Phylogenomic resolution of order- and family-level monocot relationships using 602 single-copy nuclear genes and 1375 BUSCO genes.

We assess relationships among 192 species in all 12 monocot orders and 72 of 77 families, using 602 conserved single-copy (CSC) genes and 1375 benchmarking single-copy ortholog (BUSCO) genes extracted from genomic and transcriptomic datasets. Phylogenomic inferences based on these data, using both coalescent-based and supermatrix analyses, are largely congruent with the most comprehensive plastome-based analysis, and nuclear-gene phylogenomic analyses with less comprehensive taxon sampling. The strongest discordance between the plastome and nuclear gene analyses is the monophyly of a clade comprising Asparagales and Liliales in our nuclear gene analyses, versus the placement of Asparagales and Liliales as successive sister clades to the commelinids in the plastome tree. Within orders, around six of 72 families shifted positions relative to the recent plastome analysis, but four of these involve poorly supported inferred relationships in the plastome-based tree. In Poales, the nuclear data place a clade comprising Ecdeiocoleaceae+Joinvilleaceae as sister to the grasses (Poaceae); Typhaceae, (rather than Bromeliaceae) are resolved as sister to all other Poales. In Commelinales, nuclear data place Philydraceae sister to all other families rather than to a clade comprising Haemodoraceae+Pontederiaceae as seen in the plastome tree. In Liliales, nuclear data place Liliaceae sister to Smilacaceae, and Melanthiaceae are placed sister to all other Liliales except Campynemataceae. Finally, in Alismatales, nuclear data strongly place Tofieldiaceae, rather than Araceae, as sister to all the other families, providing an alternative resolution of what has been the most problematic node to resolve using plastid data, outside of those involving achlorophyllous mycoheterotrophs. As seen in numerous prior studies, the placement of orders Acorales and Alismatales as successive sister lineages to all other extant monocots. Only 21.2% of BUSCO genes were demonstrably single-copy, yet phylogenomic inferences based on BUSCO and CSC genes did not differ, and overall functional annotations of the two sets were very similar. Our analyses also reveal significant gene tree-species tree discordance despite high support values, as expected given incomplete lineage sorting (ILS) related to rapid diversification. Our study advances understanding of monocot relationships and the robustness of phylogenetic inferences based on large numbers of nuclear single-copy genes that can be obtained from transcriptomes and genomes.

Monocot plastid phylogenomics, timeline, net rates of species diversification, the power of multi-gene analyses, and a functional model for the origin of monocots.

PREMISE OF THE STUDY: We present the first plastome phylogeny encompassing all 77 monocot families, estimate branch support, and infer monocot-wide divergence times and rates of species diversification. METHODS: We conducted maximum likelihood analyses of phylogeny and BAMM studies of diversification rates based on 77 plastid genes across 545 monocots and 22 outgroups. We quantified how branch support and ascertainment vary with gene number, branch length, and branch depth. KEY RESULTS: Phylogenomic analyses shift the placement of 16 families in relation to earlier studies based on four plastid genes, add seven families, date the divergence between monocots and eudicots+Ceratophyllum at 136 Mya, successfully place all mycoheterotrophic taxa examined, and support recognizing Taccaceae and Thismiaceae as separate families and Arecales and Dasypogonales as separate orders. Only 45% of interfamilial divergences occurred after the Cretaceous. Net species diversification underwent four large-scale accelerations in PACMAD-BOP Poaceae, Asparagales sister to Doryanthaceae, Orchidoideae-Epidendroideae, and Araceae sister to Lemnoideae, each associated with specific ecological/morphological shifts. Branch ascertainment and support across monocots increase with gene number and branch length, and decrease with relative branch depth. Analysis of entire plastomes in Zingiberales quantifies the importance of non-coding regions in identifying and supporting short, deep branches. CONCLUSIONS: We provide the first resolved, well-supported monocot phylogeny and timeline spanning all families, and quantify the significant contribution of plastome-scale data to resolving short, deep branches. We outline a new functional model for the evolution of monocots and their diagnostic morphological traits from submersed aquatic ancestors, supported by convergent evolution of many of these traits in aquatic Hydatellaceae (Nymphaeales).

Hikers poisoned: Veratrum steroidal alkaloid toxicity following ingestion of foraged Veratrum parviflorum.

