Format: ORAL

John Paul Bradican1,2, Salvatore Tomasello1, Judith Vollmer3, Evelin Krol4, Elvira Hrandl1

1 Albrecht-von-Haller Institute for Plant Sciences, Göttingen, Germany 2 Georg-August University School of Sciences (GAUSS), Göttingen, Germany 3 Linköping University, Linköping, Sweden 4 Georg-August University of Göttingen, Göttingen, Germany

Young species complexes represent prime subjects for the study of speciation, hybridization and range expansion. The apomictic mode of propagation sometimes expressed in such groups can exacerbate the morphological and taxonomic complexity characteristic of hybridizing species complexes, as well as facilitating rapid expansion into new habitats. We focus on the facultatively apomictic Ranunculus auricomus complex in order to investigate the evolution, biogeography and taxonomic status of geographically marginal populations of this young (1 mya) and rapidly radiating group. At the southern and northern edge of the groups range apomixis is the primary mode of propagation, with sexual reproduction occurring only rarely. Taxonomically, Ranunculus auricomus agg. is composed of a handful of sexually reproducing basal lineages occuring in temperate Europe, which through repeated hybridization have begotten manifold polyploid apomictic lineages. Given this, we also examine the patterns of ancestry in marginal areas, utilizing phylogenomic methods including subgenomic phasing. At the southern periphery we find no additional sexually reproducing species, supporting the recognition of many newly described apomictic hybrid taxa in the region as nothotaxa. In the circumboreal-circumarctic zones we focus on a particular morphogroup, typified by the diminutive Ranunculus monophyllus Ovcz. Individuals included in this morphogroup exhibit dwarf growth, high ploidy levels (4x-6x) and obligate apomixis. In order to test the plasticity of traits distinguishing R. monophyllus from other morphogroups, we conducted climate chamber experiments which showed little phenotypic plasticity in key morphological traits in response to temperature. We conclude that dwarf growth is adaptive and evolved multiple times during colonization of Northern marginal areas. Biogeographical analyses of the whole complex based on phylogenomic data will show the expansion of the R. auricomus complex in space and time, contributing to our understanding of geographical parthenogenesis.