Characterization of mitochondrial genomes of three Andrena bees (Apoidea: Andrenidae) and insights into the phylogenetics.

Andrena is a large bee genus of >1500 species, which includes many important pollinators of agricultural systems. In this study, we present three mitochondrial genomes (mitogenomes) of Andrena species, which are the pollinators of Camellia oleifera. Compared with putative ancestral gene arrangement of insects, the three mitogenomes present identical gene rearrangement events, including local inversion (trnR) and gene shuffling (trnQ/trnM, trnK/trnD, and trnW/trnC-trnY). Most PCGs initiate with standard ATN codon and share the stop codon of TAA or TAG, whereas truncated stop codon T was detected in the atp6 gene of A. chekiangensis. Furthermore, the nad4 gene end with a single T in all three Andrena species. All tRNAs could be folded into clover-leaf secondary structure except for trnS1, with the dihydrouracil (DHU) arm forming a simple loop. Phylogenetic analysis is performed on 17 Andrena mitogenomes. Maximum likelihood and Bayesian methods generate identical topology, in which A. hunanensis and A. striata form a group and are close to A. camellia. Although A. chekiangensis is also difficult to be distinguished from A. camellia by morphological methods, A. chekiangensis and A. haemorrhoa form a clade and are grouped with the other taxa of the genus Andrena.