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Abstract
Marine associated oribatid mites belong mainly to the Ameronothroidea which represent a very small percentage of all Oribatida. Over the last decades the systematics and evolutionary history of this group has been discussed controversially and still there is no consensus concerning several issues. The extreme marine environment may have resulted in parallel morphologies complicating the classification and estimation of phylogeny based on discrete morphological traits. In the present study, we performed a molecular genetic study using a mitochondrial and two nuclear markers to infer the phylogeny of this group. Additionally, we reconstructed the phylogeny of Ameronothroidea based on morphological data using different algorithms. Both methods resulted in largely congruent topologies and highlight the following important points: the Ameronothroidea represent a paraphyletic assemblage; the Podacaridae are a distinct family and should be excluded from Ameronothridae; the Fortuyniidae, Selenoribatidae and Tegeocranellidae constitute a monophyletic lineage; and certain genera of Selenoribatidae need a revision. These results demonstrate that the classification of Ameronothroidea and certain positions within this group need to be thoroughly reconsidered and revised. The present study also shows that phylogenetic estimates based on coded morphological data can be a very helpful tool for verifying and supporting molecular phylogenies.
Based on morphological, morphometric and genetic data Scutovertex ianus sp. nov. is described as a new oribatid mite species. The traditional comparison with the morphologically most similar congeneric S. minutus and S. sculptus demonstrated that the new species shares certain characters with both species, but can be clearly identified by indistinct cuticular notogastral foveae in combination with short spiniform notogastral setae. Furthermore the eggs of S. ianus exhibit a different fine structure of the exochorion. The morphometric analysis of 16 continuous morphological variables separated the three species, S. minutus, S. sculptus and S. ianus with a certain overlap indicating minor size and shape differences in overall morphology. The molecular phylogenetic analysis of mitochondrial COI gene sequences supported the monophyly of all three investigated species and confirmed S. ianus as separate species with high bootstrap values. Each performed analysis approves the discreteness of S. ianus and the results contradict the formerly supposed large intraspecific variability of the representatives of the genus Scutovertex. The records of S. ianus are as yet restricted to the Eastern part of Austria and to one location in Germany, but findings of intermediary Scutovertex specimens from other European countries may refer to this new species.