Dora's Research
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Vertebrate Phylogenetics: I am currently
working on understanding the origins and phylogenetic relationships of
seven North American snakes that I recognize as relicts. Most snakes in
North America can be traced to a South American or Asian origin. However,
the origin of these seven remains a biogeographic and phylogenetic
mystery. My work examines molecular and morphological evidence that
suggests that these relict seven are neither South American nor Asian in
origin but rather of an ancient European origin. Molecular data include
micro-complement fixation and mitochondrial gene sequence data.
Morphological data include skull and hemipenis morphology, and
ultrastructure of snake scales. Pinned to this phylogenetic tree are the
cytogenetic profiles for each of these snakes in hopes of better
understanding how snake chromosomes evolve. The result of this work will
contribute to the understanding of the origin of North American
biodiversity, and provide a framework for studying snake phylogenetics and
systematics. Below I show the relationships of these relicts in a three
dimensional tree. An explanation of this tree can be found in Pinou et al
(1996) Journal of Theoretical Biology 182:505-512.
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Snake Hemipenes: The reproductive organs of male snakes have a
very ornate morphology. I’m interested in seeing how the morphology varies
among closely related snakes and what, if any, role selection plays in
maintaining this morphological diversity. Below I show the hemipenes of
Heterodon simus and Heterodon platyrhinos. The hemipenes of
these two closely related snake species appear to have a different
three-dimensional shape.
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Heterodon platyrhinos
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Heterodon simus
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Snake Scale Microdermatoglyphics: Scanning electron microscopy
permits us to examine the ultrastructure of reptilian scales. Different
genera of snakes appear to have their own distinguishing ultrastructural
pattern. Below I show the keeled and smooth scales for two North American
green snakes: Opheodrys aestivus and Liochlorophis vernalis.
These scales are magnified 2,000 times in order to reveal the
micro-structural pattern of the scale. I’m interested in understanding how
these patterns reflect the phylogenetic relationships of snakes.
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Picture of keeled scale of O. aestivus and smooth
scale of L. vernalis
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