Mitochondria are critical organelles in almost all eukaryotic cells in generating most of the chemical energy needed to power the cell's biochemical reactions. Mitochondria contain their own genomic sequences, mitogenomes, which are being widely used in species identification, phylogenetic, population genetics, and comparative genomics. However, the structural variations of mitogenomes are largely unclear.  

A recent study published in Zoological Research and conducted by the scientists from Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences reported new mitogenome structures in the Meliponini.   

The mitogenome variations and their phylogenetic signature over three social bee tribes, Apini (honeybees), Meliponini (stingless bees) and Bombini (bumblebees), were investigated. Taxa within these three tribes are iconic around the world for their roles in pollination and economic production, as well as their social behaviors. Comparative analyses based on extensive sampling regarding 154 individuals, including 73 de novo assembled new mitogenomes and 81 previously reported mitogenomes were incorporated.   

The scientists found that the mitogenomes of Apini and Bombini are the typical type, while those of Meliponini show diverse variations in mitogenome sizes and organizations. Phylogenetic analyses supported the Meliponini as sister to Bombini, and then the two tribes as sister to Apini. Molecular evolutionary genetics analysis showed the potential effects of large inverted repeats on animal mitogenome evolution and confirmed that Meliponini is a hotspot in mitogenome evolution.  

Using low sampling size to represent the whole genus, tribe, family, or even order in mitogenomic studies could easily overlook potential variations at lower taxonomic levels, which might lead to some incorrect inferences.   

This study demonstrated that comprehensive sampling is necessary to fully understand the patterns of mitogenome structure variations and their implications for phylogenetic inference.