Phylogenomics sheds new light on the drivers behind a long-lasting systematic riddle: the figwort family Scrophulariaceae

Abstract

The figwort family, Scrophulariaceae, comprises c. 2000 species whose evolutionary relationships at the tribal level have proven difficult to resolve, hindering our ability to understand their origin and diversification.We designed a specific probe kit for Scrophulariaceae, targeting 849 nuclear loci and obtaining plastid regions as by-products. We sampled c. 87% of the genera described in the family and use the nuclear dataset to estimate evolutionary relationships, timing of diversification, and biogeographic patterns.Ten tribes, including two new tribes, Androyeae and Camptolomeae, are supported, and the phylogenetic positions of Androya, Camptoloma, and Phygelius are unveiled. Our study reveals a major diversification at c. 60 million yr ago in some Gondwanan landmasses, where two different lineages diversified, one of which gave rise to nearly 81% of extant species. A Southern African origin is estimated for most modern-day tribes, with two exceptions, the American Leucophylleae, and the mainly Australian Myoporeae. The rapid mid-Eocene diversification is aligned with geographic expansion within southern Africa in most tribes, followed by range expansion to tropical Africa and multiple dispersals out of Africa.Our robust phylogeny provides a framework for future studies aimed at understanding the role of macroevolutionary patterns and processes that generated Scrophulariaceae diversity.