The role of Pleistocene dispersal in shaping species richness of sky island wintergreens from the Himalaya-Hengduan Mountains.

In addition to topography and climate, biogeographic dispersal has been considered to influence plant diversity in the Himalaya-Hengduan Mountains (HHM), yet, the mode and tempo of sky island dispersal and its influence on species richness has been little explored. Through phylogenetic analysis of Gaultheria ser. Trichophyllae, a sky island alpine clade within the HHM, we test the hypothesis that dispersal has affected current local species richness. We inferred the dynamics of biogeographic dispersal with correlation tests on direction, distance, occurrence time, and regional species richness. We found that G. ser. Trichophyllae originated at the end of the Miocene and mostly dispersed toward higher longitudes (eastward). In particular, shorter intra-regional eastward dispersals and longer inter-regional westward dispersals were most frequently observed. We detected a prevalence of eastward intra-region dispersals in both glacial periods and interglacials. These dispersals may have been facilitated by the reorganization of paleo-drainages and monsoon intensification through time. We suggest that the timing of dispersal corresponding to glacial periods and the prevalence of intra-region dispersal, rather than dispersal frequency, most influenced the pattern of species richness of G. ser. Trichophyllae. This study facilitates a more comprehensive understanding of biodiversity in the sky islands within the HHM.

Patterns of genetic variation and morphology support the recognition of five species in the Gaultheria leucocarpa Blume (Ericaceae) group from mainland China.

Gaultheria leucocarpa and its varieties form a clade of aromatic shrubs that is widely distributed in subtropical and East Asian tropical regions. The group is taxonomically difficult and in need of thorough taxonomic investigation. This study focused on taxonomic delimitation within the G. leucocarpa group from mainland China. Field surveys covering the distributional range of G. leucocarpa in mainland China were conducted, wherein four populations from Yunnan and one from Hunan were found bearing morphological and habitat differences. A 63-species phylogenetic tree of Gaultheria based on one nuclear and three chloroplast markers that included samples from the G. leucocarpa group was reconstructed with maximum likelihood to clarify the monophyly of the G. leucocarpa group. Taxonomic relationships among populations were investigated with morphology and population genetics, the latter by using two chloroplast genes and two low-copy nuclear genes. Based on the sum of morphological and genetic analyses, we described three species of Gaultheria as new to science, clarified the taxonomic status of G. leucocarpa var. pingbienensis, elevating it to the species level, and resurrected G. crenulata and treated the varieties G. leucocarpa var. crenulata, and G. leucocarpa var. yunnanensis as synonyms of this species. We provide a key to the five species now recognized, along with descriptions and photographs.

The phylogeny and global biogeography of Primulaceae based on high-throughput DNA sequence data.

The angiosperm family Primulaceae is morphologically diverse and distributed nearly worldwide. However, phylogenetic uncertainty has obstructed the identification of major morphological and biogeographic transitions within the clade. We used target capture sequencing with the Angiosperms353 probes, taxon-sampling encompassing nearly all genera of the family, tree-based sequence curation, and multiple phylogenetic approaches to investigate the major clades of Primulaceae and their relationship to other Ericales. We generated dated phylogenetic trees and conducted broad-scale biogeographic analyses as well as stochastic character mapping of growth habit. We show that Ardisia, a pantropical genus and the largest in the family, is not monophyletic, with at least 19 smaller genera nested within it. Neotropical members of Ardisia and several smaller genera form a clade, an ancestor of which arrived in the Neotropics and began diversifying about 20 Ma. This Neotropical clade is most closely related to Elingamita and Tapeinosperma, which are most diverse on islands of the Pacific. Both Androsace and Primula are non-monophyletic by the inclusion of smaller genera. Ancestral state reconstructions revealed that there have either been parallel transitions to an herbaceous habit in Primuloideae, Samolus, and at least three lineages of Myrsinoideae, or a common ancestor of nearly all Primulaceae was herbaceous. Our results provide a robust estimate of phylogenetic relationships across Primulaceae and show that a revised classification of Myrsinoideae and several other clades within the family is necessary to render all genera monophyletic.

