Whole-Genome Sequence Analysis of Italian Honeybees (Apis mellifera).

Giulietta Minozzi,Emanuele Carpana,Alessandra Stella,Cecilia Costa,Gustavo Gandini,Maria Grazia De Iorio,Rita Rizzi,Barbara Lazzari,Giulio Pagnacco,Elena Facchini,Paola Crepaldi

doi:10.3390/ani11051311

Abstract

Simple SummaryThe purpose of this study was to (i) explore the population structure of the A.m. ligustica which is widely distributed along the entire Italian peninsula, (ii) quantify the introgression of A.m. carnica, Buckfast, and A.m. mellifera bees in the two autochthonous Italian subspecies A.m. ligustica and A.m. sicula, and to (iii) to propose conservation strategies for the two autochthonous subspecies. Whole-genome sequencing was performed by Illumina technology obtaining a total of 4,380,004 single nucleotide polymorphisms (SNPs). Results of the analysis of the patterns of genetic variation allowed us to identify and subgroup bees according to their type. Morphometric analysis of 5800 worker bees was in agreement with genomic data. The investigation revealed the genetic originality of the Sicula, and in A.m. ligustica limited genetic introgression from the other breeds.At the end of the last glaciation, Apis mellifera was established in northern Europe. In Italy, Apis mellifera ligustica adapted to the mild climate and to the rich floristic biodiversity. Today, with the spread of Varroa destructor and with the increasing use of pesticides in agriculture, the Ligustica subspecies is increasingly dependent on human action for its survival. In addition, the effects of globalization of bee keeping favored the spread in Italy of other honeybee stocks of A. mellifera, in particular the Buckfast bee. The purpose of this study was to characterize the Italian honeybee’s population by sequencing the whole genome of 124 honeybees. Whole genome sequencing was performed by Illumina technology, obtaining a total coverage of 3720.89X, with a mean sample coverage of 29.77X. A total of 4,380,004 SNP variants, mapping on Amel_HAv3.1 chromosomes, were detected. Results of the analysis of the patterns of genetic variation allowed us to identify and subgroup bees according to their type. The investigation revealed the genetic originality of the Sicula, and in A.m. ligustica limited genetic introgression from the other breeds. Morphometric analysis of 5800 worker bees was in agreement with genomic data.

Highlights

IntroductionAt the end of the last glaciation, Apis mellifera (A.m.) was established in northern
Introduction conditions of the Creative CommonsAt the end of the last glaciation, Apis mellifera (A.m.) was established in northernEurope spreading in numerous subspecies [1]
One hundred and twenty-four colonies were sampled in different regions of Italy and sequenced with a mean coverage of 29.77X, expanding and focusing in Italy the study conducted by Wallberg et al [4] who sampled 140 colonies belonging to 14 different populations of A. mellifera from all over the world, including samples from the A, O, C

Summary

Introduction

At the end of the last glaciation, Apis mellifera (A.m.) was established in northern. Europe spreading in numerous subspecies [1]. The long climate optimum during the last 10,000 years has consolidated their adaptation to different eco-geographical areas. The A.m. presents over 30 subspecies described in the 1980s by Friedrich Ruttner on a morphometric basis and by Father Adam (Karl Kehrle) of Buckfast Abbey, on production and behavioral traits [2,3]. The native distribution of A. mellifera encompasses, in addition to Europe, Western Asia, Africa, and the Middle East. The different subspecies have been divided into 4 main branches: A (African subspecies), C (eastern European subspecies), M (western and northern European subspecies) and O (Middle Eastern subspecies) [2]. The high level of honeybee genetic diversity reflects differentiation and adaptation to different climatic and ecological conditions [4]

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