Molecular and Chromosomal Evolution of DsTc1_5 and DsPogo_8 Elements (Tc1-Mariner) in Species of the Dichotomius Genus (Coleoptera: Scarabaeidae): Contributions to the Speciation Process

Abstract

In Dichotomius genus, transposable elements (TE) have been related to chromosome remodeling, genomic evolution, and, possibly, to the speciation process. The objective of this study was to verify the interpopulational and interspecific conservation/variation of Tc1-Mariner elements (possibly autonomous) in Dichotomius species, aiming to identify possible contributions in the speciation process of this group. The analysis was performed on four species of Dichotomius, belonging to the Selenocopris subgenus. We verified the presence of the DsPogo_8 and DsTc1_5 elements by PCR and sequencing. We also isolated and sequenced the 28S and 16S rRNA genes aiming at the phylogenetic reconstruction of the analyzed species. Chromosomal mapping of TEs DsTc1_5 and DsPogo_8 was performed by fluorescent in situ hybridization. The results revealed the presence of the elements in the different species analyzed, except for DsTc1_5 in D. (S.) geminatus. These results suggest a vertical inheritance, with the presence of these elements in the common ancestor of these species. In the analyzed species, the nucleotide similarity of DsTc1_5 was higher than that of the 28S and 16S rRNA genes, suggesting the occurrence of horizontal transfer. The phylogenetic tree indicated that the absence of DsTc1_5 in D. (S.) geminatus is related to stochastic loss of this TE. Chromosomal mapping revealed dispersed signals, with predominance in euchromatic regions and wide variation in the chromosomal localization pattern of DsTc1_5 and DsPogo_8, both interpopulational and interspecific. This variation indicates that DsTc1_5 and DsPogo_8 may have contributed to prezygotic and postzygotic isolation, thus contributing to the speciation of these species.