CK,
Have you seen the following paper?

RF Hoyer
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Molecular Ecology (2008) 17, 1918–1929 doi: 10.1111/j.1365-294X.2008.03725.x
© 2008 The Author
Journal compilation © 2008 Blackwell Publishing Ltd
Blackwell Publishing Ltd Good species despite massive hybridization: genetic
research on the contact zone between the water snakes
Nerodia sipedon and N. fasciata in the Carolinas, USA
K. MEBERT
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
Abstract
Genomic markers generated with the amplified fragment length polymorphism method
revealed extensive, panmictic-like hybridization along the narrow contact zone between
the water snakes Nerodia sipedon and Nerodia fasciata in the Carolinas, USA. However,
asymmetric distributions of diagnostic markers between both species and low frequencies
of backcrossed hybrids with a high value of interspecific mixture infer selection against
certain genotypes. This is consistent with a pronounced genetic and morphological preponderance
of N. fasciata characters in the hybrid zone. Despite massive hybridization within
the contact zone, the existence of nearly fixed genetic markers and the potential inferiority of
certain hybrid genotypes support the species status of the two taxa and corroborate known,
but nondiagnostic differences in morphology and ecology. This study stretches the
applicability of species concepts to cases, where the genetic compatibility between two
closely related species is very high, yet, they still evolve and persist as independent entities.
Keywords: AFLP, hybridization, incomplete speciation, Nerodia fasciata, Nerodia sipedon, snake
Received 11 March 2007; revision received 8 January 2008; accepted 24 January 2008

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