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Vol. 41 No. 3, 2002
Comparison of Recessive Lethal Accumulation in Inversion-bearing and Inversion-free Chromosomes in Drosophila
Yung-Yu Yang1, Fei-Jann Lin2 and Hwei-yu Chang1,2,*
1Department of Entomology, National Taiwan University, Taipei, Taiwan 106
2Institute of Zoology, Academia Sinica, Taipei, Taiwan 115
Yung-Yu Yang, Fei-Jann Lin and Hwei-yu Chang (2002) Frequencies of recessive lethal alleles in 3 Drosophila
species were investigated to test the“trapping hypothesis”(i.e., the
accumulation of deleterious alleles by large inversions in a population
with seasonal subdivision into small units). The low recessive lethal
frequencies of the 3rd chromosome of D. albomicans and the 2nd chromosome of D. formosana
are consistent with their low inversion heterozygosities as predicted
by the hypothesis. In addition, the frequencies of recessive lethal
alleles on the 2nd and the 3rd chromosomes of D. melanogaster are also correlated with those of inversions. However, the correlation is not as obvious as in the D. albomicans and D. formosana
cases, and this is probably due either to interactions between
inversions or to the population structure. Locations of those lethal
genes may be correlated with inversion breakpoints in D. melanogaster.
The correlation between recessive lethals and inversions suggests that
genetic load instead of heterozygous superiority is a major reason for
maintaining inversion polymorphism in natural populations of Drosophila with a large simple inversion, and seasonal subdivision into small, inbreeding subpopulations.
Key words: Chromosomal inversions, Drosophila, Recessive lethal alleles.
*Correspondence: E-mail: hwei@gate.sinica.edu.tw
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