Molecular phylogeny and historical biogeography of the Holarctic wetland leaf beetle of the genus Plateumaris

Leaf beetles of the genus Plateumaris inhabit wetlands across the temperate zone of the Holarctic region. To explore the phylogeographic relationships among North American, East Asian, and European members of this genus and the origin of the species endemic to Japan, we studied the molecular phylogeny of 20 of the 27 species in this genus using partial sequences of mitochondrial cytochrome oxidase subunit I (COI) and the 16S and nuclear 28S rRNA genes. The molecular phylogeny revealed that three species endemic to Europe are monophyletic and sister to the remaining 11 North American and six Asian species. Within the latter clade, North American and Asian species did not show reciprocal monophyly. Dispersal-vicariance analysis and divergence time estimation revealed that the European and North America-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene. Two Japanese endemics originated from different divergence events; one differentiated from the mainland lineage after differentiation from the North American lineage, whereas the other showed a deep coalescence from the North American lineage with no present-day sister species on the East Asian mainland. This study of extant insects provides molecular phylogenetic evidence for ancient vicariance between Europe and East Asia-North America, and for more recent (but pre-Pleistocene) faunal exchanges between East Asia and North America.     

Phylogeny and biogeography of Aralia sect. Aralia (Araliaceae)

Aralia sect. Aralia (Araliaceae) consists of approximately eight species disjunctly distributed in Asia and North America. Phylogenetic and biogeographic analyses were conducted using sequences of the internal transcribed spacer regions of the nuclear ribosomal DNA. Aralia racemosa from eastern North America was sister to A. californica from western North America. Aralia cordata from eastern Asia did not form a species-pair relationship with the eastern North American A. racemosa. The two subspecies of A. racemosa formed a monophyletic group. Biogeographic analyses showed a close area relationship between eastern North America and western North America. The Himalayas were cladistically basal and eastern Asia was placed between the Himalayas and North America. The biogeographic analysis supported the origin of the eastern Asian and eastern North American disjunct pattern in Aralia sect. Aralia via the Bering land bridges. Comparisons with results of phylogenetic analyses of other genera suggested that (1) the floristic connection between eastern North America and western North America may be stronger than previously thought; and (2) the biogeographic patterns in the Northern Hemisphere are complex. Furthermore, a lack of correlation between sequence divergence values and phylogenetic positions was observed, suggesting the importance of a phylogenetic framework in biogeographic analyses.     

Phylogeny and Phytogeography of Eupatorium (Eupatorieae, Asteraceae): Insights from Sequence Data of the nrDNA ITS Regions and cpDNA RFLP

Eupatorium were examined by sequencing the internal transcribed spacers (ITS) of nuclear ribosomal DNA and restriction site analysis of chloroplast DNA. Molecular data provided strong evidence that (1) this genus originated in North America, (2) the genus diverged into three morphological species groups, Eutrochium, Traganthes and Uncasia in North America, and (3) one of the North American Uncasia lineages migrated into temperate Europe and eastern Asia over the Bering land bridge. The estimated divergence times support a late Miocene to early Pliocene migration from North America to Eurasia via the Bering land bridge. A European species was sister to all of the eastern Asian species examined. The disjunct distribution pattern of the genus Eupatorium is incongruent with the classical Arcto-Tertiary geoflora concept. Received 13 September 1999/ Accepted in revised form 4 January 2000     

Phylogenomics,biogeography, and evolution of morphology and ecological niche of the eastern Asian–eastern North American Nyssa (Nyssaceae)

