Cranial Variability in Amazonian Marmosets A
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CRANIAL VARIABILITY IN AMAZONIAN MARMOSETS A Dissertation by JOHN MARSHALL AGUIAR Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2009 Major Subject: Wildlife and Fisheries Sciences CRANIAL VARIABILITY IN AMAZONIAN MARMOSETS A Dissertation by JOHN MARSHALL AGUIAR Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Thomas E. Lacher, Jr. Committee Members, John Bickham Duane A. Schlitter James B. Woolley Head of Department, Thomas E. Lacher, Jr. December 2009 Major Subject: Wildife and Fisheries Sciences iii ABSTRACT Cranial Variability in Amazonian Marmosets. (December 2009) John Marshall Aguiar, B.A.; B.A., University of Richmond; M.A., Old Dominion University Chair of Advisory Committee: Dr. Thomas E. Lacher, Jr. The family Callitrichidae encompasses the marmosets and tamarins, the smallest of the anthropoid primates and one of the most species-rich of platyrrhine families. Seven new species of Amazonian marmosets (Callithrix, Callitrichidae) have been discovered in recent years, as well as the exceptional dwarf marmoset Callibella humilis. Most of these species were described on the basis of their pelage and presumed separation by major rivers. I performed analyses of craniometric variables by taxa and by river basins, in order to determine if there are significant cranial distinctions between taxa separated by rivers. I analyzed quantitative cranial and mandibular characters of Callibella humilis to determine if it could be distinguished from other callitrichids. I found that Callibella is clearly distinct from all other genera of marmosets and tamarins, in particular in the morphology of the lower jaw. I also analyzed representative species of Amazonian Callithrix and found support for the theory of separation by river-barriers. In my analyses the Amazonian marmosets were divided into three separate species groups, with the easternmost species (Callithrix argentata and C. leucippe) strongly distinct and iv separated from the others by the broad Rio Tapajós. Two additional species, C. chrysoleuca and C. saterei, formed a discrete group in the central Amazon, and the westernmost species – C. melanura, C. nigriceps and the Rondônia marmoset – formed a third distinct group. These results from cranial morphology align with recent genetic studies indicating that the Amazonian marmosets are strongly divided by the Rio Tapajós, and offer additional support to the theory of river-barriers. Although these species are typically considered to be of low conservation priority, many of them are found in areas experiencing accelerated deforestation. An initial analysis of protected-area coverage for the Amazonian marmosets demonstrates that while some species may be found in a number of protected areas, others are virtually uncovered, and the lack of comprehensive information on their distributions may preclude an effective conservation strategy. The dwarf marmoset Callibella is known from an exceptionally restricted range, with almost no protected areas, and this unique species should be a conservation priority. v ACKNOWLEDGEMENTS A great many lives have affected mine during the course of this research, like a river of stars swirling through the galaxy – each with its own unique tug and pull of gravity, all combining their effects to shape the course of my very long and eccentric orbit. As with the galactic disc, some stars have shone more brightly, and others have departed on separate vectors, but each has influenced me in some strong or subtle way. Brightest among the luminous host is my advisor, Dr. Tom Lacher, who has provided steady guidance, sound advice, and vital perspective, as well as an occasional dose of motivation. He has supported me at all times, in every aspect of this endeavor – and as Stephen Maturin might say, I fear he has burdened me with a debt I can never fully repay. I have also been glad to know his wife Susana, one of my very favorite Brazilians, who (along with her husband) has always encouraged me on my long road towards learning Portuguese. Another triad of bright stars are my committee members, Dr. John Bickham, Dr. Duane Schlitter and Dr. Jim Woolley, who have been superb in their willingness to help with matters great and small. The logistics of my travel and research could not have been navigated without support from the staff of the Department of Wildlife and Fisheries Sciences, in particular Vicki Buckbee, Dawn Miles and Diann Radke. I owe special thanks to Janice Crenshaw for helping me through my first semesters, and for her efforts in helping me locate and pursue scholarship opportunities. Tariq Ayyub provided excellent computer support vi during my final, intense visits to the department, and Shirley Konecny deserves special mention for her kindness and mother-birding. Thanks are