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CLINAL DISTRIBUTION OF A CHROMOSOMAL REARRANGEMENT: A PRECURSOR TO CHROMOSOMAL SPECIATION?
Author(s) -
McAllister Bryant F.,
Sheeley Sara L.,
Mena Paulina A.,
Evans Amy L.,
Schlötterer Christian
Publication year - 2008
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2008.00435.x
Subject(s) - cline (biology) , biology , evolutionary biology , chromosomal polymorphism , genetics , biological dispersal , genetic algorithm , chromosomal rearrangement , natural selection , adaptation (eye) , local adaptation , chromosome , selection (genetic algorithm) , microevolution , hybrid zone , karyotype , genetic variation , gene flow , gene , population , demography , artificial intelligence , sociology , neuroscience , computer science
Geographically structured genetic variants provide an effective means to assess sources of natural selection and mechanisms of adaptation to local environments. Correlated selection pressures along environmental gradients favor subdivision of genomes through chromosomal rearrangement. This study examines populations of Drosophila americana to evaluate selection pressures affecting chromosomal forms distinguished by a centromeric fusion. Analyses of chromosomal polymorphism throughout the Mississippi River Valley in the central United States reveal the presence of a distinct latitudinal cline for the chromosomal rearrangement. The cline has a width of 623 km centered at 35.97°N and displays a characteristic sigmoid shape consistent with a balance between selection and dispersal. Extreme low temperature during January, an indicator of winter severity, was identified as the environmental variable that most accurately predicts arrangement frequency. An intriguing relationship identified between the chromosomal cline and operational sex ratio indicates that these alternative arrangements of the X chromosome may influence sex‐specific survival. A hypothesis for the cline is presented wherein variation associated with the alternative chromosome forms influences distinct overwintering strategies. The resulting subdivision within the genome embodies a transitory stage of a speciation process in which locally adapted gene complexes provide a foundation for species formation.