Long-term stasis in acariform mites provides evidence for morphologically stable evolution: Molecular vs. morphological differentiation in Linopodes (Acariformes; Prostigmata).

Molecular species delimitation, usually by COI DNA barcoding, shows that cryptic speciation is a common phenomenon observed in most animal phyla. Cryptic species have frequently been observed among all major taxa of mites. The mites of the eupodoid genus Linopodes are cosmopolitan in distribution and are most often found in soil-related habitats. Currently, the genus consists of 22 morphologically similar species, which, in practice, are indistinguishable on the basis of their morphological features. The diagnostic issue of the Linopodes species may be caused by the poor delineation of the species, which need taxonomic revision, or the low morphological variability among cryptic species. In this paper, we present the results of molecular species delimitation carried out using sampled Linopodes populations and the level of morphological inter/intraspecific variation within defined groups. We compared COI, 18S and 28S sequence data together with morphological characters. The molecular delimitation revealed seven well-defined species of Linopodes based on DNA sequences. A well-supported phylogenetic tree revealed the same seven species, while morphological analysis showed negligible phenotypic differentiation among the species revealed. We demonstrate that mites can undergo changes in their DNA accompanied by morphological stasis lasting at least 80 MY.

Molecular phylogeny of Eupodidae reveals that the family Cocceupodidae (Actinotrichida; Eupodoidea) and its genus Filieupodes are valid taxa.

The family Eupodidae is one of eight families belonging to the superfamily Eupodoidea. Although the Eupodidae are very common mites, they are still poorly investigated and the systematic parameters of the family are vague with unclear intrafamilial relationships between its genera. According to the hypothesis of Jesionowska (Genus 21(4):637-658, 2010), the eupodid genera Cocceupodes, Linopodes and her new genus Filieupodes should be transferred from the Eupodidae to a separate family named Cocceupodidae. The opposite hypothesis of Khaustov (ZooKeys 422:11-22, 2014) considers the family Cocceupodidae an artificial taxon and the genus Filieupodes a junior synonym of Cocceupodes and assignes the family Eupodidae its primary definition. Here, we present the first molecular reconstruction of phylogenetic relationships within the Eupodidae. We test the taxonomic status of the Eupodidae and refer to the previous hypotheses based on morphological data. According to the reconstructed phylogram based on nuclear (18S + 28S rDNA) and mitochondrial (COI) sequences as well as morphological characters tracing this analysis, we have concluded that: (1) the genera Linopodes, Filieupodes and Cocceupodes are a separate monophyletic lineage of familial rank and the sister group of Eupodidae s.s., and (2) the genus Filieupodes should be considered a separate genus being a sister group of the Linopodes-Cocceupodes clade.