A first complete phylogenomic hypothesis for diploid blueberries (Vaccinium section Cyanococcus).

PREMISE: The true blueberries (Vaccinium sect. Cyanococcus; Ericaceae), endemic to North America, have been intensively studied for over a century. However, with species estimates ranging from nine to 24 and much confusion regarding species boundaries, this ecologically and economically valuable group remains inadequately understood at a basic evolutionary and taxonomic level. As a first step toward understanding the evolutionary history and taxonomy of this species complex, we present the first phylogenomic hypothesis of the known diploid blueberries. METHODS: We used flow cytometry to verify the ploidy of putative diploid taxa and a target-enrichment approach to obtain a genomic data set for phylogenetic analyses. RESULTS: Despite evidence of gene flow, we found that a primary phylogenetic signal is present. Monophyly for all morphospecies was recovered, with two notable exceptions: one sample of V. boreale was consistently nested in the V. myrtilloides clade and V. caesariense was nested in the V. fuscatum clade. One diploid taxon, Vaccinium pallidum, is implicated as having a homoploid hybrid origin. CONCLUSIONS: This foundational study represents the first attempt to elucidate evolutionary relationships of the true blueberries of North America with a phylogenomic approach and sets the stage for multiple avenues of future study such as a taxonomic revision of the group, the verification of a homoploid hybrid taxon, and the study of polyploid lineages within the context of a diploid phylogeny.

Population dynamics linked to glacial cycles in Cercis chuniana F. P. Metcalf (Fabaceae) endemic to the montane regions of subtropical China.

The mountains of subtropical China are an excellent system for investigating the processes driving the geographical distribution of biodiversity and radiation of plant populations in response to Pleistocene climate fluctuations. How the major mountain ranges in subtropical China have affected the evolution of plant species in the subtropical evergreen broadleaved forest is an issue with long-term concern. Here, we focused on Cercis chuniana, a woody species endemic to the southern mountain ranges in subtropical China, to elucidate its population dynamics. We used genotyping by sequencing (GBS) to investigate the spatial pattern of genetic variation among 11 populations. Geographical isolation was detected between the populations located in adjacent mountain ranges, thought to function as geographical barriers due to their complex physiography. Bayesian time estimation revealed that population divergence occurred in the middle Pleistocene, when populations in the Nanling Mts. separated from those to the east. The orientation and physiography of the mountain ranges of subtropical China appear to have contributed to the geographical pattern of genetic variation between the eastern and western populations of C. chuniana. Complex physiography plus long-term stable ecological conditions across glacial cycles facilitated the demographic expansion in the Nanling Mts., from which contemporary migration began. The Nanling Mts. are thus considered as a suitable area for preserving population diversity and large population sizes of C. chuniana compared with other regions. As inferred by ecological niche modeling and coalescent simulations, secondary contact occurred during the warm Lushan-Tali Interglacial period, with intensified East Asia summer monsoon and continuous habitat available for occupation. Our data support the strong influence of both climatic history and topographic characteristics on the high regional phytodiversity of the subtropical evergreen broadleaved forest in subtropical China.

Perrottetiataronensis B.M.Barthol. & K.Armstr., sp. nov. (Dipentodontaceae), a new species from northwestern Yunnan Province, China and northern Kachin State, Myanmar and a re-examination of the Asian and Australasian taxa of Perrottetia.

Perrottetiataronensis from the Dulong Jiang valley in northwestern Yunnan Province, China and the Babulongtan mountain range in northern Kachin State, Myanmar is here described as a new species of the Dipentodontaceae. It is the third species of the genus to be recognized for China and the first to be reported for Myanmar. It is similar to P.alpestris s.s. but differs by characters of its leaf margins, inflorescences, and fruit. The three subspecies of P.alpestris recognized by Hou in "Flora Malesiana" are here recognized as three distinct species, i.e., P.alpestris, P.moluccana, and P.philippinensis on the basis of differences in diagnostic characters and distribution. The report in the "Flora of China" of the Taiwan species P.arisanensis from Yunnan is determined to be incorrect due to misidentification of two specimens at KUN.

Plastid phylogenomic insights into relationships of all flowering plant families.

