Phylogeny and diversification history of the large Neotropical genus Philodendron (Araceae): Accelerated speciation in a lineage dominated by epiphytes.

PREMISE OF THE STUDY: Philodendron is a large genus of ~560 species and among the most conspicuous epiphytic components of Neotropical forests, yet its phylogenetic relationships, timing of divergence, and diversification history have remained unclear. We present a comprehensive phylogenetic study for Philodendron and investigate its diversification, including divergence-time estimates and diversification rate shift analyses. METHODS: We performed the largest phylogenetic reconstruction for Philodendron to date, including 125 taxa with a combined dataset of three plastid regions (petD, rpl16, and trnK/matK). We estimated divergence times using Bayesian evolutionary analysis sampling trees and inferred shifts in diversification rates using Bayesian analysis of macroevolutionary mixtures. KEY RESULTS: We found that Philodendron, its three subgenera, and the closely related genus Adelonema are monophyletic. Within Philodendron subgenus Philodendron, 12 statistically well-supported clades are recognized. The genus Philodendron originated ~25 mya and a diversification rate upshift was detected at the origin of subgenus Philodendron ~12 mya. CONCLUSIONS: Philodendron is a species-rich Neotropical lineage that diverged from Adelonema during the late Oligocene. Within Philodendron, the three subgenera currently accepted are recovered in two lineages: one contains the subgenera Meconostigma and Pteromischum and the other contains subgenus Philodendron. The lineage containing subgenera Meconostigma and Pteromischum underwent a consistent diversification rate. By contrast, a diversification rate upshift occurred within subgenus Philodendron ~12 mya. This diversification rate upshift is associated with the species radiation of the most speciose subgenus within Philodendron. The sections accepted within subgenus Philodendron are not congruent with the clades recovered. Instead, the clades are geographically defined.

Dynamic diversification history with rate upshifts in Holarctic bell-flowers (Campanula and allies).

Campanula s.l. is one of the most speciose flowering plant lineages of the Holarctic (ca. 600 species). In the present study we sequenced three regions of the plastid genome (petD, rpl16 and trnK/matK) across a broad sample of Campanula s.l., which markedly improved phylogenetic resolution and statistical support compared to previous studies. Based on this robust phylogenetic hypothesis we estimated divergence times using BEAST, diversification rate shifts using Bayesian Analysis of Macroevolutionary Mixture (BAMM) and TreePar, and ancestral ranges using Biogeography with Bayesian (and likelihood) Evolutionary Analyses in R. Campanula s.l. is estimated to have originated during the Early Eocene but the major diversification events occurred between the Late Oligocene and Middle Miocene. Two upward diversification rate shifts were revealed by BAMM, specific to the crown nodes of two Campanula clades: CAM17, a mostly South European-SW Asian lineage originating during the Middle Miocene and containing nearly half of all known Campanula species; and CAM15B, a SW Asian-Sino-Himalayan lineage of nine species originating in the early Pleistocene. The dynamic diversification history of Campanula and the inferred rate shifts are discussed in a geo-historical context.

Allopatric diversification, multiple habitat shifts, and hybridization in the evolution of Pericallis (Asteraceae), a Macaronesian endemic genus.

