A temperate radiation in a tropical plant family – factors underpinning evolution of the Eurasian Vincetoxicum (Apocynaceae) complex

• Applicant: Professorin Dr. Sigrid Liede-Schumann
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437386703

Temperate herbaceous clades in mainly tropical, woody Angiosperm families often have undergone accelerated episodes of species diversifications and / or disparification – radiations – in the recent past, frequently associated with the colonization of new habitats. However, little is known about the factors driving such radiations outside some well-studied biogeographic hotspots like, e.g., mountains or islands. In the pollinia-forming, tropical subfamily Asclepiadoideae of Apocynaceae, only three lineages have undergone a substantial radiation in the temperate zones, of which Vincetoxium (s.l.) is the youngest one. Vincetoxicum is a genus comprising several tropical lianescent clades and two herbaceous temperate radiations. One of these, the "Vincetoxicum s.str." clade, has expanded from the Far East via the Asian mountain chains into the Asian steppes and into Europe, from where it has entered the New World with neophytes. To understand the evolutionary history of this recent temperate radiation, we will study three lines of evidence: morphometric, molecular, and chemical. Especially, we test one of the most likely factors contributing to the evolutionary success of this clade, its unusual chemistry featuring phenanthroindolizidine-alkaloids (PIAs). Synthetic analysis will elucidate the phenotypic variation, the genetic basis, and the supposed chemical defence strategy in this clade to test the hypothesis that the most successful lineages are the ones with the best chemical defence system. We will (1) develop a comprehensive morphological dataset allowing the delimitation of "morphospecies"; (2) provide a densely sampled phylogeny of the Vincetoxicum s.str. clade using targeted sequencing of low-copy nuclear genes, allowing the delimitation of coalescent-based species; (3) check the congruence of morphospecies and coalescent-based species and derive a stable species concept for Eurasian Vincetoxicum based on different lines of evidence; a tool urgently needed for future monitoring of Vincetoxicum in the light of climate change and conservation; (4) test the hypothesis that the most successful species are the ones with the best chemical defence system, using quantity and diversity of PIAs as a proxy for the strength of the defence.

• DFG Programme: Research Grants
• International Connection: Ukraine, USA
• Cooperation Partners: Professor Dr. Kevin P.C. Minbiole; Professor Dr. Sergei L. Mosyakin; Professorin Dr. Shannon C.K. Straub