A new Diaforobiotus species (Tardigrada: eutardigrada: richtersiusidae) from the Mexican transition zone, described based on multiple lines of evidence

The genus Diaforobiotus was established to accommodate species formerly assigned to the genus Macrobiotus (family Macrobiotidae), and is now placed within the family Richtersiusidae. Currently, the genus includes five species, one of which—Diaforobiotus islandicus—has been recorded in Mexico. Although most of the country lacks studies focused on tardigrades, the Trans-Mexican Volcanic Belt (TMVB) is interesting since it is positioned between two major biogeographic regions (the Neotropical and the Nearctic) and it serves both as a transition zone and as a hotspot of endemism. In this work, a new tardigrade species, Diaforobiotus quetzalcoatli sp. nov., found in Mount Tlaloc (a locality belonging to the TMVB, in central Mexico) is described. This new species is supported and described with an integrative approach using light, confocal, and scanning electron microscopy, as well as DNA sequences of four molecular markers (COI, ITS-2, 18S rRNA, and 28S rRNA). Phylogenetic analyses revealed that D. quetzalcoatli sp. nov. is closely related to Diaforobiotus occidentalis from Canada, and species delimitation analyses based on COI and ITS2 markers provide strong evidence that Mexican specimens represent a sixth distinct species within Diaforobiotus.