Research Interests:
As an evolutionary and
organismal biologist, my research is interdisciplinary and addresses
questions that span several levels of organization, from genomics and
developmental genes to morphology andpaleobiology. My research is
rooted in comparative methods and evaluates hypotheses with
bioinformatic, anatomical, histological, and genomic data. My recent
work falls into the following categories:

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Karyotypic
evolution in reptiles
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Comparative
Genomics: How has evolution shaped reptile and bird genes and what does
this tell us about amniote genomes and development in general? Except
for a handful of model organisms, the genomes of vertebrates are poorly
known. Given their vital phylogenetic position as a hub connecting
amphibians to birds and mammals, reptiles are especially neglected. My
ongoing research into the genomics of birds and reptiles is aimed at
helping to fill this gap. I am researching the evolution of genome
size and karyotype in reptiles, in addition to specific genes.
For example, I am investigating bone morphogenetic proteins (BMPs), which are
conserved in vertebrates and act as regulators of
bone formation,
maintenance, and repair. Because
BMPs directly influence bone development, which is the primary
component of vertebrate fossils, they have been a critical linchpin
integrating paleontology, development, and genetics to address various
evodevo questions, including digit identity in birds and feather
evolution. My research suggests that the second exon in bmp2 has
undergone positive selection during the evolution of Aves from other
reptiles, coincident with the trend of skeletal co-ossification on the
line to birds.
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Relationship
between bone cell size and genome size
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Paleogenomics: What characterizes
genome architecture in extinct animals compared with living
relatives and what does this reveal about genome macroevolution and the
biology of extinct organisms? Ninety-nine percent of all
animal
species to have ever lived are now
extinct, leaving us with a preciously small sample from which to
understand the scope of biological phenomena. Recovering some
part of that biological information is vital for understanding biology
broadly and deeply. Moreover, the evolution of genome architecture
in vertebrates, or any other lineage, is difficult to study
because genomic information is often absent for long extinct relatives.
I use an approach that combines genomics and paleohistology with
bayesian comparative statistics to characterize the genomes of extinct
organisms. For example, I have shown that the small, gene-dense genomes
of birds evolved in saurischian dinosaurs between 230 and 250 million
years ago, long before this lineage gave rise to the first birds. Yet,
a subsequent analysis I performed on pterosaurs suggests that there may
be a preadaptive relationship between the evolution of genome
architecture and the physiology needed for volant flight in
vertebrates. Moreover, because active and extinct interspersed mobile
genetic elements are the primary determinant of genome size in animals,
we were able translate raw genome size into estimates of mobile element
abundance for extinct animals.
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My
research has been featured in many popular outlets, including the New
York Times,
Science
Magazine, Heredity, the Boston Globe, Science News, Cosmos Magazine,
Discover Magazine, Science and Vie, Arstechnica.com, ScienceDaily.com,
NBC, ABC, the Discovery Channel, the BBC, and dozens of U.S. and
international newspapers.
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Paleobiology
& Organismal Biology: How do organismal innovations arise and
evolve within animals?
The biology and evolution of birds, and their utility as a comparative
model with mammals to understand the evolution of biologic innovations,
must be considered within the light of dinosaur biology. I am therefore
interested in elucidating dinosaur biology and evolution using various
approaches. For instance, using comparative morphology, I studied the
enigmatic three-layered trellis of ossified tendons in duck-billed
dinosaurs, homologizing them to spinal muscles in crocodilians and
birds, many of which also experience intratendinous ossification. Using
comparative osteohistology I also determined that intratendinous
ossification began developmentally much earlier in ornithischian
dinosaurs than in birds. Functionally, ossified tendons have always
been a mystery. My biomechanical research suggests that ossified
tendons passively supported the spines of ornithischian dinosaurs,
aiding in holding their tails off the ground and possibly returning
elastic energy during locomotion.
