Evolutionary genetics of Carpodacus mexicanus, a recently colonized host of a bacterial pathogen, Mycoplasma gallisepticum



We present molecular data documenting
how introduction to the eastern United States and an
epizootic involving a bacterial pathogen has affected
the genetic diversity of house finches, a cardueline
songbird. Population bottlenecks during introduction
can cause loss of genetic variation and may negatively
affect a population’s ability to adapt to novel stressors
such as disease. Although a genome-wide survey using
Amplified Fragment Length Polymorphism (AFLP)
markers suggests little loss of genetic diversity in
introduced populations, an epizootic of bacterial
has nonetheless caused dramatic declines
in the eastern US population. Sequence analysis of a
candidate gene for pathogen resistance in the Major
Histocompatibity Complex (MHC) in pre- and post-
epizootic population samples reveals allele frequency
shifts since introduction of the pathogen, but similar
shifts are also observed in control populations not ex-
posed to the bacteria, and in a neutral non-coding lo-
cus. Expression studies using a novel subtractive
hybridization approach indicate decreased expression
of the class II MHC locus upon exposure to
, a pattern also seen in MHC class I loci in mice
infected with cytomegalovirus and consistent with
manipulation of the finch immune system by
. These results will be further expanded using
experimental studies as well as examination of evolu-
tion of the pathogen genome itself.

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Last updated on 05/24/2016