The Empidoid Flies (Diptera: Brachystomatidae, Empididae, Hybotidae) of Wrangel Island (Chukotka Autonomous Okrug): Composition and Distribution of the Fauna

摘要

This paper summarizes the material on empidoid flies of the families Brachystomatidae (2 species), Empididae (22 species), and Hybotidae (3 species) collected on Wrangel Island in the 20th (mostly in 1966, 1971, and 1972) and 21st (2006 and 2015–2020) centuries. The studied fauna is characterized by high species richness (at least double that on other Arctic islands) and the presence of probable endemics as well as North American species unknown from other regions of the Palaearctic. Despite clear correlation between the distribution of the commonest species and the gradient of mesoclimatic conditions, the activity of most of these species varies significantly even within one subzonal vegetation variant; this fact implies that they exist on the island outside their climatic optimum. Most of the rare species (one-third of the fauna), including the majority of probable endemics, were collected in the mountains of the southern part of Wrangel Island, which have the most varied relief and, correspondingly, a broad range of microclimatic conditions. Taxocenes with stable sets of the most abundant species ( Rhamphomyia albopilosa , Rh. hovgaardii , Rh. nigrita , Rh. taimyrensis , Rh. septentrionalis , Rh. shewelli , Platypalpus subtectifrons ) occur in the warmest central part of the island, constituting an enclave of the typical tundra subzone. The presence of common dominants determines their similarity with the Empidoidea taxocenes of the southern islands of the Canadian Arctic Archipelago. Some species ( Rhamphomyia erinacioides , Rh. sublongiseta , Rh. gorodkovi , Rh. mallochi , Rh. frigida ) prefer areas with the most rigorous climate and strong influence of the sea; among these species, only Rh. erinacioides is broadly distributed over the Arctic islands. High numbers of all these five species were recorded in the southwestern part of Wrangel Island (the northern variant of the Arctic tundra subzone); the taxocenes with a similar set of predominant species are unknown from other Arctic islands.