My main interest is studying the factors promoting avian diversity in South America. Specifically, I study phylogeographic patterns of hummingbird species in the Andes and Yellow Warbler populations in the Galápagos Islands, paying particular attention to the role of geography, natural selection, and genetic drift in differentiation.
The impressive latitudinal range the Speckled Hummingbird (Adelomyia melanogenys) exhibits (from the Andes of Venezuela to Bolivia) makes it suitable to examine mechanisms promoting genetic and morphologic differentiation in the different habitats where it is found along the cordillera and at different elevations. To conduct these studies, I use a combination of methods from morphometrics, multilocus phylogenies, and remote sensing data.
In contrast to the examination of evolutionary aspects of diversification in the Andes, I am also interested in patterns of recent differentiation in the Yellow Warbler subspecies (Dendroica petechia aureola) from the Galápagos and Cocos Island. I expanded on the Yellow Warbler phylogeny, including samples from these islands to determine lineage relationships as well as to reconstruct migration and colonization routes.
One part of my doctoral research looked into the patterns of genetic diversity and morphological variation in Adelomyia hummingbirds. The six monophyletic clades recovered have lineage limits at well-defined geographic barriers indicating the important impact of geographic isolation on genetic diversification. In contrast, morphological analyses suggested that, despite deep genetic breaks, ecology was important in promoting differentiation. The combination of morphometrics, multilocus phylogenies, and remote sensing data proved to be a useful tool in informing speciation patterns of diversification in Adelomyia.
Subspecies Adelomyia melanogenys melanogenys from east Ecuadorian and Peruvian Andes (A),
A. m. maculata from west Ecuadorian Andes (B), and A. m. inornata from the Andes of Bolivia (C)
Origin of Yellow Warbler Populations (Dendroica petechia aureola) in the Galápagos and Cocos Island (Makes the Cover of Journal of Evolutionary Biology )
I also examined patterns of recent differentiation in the yellow warbler subspecies (Dendroica petechia aureola) from the Galápagos and Cocos Island. Bayesian Inference analysis suggests aureola yellow warblers diverged from Central American lineages 300,000 years ago colonizing the Pacific islands through the Galápagos first and back to the Cocos Island. Within the Galápagos archipelago patterns of genetic variation in microsatellite and mitochondrial markers suggested prevailing current wind patterns may play a role in structuring populations across islands. No intra-island patterns of morphological variation were found, even across step ecological gradients, suggesting that either (i) high levels of gene flow may be homogenizing the effects of selection, (ii) populations may not have had enough time to accumulate the differences in morphological traits, or (iii) yellow warblers show lower levels of ‘evolvability’ than some other Galápagos species. Thus, by incorporating genetic data and morphological variation these results provide an understanding of microevolutionary processes occurring in island forms.
Yellow Warbler Dendroica petechia aureola
Field work in the highlands in Santa Cruz Island
Yellow Warbler caught in mistnet
Processing birds in the lowlands on Isabela Island with Charles Darwin Foundation’s Technical Assistance Director Felipe Cruz
In collaboration with the NASA/Jet Propulsion Laboratory, I am generating distributional images which will contain patterns of genetic diversity, morphological differentiation, and physiological adaptation to examine the underlying effects of the various mechanisms responsible for the patterns observed and relate them to detailed habitat characteristics and to geography. I will be able to identify particular geographical regions and gradients where these differentiations and adaptations are produced and maintained and where conservation efforts should be allocated to preserve evolutionary processes in the Tropical Andes region.
Ecological modelling for the Speckled Hummingbird in Ecuador based on
various climatic and environmental variables from satellite data
Elevational gradients are of particular interest to me because they present a unique scenario where different selection regimes can act within relatively short distances, creating a mosaic of selecting agents as one examines populations up and down the gradient. In particular, I am interested in the effect of elevation on the flight mechanics of the hovering flight of the Speckled Hummingbird. In my past research, I have found that hummingbirds at higher elevations, such as 3000 m, modulate their flight as a response to the hypoxic and hypobaric conditions, compared to a the lower energy hovering flight of their conspecifics at lower elevations.
Left: Flight ecophysiology of the Speckled Hummingbird; Right: Cloud Forest in Manu National Park, Peru
In a 2011 publication in the Journal of Global Change Biology, written in collaboration with other researchers, we showed that Neotropical hummingbirds are expected to shift altitudinally upwards in the Andes in response to climate change, which is predicted to influence their flight performance.
Chaves, J.A., P.G. Parker, and T.B. Smith. 2012. Origin and population history of a recent colonizer, the yellow warbler in Galapágos and Cocos Islands. J. Evol. Biol. 25: 509-521. PDF.
Chaves, J.A., J.Weir, and T. B. Smith. 2011. Diversification in Adelomyia hummingbirds follows Andean uplift. Molecular Ecology 20:4564-4576. PDF.
