeding, similar to temperate and Arctic birds in the Northern Hemisphere but unlike tropical Zonotrichia capensis costaricensis. In contrast, we found that Z. c. australis also exhibit similar aggressive behaviors in early breeding and midbreeding, unlike many birds in the Northern Hemisphere.
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Affiliation(s)
- Elizabeth A Addis
- Department of Biology, Gonzaga University, Spokane, Washington 99258; 2Department of Biology, University of Washington, Seattle, Washington 98195; 3Instituto de Ecologia y Biodiversidad, Departamento de Ciencias Ecologicas, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile; 4Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616
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González-Gómez PL, Merrill L, Ellis VA, Venegas C, Pantoja JI, Vasquez RA, Wingfield JC. Breaking down seasonality: androgen modulation and stress response in a highly stable environment. Gen Comp Endocrinol 2013; 191:1-12. [PMID: 23707496 DOI: 10.1016/j.ygcen.2013.05.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 05/02/2013] [Accepted: 05/03/2013] [Indexed: 11/18/2022]
Abstract
Previous studies show that most birds inhabiting temperate regions have well defined life history stages, and they modulate the production of testosterone (T) and corticosterone (CORT) in response to changes in seasonality. In this study we aimed to examine baseline and stress-induced levels of CORT and circulating T in relation with life history stages in the rufous-collared sparrow, Zonotrichia capensis. We carried out this study for a year in a population inhabiting riparian habitats in the Atacama Desert in Chile, one of the most climatically stable and driest places in the world. This environment shows minimal yearly change in average temperature and precipitation is virtually zero. We found individuals breeding, molting and overlapping breeding and molt year round, although most individuals were molting during March and in breeding condition during October. T levels were not related to individual breeding condition, and at population level they were not significantly different across sampling months. Baseline levels of CORT did not vary across the year. Stress-induced levels of CORT were suppressed during March when most of the birds were molting. This phenomenon was also observed in birds not molting during this period suggesting a mechanism other than molt in determining the stress-response suppression. Our results strongly suggest that in this study site, long-term extremely stable conditions could have relaxed the selective pressures over the timing of life history stages which was evidenced by the breeding and molt schedules, its overlap and endocrine profiles.
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Affiliation(s)
- Paulina L González-Gómez
- Department of Neurobiology, Physiology, and Behavior, University of California Davis, 1 Shields Avenue, CA 95616, USA.
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10
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Current world literature. Curr Opin Endocrinol Diabetes Obes 2012; 19:233-47. [PMID: 22531108 DOI: 10.1097/med.0b013e3283542fb3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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