by Dylan Wood and Jashan Abraham
Apis mellifera is among the most important species globally and is of huge economic and ecological importance. The species is a key pollinator responsible for agricultural services estimated at >$200 billion which directly impacts over 30% of our food production. Humans have been taking advantage of these services for over 7000 years. However, today there are a growing number of concerns regarding this fundamental specimen. Unexplained colony loss and global genomic variation are threatening this honeybee.
Wallberg et al. published this year on their findings into genome sequence variation in A. mellifera. The study took 140 workers bees from 14 separate populations spread worldwide and obtained an impressively stringent genome data set displaying 8.3 single-nucleotide polymorphisms (SNPs). Over a million of the SNP’s were found to be polymorphic in nature within the 4 tested groups of A. mellifera. A high degree of allele sharing was also shown across the tested populations. They found that large levels of global gene flow and random mating have led to this high level of genome variation They also state that population sizes have varied greatly in the past, most likely due to climatic changes. Analysis of the 140 worker bees showed no signs that this species originated in Africa, but that a more likely relationship is with the Asian Apis species.
The results implicate sperm competition as a major driver in honeybee evolution as a whole. Other genes identified showed that worker bee traits are often involved in adaptation, supporting a case for kin selection. Specific mutations were identified for adaptations to variations in climate, exposure to different pathogens, morphology and behaviour. The study also displays a number of differences between European and African A. mellifera, including disease resistance and the reproductive advantages in the Africanised form. These findings contrast with the previous ideology that, as suggested by molecular dating, the diverging populations of A. mellifera split around a million years ago. Indeed, further evaluation of the results of the study by Walberg et al indicate human transportation of colonies and selective breeding for desired traits played a huge role in the development of variation within A. mellifera. Finally, climactic influences upon the habitats of wild A. mellifera colonies likely played a greater role in their diversification and development than previously thought.
The results of the study provide a solid framework for further work to be undertaken on the genes outlined here. Research can now become more streamlined and focused upon protecting these bees against pathogens, rewriting management strategies and evaluating current conservation and farming methods. The invested interest in this species is clear from its aforementioned price tag of >$200bn which clearly defines the importance of studies such as this. A need for the recognition and identification of the biological mechanisms behind disease resistance is apparent here. Protecting this species and its obvious benefits must take into account the high genetic variability of populations, the threat to disease and the genetic barriers behind them and the risks of climate change to Apis mellifera; all of which are well studied in this paper.
Walberg, A., Han, F., Wellhagen, G., Dahle, B., Kawata, M., Haddad, N., Simoes, Z.L.P., Allsopp, M.H., Kandemir, I., Dea la Rua, P., Pirk, C.W., Webster, M.T. “A worldwide survey of genome sequence variation provides insight into the evolutionary history of the honeybee Apis mellifera” Nature 24.08.2014