Nyssa (Nyssaceae, Cornales) represents a classical example of the well‐known eastern Asian–eastern North American floristic disjunction. The genus consists of three species in eastern Asia, four species in eastern North America, and one species in Central America. Species of the genus are ecologically important trees in eastern North American and eastern Asian forests. The distribution of living species and a rich fossil record of the genus make it an excellent model for understanding the origin and evolution of the eastern Asian–eastern North American floristic disjunction. However, despite the small number of species, relationships within the genus have remained unclear and have not been elucidated using a molecular approach. Here, we integrate data from 48 nuclear genes, fossils, morphology, and ecological niche to resolve species relationships, elucidate its biogeographical history, and investigate the evolution of morphology and ecological niches, aiming at a better understanding of the well‐known EA–ENA floristic disjunction. Results showed that the Central American (CAM) Nyssa talamancana was sister to the remaining species, which were divided among three, rapidly diversified subclades. Estimated divergence times and biogeographical history suggested that Nyssa had an ancestral range in Eurasia and western North America in the late Paleocene. The rapid diversification occurred in the early Eocene, followed by multiple dispersals between and within the Erasian and North American continents. The genus experienced two major episodes of extinction in the early Oligocene and end of Neogene, respectively. The Central American N. talamancana represents a relic lineage of the boreotropical flora in the Paleocene/Eocene boundary that once diversified in western North America. The results supported the importance of both the North Atlantic land bridge and the Bering land bridge (BLB) for the Paleogene dispersals of Nyssa and the Neogene dispersals, respectively, as well as the role of Central America as refugia of the Paleogene flora. The total‐evidence‐based dated phylogeny suggested that the pattern of macroevolution of Nyssa coincided with paleoclimatic changes. We found a number of evolutionary changes in morphology (including wood anatomy and leaf traits) and ecological niches (precipitation and temperature) between the EA–ENA disjunct, supporting the ecological selection driving trait evolutions after geographic isolation. We also demonstrated challenges in phylogenomic studies of lineages with rapid diversification histories. The concatenation of gene data can lead to inference of strongly supported relationships incongruent with the species tree. However, conflicts in gene genealogies did not seem to impose a strong effect on divergence time dating in our case. Furthermore, we demonstrated that rapid diversification events may not be recovered in the divergence time dating analysis using BEAST if critical fossil constraints of the relevant nodes are not available. Our study provides an example of complex bidirectional exchanges of plants between Eurasia and North America in the Paleogene, but “out of Asia” migrations in the Neogene, to explain the present disjunct distribution of Nyssa in EA and ENA.     

Evolution of the Eastern Asian and Eastern North American disjunct genus Symplocarpus (Araceae): insights from chloroplast DNA restriction site data

Chloroplast DNA (cpDNA) variation was surveyed with 20 restriction endonucleases for the eastern Asian and eastern North American disjunct genus Symplocarpus (Araceae). The cpDNA phylogeny reveals a sister group relationship between S. foetidus from eastern North America and S. renifolius from eastern Asia. The cpDNA divergence between the two intercontinental sister species is 0.61%, which suggests an estimated divergence time of 6.1 million years ago during the late Miocene. The Bering land bridge hypothesis is compatible with the estimated time of divergence for the migration of Symplocarpus between eastern Asia and North America. Furthermore, a single origin of the exothermic spadices in Symplocarpus is suggested by the phylogeny. The cpDNA data also provide independent support for the recognition of three species within the genus.     

Molecular phylogeny and historical biogeography of the genus Tuber, the 'true truffles'

Aim Various data sets and methods of analysis were combined to produce the first comprehensive molecular phylogeny of the genus Tuber and to analyse its biogeography. Location Europe, North Africa, China, Asia, North America. Methods Phylogenetic relationships among Tuber species were reconstructed based on a data set of internal‐transcribed spacer (ITS) sequences and various phylogenetic inference methods, specifically maximum parsimony, Bayesian analysis and neighbour joining. Tajima’s relative rate test showed that Tuber 18S rRNA, 5.8S rRNA, 5.8S‐ITS2 rRNA and β‐tubulin sequences evolved in a clock‐like manner. These genes, combined or not, were employed for molecular clock estimates after construction of linearized trees using mega 3.1. We reconstructed ancestral areas in the Northern Hemisphere by means of a dispersal–vicariance analysis (diva 1.1) based on current distribution patterns of the genus Tuber determined from the literature. Results The resulting molecular phylogeny divided the genus Tuber into five distinct clades, in agreement with our previously published studies. The Puberulum, Melanosporum and Rufum groups were diversified in terms of species and geographical distribution. In contrast, the Aestivum and Excavatum groups were less diversified and were located only in Europe or North Africa. Using a global molecular clock analysis, we estimated the divergence times for the origin of the genus and for the origin of several groups. diva inferred nine dispersal events and suggested that the ancestor of Tuber was originally present in Europe or was widespread in Eurasia. Equally optimal distributions were obtained for several nodes, suggesting different possible biogeographical patterns. Main conclusions Our analyses identified several discrepancies with the classical taxonomy of the genus, and we propose a new phylogenetic classification. According to molecular clocks, the radiation of the genus Tuber could have started between 271 and 140 Ma. Used in combination with the results obtained from time divergence estimates, this allows us to propose two equally probable scenarios of intra‐ and inter‐continental diversification of the genus according to the geographic distribution of the most recent common ancestor in Europe or Eurasia. The biogeographical patterns imply intra‐continental dispersal events between Europe and Asia and inter‐continental dispersal events between North America and Europe or Asia, which are compatible with land connections during the Tertiary.     