INTRODUCTION: Steroidal alkaloids are found in plants of the genus Veratrum. Their toxicity manifests as gastrointestinal symptoms followed by a Bezold-Jarisch reflex: hypopnea, hypotension, and bradycardia. Some Veratrum steroidal alkaloids are also teratogens interfering with the hedgehog-2 signaling pathway, which causes cyclopsia and holoprosencephaly. We present a case of accidental poisoning from Veratrum parviflorum mistaken for the edible Allium tricoccum (ramps, wild leek). CASE HISTORY: A 27-year-old man and his 25-year-old wife presented to the emergency department with nausea, vomiting, hypotension, and bradycardia after foraging and ingesting plants that they believed to be a local native species of wild leek. METHODS: We collected and analyzed the implicated fresh plant material and both patients' serum/plasma. We used liquid chromatography-mass spectroscopy and high-resolution electrospray ionization time of flight tandem mass spectrometry to extract and characterize steroidal alkaloids from the foraged plant and patients' serum. RESULTS: Our V. parviflorum samples contained verazine, veratramine, veratridine, and cyclopamine. DISCUSSION: Steroidal alkaloids have been previously isolated from Veratrum viride and Veratrum album and toxicity has been reported mainly from V. album species. CONCLUSION: V. parviflorum toxicity manifests with gastrointestinal and cardiac symptoms. Treatment is symptomatic and supportive as with previous case reports of toxicity with other Veratrum species.

Data supporting the nuclear phylogenomics of the palm subfamily Arecoideae (Arecaceae).

This data article provides data and supplemental materials referenced in "Nuclear phylogenomics of the palm subfamily Arecoideae (Arecaceae)" (Comer et al., 2016) [1]. Raw sequence reads generated for this study are available through the Sequence Read Archive (SRA Study Accession: SRP061467). An aligned supermatrix of 168 nuclear genes for 35 taxa (34 palms and one outgroup taxon) is provided. Also provided are individual maximum likelihood gene trees used for the coalescent based analyses, output from the maximum parsimony analyses, and two figures.

Nuclear phylogenomics of the palm subfamily Arecoideae (Arecaceae).

Palms (Arecaceae) include economically important species such as coconut, date palm, and oil palm. Resolution of the palm phylogeny has been problematic due to rapid diversification and slow rates of molecular evolution. The focus of this study is on relationships of the 14 tribes of subfamily Arecoideae and their inferred ancestral areas. A targeted sequencing approach was used to generate a data set of 168 single/low copy nuclear genes for 34 species representing the Arecoideae tribes and the other palm subfamilies. Species trees from the concatenated and coalescent based analyses recovered largely congruent topologies. Three major tribal clades were recovered: the POS clade (Podococceae, Oranieae, Sclerospermeae), the RRC clade (Roystoneeae, Reinhardtieae, Cocoseae), and the core arecoid clade (Areceae, Euterpeae, Geonomateae, Leopoldinieae, Manicarieae, Pelagodoxeae). Leopoldinieae was sister to the rest of the core arecoids (Geonomateae, Manicarieae+Pelagodoxeae, and Areceae+Euterpeae). The nuclear phylogeny supported a North American origin for subfamily Arecoideae, with most tribal progenitors diversifying within the Americas. The POS clade may have dispersed from the Americas into Africa, with tribe Oranieae subsequently spreading into the Indo-Pacific. Two independent dispersals into the Indo-Pacific were inferred for two tribes within the core arecoids (tribes Areceae and Pelagodoxeae).

Plastid genomes reveal support for deep phylogenetic relationships and extensive rate variation among palms and other commelinid monocots.

Despite progress based on multilocus, phylogenetic studies of the palms (order Arecales, family Arecaceae), uncertainty remains in resolution/support among major clades and for the placement of the palms among the commelinid monocots. Palms and related commelinids represent a classic case of substitution rate heterogeneity that has not been investigated in the genomic era. To address questions of relationships, support and rate variation among palms and commelinid relatives, 39 plastomes representing the palms and related family Dasypogonaceae were generated via genome skimming and integrated within a monocot-wide matrix for phylogenetic and molecular evolutionary analyses. Support was strong for 'deep' relationships among the commelinid orders, among the five palm subfamilies, and among tribes of the subfamily Coryphoideae. Additionally, there was extreme heterogeneity in the plastid substitution rates across the commelinid orders indicated by model based analyses, with c. 22 rate shifts, and significant departure from a global clock. To date, this study represents the most comprehensively sampled matrix of plastomes assembled for monocot angiosperms, providing genome-scale support for phylogenetic relationships of monocot angiosperms, and lays the phylogenetic groundwork for comparative analyses of the drivers and correlates of such drastic differences in substitution rates across a diverse and significant clade.

Resolving relationships within the palm subfamily Arecoideae (Arecaceae) using plastid sequences derived from next-generation sequencing.

