Scientists at the Biodiversity Unit of the University of Turku, Finland, looked at the insect biodiversity of Kibale National Park in Uganda. A study based on long-term collecting gives new information that is useful for conserving dark biodiversity, showing how the diversity is distributed in different habitats.

Dark taxa and dark biodiversity refer to biodiversity which is poorly known or unknown, and is thus often hard to take into account in conservation efforts. Most of the Earth's species are still unknown to science, which makes it hard to stop biodiversity loss. Dark taxa are especially common in tropical forests; in habitats whose species diversity, structural diversity and functional diversity are still poorly known.

The Biodiversity Unit of the University of Turku specialises in studying unknown global biodiversity and biodiversity loss. Numerous new species are discovered every year by the unit's scientists, and the unit develops new methods for slowing down the ongoing loss of global biodiversity. Active locations of interest include the tropical forests of Africa and Amazonia, both of which are threatened by human activity. The biodiversity of both areas is still poorly known, making it hard to conserve the species effectively.

A recent study looked at the biodiversity of parasitoid wasps in Kibale National Park in Uganda. Parts of the forest at Kibale have been influenced by human activity during the past decades, while other parts are largely undisturbed.

Ichneumonid wasps are one of the most diverse animal taxa on Earth. They regulate other species by parasitising immature insects and spiders. The study focused on the subfamily Pimplinae.

”Ichneumonids are a very poorly known taxon in Africa – we estimate that over half of the species we found are new to science. Since there was very little known about tropical ichneumonids, we started looking at the conservation of these wasps by looking at how their diversity is distributed in different habitats. Our results clearly show that African forest, including forest that is recovering from logging, maintains a species rich Pimplinae fauna compared to, say, nearby farmland. Species rich habitats can be considered especially valuable in conserving unknown dark biodiversity,” says Doctoral Researcher Emil Österman from the Biodiversity Unit of the University of Turku.

Parasitoid wasps occupy a high position in food webs, which makes them vulnerable to biodiversity loss. Disturbances at lower levels of the food web carry over to parasitoid wasp diversity and threat levels. This makes Pimplinae suitable as indicators of biodiversity; changes in their species richness and abundances reflect those of other taxa.

“Many of our finds weren't unexpected, but we didn't have data based on long-term collecting in the field. Now we can tell in greater detail how many more species there are in natural forest, and to what extent disturbed or logged tropical forest can harbour species. This is useful information for conservation efforts in the Afrotropics,” says Doctor Tapani Hopkins from the Biodiversity Unit of the University of Turku.

The study also looked at how the African biodiversity compares to that of tropical forest in the New World. The Biodiversity Unit's scientists have previously obtained similar material based on long-term collecting in western Amazonia and the coastal forest of Brazil.

“Conserving dark taxa effectively requires a detailed knowledge of how biodiversity is distributed, both locally and at a global scale. Our research suggests that Pimplinae may have the highest species richness in the South American rainforest areas, but African forest also maintains a rich fauna. We will continue our field studies at different tropical forest sites, because that is where biodiversity is disappearing especially quickly. It is a fight against time. When rainforest is destroyed, we loss countless species which we know nothing about,” says Professor Ilari E. Sääksjärvi from the Biodiversity Unit of the University of Turku.

The study was carried out as part of the Sustainability Transformation Doctoral Education Pilot (SusTra), funded by the Ministry of Education and Culture and the Research Council of Finland. The study was also funded by the Alfred Kordelin Foundation, the Entomological Society of Finland, the Finnish Cultural Foundation, Oskar Öflunds Stiftelse, Svensk-Österbottniska Samfundet, and Waldemar von Frenckells stiftelse.

The results were published in the scientific journal Insect Conservation and Diversity. The research article is available at: https://resjournals.onlinelibrary.wiley.com/doi/10.1111/icad.70017