Chaves, J.A. and T. B. Smith. 2011. Evolutionary patterns of diversification in the Andean hummingbird genus Adelomyia. Molecular Phylogenetics and Evolution 60: 207-218. PDF.
Buermann, W. J. A. Chaves, R. Dudley, J. A. Mcguire, T. B. Smith, and D. L. Altshuler. 2011. Projected changes in elevational distribution and flight performance of montane Neotropical hummingbirds in response to climate change. Global Change Biology 17: 1671-1680. PDF.
Chaves, J.A., John P. Pollinger, Thomas B. Smith, Gretchen LeBuhn. 2007. The role of geography and ecology in shaping the phylogeography of the speckled hummingbird (Adelomyia melanogenys) in Ecuador. Molecular Phylogenetics and Evolution 43: 795-807. PDF.
Chaves, J.A. and Juan F. Freile. 2005. Aves Comunes de Otonga y los Bosques Nublados Noroccidentales del Ecuador. Fundacion Otonga, Ecuador.
Chaves, J.A. 2004. Phylogeography, evolution and flight ecophysiology of the speckled hummingbird (Adelomyia melanogenys) in Ecuador. Master's Thesis Degree. Department of Biology. San Francisco State University, San Francisco CA.
Freile, J.F. M. Moreano, E. Bonaccorso, T. Santander y J. A. Chaves. 2004. Notas sobre la historia natural, distribución y conservación de algunas especies de aves amenazadas del suroccidente de Ecuador. Cotinga (21): 18-24. PDF.
Freile, J.F. and J. A. Chaves. 2004. Interesting distributional records and notes on the biology of bird species from a cloud forest reserve in north-west Ecuador. Bulletin of the Brithish Ornithologists' Club. 124 (1): 6-16. PDF.
Rampón B. and J. A. Chaves. 2004. Quinde, Hummingbirds of Ecuador. Barcelona 2004.
Freile, J.F., J. A. Chaves, G. Iturralde and E. Guevara. 2003. Notes of the distribution, habitat and conservation of the cloud-forest pygmy-owl (Glaucidium nubicola) in Ecuador. Ornitología Neotropical 14: 275-278.
Chaves, J. A. 2001. Comparación de avifaunas en dos bosques nublados del Chocó ecuatoriano. Epiphytes and canopy fauna of the Otonga Rain Forest (Ecuador) Nieder, J. & Barthlott, W (eds.). Vol 2. pag: 311 – 326.
Chaves, J. A. 2001. Selección de hábitat y conducta alimenticia de aves frugívoras en dos bosques nublados de las estribaciones occidentales de los Andes del Ecuador. Licenciatura thesis degree, Departamento de Biología, Pontificia Universidad Católica del Ecuador, Quito, Ecuador.
Chaves, J. A. 2000. Use of Cecropia and Ficus trees by fruit-eating birds in Ecuadorian chocoan andean cloud forests. 3rd International Symposium-Workshop on Frugivores and Seed Dispersal, Biodiversity and Conservation Perspectives.
Freile, J. F. and J. A. Chaves. 2000. Field observations on copulation by White-rumped Hawk. Buteo leucorrhous. Cotinga 14: 12.
Freile, J. F. and J. A. Chaves. 1999. Photospot: Colombian Screech-Owl, Otus ingens colombianus. Cotinga 12: 95-96.
Cresswell, W., S. Yerokhov, N. Berezovikov, R. Mellanby, S. Bright, P. Catry, J. Chaves, J. Freile, A. Gretton, A. Zykin, R. McGregor, and D. McLaughlin. 1999. Important wetlands in northern and eastern Kazakhstan. Wildfowl 50: 181-194.
Cresswell, W., M. Hughes, R. Mellanby, S. Bright, P. Catry, J. Chaves, J. Freile, A. Gabela, H. Martineau, R. MacLeod, F. McPhie, N. Anderson, S. Holt, S. Barabas, C. Chapel, and T. Sánchez. 1999. Densities and habitat preferences of Andean endemic birds in pristine and degraded habitats in Northeastern Ecuador. Bird Conservation International 9: 129-145.
Cresswell, W., R. Mellanby, S. Bright, P. Catry, J. Chaves, J. Freile, A. Gabela, M. Hughes, H. Martineau, R. MacLeod, F. McPhie, N. Anderson, S. Holt, S. Barabas, C. Chapel, and T. Sánchez. 1999. Bird of the Guandera Reserve, Carchi province, northeastern Ecuador. Cotinga 11: 55-63.
2006 Hummingbird Research. Mariri Magazine. Freelance Writer. "To Catch a Hummingbird." http://www.mariri.net/index.php?option=com_content&task=view&id=15&Itemid=1
Some of my illustrations from the plates of the field guide, Aves Comunes de Otonga y los Bosques Nublados Noroccidentales del Ecuador (English translation: Common Birds of Otonga and the Cloud Forests of Northwestern Ecuador).