Phylogeny and species diversity of Tasmanian mountain shrimps and their relatives (Crustacea, Anaspidesidae)

Genetic structure and new occurrence records of the iconic Tasmanian mountain shrimp Anaspides tasmaniae (Thomson, 1893) (Anaspidesidae : Anaspidacea) reveal relictual distribution in southern Tasmania

The iconic ‘mountain shrimps’ of the genus Anaspides Thomson, 1894, are endemic to Tasmania, inhabiting various freshwater habitats such as mountain tarns and creeks, as well as streams inside caves. They are often labelled as ‘living fossils’ because of their close resemblance to their Triassic relatives. Prior to 2015, only two species were recognised but recent studies have uncovered a total of at least seven species. The type species of Anaspides, A. tasmaniae (Thomson, 1893), was previously believed to occur throughout Tasmania, but following a review in 2016, this species was confirmed only from a small range on the east and south-east side of Mt Wellington, with Anaspides from other parts of Tasmania referable to other species. We herein provide a detailed assessment of the distribution and genetic structure of A. tasmaniae based on extensive field surveys throughout the ranges of all species of Anaspides. The distribution of A. tasmaniae is extended to include four separate localities in and around the Mt Field National Park, 50 km north-west of Mt Wellington. The recovered genetic structure of A. tasmaniae based on 48 specimens indicates that the disjunct distribution is unlikely to be the result of artificial translocation but, instead, probably reflects postglacial relictualisation of a formerly continuous range present during Pleistocene glacial maxima. Of particular interest is the record of syntopy in Anaspides, observed at the entrance of Khazad Dum cave, where both A. tasmaniae and A. swaini inhabit the inflow stream.

Integrative taxonomy of Abacarus mites (Eriophyidae) associated with hybrid sugarcane plants, including description of a new species

Phytophagous mites belonging to the Eriophyoidea are extremely diverse and highly host-specific. Their accurate morphological identification is hampered by their reduced size and simplified bodies and by the existence of cryptic species complexes. Previous studies have demonstrated the urgency of applying multisource methods to accurate taxonomic identification of eriophyoid mites, especially species belonging to the genus Abacarus. This genus comprises 65 species, of which 37 are associated with grasses and four with sugarcane Saccharum (Poaceae). Recently, Abacarus specimens very similar to Abacarus sacchari were collected from the sugarcane crop in Brazil; however, their taxonomic placement was uncertain. In this study, we used an integrative approach to determine whether A. aff. sacchari specimens belong to A. sacchari or constitute a cryptic species. Morphological data were combined with molecular phylogeny based on the nucleotide sequences of three markers, one mitochondrial (COI) and two nuclear (D2 region of 28S and ITS). Morphological differences were observed between A. aff. sacchari, A. sacchari and A. doctus. The phylogenetic relationships among these three taxa and the genetic distances separating them revealed an interspecific divergence. The results of the morphological and molecular methods were congruent and supported the existence of a new species: Abacarus neosacchari n. sp. Duarte and Navia, herein described. This species belongs to the Abacarus cryptic species complex associated with sugarcane in the Americas. The results of this study, presenting the occurrence of multiple Abacarus species associated with sugarcane, contribute to the knowledge on plants and mites diversity by adding up one more clue highlighting that plant hybridization can be an important mechanism contributing to the speciation of plant-feeding arthropods.