also due to Dr. Jane Packard, whose encouragement of my science writing is much appreciated. Few can appreciate the intensity, stress and challenge of the graduate experience as deeply as those who have only lately survived it, and so thanks are due to Elizabeth Kennedy, for counsel and support in difficult times, and friendship in the better; and also to Michael Corson, for his patient and unfailing encouragement, and for whom going above and beyond is a signature style. And, thanks to Tom Dolan, fellow wanderer on a parallel course. I have been fortunate to have an advisor who supported my research travel to the fullest extent, and fortunate that this travel has taken me through many countries, chief among them Brazil. On my first trip to Brazil I was privileged to meet Dr. Adelmar Coimbra-Filho, who has devoted his life to the conservation of the lion tamarins, and what fragments yet remain of their ancient forest home. On that first trip I also met Ilmar Bastos Santos, whose enthusiastic support, both personal and professional, was invaluable for that and subsequent journeys. Thanks are also due to Dr. Leonardo Sena, for his open and generous assistance during my travels in and around Belém. I owe special gratitude to Vicki Haines (Vitôria), who was a lifesaver during my first visit to the Brazilian Amazon, and to Delfinay Barbosa (Dedão) and his brother Ruy, who kindly took time out of their own lives to guide me in search of a monkey none of us had ever seen. vii I am especially grateful to Marc van Roosmalen for making the type skull of Callibella humilis available to examine while I was in Brazil, as well as for the dinners and conversation at his home. Thanks are also due to José de Sousa e Silva Júnior and Suely Aguiar of the Museu Paraense Emílio Goeldi in Belém; João Alves de Oliveira of the Museu Nacional in Rio de Janeiro; Mario de Vivo of the Museu de Zoologia da Universidade de São Paulo; and the staff of the Instituto Nacional de Pesquisas Amazônicas in Manaus, for access to their respective collections in Brazil. I also appreciate the opportunity to examine specimens under the care of Linda Gordon and Richard Thorington, Jr. at the United States National Museum of Natural History in Washington, D.C.; Robert Randall at the American Museum of Natural History in New York; Maria Rutzmoser at the Harvard Museum of Comparative Zoology in Cambridge, Massachusetts; and Bruce Patterson at the Field Museum in Chicago. Additional thanks are also due to Olavi Grönwall of the Naturhistoriska Riksmuseet in Oslo, Sweden; Manfred Ade of the Humboldt Museum für Naturkunde in Berlin, Germany; the staff of the Museum National de Histoire Naturelle in Paris, France; and most especially Chris Smeenk of the Rijksmuseum van Natuurlijk Historie in Leiden, the Netherlands. I am also grateful to Colin Groves and Michael Willig for constructive comments on the details of marmoset morphology and statistical analysis. In addition, thanks are due to Daniel Juhn and Kellee Koenig of Conservation International, who helped me to locate and manipulate the satellite image which became Figure 12. I would like to thank Susan Ford, Lesa Davis, and Leila Porter, organizers of the Marmoset and Callimico Symposium at the 2005 meeting of the American Association of Physical viii Anthropology, for inviting myself and Dr. Lacher to participate in the symposium. Additional thanks are due to Susan Ford for her kind advice and support. Deep thanks are due to Krista Adamek, who spent countless hours working with shapefiles to create the maps, data and supporting materials for Chapters I and V. She did much of this while under course and project deadlines of her own; but whatever the request, she was willing, capable and enthusiastic, and without her the maps most likely could not have been done. Thanks also to Rich Miller, for a vital and timely save. Finally, several exceptional colleagues at Conservation International deserve a special mention. Kim Meek helped in many ways, and she taught me a great deal about editing and graphic design in a professional environment. Karyn Tabor helped immensely at several key, stressful junctures, and more than once spent hours of her own time solving technical problems for me. And Edward Lohnes, a good pal and stand-up bloke, cheerfully and willingly helped in countless ways. And a special thanks must go to Stephen Nash, Scientific Illustrator for Conservation International, who has been a kind and generous colleague, and whose artwork is found on so many of the following pages. This dissertation would be far less colorful – and the marmosets themselves only distant, abstract names – were it not for his ready permission to use so many of his illustrations. I feel privileged to be able to include a few of them here, and dream of a day when I can show him a new species to capture with pencil and brush.