Linking evolutionary lineage with parasite and pathogen prevalence in the Iberian honey bee.

The recent decline in honey bee colonies observed in both European countries and worldwide is of great interest and concern, although the underlying causes remain poorly understood. In recent years, growing evidence has implicated parasites and pathogens in this decline of both the vitality and number of honey bee colonies. The Iberian Peninsula provides an interesting environment in which to study the occurrence of pathogens and parasites in the host honey bee populations due to the presence of two evolutionary lineages in A. m. iberiensis (Western European [M] or African [A]). Here, we provide the first evidence linking the population structure of the Iberian honey bee with the prevalence of some of its most important parasites and pathogens: the Varroa destructor mite and the microsporidia Nosema apis and Nosema ceranae. Using data collected in two surveys conducted in 2006 and 2010 in 41 Spanish provinces, the evolutionary lineage and the presence of the three parasitic organisms cited above were analyzed in a total of 228 colonies. In 2006 N. apis was found in a significantly higher proportion of M lineage honey bees than in the A lineage. However, in 2010 this situation had changed significantly due to a higher prevalence of N. ceranae. We observed no significant relationships in either year between the distributions of V. destructor or N. ceranae and the evolutionary lineage present in A. m. iberiensis colonies, but the effects of these organisms on the genetic diversity of the honey bee populations need further research.