What is a species in Veronica? Reflections on the occasion of Manfred A. Fischer's 80th birthday

The species is the central category of organizing the diversity of life. Yet, many different species concepts, such as the morphological, biological, ecological, and phylogenetic concepts, have been used by biologists, preventing clear comparability. Based on the history of species description in the genus Veronica, I demonstrate that the biosystematics approach by Manfred A. Fischer from the 1960s onwards has started to renew our understanding of what a species is in this genus. Detailed investigations of morphology, ecology, reproductive barriers, and, later, genetic cohesion and testing of species limits have continued from his earliest analyses of the V. hederifolia- complex. We now recognize 455 species in the genus Veronica but still only few species have been rigorously analyzed, leaving certainly a lot of work for future systematists working on this beautiful genus.