Chironomidae (Diptera: Insecta) in oceanic islands: New records for the Azores and biogeographic notes

Oceanic islands freshwater systems are unique due to their volcanic origin, oceanic situation, catchment morphology and the presence of distinct freshwater communities when compared with continental systems. This study provides an update of Azorean chironomid fauna records, distribution data and includes biogeographical comments, based on collections covering a range of freshwater habitats on several islands over 2005 to 2008. Island species area-relationships or ISAR was performed as a descriptive model for species accumulation patterns in each island in relation to their area. Six new chironimid species records are given for the Azores archipelago: Orthocladiinae: Orthocladius (Eudactylocladius) fuscimanus (Kieffer, 1908), Pseudorthocladius (Pseudorthocladius) curtistylus (Goetghebuer, 1921), Synorthocladius semivirens (Kieffer, 1909), Parachaetocladius abnobaeus (Wu¨ lker, 1959); Chironominae: Chironomus (Chironomus) annularis (Meigen, 1818), Parachironomus tenuicaudatus (Malloch, 1915). As a result, the Azorean chironomid fauna has increased from 38 to 44 species, spread across 33 genera. Most recorded chironomids are primarily of western Palaearctic origin; Nearctic, Oriental and Neotropical regions are comparatively poorly represented. A checklist is provided, incorporating and updating previous records. Chirononidae distribution pattern among the islands is analyzed and island species area-relationship (ISAR) analyses, performed to provide a descriptive model for species accumulation patterns in each island, indicated a positive correlation between species richness (number of species) and the area of the Azorean islands, supporting MacArthur and Wilson’s equilibrium theory of island biogeography. Chironomidae could be promising for searching candidate bioindicators to answer the demand of Water Frame Directive.