After receiving his doctorate in 1999 at the University of Applied Life Sciences (BOKU), Vienna, Christian Lexer used a three-year post-doctorate (2000–2003) at the University of Indiana, USA, to conduct ground-breaking research on speciation via hybridization in sunflowers. Subsequently, Christian Lexer moved as a population geneticist to the Royal Botanic Gardens Kew, UK, where he significantly contributed to a better understanding of speciation in the absence of geographic separation, a fervidly debated scientific topic at that time. After several years in England (2003–2007), Christian Lexer moved to Switzerland in 2008, where he became Associate Professor in Evolutionary Biology at the University of Freiburg/Fribourg, teaching in and conducting research on, among others, genetics and genomics of poplars. Eventually, Christian Lexer moved back to Austria, where, since 2016, he held the professorship for Evolutionary and Systematic Botany at the Department of Botany and Biodiversity Research of the University of Vienna. Christian Lexer was an outstanding evolutionary biologist and botanist, who, using genetic and genomic approaches, highly successfully tackled core questions of these research fields. These included studying the ecology and evolution of barriers to inter-specific gene flow, the evolution of species isolation and local adaptation of co-occurring and hybridizing species (in recent years mostly in European poplars), and population genomics and range formation of hyper-diverse, South American plant lineages from the pineapple family. Although his research focused on selected model groups, Christian Lexer continuously pushed a holistic approach, where population genetics, evolutionary biology, systematics and biogeography are considered parts of a professional continuum and their joint and equally valued application is necessary to address pressing questions of biodiversity research. This perspective is directly evident in Christian Lexer’s impressive scientific output encompassing more than a hundred scientific publications. Christian Lexer was held in high esteem not only by his colleagues and collaborators for his goal-oriented and effective way of working and his quiet and imperturbably polite manners, but also by his students for his continuous support and assistance, preparing them most efficiently for their future scientific career. Numerous longtime scientific relations are proof of the distinguished personality of Christian Lexer. The University of Vienna loses with Christian Lexer an internationally renowned researcher and an experienced research group leader. We will sorely miss him as researcher, colleague, teacher and mentor. Christian Lexer is survived by his wife and two sons. Our deepest sympathy is with them, and with all his family during these difficult days.

Gerhard Ecker & Dean's Team