Clinal nature of the frequencies of ovarioles and spermathecae in Cape worker honeybees, Apis mellifera capensis

Abstract

It was determined that 300 Cape workers, Apis mellifera capensis (collected from each of 6 colonies at each of 5 localities about 200 km apart along an 800 km transect in the Western and Eastern Cape Provinces, South Africa) was the sample size required to statistically estimate the proportions of workers with spermathecae at each location at 95% confidence levels. Because of the extremely clinal nature of this honeybee population, we tested the hypotheses that (1) ovarian number and development of the spermatheca covary in Cape workers, and (2) covary clinally as well. A regression analysis revealed that the frequencies of bees with spermathecae significantly decreased from west to east, with Stellenbosch having the highest and Grahamstown the lowest frequencies. Spermatheca size also significantly decreased from west to east. A multiple regression analysis revealed that the number of ovarioles significantly decreased from west to east and also differed significantly between workers with and without a spermatheca. Moreover, the number of ovarioles was significantly correlated with the size of the spermatheca and workers without it had significantly fewer ovarioles. Both hypotheses are confirmed. The outcomes of these measurements will provide a more quantitative basis for estimates of effective social parasitism among these bees along a geographic continuum.