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Although the monophyly of Phedimus has been strongly demonstrated, the species relationships among approximately 20 species of Phedimus have been difficult to determine because of the uniformity of their floral characteristics and extreme variation of their vegetative characters, often accompanied by high polyploid and aneuploid series and diverse habitats. In this study, we assembled 15 complete chloroplast genomes of Phedimus species from East Asia and generated a plastome-based backbone phylogeny of the subgenus Aizoon. As a proxy for nuclear phylogeny, we reconstructed the nuclear ribosomal DNA internal transcribed spacer (nrDNA ITS) phylogeny independently. The 15 plastomes of subg. Aizoon were highly conserved in structure and organization; hence, the complete plastome phylogeny fully resolved the species relationships with strong support. We found that P. aizoon and P. kamtschaticus were polyphyletic and morphologically distinct or ambiguous species, and they most likely evolved from the two species complex. The crown age of subg. Aizoon was estimated to be 27 Ma, suggesting its origin to be in the late Oligocene; however, the major lineages were diversified during the Miocene. The two Korean endemics, P. takesimensis and P. zokuriensis, were inferred to have originated recently during the Pleistocene, whereas the other endemic, P. latiovalifolium, originated in the late Miocene. Several mutation hotspots and seven positively selected chloroplast genes were identified in the subg. Aizoon.

The genus Allium, with over 900 species, is one of the largest monocotyledonous genera and is widely accepted with 15 recognized subgenera and 72 sections. The robust subgeneric and sectional relationships within Allium have long been not resolved. Based on 76 species of Allium (a total of 84 accessions), we developed a highly resolved plastome phylogenetic framework by integrating 18 newly sequenced species (20 accessions) in this study and assessed their subgeneric and sectional relationships, with special emphasis on the two subgenera Anguinum and Rhizirideum. We retrieved the three major evolutionary lines within Allium and found that the two subgenera Anguinum and Rhizirideum are monophyletic whereas others are highly polyphyletic (e.g., Allium, Cepa, Polyprason, and Melanocrommyum). Within the subgenus Anguinum, two strongly supported sublineages in East Asian and Eurasian-American were found. Allium tricoccum in North America belonged to the Eurasian clade. The distinct taxonomic status of A. ulleungense and its sister taxon were further determined. In subg. Rhizirideum, the Ulleung Island endemic A. dumebuchum shared its most recent common ancestor with the species from Mongolia and the narrow Korean endemic A. minus. Two Ulleung Island endemics were estimated to originate independently during the Pleistocene. In addition, a separate monotypic sectional treatment of the east Asian A. macrostemon (subg. Allium) and sister relationship between A. condensatum and A. chinense was suggested.

Dendroseris D. Don comprises 11 species endemic to the Juan Fernández islands in Chile. They demonstrate spectacular and unusual growth forms of rosette trees with extremely variable morphology and occupy wide ecological ranges on the islands. These unique plants are now highly threatened with extinction with very small population sizes, typically consisting of 10 or fewer individuals in wild. Despite morphological and ecological divergence among species of Dendroseris, their monophyly has been supported in previous studies, but with little resolution among subgeneric groups. We assembled seven complete plastome sequences from seven species of Dendroseris, including representatives from three subgenera, and carried out comparative phylogenomic analyses. The plastomes are highly conserved in gene content and order, with size ranging from 152,199 to 152,619 bp and containing 130 genes (87 coding genes, 6 rRNA genes, and 37 tRNA genes). Plastid phylogenomic analyses based on both the complete plastome sequences and 81 concatenated coding genes only show Dendroseris nested within Sonchus sensu lato, and also that inter-subgeneric relationships are fully resolved. Subg. Phoenicoseris is resolved as sister to the remaining species of the genus and a sister relationship between the two subgenera Dendroseris and Rea. Ten mutation hotspots from LSC and SSC regions and variable SSRs are identified as potential chloroplast markers for future phylogenetic and phylogeographic studies of Sonchus and related groups.

Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five haplotypes, haplotype diversity = 0.6099). All haplotypes found in glaciated regions represented a subset of haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.