Career and research
In 1977, Witte joined the Institute of Biology at Leiden University and moved with his wife, Els Witte‑Maas, and colleague Marteen van Oijen to Mwanza, Tanzania, as part of the Haplochromis Ecology Survey Team (HEST). During the first five years of his appointment, Witte conducted fieldwork in Lake Victoria documenting the diversity of haplochromine cichlids, a group that had radiated into more than 500 endemic species over a relatively short geological period. In 1982, he became the director of HEST, where he supervised extensive surveys that documented the diversity, morphology, and ecology of Lake Victoria's cichlids.
Witte's early research focused on the taxonomy and ecology of Lake Victoria cichlids, particularly species adapted to distinct ecological niches such as algae grazers, detritivores, insectivores, and piscivores. He collaborated with East African and international researchers to document species flocks and characterize fine-scale morphological differences among them.
Throughout the 1980s and 1990s, Witte documented the collapse of many endemic cichlid populations in Lake Victoria, caused by the introduction of the Nile perch (Lates niloticus), eutrophication, and climate change. He witnessed numerous species disappear, a phenomenon that was described in the book Darwin’s Dreampond by Tijs Goldschmidt. His observations demonstrated the fragility of species boundaries and became central to understanding evolutionary resilience, speciation reversal, and extinction in sympatric radiations. He also recorded signs of adaptive recovery, including the reappearance of some species and the formation of hybrid swarms, showing that evolutionary processes continued to operate under altered ecological conditions.
In addition to his research, Witte was also a dedicated educator and mentor. At Leiden University, he was voted Best Teacher in Biology (2005) and Best Teacher in the Faculty (2009) in recognition of his contributions to teaching. He trained Dutch and African students in field ecology and ichthyology, collaborating with institutions in Kenya, Uganda, and Tanzania.
During his career, Witte authored over 100 scientific publications and described many new cichlid species.