BACKGROUND: Flowering plants (angiosperms) are dominant components of global terrestrial ecosystems, but phylogenetic relationships at the familial level and above remain only partially resolved, greatly impeding our full understanding of their evolution and early diversification. The plastome, typically mapped as a circular genome, has been the most important molecular data source for plant phylogeny reconstruction for decades. RESULTS: Here, we assembled by far the largest plastid dataset of angiosperms, composed of 80 genes from 4792 plastomes of 4660 species in 2024 genera representing all currently recognized families. Our phylogenetic tree (PPA II) is essentially congruent with those of previous plastid phylogenomic analyses but generally provides greater clade support. In the PPA II tree, 75% of nodes at or above the ordinal level and 78% at or above the familial level were resolved with high bootstrap support (BP ≥ 90). We obtained strong support for many interordinal and interfamilial relationships that were poorly resolved previously within the core eudicots, such as Dilleniales, Saxifragales, and Vitales being resolved as successive sisters to the remaining rosids, and Santalales, Berberidopsidales, and Caryophyllales as successive sisters to the asterids. However, the placement of magnoliids, although resolved as sister to all other Mesangiospermae, is not well supported and disagrees with topologies inferred from nuclear data. Relationships among the five major clades of Mesangiospermae remain intractable despite increased sampling, probably due to an ancient rapid radiation. CONCLUSIONS: We provide the most comprehensive dataset of plastomes to date and a well-resolved phylogenetic tree, which together provide a strong foundation for future evolutionary studies of flowering plants.

Vaccinium exiguum (Ericaceae, Vaccinieae), a new species from the ultramafic summit of Mt. Victoria, Palawan Island, Philippines.

Vaccinium exiguum from the ultramafic summit of Mt. Victoria, Palawan Island, Philippines is here described as a new species of Ericaceae. It closely resembles V. hamiguitanense but is distinct by having much shorter petioles and leaves, longer and glabrous calyx lobes with serrate lobe margins, a larger corolla with deeper sulcations, and longer stamens with spurs oriented laterally. Vaccinium exiguum represents the third Vaccinium species found on the Island of Palawan and 36th in the Philippines.

Grade of Membership models reveal geographical and environmental correlates of floristic structure in a temperate biodiversity hotspot.

Identifying the contours and correlates of species turnover is central to understanding the nature of biogeographical regions. The Hengduan Mountains region of south-central China (HMR) is well known for its high diversity of plants, but its boundaries and internal floristic structure are poorly understood, especially in relation to geographical and environmental factors. With data on occurrences and elevational ranges of seed plants across the HMR and adjacent areas of the greater Qinghai-Tibet Plateau, we identified motifs (distinct species assemblages) by Grade of Membership models, and characterized relative contributions of geography, elevation, and climate to their spatial patterns. Motifs segregate primarily by latitude, elevation, and correlated environmental variables, most sharply across the tropical-temperate divide. Secondarily, they segregate by longitude and geographical features, and reveal a novel divide across the Jinsha River. A core set of motifs corresponds to previous delineations of the HMR. The HMR biodiversity hotspot is more a mosaic of floristic elements than a cohesive entity. Grade of Membership models effectively reveal the geographical contours of biotic structure, and are a valuable new tool for biogeographical analysis.

New combinations and synonyms in Rehderodendron (Styracaceae).

We demonstrate with morphological characters that the species Pterostyrax burmanicus W.W.Sm. & Farrer and Parastyrax macrophyllus C.Y.Wu & K.M.Feng (Styracaceae) are best placed in the genus Rehderodendron Hu. Rehderodendron burmanicum (W.W.Sm. & Farrer) W.Y.Zhao, P.W.Fritsch & W.B.Liao, comb. nov. and Rehderodendron macrophyllum (C.Y.Wu & K.M.Feng) W.Y.Zhao, P.W.Fritsch & W.B.Liao, comb. nov., are created. We also provide a lectotype for R. macrophyllum. These revisions result in the reduction of Pterostyrax Siebold & Zucc. to three species and this genus is no longer considered to be documented from Myanmar. Further, Parastyrax W.W.Sm. becomes a monotypic genus comprising only P. lacei (W.W.Sm.) W.W.Sm., distributed in Kachin State, northeast Myanmar and Yunnan Province, south-western China.