Molecular phylogeny and biogeography of Linanthus (Polemoniaceae)

To better understand the evolutionary history of Linanthus (Polemoniaceae) and its relatives, molecular phylogenies based on DNA sequence data from the internal transcribed spacer (ITS) region of nrDNA and the chloroplast gene matK were estimated using several methods. Our data suggest two separate and well-supported lineages of Linanthus in close association with two other genera-Leptodactylon and Phlox. These results agree with previous molecular systematic work on the Polemoniaceae, but do not support the traditional classification of the genus as a natural group, nor do they support the sectional classification within the genus. With a distribution centered primarily in western North America and a high degree of endemism in the California Floristic Province, it has been suggested by Raven and Axelrod that the origin and diversification of Linanthus and its relatives were tied to the development of a summer-dry climate in western North America, which began around 13-15 million years ago (mya). Increased drying during the Pliocene (1.2-5 mya) has also been hypothesized by Axelrod to have led to an increase in plant speciation in California and adjacent areas. Divergence times within the Linanthus lineages were estimated from the ITS and matK gene trees. A log-likelihood ratio test could not reject clock-like evolution for the matK data; however, the clock was strongly rejected for the ITS data set. Although ITS molecular evolution was not clock-like, the estimated times of divergence were similar to those of the matK data set. Within both lineages of Linanthus there seems to have been considerable diversification that has occurred since the Pliocene.     

Nuclear rDNA-based molecular clock of the evolution of triatominae (Hemiptera: reduviidae), vectors of Chagas disease

The evolutionary history and times of divergence of triatomine bug lineages are estimated from molecular clocks inferred from nucleotide sequences of the small subunit SSU (18S) and the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA of these reduviids. The 18S rDNA molecular clock rate in Triatominae, and Prosorrhynchan Hemiptera in general, appears to be of 1.8% per 100 million years (my). The ITS-2 molecular clock rate in Triatominae is estimated to be around 0.4-1% per 1 my, indicating that ITS-2 evolves 23-55 times faster than 18S rDNA. Inferred chronological data about the evolution of Triatominae fit well with current hypotheses on their evolutionary histories, but suggest reconsideration of the current taxonomy of North American species complexes.     

Molecular phylogeny of the genus Pieris (Ericaceae) with special reference to phylogenetic relationships of insular plants on the Ryukyu Islands

Phylogenetic relationships within the genus Pieris (Ericaceae) were investigated based on the rbcL and matK genes along with five spacer sequences of chloroplast DNA to address questions regarding the phylogeography of the genus in association with insular plants on the Ryukyu Islands. The most parsimonious trees indicated that P. floribunda from eastern North America is a sister taxon to the remaining taxa examined, and suggested that the East Asian taxa examined are monophyletic. A morphologically cohesive group, section Pieris, was revealed to be paraphyletic. Within the East Asian clade, insular endemics from the Ryukyu Islands, Taiwan, and mainland Japan formed a sister group to P. formosa from the Himalayas and southern China. Our data suggest that the insular endemics of the Ryukyu Islands and Taiwan arose via allopatric divergence as a result of a paleogeographical land configuration of a landbridge during the early–middle Pleistocene in the Quaternary Period.     

中国鹅膏菌属(担子菌)的物种多样性

鹅膏菌属（Ａｍａｎｉｔａ）是一个近世界性广布的大属,全球已被描述而又被承认的有近５００种。在文献中,我国此属已记载约２００种。然而,许多种都是原初描述于欧洲或北美的种类。近来的研究表明,东亚的鹅膏菌独特且有其自身的分布范围。东亚的有些种虽与产于欧洲或北美的某些种相似,但仔细的野外观察,详尽的形态解剖学和分子进化生物学研究结果表明,东亚的鹅膏菌是独立的分类群。在欧洲,人们有采集著名食菌恺撒鹅膏菌的习     

