Abstract
The complementary sex determiner (csd) gene determines the sex of the western honey bee (Apis mellifera L.). Bees that are heterozygous at the csd locus develop into females; whereas hemizygous bees develop into males. The co-occurrence of two identical csd alleles in a single diploid genome leads to the genetic death of the bee. Thus, the maintenance of csd diversity in the population is favoured. The number and distribution of csd alleles is particularly interesting in light of the recent decline in the honey bee population. In this study, we analysed the distribution of csd alleles in two Polish populations separated by about 100 km. We analysed the maternal alleles of 193 colonies and found 121 different alleles. We also analysed the distribution and frequency of the alleles, and found that they are distributed unevenly. We show that the methods that have been used so far to estimate the total worldwide number of csd alleles have significantly underestimated their diversity. We also show that the uneven distribution of csd alleles is caused by a large number of infrequent alleles, which most likely results from the fact that these alleles are generated very frequently.
Highlights
Western honey bees, like other Hymenoptera, are haplodiploids, which means that the males develop from unfertilised oocytes and are haploid; whereas the females develop from fertilised oocytes and are diploid[1]
The csd-PSD contains a hypervariable region (HVR), which consists of a variable number of A/T-rich nucleotide repeats, and encodes mainly tyrosine and asparagine residues
Lechner et al have shown that the evolutionary processes that lead to the variations in the length of csd HVR are as much as 2.4-times faster than the corresponding processes in microsatellites
Summary
Like other Hymenoptera, are haplodiploids, which means that the males develop from unfertilised oocytes and are haploid; whereas the females develop from fertilised oocytes and are diploid[1]. The key factor that is responsible for optimal reproduction is the maintenance of a high diversity of csd alleles in the bee population[10, 11]. The csd-PSD contains a hypervariable region (HVR), which consists of a variable number of A/T-rich nucleotide repeats, and encodes mainly tyrosine and asparagine residues. Lechner et al have shown that the evolutionary processes that lead to the variations in the length of csd HVR are as much as 2.4-times faster than the corresponding processes in microsatellites. The results show that the csd alleles are not distributed uniformly, and that the methods that have been used in studies so far have underestimated the worldwide number of csd alleles, which raises new questions concerning rate of their emergence and propagation in the honey bee population
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