A chloroplast tree for Viburnum (Adoxaceae) and its implications for phylogenetic classification and character evolution

Abstract

• Premise of the study: Despite recent progress, significant uncertainties remain concerning relationships among early-branching lineages within Viburnum (Adoxaceae), prohibiting a new classification and hindering studies of character evolution and the increasing use of Viburnum in addressing a wide range of ecological and evolutionary questions. We hoped to resolve these issues by sequencing whole plastid genomes for representative species and combining these with molecular data previously obtained from an expanded taxon sample.• Methods: We performed paired-end Illumina sequencing of plastid genomes of 22 Viburnum species and combined these data with a 10-gene data set to infer phylogenetic relationships for 113 species. We used the results to devise a comprehensive phylogenetic classification and to analyze the evolution of eight morphological characters that vary among early-branching lineages.• Key results: With greatly increased levels of confidence in most of the early branches, we propose a phylogenetic classification of Viburnum, providing formal phylogenetic definitions for 30 clades, including 13 with names recognized under the International Code of Nomenclature for Algae, Fungi, and Plants, eight with previously proposed informal names, and nine newly proposed names for major branches. Our parsimony reconstructions of bud structure, leaf margins, inflorescence form, ruminate endosperm, extrafloral nectaries, glandular trichomes, palisade anatomy, and pollen exine showed varying levels of homoplasy, but collectively provided morphological support for some, though not all, of the major clades.• Conclusions: Our study demonstrates the value of next-generation plastid sequencing, the ease of creating a formal phylogenetic classification, and the utility of such a system in describing patterns of character evolution.

Comparative micromorphology and anatomy of flowers and floral secretory structures in two Viburnum species

“…Moreover, stellate non-glandular trichomes covering densely the bracts, pedicels, and peduncles in V. lantana and simple non-glandular trichomes on adaxial surface of the petals in V. opulus were found. On leaves and stems of various Viburnum species belonging to different species and clades, many investigators have observed a similar type of glandular (Table 3) and non-glandular trichomes as well, differing in the size, number, and arrangement of trichome cells (Winkworth and Donoghue 2005; Prabhu and Ponnudurai 2011; Clement et al 2014; Moura et al 2015). As reported by the authors mentioned, the structure of trichomes present in different Viburnum species is a taxonomic trait that is important for the phylogenesis of the genus.…”

“…This type of nectaries are not present in other representatives of the family Adoxaceae, which exhibit trachomatous nectaries located at corolla lobe bases ( Adoxa , Sinadoxa , Tetradoxa ) or whole sterile flowers in the inflorescence were converted into nectaries (some species of Sambucus ) (Vogel 1997; Donoghue et al 2003). Some Viburnum and Sambucus species have extrafloral nectaries as well; they are mainly attractive to ants, which may protect plants against herbivore attacks (Fahn 1987; Weber et al 2012; Clement et al 2014). …”

“…The patterns of diversification in Viburnum have been investigated by Moore and Donoghue (2007, 2009) and Clement et al (2014). Earlier descriptions of the taxonomic differences between Viburnum species were primarily focused on the presence of extrafloral nectaries (Weber et al 2012; Clement et al 2014), form of the inflorescence (Jin et al 2010; Tank and Donoghue 2010), flower morphology and vascularisation (Wilkinson 1948), structure of the pollen grain exine (Donoghue 1985; Maciejewska 1997), as well as the density and type of trichomes (Clement and Donoghue 2011; Prabhu and Ponnudurai 2011; Clement et al 2014). …”

Revisiting the phylogeny of Dipsacales: New insights from phylogenomic analyses of complete plastomic sequences

“…We followed Clement et al () for selection of CR and NCR. In addition, we also included some extra genes and regions (i.e., accD , ndhB , ndhK , rps7 , ycf5 , atpF‐atpH , petB ‐ petD , and petN‐psbM ) that were not used by Clement et al () for analyses.…”

“…Over the past two decades, enormous progress has been made in understanding overall phylogenetic relationships and evolution in Dipsacales (Donoghue et al, 1992Eriksson & Donoghue, 1997;Pyck & Smets, 2000;Bell et al, 2001Bell et al, , 2012, 2005Zhang et al, 2003;Bell, 2004;Moore & Donoghue, 2007;Theis et al, 2008;Winkworth et al, 2008aWinkworth et al, , 2008bCarlson et al, 2009;Jacobs et al, 2009Jacobs et al, , 2010aJacobs et al, , 2010bJacobs et al, , 2011Landrein et al, 2012;Clement et al, 2014;Wang et al, 2015;Landrein & Prenner, 2016). Although most genera and all families in Dipsacales have been included in molecular studies cited above, no single study has included representatives for each clade by using plastomic sequences.…”