PREMISE OF THE STUDY: Geographic isolation, habitat shifts, and hybridization have contributed to the diversification of oceanic island floras. We investigated the contribution of these processes to the diversification of Pericallis, a genus endemic to Macaronesia. METHODS: Data from the chloroplast psaI-accD and trnV-ndhC regions and the nuclear ribosomal internal transcribed spacer region (ITS) were sampled for multiple accessions of all taxa and used to establish phylogenetic hypotheses. Habitat preferences were optimized to investigate habitat shifts, and divergence times were estimated. Species nonmonophyly was investigated using Bayes factors. KEY RESULTS: Much of the diversification in Pericallis has occurred recently, within the past 1.7 Ma. Three habitat shifts have occurred in the evolution of the genus. However, geographic isolation has played a greater role in its diversification. Novel allopatric patterns were revealed within some species, highlighting the significance of geographic isolation in the evolution of Pericallis. One species (P. appendiculata) that resolved as monophyletic in the ITS analysis was polyphyletic in the chloroplast analysis. Bayes factors provide strong support for the nonmonophyly of P. appendiculata haplotypes, and their phylogenetic placement suggests that ancient hybridization is responsible for the haplotype diversity observed. CONCLUSIONS: Multiple markers and extensive sampling provided new insights into the evolution of Pericallis. In contrast to previous studies, our results reveal a more significant role for allopatry than habitat shifts and new evidence for ancient hybridization in the evolution of Pericallis. Our study highlights the power of broad taxon sampling for unraveling diversity patterns and processes within oceanic island radiations.

New Insights Into the Relationships Within Subtribe Scorzonerinae (Cichorieae, Asteraceae) Using Hybrid Capture Phylogenomics (Hyb-Seq).

Subtribe Scorzonerinae (Cichorieae, Asteraceae) contains 12 main lineages and approximately 300 species. Relationships within the subtribe, either at inter- or intrageneric levels, were largely unresolved in phylogenetic studies to date, due to the lack of phylogenetic signal provided by traditional Sanger sequencing markers. In this study, we employed a phylogenomics approach (Hyb-Seq) that targets 1,061 nuclear-conserved ortholog loci designed for Asteraceae and obtained chloroplast coding regions as a by-product of off-target reads. Our objectives were to evaluate the potential of the Hyb-Seq approach in resolving the phylogenetic relationships across the subtribe at deep and shallow nodes, investigate the relationships of major lineages at inter- and intrageneric levels, and examine the impact of the different datasets and approaches on the robustness of phylogenetic inferences. We analyzed three nuclear datasets: exon only, excluding all potentially paralogous loci; exon only, including loci that were only potentially paralogous in 1-3 samples; exon plus intron regions (supercontigs); and the plastome CDS region. Phylogenetic relationships were reconstructed using both multispecies coalescent and concatenation (Maximum Likelihood and Bayesian analyses) approaches. Overall, our phylogenetic reconstructions recovered the same monophyletic major lineages found in previous studies and were successful in fully resolving the backbone phylogeny of the subtribe, while the internal resolution of the lineages was comparatively poor. The backbone topologies were largely congruent among all inferences, but some incongruent relationships were recovered between nuclear and plastome datasets, which are discussed and assumed to represent cases of cytonuclear discordance. Considering the newly resolved phylogenies, a new infrageneric classification of Scorzonera in its revised circumscription is proposed.

An empirical assessment of a single family-wide hybrid capture locus set at multiple evolutionary timescales in Asteraceae.

PREMISE: Hybrid capture with high-throughput sequencing (Hyb-Seq) is a powerful tool for evolutionary studies. The applicability of an Asteraceae family-specific Hyb-Seq probe set and the outcomes of different phylogenetic analyses are investigated here. METHODS: Hyb-Seq data from 112 Asteraceae samples were organized into groups at different taxonomic levels (tribe, genus, and species). For each group, data sets of non-paralogous loci were built and proportions of parsimony informative characters estimated. The impacts of analyzing alternative data sets, removing long branches, and type of analysis on tree resolution and inferred topologies were investigated in tribe Cichorieae. RESULTS: Alignments of the Asteraceae family-wide Hyb-Seq locus set were parsimony informative at all taxonomic levels. Levels of resolution and topologies inferred at shallower nodes differed depending on the locus data set and the type of analysis, and were affected by the presence of long branches. DISCUSSION: The approach used to build a Hyb-Seq locus data set influenced resolution and topologies inferred in phylogenetic analyses. Removal of long branches improved the reliability of topological inferences in maximum likelihood analyses. The Astereaceae Hyb-Seq probe set is applicable at multiple taxonomic depths, which demonstrates that probe sets do not necessarily need to be lineage-specific.