Sex Determination and Genome Size in Catolaccus grandis (Burks, 1954) (Hymenoptera: Pteromalidae)
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abstract
Complementary sex determination (CSD) is a common form of the haplodiploid sex determination system found in all wasps, ants, and bees (Hymenoptera). Exceptions exist to CSD, but too few have been documented to make phylogenetic conclusions. Males that are homozygous at CSD loci are diploid and often sterile. Any effect that increases homozygosity (inbreeding and small population size) should increase the proportion of diploid males. We use flow cytometry to determine the genome size of males and females of the parasitic wasp Catolaccus grandis (Burks) (Hymenoptera: Pteromalidae) (1 C = 455.4 3.4 mb). We then score haploid and diploid males (and females) from populations that were 25% and 50% inbred. None of the 314 males scored were diploid. We conclude that the CSD system is very unlikely to exist in this species and discuss the implications for sex determination systems in the Pteromalidae and other chalcidoids.
