Complex Evolutionary History of Mboumar, a Mariner Element Widely Represented in Ant Genomes

Mboumar-9 is an active mariner-transposable element previously isolated in the ant Messor bouvieri. In this work, a mariner-like element, Mboumar, isolated from 22 species of ants, is analyzed. These species belong to nine different subfamilies, including Leptanillinae, the most primitive ant subfamily, and Myrmicinae and Formicidae, the most derived ones. Consequently, Mboumar-like elements seem to be well-represented in ant genomes. The phylogenetic tree drawn for mariner elements is highly inconsistent with the phylogeny of host ants, with almost identical elements found in clearly distant species and, on the contrary, more variable elements in closely related species. The inconsistency between the two phylogenetic trees indicates that these transposable elements have evolved independently from the speciation events of the ants that host them. Besides, we found closer genetic relationships among elements than among their host ants. We also found potential coding copies with an uninterrupted open reading frame of 345 aa in 11 species. The putative transposase codified by them showed a high sequence identity with the active Mboumar-9 transposase. The results of selection tests suggest the intervention of purifying selection in the evolution of these elements. Overall, our study suggests a complex evolutionary history of the Mboumar-like mariner in ants, with important participation of horizontal transfer events. We also suggest that the evolutionary dynamics of Mboumar-like elements can be influenced by the genetic system of their host ants, which are eusocial insects with a haplodiploid genetic system.