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Title: Variation in and responses to brood pheromone of the honey bee (Apis mellifera L.)

Author
item METZ, BRADLEY - TEXAS A&M UNIVERSITY
item PANKIW, TANYA - TEXAS A&M UNIVERSITY
item TICHY, SHANE - AGILENT TECHNOLOGIES, INC.
item ARONSTEIN, KATHERINE
item CREWE, ROBIN - UNIVERSITY OF PRETORIA

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2010
Publication Date: 4/12/2010
Citation: Metz, B.N., Pankiw, T., Tichy, S.E., Aronstein, K.A., Crewe, R.M. 2010. Variation in and responses to brood pheromone of the honey bee (Apis mellifera L.). Journal of Chemical Ecology. 36(4):432-440.

Interpretive Summary: Adaptations to tropical and temperate climates have shaped significant differences in the foraging behaviors among African and European honey bees. Foraging behaviors, among other factors (e.g., genotype, amount of stored pollen) is effected by larval chemicals called brood pheromone. Brood pheromone was characterized from same-stage larvae derived from honey bee sources having European mitochondrial DNA from Texas and Georgia, USA and African mitochondrial DNA from Texas, USA and Pretoria, South Africa. The proportions of the 10 fatty acid ester components (blend) were sufficiently different among the sources to correctly classify 77% of the samples using discriminant analysis. The Texas-European derived pheromone was evenly categorized among Texas-Africanized, Georgia-European, and South African blends suggesting the introgression of African genes in this population. South African pheromone was comprised of a blend that was a 1:1 ratio of saturated to unsaturated esters, whereas all other source blends had ratios ranging from 0.37 to 0.45:1. USA honey bee colonies were most responsive in pollen foraging bioassays to synthetic blends of the pheromone that were derived from larvae of the same population but unrelated colony sources. Texas-Africanized colonies showed a significant positive pollen foraging response to the Texas-Africanized blend and a significant negative foraging response to the Georgia-European blend. Pollen foraging responses to the blends tested suggested that brood pheromone may be co-adapted as a “race” recognition cue. The responsiveness of bees to sucrose was also assayed to measure the effects of brood pheromone rearing environment on this physiologically, neuronally mediated response. Georgia-European pheromone affected the greatest change in sucrose responsiveness in Georgia-European workers compared to the Texas-Africanized blend and control. Texas-Africanized worker sucrose responsiveness was not affected by any pheromone blend tested. Overall, it appeared that the blend of brood pheromone changed with honey bee population and that foraging and sucrose responsiveness to blends of brood pheromone was a complex interaction.

Technical Abstract: Brood pheromone was characterized from same-stage larvae derived from honey bee sources having European mitochondrial DNA from Texas and Georgia, USA and African mitochondrial DNA from Texas, USA and Pretoria, South Africa. The proportions of the 10 fatty acid ester components (blend) were sufficiently different among the sources to correctly classify 77% of the samples using discriminant analysis. The Texas-European derived pheromone was evenly categorized among Texas-Africanized, Georgia-European, and South African blends suggesting the introgression of African genes in this population. South African pheromone was comprised of a blend that was a 1:1 ratio of saturated to unsaturated esters, whereas all other source blends had ratios ranging from 0.37 to 0.45:1. USA honey bee colonies were most responsive in pollen foraging bioassays to synthetic blends of the pheromone that were derived from larvae of the same population but unrelated colony sources. Texas-Africanized colonies showed a significant positive pollen foraging response to the Texas-Africanized blend and a significant negative foraging response to the Georgia-European blend. Pollen foraging responses to the blends tested suggested that brood pheromone may be co-adapted as a “race” recognition cue. The responsiveness of bees to sucrose was also assayed to measure the effects of brood pheromone rearing environment on this physiologically, neuronally mediated response. Georgia-European pheromone affected the greatest change in sucrose responsiveness in Georgia-European workers compared to the Texas-Africanized blend and control. Texas-Africanized worker sucrose responsiveness was not affected by any pheromone blend tested. Overall, it appeared that the blend of brood pheromone changed with honey bee population and that foraging and sucrose responsiveness to blends of brood pheromone was a complex interaction.