PREMISE OF THE STUDY: Several studies have incorporated molecular and morphological data to study the phylogeny of the palms (Arecaceae), but some relationships within the family remain ambiguous-particularly those within Arecoideae, the most diverse subfamily including coconut and oil palm. Here, two next-generation, targeted plastid-enrichment methods were compared and used to elucidate Arecoideae phylogeny. METHODS: Next-generation sequencing techniques were used to generate a plastid genome data set. Long range PCR and hybrid gene capture were used to enrich for chloroplast targets. Ten taxa were enriched using both methods for comparison. Chloroplast sequence data were generated for 31 representatives of the 14 Arecoideae tribes and five outgroup taxa. The phylogeny was reconstructed using maximum likelihood, maximum parsimony, and Bayesian analyses. KEY RESULTS: Long range PCR and hybrid gene capture both enriched the plastid genome and provided similar sequencing coverage. Subfamily Arecoideae was resolved as monophyletic with tribe Chamaedoreeae as the earliest-diverging lineage, implying that the development of flowers in triads defines a synapomorphy for the Arecoideae clade excluding Chamaedoreeae. Three major clades within this group were recovered: Roystoneeae/Reinhardtieae/Cocoseae (RRC), Areceae/Euterpeae/Geonomateae/Leopoldinieae/Manicarieae/Pelagodoxeae (core arecoids), and Podococceae/Oranieae/Sclerospermeae (POS). An Areceae + Euterpeae clade was resolved within the core arecoids. The POS clade was sister to a RRC + core arecoids clade, implying a shared ancestral area in South America for these three clades. CONCLUSIONS: The plastome phylogeny recovered here provides robust resolution of previously ambiguous studies and new insights into palm evolution.

Resolving ancient radiations: can complete plastid gene sets elucidate deep relationships among the tropical gingers (Zingiberales)?

BACKGROUND AND AIMS: Zingiberales comprise a clade of eight tropical monocot families including approx. 2500 species and are hypothesized to have undergone an ancient, rapid radiation during the Cretaceous. Zingiberales display substantial variation in floral morphology, and several members are ecologically and economically important. Deep phylogenetic relationships among primary lineages of Zingiberales have proved difficult to resolve in previous studies, representing a key region of uncertainty in the monocot tree of life. METHODS: Next-generation sequencing was used to construct complete plastid gene sets for nine taxa of Zingiberales, which were added to five previously sequenced sets in an attempt to resolve deep relationships among families in the order. Variation in taxon sampling, process partition inclusion and partition model parameters were examined to assess their effects on topology and support. KEY RESULTS: Codon-based likelihood analysis identified a strongly supported clade of ((Cannaceae, Marantaceae), (Costaceae, Zingiberaceae)), sister to (Musaceae, (Lowiaceae, Strelitziaceae)), collectively sister to Heliconiaceae. However, the deepest divergences in this phylogenetic analysis comprised short branches with weak support. Additionally, manipulation of matrices resulted in differing deep topologies in an unpredictable fashion. Alternative topology testing allowed statistical rejection of some of the topologies. Saturation fails to explain observed topological uncertainty and low support at the base of Zingiberales. Evidence for conflict among the plastid data was based on a support metric that accounts for conflicting resampled topologies. CONCLUSIONS: Many relationships were resolved with robust support, but the paucity of character information supporting the deepest nodes and the existence of conflict suggest that plastid coding regions are insufficient to resolve and support the earliest divergences among families of Zingiberales. Whole plastomes will continue to be highly useful in plant phylogenetics, but the current study adds to a growing body of literature suggesting that they may not provide enough character information for resolving ancient, rapid radiations.

A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family Melanthiaceae.

• Since the occurrence of giant genomes in angiosperms is restricted to just a few lineages, identifying where shifts towards genome obesity have occurred is essential for understanding the evolutionary mechanisms triggering this process. • Genome sizes were assessed using flow cytometry in 79 species and new chromosome numbers were obtained. Phylogenetically based statistical methods were applied to infer ancestral character reconstructions of chromosome numbers and nuclear DNA contents. • Melanthiaceae are the most diverse family in terms of genome size, with C-values ranging more than 230-fold. Our data confirmed that giant genomes are restricted to tribe Parideae, with most extant species in the family characterized by small genomes. Ancestral genome size reconstruction revealed that the most recent common ancestor (MRCA) for the family had a relatively small genome (1C = 5.37 pg). Chromosome losses and polyploidy are recovered as the main evolutionary mechanisms generating chromosome number change. • Genome evolution in Melanthiaceae has been characterized by a trend towards genome size reduction, with just one episode of dramatic DNA accumulation in Parideae. Such extreme contrasting profiles of genome size evolution illustrate the key role of transposable elements and chromosome rearrangements in driving the evolution of plant genomes.

Infrageneric phylogeny of Schoenocaulon (Liliales: Melanthiaceae) with clarification of cryptic species based on ITS sequence data and geographical distribution.

As currently defined, the 24 species of Schoenocaulon occur in three disjunct areas: north central Florida (one species, S. dubium), southern Peru (portion of the range of S. officinale), and the region from southeastern New Mexico-Texas south to Venezuela; the 20 species endemic to Mexico are geographically restricted. Species delimitations, often based on tepal morphology, have been problematic. Our analyses of ITS sequence data for all 27 species and infraspecific taxa support recognition of two new species and recircumscription and placement of elements of the polyphyletic S. ghiesbreghtii and S. mortonii complexes. For taxa with adequate sampling, our data also indicate 11-12 cladospecies and 3-6 metaspecies according to the apomorphic species concept. The resolved phylogeny, correlated with geography and morphology, allows insight into biogeographical diversification and the evolution of some unusual morphological characters within the genus, such as nectary differentiation and tepal margin type.