Phylogenetic relationships in the southern African genusDrosanthemum(Ruschioideae, Aizoaceae)

Abstract

Background Drosanthemum, the only genus of the tribe Drosanthemeae, is widespread over the Greater Cape Floristic Region in southern Africa. With 114 recognized species, Drosanthemum, together with the highly succulent and species-rich tribe Ruschieae, constitute the ‘core ruschioids’ in Aizoaceae. Within Drosanthemum, nine subgenera have been described based on flower and fruit morphology. Their phylogenetic relationships, however, have not yet been investigated, hampering understanding of monophyletic entities and patterns of geographic distribution. Methods Using chloroplast and nuclear DNA sequence data, we performed network- and tree-based phylogenetic analyses of 73 species of Drosanthemum with multiple accessions for widespread species. A well-curated, geo-referenced occurrence dataset comprising the 134 genetically analysed and 863 further accessions was used to describe the distributional ranges of intrageneric lineages and the genus as a whole. Results Phylogenetic inference supports nine clades within Drosanthemum, seven of which group in two major clades, while the remaining two show ambiguous affinities. The nine clades are generally congruent to previously described subgenera within Drosanthemum, with exceptions such as cryptic species. In-depth analyses of sequence patterns in each gene region were used to reveal phylogenetic affinities inside the retrieved clades in more detail. We observe a complex distribution pattern including widespread, species-rich clades expanding into arid habitats of the interior (subgenera Drosanthemum p.p., Vespertina, Xamera) that are genetically and morphologically diverse. In contrast, less species-rich, genetically less divergent, and morphologically unique lineages are restricted to the central Cape region and more mesic conditions (Decidua, Necopina, Ossicula, Quastea, Quadrata, Speciosa). Our results suggest that the main lineages arose from an initial rapid radiation, with subsequent diversification in some clades.

The eco‐evolutionary significance of rainfall constancy for facultative CAM photosynthesis

“…Although node support is generally high within the two clades, relationships among these two main clades and the smaller sister clade are not well supported (Fig. S9; Klak et al ., 2013; Liede‐Schumann et al ., 2020). We considered phylogenetic uncertainty in our downstream analyses, which compared relationships of individuals mainly at more recent time scales (≤2 Myr).…”

“…We made use of a recently published, well sampled molecular phylogenetic data set of the genus Drosanthemum (based on four plastid DNA markers with a combined length of 2950 bp each for 134 Drosanthemum accessions in total) including the 82 georeferenced accessions investigated in this study that represent about 62 species (for vouchers see Supporting Information Table S1). The different accessions were selected to cover all major clades in the phylogenetic tree (Liede‐Schumann et al ., 2020). Different accessions represent different individual plants collected in the field at georeferenced locations by the late H.E.K.…”

“…We estimated relationships and divergence times among the individuals investigated in this study by using all (134) Drosanthemum accessions plus seven accessions of the Ruschieae as outgroup taxa represented in the phylogeny of Liede‐Schumann et al . (2020) (see Table S1). Because no fossil information suitable to calibrate the tree to absolute time is available in the study group (Klak et al ., 2017), we constrained the root node ( Drosanthemum + outgroup) with a prior set to represent the uncertainty in age estimates for this node revealed in previous studies ( c .…”

5S-IGS rDNA in wind-pollinated trees (FagusL.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species

“…Further applications of 5S-IGS HTS data include taxonomy (co-)informed by genetics (e.g. Grimm & Denk, 2014;Liede-Schumann et al, 2020) and the assessment of global biodiversity in addition to the traditional counting of numbers of species (e.g. Forest et al, 2018).…”

Metagenomic Analysis Using Phylogenetic Placement—A Review of the First Decade

“…Finally, an often overlooked source of query sequences are high-quality reference sequence databases. Here, the use-case of placement shifts away from taxonomic assignment: instead such data can be used to attempt an outgroup rooting of an existing tree, using already classified sequences ( Hubert et al, 2014 ; Liede-Schumann et al, 2020 ; Morel et al, 2020 ). The result of placement, in this case, is a set of suggested branches on which to root the tree, including a probability estimate for each root placement onto each branch ( Liede-Schumann et al, 2020 ).…”