New species of killifish from Kenya already critically endangered

Nothobranchius sylvaticus, from the Latin meaning "pertaining to the forest," is also the first known endemic killifish to persist in a forest.

Prof. Dirk Bellstedt, emeritus professor of biochemistry at Stellenbosch University (SU), was part of the team of international scientists who sampled the fish from ephemeral swamps in the Gongoni Forest in south-eastern coastal Kenya. These expeditions in 2017 and 2018 were part of an "Off the beaten track" research project, supported by the Volkswagen Foundation in Germany.

The team performed both a principal component analysis, based on the physical traits of the fish, as well as DNA sequencing, to confirm that it is indeed a new species. A dated phylogenetic analysis, the most comprehensive for the genus, indicated that the N. sylvaticus lineage diverged from its sister species about 7.09 million years ago.

According to Bellstedt, this finding indicates that the Gongoni Forest itself is more than 7.09 million years old. Comprising only about 8.2 square kilometers, this ancient forest is a typical example of the East African Mosaic -- a combination of savannah interspersed with forest patches that stretches from as far south as Pondoland in South Africa to as far north as southern coastal Somalia.

Since 2015, the team has been combining next-generation DNA sequencing of fish groups, such as Africa's famous cichlid fishes, with high precision rock dating of key landforms in eastern Africa. The aim is to reconstruct the tectonic development of central Africa over the past 20 million years. During the past five to 30 million years, this region has undergone major tectonic activities and break ups.

For the scientists, the discovery of N. sylvaticus was one more example of the congruence between evolutionary events in the genus Nothobranchius with paleo-drainage dynamics, which were driven by the tectonic events that formed the East-African River Valley System.

However, due to the new species' severely restricted habitat in an ancient forest, it also faces a high conservation risk.

The type specimen was deposited at the National Museums of Kenya in Nairobi, and the comparative specimens at the Royal Museum for Central Africa in Tervuren, Belgium.