A new atlas of European caddisflies

Chaetopteryx rugulosa has a small distribution area in the Eastern Alps, and is split into several subspecies. Image: © Graf & Schmidt-Kloiber

A major new European atlas of the distribution of caddisfly species (or Trichoptera) has recently been published, providing the first comprehensive overview of their occurrence patterns across the continent. Based on data collected over 7 years from over 630,000 species occurrence records, the Distribution Atlas of European Trichoptera features 1,579 maps of a fascinating, diverse and ecologically-important insect order.

Whilst freshwater ecosystems are known to support a rich diversity of species – there are more than 14,500 caddisfly species, of which more than 1,700 occur in Europe – their distribution maps are often patchy and incomplete. Comprehensive species mapping – as carried out here by the Atlas team – is important in guiding future scientific research and environmental policy and management.

Atlas co-author Astrid Schmidt-Kloiber says, “The Atlas shows us the distribution ranges of every single caddisfly species in Europe, it reveals common species as well as rare ones and identifies Trichoptera hot spots. With the help of fellow caddisfly experts we compiled occurrence records from all over Europe into one single database, which now serves as a valuable base to establish a European IUCN Red List of threatened species.”

Limnephilus subcentralis – as many other Limnephilidae species – covers a huge range from Scandinavia to the Balkans and from Belarus to UK. Image: © Graf & Schmidt-Kloiber

The idea for the Atlas was first discussed in 2005 at the ‘First Conference on Faunistics and Zoogeography of European Trichoptera’ in Luxembourg. The Atlas project was kick-started in 2011 as part of the EU-funded BioFresh project, and includes data contributions from 83 Trichoptera experts (see this open-access Hydrobiologica article for more detail).

Co-author Wolfram Graf explains, “The Atlas is a milestone in Trichoptera research: up to now species distribution ranges were only indicated on country level – such as Fauna Europaea – or on an ecoregional level – such as through the freshwaterecology.info portal. For the Atlas we collected point records. This, for the first time, reveals the real distribution range of a species. The Atlas serves to delimitate diversity spots and refuge areas for endemic species on different scales and is therefore an essential basis for any conservation issue.”

The Atlas shows that areas of southern Europe – particularly in Spain, Italy and the Balkans – and mountainous regions (such as the Alps and the Carpathians) support both high caddisfly biodiversity and endemism. In other words, these areas harbour a high biodiversity and support certain rare species which are not found anywhere else.

Species of the family Limnephilidae are found all over Europe, but several genera have very limited distributions. Image: Distribution Atlas of European Trichoptera

Micrasema morosum is a caddisfly species predominantly found in the Alps. Image: Distribution Atlas of European Trichoptera

In general, overall caddisfly species diversity decreases with increasing latitude. There is a similar drop in species diversity in the move from Western Europe to Eastern Europe, largely because caddisfly-rich mountainous areas are lacking on the eastern plains of the continent. In several cases, distinctive Atlantic and Siberian species – which underwent speciation processes in glacial ‘refugia’ in the last ice age – overlap in areas of Central Europe. These climate-induced speciation processes in ice-free parts of the content account for the increased present-day species diversity in Southern Europe.

Areas rich in caddisfly biodiversity and endemism such as the Mediterranean are particularly threatened by the ongoing effects of climate change and other anthropogenic pressures. The Atlas identifies these areas of conservation importance, which can subsequently help raise their visibility as an issue amongst environmental policy makers in Europe.

Leptocerus interruptus is a delicate species with a wide distribution throughout Europe. Image: © Graf & Schmidt-Kloiber

Co-author Peter Neu outlines the value of the Atlas, “By delineating the distribution areas, the Atlas provides invaluable help in identifying species that are difficult to distinguish and therefore also serves as a quality control tool for all future identifications, for example, for people who identify specimens from regions whose fauna is not familiar to them, the Atlas is a great decision aid. Through the Atlas, we can further identify species for which there is still a research need.”

Wolfram Graf continues, “The Atlas enhances our knowledge on evolutionary theories as well as on zoo- and phylogeographic aspects. The depicted maps are just the beautiful surface but the basic data are the true treasure which will be analysed in-depth now. The Atlas may be an inspiration for us and others to continuously collect faunistic data in order to be able to analyse long-term developments of this fascinating insect order in a changing world.”

Astrid Schmidt-Kloiber concludes, “As the success of the Atlas very much relied on the willingness of our colleagues to contribute data, I want to take the opportunity to thank them once again for their enthusiasm and great work!”

The Distribution Atlas of European Trichoptera is published by Conch Books