Dilochia deleoniae (Orchidaceae), a new species from Mindanao, Philippines.

A new species, Dilochia deleoniae Tandang & Galindon (Orchidaceae), from Mindanao Island, Philippines is described and illustrated herein. This species is distinct from other known Philippine Dilochia species by its terrestrial habit and is distinguished from all known Dilochia species by its monopodial inflorescence, rarely branching in two, and a pale yellow to dull orange or brownish-yellow labellum devoid of purple spots.

Actinostachysminuta, a new species of grass fern from Mindanao, Philippines.

Actinostachysminuta Amoroso & Coritico (Schizaeaceae), from Mindanao, Philippines, is described herein as a new species. This species is distinguished from all other species of Actinostachys (grass ferns) by its notably short and narrow fronds, distinct triangular stipe, and bifid apex of the sorophore lamina with profuse white long hairs. This species is distinct from the other known Philippine species of Actinostachys by its diminutive epiphytic habit and a habitat restricted to the trunks of the tree fern Sphaeropterispolypoda (Baker) R.M.Tryon. A taxonomic key to the species of Philippine Schizaeaceae that incorporates the new species is provided.

Origin of angiosperms and the puzzle of the Jurassic gap.

Angiosperms are by far the most species-rich clade of land plants, but their origin and early evolutionary history remain poorly understood. We reconstructed angiosperm phylogeny based on 80 genes from 2,881 plastid genomes representing 85% of extant families and all orders. With a well-resolved plastid tree and 62 fossil calibrations, we dated the origin of the crown angiosperms to the Upper Triassic, with major angiosperm radiations occurring in the Jurassic and Lower Cretaceous. This estimated crown age is substantially earlier than that of unequivocal angiosperm fossils, and the difference is here termed the 'Jurassic angiosperm gap'. Our time-calibrated plastid phylogenomic tree provides a highly relevant framework for future comparative studies of flowering plant evolution.

Leaf adaptations and species boundaries in North American Cercis: implications for the evolution of dry floras.

PREMISE OF THE STUDY: The North American Cercis clade spans dry to mesic climates and exhibits complex morphological variation. We tested various proposed species classifications of this group and whether aspects of leaf morphology, particularly the "drip-tip" in some regional populations, are adaptive and/or linked with phylogeny. METHODS: We made measurements on over 1100 herbarium specimens from throughout North America and analyzed the data with univariate and multivariate approaches. We analyzed phylogenetically DNA sequence data from nuclear ITS and three plastid regions from 40 samples, and estimated divergence times with a relaxed-clock Bayesian analysis. We used climate and geographic position data to predict the variation observed in leaf size and shape by using stepwise multiple linear regressions. KEY RESULTS: Morphometric analyses yielded a pattern of continuous and often clinal character variation across North America, without correlated gaps in character states. Conversely, phylogenetic and divergence time analyses yielded distinct clades from California, the interior west, and eastern North America separated by between ~12 and 16 million years. Multiple regressions yielded highly significant correlations between leaf apex shape and precipitation of the warmest quarter. CONCLUSIONS: Despite a pattern of continuous morphological character variation, the long period of geographic and presumably genetic isolation warrants the delimitation of three species. Predictive modeling supports the adaptive value of acuminate apices or "drip-tips" in mesic habitats. This suggests that Cercis leaves change more rapidly than inferred from parsimony reconstruction, which has implications for the evolution of the dry floras of North America and Eurasia.

Complete Chloroplast Genome of Cercis chuniana (Fabaceae) with Structural and Genetic Comparison to Six Species in Caesalpinioideae.

