Submitted to: Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2003
Publication Date: 10/20/2003
Citation: Schneider, S. S., Leamy, L. J., Lewis, L. A., DeGrandi-Hoffman, G. The influence of hybridization between African and European honeybees, Apis mellifera, on asymmetries in wing size and shape. 2003. Evolution 57(10). pp. 2350-2364. Interpretive Summary: A feature common to all insects (and many other animals) is that they are bilaterally symmetric; that is an individual has symmetry between its right and left sides. If an individual is not bilaterally symmetric (i.e., the individual is asymmetric), it is a sign of stress and compromised vigor and fitness. We tested for the presence of asymmetry in adult worker honey bees that were the offspring from crosses between European and African queens and drones (males). Our goal was to determine if the frequency of asymmetrical individuals in workers that were offspring from the crosses was greater than in pure African or European workers. We found that wing size and shape in the crosses between African and European worker bees (i.e., hybrids) did not differ in the frequency of asymmetry from the pure African or European stocks we used for the crosses. However, asymmetry in body shape was less frequent in African workers compared to the Europeans and hybrid workers combined. The higher frequency of asymmetric individuals suggests that European bees and their hybrids may be less fit relative to African bees. We also found that workers from crosses between European and African queens and drones differ in overall wing size and shape that could affect wing aerodynamics and flight ability.
Technical Abstract: We examined the possible role of negative heterosis in the invasion process of the African honey bee by testing the hypothesis that fluctuating asymmetry (FA), a measure of developmental stability, should be higher in hybrid versus parental genotypes of African and European races. Parental and reciprocal hybrid worker genotypes were cross-fostered in common-hive rearing environments. Contrary to our prediction, we did not find greater FA for wing size and shape in the hybrids compared to both parental types. However, FA of shape was significantly lower in the African workers compared to the European and hybrid workers combined, suggesting that European bees and their hybrids may have compromised fitness relative to African bees. We also found that the two hybrid genotypes significantly differed in overall wing size and shape. If these differences affect wing aerodynamics, then the paternity of hybrids may influence worker performance and could potentially contribute to the loss of European matrilines. Hybridization had few consistent effects on directional asymmetry for wing size and shape. Thus, hybridization may influence developmental stability and wing morphology, and negative heterosis may contribute to the ability of African bees to displace European honey bee races in invaded regions.