Sub‐Paratethyan origin and Middle to Late Miocene principal diversification of the Lactucinae (Compositae: Cichorieae) inferred from molecular phylogenetics, divergence‐dating and biogeographic analysis

Abstract

The Lactucinae or Lactuca alliance include approximately 200 species distributed across the Northern Hemisphere and Africa. They were not recognised as a separate lineage until the late 20th century and their circumscription is still not fully settled. The generic classification of no other group of the Cichorieae has faced as many controversies as the Lactuca alliance and competing taxonomies coexist. This paper provides the first molecular phylogeny of the subtribe on a global scale as a major step towards its revised systematics. The sampling includes almost 60% of the species-level diversity and spans all species groups. Two datasets were created, one including the nrDNA ITS region, the other five concatenated non-coding plastid DNA loci. Maximum parsimony, maximum likelihood and Bayesian inference were used to produce a robust phylogenetic backbone. The diversification and expansion of the Lactucinae in a geohistorical context was reconstructed by estimating the age of their lineages using relaxed molecular clock dating and by inferring the ancestral areas using Bayesian binary analysis. The redelimited monophyletic Lactucinae are composed of seven lineages that also include Prenanthes, which is confirmed to have a single species, P. purpurea. The positions of two further lineages shift between Lactucinae and Crepidinae in the nuclear and plastid DNA phylogenies. Incongruence between the phylogenies suggests events of ancient reticulation or incomplete lineage sorting in the formation of these latter two lineages and in two of the seven other Lactucinae lineages. The phylogenetic results show a dilemma for Lactucinae systematics: most generic concepts proposed to date are highly artificial but the resolved phylogenetic lineages do not constitute practicable taxonomic entities with our current knowledge. Diversification of the subtribe is inferred to have taken place since the Middle Miocene. Biogeographic analysis proposes that the clade originated in the mountains of the landmass mediating between the European and Asian continents and delimited in the south by the Tethys Sea and in the north by the Paratethys Sea. Several independent migrations have occurred into various parts of Asia, Europe, tropical Africa and North America.

An empirical assessment of a single family‐wide hybrid capture locus set at multiple evolutionary timescales in Asteraceae

“…A sister group relationship between subtribes Hyoseridinae (four Sonchus species) and Crepidinae ( Nabalus albus and Taraxacum kok‐saghyz ) was revealed in all analyses of our Cichorieae tribe‐wide data sets (Table ; 24 samples). This is promising because the separation of subtribes Crepidinae and Lactucinae has proven complicated (see Kilian et al., ), yet Crepidinae is always sister to Hyoseridinae rather than to Lactucinae in our analyses (Fig. ; Appendices , ).…”

Sinoseris (Crepidinae, Cichorieae, Asteraceae), a new genus endemic to China of three species, two of them new to science

“…This seems surprising in view of their previous classification as members of Lactuca or the Lactucinae. It must be considered, however, that the generic concept of Lactuca in the late 19th and early 20th century was extremely wide and spanned members of several of the modern subtribes (Kilian et al, 2017). Disentangling the subtribes Lactucinae and Crepidinae has, moreover, proven particularly difficult due to the scarcity of nonhomoplastic morphological synapomorphies (Bremer, 1994).…”

“…The Dubyaea-Nabalus-Soroseris-Syncalathium clade has been resolved in several studies with varying partial representation of its members (Kilian et al, 2009a;Zhang et al, 2011;Liu et al, 2013;Kilian et al, 2017). Estimations divergence times for the Crepidinae by Zhang et al (2011) revealed that the Dubyaea-Nabalus-Soroseris-Syncalathium clade is likely of Pliocene origin, with a crown age of around 5 myr only; for genera such as Soroseris or Syncalathium a crown age of less than 2 and 3 myr, respectively, have been estimated.…”

Patterns of Transmission Ratio Distortion in Interspecific Lettuce Hybrids Reveal a Sex-Independent Gametophytic Barrier

“…L. sativa is distantly related to, and less crossable with, the species L. saligna. The most recent common ancestor (MRCA) for L. saligna and L. serriola has been dated, by a phylogenetic study with nuclear (ITS) and chloroplast sequences, to between 3.4 and 2 MYA (Kilian et al 2017). Phenotypically, the divergence between L. saligna and L. sativa is clearly demonstrated by the observation of nearly complete sterility in the F1 hybrid and hybrid breakdown in the F2 population.…”