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Recent Publications
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Organ, C. L. and A. M. Shedlock (in submission).
Evolution of genome contraction in bats, birds, and pterosaurs.
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Janes, D. E., C. L. Organ and N. Valenzuela (in
press). New resources inform study of genome size, content
and organization in non-avian reptiles. Integrative and Comparative
Biology.
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Organ, C. L., R. Godinez Moreno, and S. V. Edwards
(in press). Three tiers of genome evolution in reptiles. Integrative
and Comparative Biology.
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Organ, C. L. and D. Janes (in press). Sex chromosome
evolution in reptiles. Integrative and Comparative Biology.
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Organ, C. L., M. H. Schweitzer, W. Zheng, L. M.
Freimark, L. C. Cantley, J. M. Asara. (2008). Molecular
phylogenetics of mastodon and Tyrannosaurus
rex. Science. 320 (5875): 499.
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Organ, C. L. (2008). Paleogenomics. Pp. 249-251. In
McGraw Hill 2008 Yearbook of Science & Technology. McGraw-Hill
Publishers, New York, NY.
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Organ, C. L., A. M. Shedlock, A. Meade, M. Pagel, S.
V. Edwards. (2007). Origin of avian genome size and structure in
nonavian dinosaurs. Nature. 446: 180-184.
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Holmes, R. and C. L. Organ. (2007). An ossified
tendon trellis in Chasmosaurus
(Ornithischia: Ceratopsidae). Journal of Paleontology. 81(2):
411–414.
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Organ, C. L. (2006). Biomechanics of ossified
tendons in ornithopod dinosaurs. Paleobiology. 32 (4): 652-665. [pdf]
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Organ, C. L. (2006). Thoracic epaxial muscles in
living archosaurs and ornithopod dinosaurs. The Anatomical
Record Part A: Discoveries in Molecular, Cellular, and Evolutionary
Biology. 288A: 782-793. [pdf]
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Organ, C. L. and J. Adams. (2005). The histology of
ossified tendon in dinosaurs. Journal of Vertebrate Paleontology. 25
(3): 602-613. [pdf]
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Adams, J. and C. L. Organ. (2005). Histologic
determination of ontogenetic patterns and processes in hadrosaurian
ossified tendons. Journal of Vertebrate Paleontology. 25 (3): 614-622. [pdf]
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Organ, C. L., J. B. Cooley, and T. L. Hieronymus.
(2003). A non-invasive quarry mapping system. Palaios. 18(1): 74-77.
Published Abstracts
and Presentations (last 2 years only)
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Organ, C. L. and S. V. Edwards. (2006).
Paleogenomics of pterosaurs and the evolution of vertebrate flight.
Journal of Vertebrate Paleontology. 26(Supplement to 3): 107A.
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Organ, C. L., M. Pagel, and S. V. Edwards. (2006).
Dinogenomics: The genomes of dinosaurs and the origin of avian genome
architecture. Evolution Meeting (SSE).
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Organ, C. L. and S. V. Edwards. (2006).
Paleogenomics—The dinosaurian origins of avian genome
structure. Workshop on Chicken Genomics & Development. Cold
Spring Harbor Laboratory.
Grants and
Fellowships
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NIH NSRF Postdoctoral Fellowship (2005-2008):
Evolution of Bmp Genes 2 and 4 in Archosaurs ($142,200)
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National Science Foundation: Symposium - Reptile
Genomics and Evolutionary Genetics ($6,749) Co-author: Nicole
Valenzuela and Dan Janes
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Society for Integrative and Comparative Biology
Symposium Grant, Reptile Genomics and Evolutionary Genetics Symposium
(2008), San Antonio, TX ($5,000). Co-author: Dan Janes
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OEB Departmental Travel Grant ($1,500)
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International Society of Biomechanics Dissertation
Grant (2001): The Evolution of Tail Deflection and Erect
Posture Synapsida and Diapsida ($4,000)
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