Chromosomal Variability in the Antarctic Insect, Belgica antarctica (Diptera: Chironomidae)

Abstract
Chromosomal inversion polymorphism is examined in the midge Belgica antarctica Jacobs (Diptera: Chironomidae). This insect is the southernmost free-living holometabolous species and is restricted to ca. a 650-km range on western side of the Antarctic Peninsula. B. antarctica is a diploid species with a chromosome complement of 2n=6. Five chromosomal inversions were found among ca. 1200 insects from 18 localities. One inversion is sex-linked. Two inversions exhibited highly significant interpopulational differentiation in the frequency of inversion heterozygotes. Attempts to correlate inversion heterozygosity with several environmental variables including ecological complexity and 3 soil variables, i.e., pH, electrical conductivity and percent organic material, gave non-significant results. Several hypotheses are advanced to explain the observed patterns of genetic variability.

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