The subfamily Caesalpinioideae of the Fabaceae has long been recognized as non-monophyletic due to its controversial phylogenetic relationships. Cercis chuniana, endemic to China, is a representative species of Cercis L. placed within Caesalpinioideae in the older sense. Here, we report the whole chloroplast (cp) genome of C. chuniana and compare it to six other species from the Caesalpinioideae. Comparative analyses of gene synteny and simple sequence repeats (SSRs), as well as estimation of nucleotide diversity, the relative ratios of synonymous and nonsynonymous substitutions (dn/ds), and Kimura 2-parameter (K2P) interspecific genetic distances, were all conducted. The whole cp genome of C. chuniana was found to be 158,433 bp long with a total of 114 genes, 81 of which code for proteins. Nucleotide substitutions and length variation are present, particularly at the boundaries among large single copy (LSC), inverted repeat (IR) and small single copy (SSC) regions. Nucleotide diversity among all species was estimated to be 0.03, the average dn/ds ratio 0.3177, and the average K2P value 0.0372. Ninety-one SSRs were identified in C. chuniana, with the highest proportion in the LSC region. Ninety-seven species from the old Caesalpinioideae were selected for phylogenetic reconstruction, the analysis of which strongly supports the monophyly of Cercidoideae based on the new classification of the Fabaceae. Our study provides genomic information for further phylogenetic reconstruction and biogeographic inference of Cercis and other legume species.

Plastid phylogenomics resolves infrafamilial relationships of the Styracaceae and sheds light on the backbone relationships of the Ericales.

Relationships among the genera of the small, woody family Styracaceae and among families of the large, diverse order Ericales have resisted complete resolution with sequences from one or a few genes. We used plastome sequencing to attempt to resolve the backbone relationships of Styracaceae and Ericales and to explore plastome structural evolution. Complete plastomes for 23 species are newly reported here, including 18 taxa of Styracaceae and five of Ericales (including species of Sapotaceae, Clethraceae, Symplocaceae, and Diapensiaceae). Combined with publicly available complete plastome data, this resulted in a data set of 60 plastomes, including 11 of the 12 genera of Styracaceae and 12 of 22 families of Ericales. Styracaceae plastomes were found to possess the quadripartite structure typical of angiosperms, with sizes ranging from 155 to 159 kb. Most of the plastomes were found to possess the full complement of typical angiosperm plastome genes. Unusual structural features were detected in plastomes of Alniphyllum and Bruinsmia, including the presence of a large 20-kb inversion (14 genes) in the Large Single-Copy region, the loss or pseudogenization of the clpP and accD genes in Bruinsmia, and the loss of the first exon of rps16 in B. styracoides. Likewise, the second intron from clpP was found to be lost in Alniphyllum and Huodendron. Phylogenomic analyses including all 79 plastid protein-coding genes provided improved resolution for relationships among the genera of Styracaceae and families of Ericales. Styracaceae was strongly supported as monophyletic, with Styrax, Huodendron, and a clade of Alniphyllum + Bruinsmia successively sister to the remainder of the family, all with strong support. All genera of Styracaceae were recovered as monophyletic, except for Halesia and Pterostyrax, which were each recovered as polyphyletic with strong support. Within Ericales, all families were recovered as monophyletic with strong support, with Balsaminaceae sister to remaining Ericales. Most relationships recovered in plastome analyses are congruent with previous analyses based on smaller data sets. Our results demonstrate the power of plastid phylogenomics to improve phylogenetic hypotheses among genera and families, and provide new insight into plastome evolution across Ericales.

Plastid phylogenomics and adaptive evolution of Gaultheria series Trichophyllae (Ericaceae), a clade from sky islands of the Himalaya-Hengduan Mountains.

