Phylogenetic inference and comparative evolution of a complex microsatellite and its flanking regions in carnivores

Abstract

We sequenced locus Mel08, with complex short repetitive motifs, in 24 carnivore species belonging to five different families in order to explore mutational changes in the region in the context of locus and species evolution. This non-coding locus includes up to four different parts or repetitive motifs showing size variability. The variability consists of repeat additions and deletions; substitutions, insertions and/or deletions creating interruptions in the repeat; and substitutions, insertions and deletions in the flanking regions. The locus has different repeat expansions in different carnivore subfamilies. We hypothesize that the complexity of this locus is due to a high mutation rate at an ancestral DNA sequence and, thus, prompts the emergence of repeats at mutational hotspots. High levels of homoplasy were evident, with nine electromorphs representing 28 haplotypes never shared across species. The variability in flanking regions was informative for phylogenetic inference and their evolutionary content. Tree topologies were congruent with relevant hypotheses on current conflicts in carnivore phylogenies, such as: (i) the monophyly of Lutrinae, (ii) the paraphyly of Mustelinae, (iii) the basal position of the Eurasian badger, Meles meles, in the Mustelidae, (iv) the classification of skunks as a separate family, Mephitidae, and (v) the placement of the red panda, Ailurus fulgens, as a monotypic family, Ailuridae, at a basal position in the Musteloidea.