We present a new tribal classification, including one new tribe, Neospartoneae trib. nov., to accommodate three small genera of Argentine species (Diostea, Neosparton, and Lampaya). Phylogenetic inference suggests a South American origin for Verbenaceae, with approximately six colonization events having given rise to the Old World species.

BackgroundThe ability to efficiently characterize microbial communities from host individuals can be limited by co-amplification of host organellar sequences (mitochondrial and/or plastid), which share a common ancestor and thus sequence similarity with extant bacterial lineages. One promising approach is the use of sequence-specific peptide nucleic acid (PNA) clamps, which bind to, and block amplification of, host-derived DNA. Universal PNA clamps have been proposed to block host plant-derived mitochondrial (mPNA) and plastid (pPNA) sequences at the V4 16S rRNA locus, but their efficacy across a wide range of host plant species has not been experimentally tested.ResultsUsing the universal PNA clamps, we amplified and sequenced root microbial communities from replicate individuals of 32 plant species with a most recent common ancestor inferred at 140 MYA. We found the average rate of host plastid contamination across plant species was 23%, however, particular lineages exhibited much higher rates (62–94%), with the highest levels of contamination occurring in the Asteraceae. We investigated chloroplast sequence variation at the V4 locus across 500 land plant species (Embryophyta) and found six lineages with mismatches between plastid and the universal pPNA sequence, including all species within the Asteraceae. Using a modified pPNA for the Asteraceae sequence, we found (1) host contamination in Asteraceae species was reduced from 65 to 23%; and (2) host contamination in non-Asteraceae species was increased from 12 to 69%. These results demonstrate that even single nucleotide mismatches can lead to drastic reductions in pPNA efficacy in blocking host amplification. Importantly, we found that pPNA type (universal or modified) had no effect on the detection of individual bacterial taxa, or estimates of within and between sample bacterial diversity, suggesting that our modification did not introduce bias against particular bacterial lineages.ConclusionsWhen high similarity exists between host organellar DNA and PCR target sequences, PNA clamps are an important molecular tool to reduce host contamination during amplification. Here, we provide a validated framework to modify universal PNA clamps to accommodate host variation in organellar sequences.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0534-0) contains supplementary material, which is available to authorized users.

Lantaneae are an example of a taxonomically problematic, widespread and recently radiated Neotropical lineage. Taxonomy in Lantaneae is difficult because of complex, overlapping patterns of shifts in morphological traits among members; monophyly of the traditional genera cannot be assumed without additional information from molecular data. We took a multi‐locus approach to infer phylogenetic relationships in Lantaneae, resolving major clades among a broad representative sample that covers the morphological, taxonomic and geographical diversity of this group. Data from multiple, independent loci reveal individual gene trees that are incongruent with one another, with varying degrees of support. Without reliable, applicable methods to determine the sources of such incongruence and to resolve it, we present the consensus between well‐supported topologies among our data sets as the best estimate of Lantaneae phylogeny to date. According to this consensus tree, fleshy fruits in Lantaneae have been derived from dry fruits at least five times; taxonomic schemes separating genera based on fruit characteristics are artificial. Lantaneae have shifted into the Neotropics from the southern temperate subtropics and have colonized Africa in at least two separate long‐distance dispersal events. This study provides a first pass at a broad Lantaneae phylogeny, but two important areas remain unresolved: the position of Acantholippia relative to Aloysia; and species‐level relationships in the Lantana–Lippia clade. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ●●, ●●–●●.

Species belonging to the genera Aloysia and Acantholippia are difficult to place within Lantaneae due to gene tree incongruence and limited sampling in previous studies. We use an expanded sample of both genera, and DNA sequence data from six loci, to reveal that Aloysia and Acantholippia species occur in five consistently inferred, well-supported clades. The precise relationships of these clades to one another are still enigmatic, due to gene tree incongruence. However, coalescent-based species tree inference supports the inclusion of most of Acantholippia in an expanded Aloysia sensu lato, with a 4-lobed calyx as its defining feature. Five new combinations are proposed to reflect this relationship: Aloysia deserticola, Aloysia riojana, Aloysia salsoloides, Aloysia tarapacana, and Aloysia trifida. Geographic range shifts from subtropical South America to North America have occurred at least twice in Aloysia. Shifts between determinate and indeterminate inflorescence arrangement have occurred at least twice independently. The elongate, lax inflorescence, which is characteristic of most of Aloysia, is hypothesized to be derived from a condensed inflorescence.