Gaultheria series Trichophyllae Airy Shaw is an angiosperm clade of high-alpine shrublets endemic to the Himalaya-Hengduan Mountains and characterized by recent species divergence and convergent character evolution that has until recently caused much confusion in species circumscription. Although multiple DNA sequence regions have been employed previously, phylogenetic relationships among species in the group have remained largely unresolved. Here we examined the effectiveness of the plastid genome for improving phylogenetic resolution within the G. series Trichophyllae clade. Plastid genomes of 31 samples representing all 19 recognized species of the series and three outgroup species were sequenced with Illumina Sequencing technology. Maximum likelihood (ML), maximum parsimony (MP) and Bayesian inference (BI) phylogenetic analyses were performed with various datasets, i.e., that from the whole plastid genome, coding regions, noncoding regions, large single-copy region (LSC) and inverted-repeat region a (IRa). The partitioned whole plastid genome with inverted-repeat region b (IRb) excluded was also analyzed with ML and BI. Tree topologies based on the whole plastid genome, noncoding regions, and LSC region datasets across all analyses, and that based on the partitioned dataset with ML and BI analyses, are identical and generally strongly supported. Gaultheria series Trichophyllae form a clade with three species and one variety that is sister to a clade of the remaining 16 species; the latter comprises seven main subclades. Interspecific relationships within the series are strongly supported except for those based on the coding-region and IRa-region datasets. Eight divergence hotspot regions, each possessing >5% percent variable sites, were screened across the whole plastid genome of the 28 individuals sampled in the series. Results of morphological character evolution reconstruction diagnose several clades, and a hypothesis of adaptive evolution for plant habit is postulated.

Himalayan uplift shaped biomes in Miocene temperate Asia: evidence from leguminous Caragana.

Caragana, with distinctive variation in leaf and rachis characters, exhibits three centers of geographic distribution, i.e., Central Asia, the Qinghai-Tibetan Plateau (QTP), and East Asia, corresponding to distinct biomes. Because Caragana species are often ecologically dominant components of the vegetation in these regions, it is regarded as a key taxon for the study of floristic evolution in the dry regions of temperate Asia. Based on an expanded data set of taxa and gene regions from those previously generated, we employed molecular clock and biogeographical analyses to infer the evolutionary history of Caragana and link it to floristic patterns, paleovegetation, and paleoclimate. Results indicate that Caragana is of arid origin from the Junggar steppe. Diversification of crown group Caragana, dated to the early Miocene ca. 18 Ma and onwards, can be linked to the Himalayan Motion stage of QTP uplift. Diversification of the major clades in the genus corresponding to taxonomic sections and morphological variation is inferred to have been driven by the uplift, as well as Asian interior aridification and East Asian monsoon formation, in the middle to late Miocene ca. 12~6 Ma. These findings demonstrate a synchronous evolution among floristics, vegetation and climate change in arid Central Asia, cold arid alpine QTP, and mesophytic East Asia.

Diplycosia platyphylla (Ericaceae), a new species from Mindanao, Philippines.

Diplycosia platyphylla P.W.Fritsch, a new species from Mindanao Island, Philippines, is described and illustrated. This species is most similar to the Bornean Diplycosia urceolata but differs by its green or slightly flushed pink petioles 4-7 mm long, wider leaf blades, acute calyx lobe apices, and lavender mature fruiting calyx. The new species is known only from a single collection made from Mount Apo in North Cotabato Province, southern Mindanao.

AFLP Genome Scanning Reveals Divergent Selection in Natural Populations of Liriodendron chinense (Magnoliaceae) along a Latitudinal Transect.

Understanding adaptive genetic variation and its relation to environmental factors are important for understanding how plants adapt to climate change and for managing genetic resources. Genome scans for the loci exhibiting either notably high or low levels of population differentiation (outlier loci) provide one means of identifying genomic regions possibly associated with convergent or divergent selection. In this study, we combined Amplified Fragment Length Polymorphism (AFLP) genome scan and environmental association analysis to test for signals of natural selection in natural populations of Liriodendron chinense (Chinese Tulip Tree; Magnoliaceae) along a latitudinal transect. We genotyped 276 individuals from 11 populations of L. chinense using 987 AFLP markers. Both frequency-based (Dfdist and BayeScan) and correlation-based (MLM) methods were applied to detect outlier loci. Our analyses recovered both neutral and potentially adaptive genetic differentiation among populations of L. chinense. We found moderate genetic diversity within populations and high genetic differentiation among populations with reduced genetic diversity toward the periphery of the species ranges. Nine AFLP marker loci showed evidence of being outliers for population differentiation for both detection methods. Of these, six were strongly associated with at least one climate factor. Temperature, precipitation, and radiation were found to be three important factors influencing local adaptation of L. chinense. The outlier AFLP loci are likely not the target of natural selection, but the neighboring genes of these loci might be involved in local adaptation. Hence, these candidates should be validated by further studies.