MtDNA Analysis Indicates Human-Induced Temporal Changes of Serbian Honey Bees Diversity

Abstract

Local populations of Apis mellifera are rapidly changing by modern beekeeping through the introduction of nonnative queens, selection and migratory beekeeping. To assess the genetic diversity of contemporary managed honey bees in Serbia, we sequenced mitochondrial tRNAleu-cox2 intergenic region of 241 worker bees from 46 apiaries at eight localities. Nine haplotypes were observed in our samples, with C2d being the most common and widespread. To evaluate genetic diversity patterns, we compared our data with 1696 sequences from the NCBI GenBank from neighbouring countries and Serbia. All 32 detected haplotypes belonged to the Southeast Europe lineage C, with two newly described haplotypes from our sample. The most frequent haplotype was C2d, followed by C2c and C1a. To distinguish A. m. carnica from A. m. macedonica, both previously reported in Serbia, PCR-RFLP analysis on the COI gene segment of mtDNA was used, and the result showed only the presence of A.m. carnica subspecies. An MDS plot constructed on pairwise FST values showed significant geographical stratification. Our samples are grouped together, but distant from the Serbian dataset from the GenBank. This, with the absence of A. m. macedonica subspecies from its historic range of distribution in southern Serbia, indicates that honey bee populations are changing rapidly due to the anthropogenic influence.

The Diversity Decline in Wild and Managed Honey Bee Populations Urges for an Integrated Conservation Approach

“…It is important however to note that, in parallel, feral populations are present and numerous in South America and Australia. In Europe, several subspecies are under threat due to loss of genetic diversity as a result of admixture (previously isolated populations interbreeding) (Jensen et al, 2005;Ellis et al, 2018;Espregueira Themudo et al, 2020;Henriques et al, 2021;Tanasković et al, 2021). Additionally and as we will see below, migratory beekeeping, queen trade, breeding and selection for specific traits may ultimately reduce the fitness of managed and wild populations.…”

“…Had the genetic diversity of managed honey bees been increased through admixture before (Harpur et al, 2012;Oldroyd, 2012), the consequent homogenization might ultimately drive the loss of local adaptations (De la Rua et al, 2013). Recent studies showed that, since the 2nd half of the 20th century, the genetic diversity of several European honey bee populations has significantly decreased in their native range (Espregueira Themudo et al, 2020;Tanasković et al, 2021). How can this initiated and speedy loss be stopped?…”

“…Because honey bee queens mate indifferently with drones from both managed and wild-living colonies, the two groups are interconnected and beekeeping practices can have an impact on the whole population. Specifically, this double status imposes a serious threat for the genetic diversity of honey bees (Espregueira Themudo et al, 2020;Tanasković et al, 2021), potentially compromising the ability to cope with the existing and oncoming stresses. We propose an integrated approach to protect the genetic diversity of both managed and wild populations of honey bees.…”

Further Evidence of Population Admixture in the Serbian Honey Bee Population

“…Previous analysis showed that of four C lineage subspecies, Serbia harbors two (A. m. macedonica and A. m. carnica) which are clinaly distributed from the northwest (carnica) to the southeast (macedonica) with a hybrid zone between them [23,26,44,45]. Furthermore, nine described mtDNA haplotypes for tRNA leu -cox2 of which two are novel [46] and three distinct ecotypes belonging to specific geographical regions [47] reflect significant genetic variability of A. mellifera in this region. In the past 30 years, the variability of Serbian honey bees has been extensively described on morphological [26,48], etiological [49,50], and genetic levels [26,44,45,47,[51][52][53].…”

“…Serbia is one of the countries that has embedded in its legislation the preservation of autochthonous species, subspecies, and races, and as per the Law on Animal Breeding from 2009, breeding and keeping of only A. m. carnica are allowed in its territory [55]. Recent work based on the variability of the tRNA leu -cox2 mtDNA region [46] suggests that the composition and distribution of honey bee populations in Serbia has changed over the past decade, invoking the need for further examination of genetic variability on various levels.…”