Abstract
This study presents the first ever published Checklist and red list of endangered true bug (Insecta, Heteroptera) species of Lower Austria. Altogether 793 species (approx. 90% of the complete Austrian Heteroptera fauna) are listed with past er present occurrence in the district. Red List categorization is based on literature research, verification of voucher specimens in several collections and own collecting efforts in the district since 1998, resulting in approximately 40.000 data points. The high species diversity is caused by the geographical situation of Lower Austria where two major biogeographical regions (the continental and the pannonian) meet. Being part of the alps and the steppe, with altitudes from 137 - 2076m and precipitation from below 400mm to above 2000mm, with diverse geologies, soils and land use histories a high diversity of habitat types is developed, which host a high species diversity. This diversity is threatened by a equaily diverse spectrum of causes of threat. Most relevant among these are habitat loss due to intensified land and water use for infrastructure, agriculture, forestry, hydraulic engineering, drainage, etc. and habitat change due to eutrophication, pesticides, discontinuation of land use, etc. Further factors, such as tragmentation, intensify the multiple Stressors acting on species. The most important habitat types of the Heteroptera of Lower Austria are pannonic Inland sanddunes and salt steppes, natural grasslands, semi-natural dry grasslands, edge habitats like hedgerows and woodland edges, shrub heathland, wet meadows, bogs and fens, and natural or near-natural aquatic habitat types. In the Red List of endangered species 30 species (3,8%) are classified as "regionally extinct" (category 0), 22 species (2,8%) as "critically endangered" (category 1), 19 species (2,4%) as "endangered" (category 2), 33 species (4,1%) as "vulnerable" (category 3). For 54 species (6,8%) data availability restrains a clear classification, although it is suspected that these species belong to either category 1, 2, or 3 (category 5). For 125 species (15,8%) it is currently impossible to decide their State of endangerment at all due to lack of data ("data deficient", category 5), most often due to unsolved taxonomic prolems or to their rarity. Finally, 510 species (64,3%) are classified as of "least concern". The occurrence of 29 species (3,6%) is considered as of national relevance, because they do not occur elsewhere in Austria or even Central Europe. A high national responsibility exists for the protection of these species and their habitats or food plants, all of which - except one - are classified in category 0, 1,2, 3, or 5. Most endangered species (categories 0, 1, 2, and 3) of Lower Austria occur in the pannonic-steppic region (e.g. 80% of the critically endangered species). Approximately 20% of the aquatic and semiaquatic species were classified in one of these categories and further 21% were classified as data deficient, which is above the average of the complete Heteroptera fauna and indicates the particular need for faunistic inventories of aquatic species. The continuous inventoring of the Heteroptera of Lower Austria reveals ongoing changes and provides a solid basis for further studies. Faunistic inventories are a good conservation investment and ultimately the base for protection of nature,
