Molecular Phylogeny of the Lactuca Alliance (Cichorieae Subtribe Lactucinae, Asteraceae) with Focus on Their Chinese Centre of Diversity Detects Potential Events of Reticulation and Chloroplast Capture

Abstract

The first comprehensive molecular phylogenetic reconstruction of the Cichorieae subtribe Lactucinae is provided. Sequences for two datasets, one of the nuclear rDNA ITS region, the other of five concatenated non-coding chloroplast DNA markers including the petD region and the psbA-trnH, 5′trnL(UAA)-trnF, rpl32-trnL(UAG) and trnQ(UUG)-5′rps16 spacers, were, with few exceptions, newly generated for 130 samples of 78 species. The sampling spans the entire subtribe Lactucinae while focusing on its Chinese centre of diversity; more than 3/4 of the Chinese Lactucinae species are represented. The nuclear and plastid phylogenies inferred from the two independent datasets show various hard topological incongruences. They concern the internal topology of major lineages, in one case the placement of taxa in major lineages, the relationships between major lineages and even the circumscription of the subtribe, indicating potential events of ancient as well as of more recent reticulation and chloroplast capture in the evolution of the subtribe. The core of the subtribe is clearly monophyletic, consisting of the six lineages, Cicerbita, Cicerbita II, Lactuca, Melanoseris, Notoseris and Paraprenanthes. The Faberia lineage and the monospecific Prenanthes purpurea lineage are part of a monophyletic subtribe Lactucinae only in the nuclear or plastid phylogeny, respectively. Morphological and karyological support for their placement is considered. In the light of the molecular phylogenetic reconstruction and of additional morphological data, the conflicting taxonomies of the Chinese Lactuca alliance are discussed and it is concluded that the major lineages revealed are best treated at generic rank. An improved species level taxonomy of the Chinese Lactucinae is outlined; new synonymies and some new combinations are provided.

Phylogenetic relationships within Lactuca L. (Asteraceae), including African species, based on chloroplast DNA sequence comparisons

“…S1-S4) and trees from Wang et al (2013). 79 trnL-F and 33 ndhF accessions were selected to represent Lactuca and related genera.…”

“…From the image of the L. tinctociliata specimen used in this study, we can see b Fig. 1 RAxML phylogram ('best ML tree') of the concatenated sequences of ndhF gene and trnL-F gene used in this study; Bootstrap (BS [ 50) support values are given above the branches and Posterior Probability (PP [ 0.5) support values are below; the names of Chinese taxa are referred to Wang et al (2013); star L. tinctociliata was mis-identified and it could be Launaea cornuta; L. ugandensis should be Lactuca sp.…”

“…et Pančić) Rouy, Tuberosae Boiss., Micranthae Boiss., Sororiae Franchet) and two geographical groups (African and North American). Recently, Wang et al (2013) constructed a DNA-based phylogenetic tree of the Lactuca alliance with a focus on the Chinese centre of diversity. This study fills the gap in our understanding of Asian diversity centre of Lactuca species and related genera, especially for the Chinese species.…”

“…Zohary (1991) established a concept of the 'lettuce gene pool ' andKoopman et al (1998, 2001) modified Zohary's lettuce gene pool concept and provided the first molecular phylogenetic relationships among Lactuca species based on nrDNA ITS-1 and AFLPs. Koopman et al (1998) Koopman et al (2001) and Wang et al (2013), there is limited information about the molecular phylogenetic relationships within the genus Lactuca, especially for the African species since they were first described (Jeffrey 1966;Stebbins 1937b).…”

Novelties on the distribution of Lepechinia flammea (Lamiaceae), rediscovery of L. glomerata in Jalisco, Mexico, and their phylogenetic position within Lepechinia

“…However, the sister relationship between L. flammea and L. nelsonii in the nDNA tree (albeit only moderately supported) is somewhat surprising based on a priori expectations. The conflicting topologies between genetic compartments may be indicative of chloroplast capture or hybridization as has been suggested or documented for other core eudicots (Rieseberg and Soltis, 1991;Fehrer et al, 2007;Acosta and Premoli, 2010;Salmaki et al, 2013;Wang et al, 2013;Scheunert and Heubl, 2014;Wan et al, 204) The similarity in flower color (and size) between Lepechinia nelsonii and L. flammea may be especially important because it could facilitate hybridization between the two species. Lepechinia nelsonii is hummingbird pollinated, and given the size and color of L. flammea it may be as well.…”