Such patchy distribution of elements prevents any anticipation of TE presence in incoming sequenced genomes, even closely related ones.
The patchy distribution Tc1-like elements coupled with the extreme level of similarity between Tc1-like elements in the distantly divergent host species are incompatible with vertical inheritance, but are strongly indicative of multiple horizontal introductions.
The cores exhibit clearly oscillatory or patchy zonation, high trace element contents, high Th/U ratios of 0.13 to 2.12, steep MREE HREE patterns, and significant negative Eu anomalies.
The mosaic composition of the different fit/ mcf variants, the presence of transposable elements and the patchy phylogenetic distribution of the toxin could indicate a highly mobile nature of this gene.
Furthermore, we saw ectopic calcifications in the eye (Fig. 1O,P,Q) and the ethmoid plate cartilage (Fig. 1O,P), as well as patchy mineralization of craniofacial bone elements (Fig. 1O P′) and mineralization of the bulbus arteriosus – the outflow tract of the heart (Fig. 1R,S; supplementary material Fig. S1J,K).
Some TE superfamilies were found to be widespread in vertebrates, but most elements showed a more patchy distribution, indicative of multiple events of loss or gain.
For these reasons, we conclude that the patchy phylogenetic distribution of the Group 1 Tc1 elements is best explained by their repeated horizontal transfers between northern hemisphere lampreys and multiple independent teleost lineages.
Phylogenetic analysis, in conjunction with their patchy taxonomic distribution, suggests that these intron-HEG elements have been transferred horizontally among organelles and bacteria.
In a patchy landscape, specialist species that are limited to particular elements are expected to show low gene diversity, low connectivity and high differentiation among patches.
The research in the Tadrart Acacus has adopted a multi-pronged approach including archaeological techniques, ethnographic tools, and historical perspectives, to identify the major elements of the Kel Tadrart adaptation to patchy natural resources and arid climate.
Feschotte [ 19] reported a similarly patchy distribution for the Merlin DNA transposons; Merlin like elements are abundant, for example, in anopheline mosquitoes but are absent from D. melanogaster, D. pseudoobscura, and A. mellifera.