Phylogenetic relationships in Ephedra (Ephedraceae) inferred from chloroplast and nuclear DNA sequences

Sequences of the nuclear ribosomal DNA internal transcribed spacer region 1 and the chloroplast-encoded genes maturase K and ribulose-1,5 biphosphate carboxylase large subunit were obtained from species of Ephedra (Ephedraceae) representing the geographic range and morphological diversity of the genus. Phylogenetic analyses of the DNA data indicate that relationships within the genus are better predicted by geographic region of origin than by ovulate cone characters. The sampled species with dry, winged (versus fleshy) ovulate cone bracts or single-seeded cones do not form monophyletic groups and therefore the previous classification systems of Ephedra based on these aspects of bract morphology appear to be largely unnatural. Three groups were identified among the Old World species studied, one comprising European and Mediterranean species and two including only Asian species. The sequence data suggest a possible early divergence of a New World clade of Ephedra from among the Old World groups. The South American species form a distinct clade apparently related to one of two groups of North American species, which accords with a frequent floristic pattern of close relationships between species groups in western South America and southwestern North America.     

Phylogenetic analysis of Toxicodendron （Anacardiaceae） and its biogeographic implications on the evolution of north temperate and tropical intercontinental disjunctions

Toxicodendron is a genus in the Rhus complex of Anacardiaceae with a disjunct distribution between eastern Asia and North America, extending to southeastern Asia and the neotropics. Nuclear （internal transcribed spacer, external transcribed spacer, and NIA-i3） and chloroplast （ndhF and trnL-F） sequences were used to construct phylogenetic relationships of Toxicodendron. Phylogenetic analysis of these data strongly support Toxieodendron as a monophyletic group distinct from other genera of the Rhus complex, and the phylogeny does not fully corroborate classification at the sectional level. Two temperate disjunct lineages were detected, one from section Toxicodendron and the other between the eastern North American Toxicodendron vernix and the eastern Asian Toxicodendron vernieifluum. Their divergence times were estimated to be 13.46 （7.95-19.42） and 7.53 （2.76-12.86） mya, respectively. The disjunction between section Griffithii （taxa from warm temperate to tropical Asia） and Toxieodendron striatum （from the neotropics） was supported and their divergence time was estimated to be 20.84 （11.1 6-30.52） mya in the early Miocene. Our biogeographic results and the paleontological data support the Bering land bridge as the most likely route to explain the temperate disjunctions, yet the tropical disjunction in Toxicodendron seems to be best explained by the North Atlantic land bridge hypothesis.     

A systematic study of North American Angelica species (Apiaceae) based on nrDNA ITS and cpDNA sequences and fruit morphology

Angelica is a taxonomically complex genus widespread throughout the North Temperate Zone. Previous phylogenetic studies of the genus have focused primarily on its East Asian species. The relationships among its North American members, the monophyly of these species, and the value of fruit morphology in circumscribing its taxa have yet to be examined. This study represents the most comprehensive sampling of Angelica to date (100 species) and includes all 26 species in North America. Relationships are inferred using Bayesian inference, maximum likelihood, and maximum parsimony analyses of ITS sequences and, for multiple accessions of each North American species, cpDNA ndhF-rpl32, rpl32-trnL, and psbM-psbD sequences. The fruit morphological characters examined were those considered phylogenetically important in East Asian Angelica. The results revealed that the North American species fell into three major clades: North American Angelica clade, Archangelica clade, and the Eurasian Angelica clade. Angelica dawsonii has affinities with Lomatium brandegeei. Fourteen species within the North American Angelica clade were strongly supported as monophyletic. Two paraphyletic species resulted in new combinations in A. lineariloba and A. venenosa. Conflict between the ITS-derived and cpDNA-derived phylogenies and the lack of resolution in portions of the trees may be due to chloroplast capture and rapid species radiation. Fruit morphology supported some interspecific relationships based on molecular data, and relationships revealed by ITS and cpDNA data were roughly in accordance with fruit classification type and geographic distribution region, respectively. A diagnostic key based on fruit morphology is provided for the identification of the North American Angelica taxa.     

A fossil-calibrated relaxed clock for Ephedra indicates an Oligocene age for the divergence of Asian and New World clades and Miocene dispersal into South America

Ephedra comprises approximately 50 species, which are roughly equally distributed between the Old and New World deserts, but not in the intervening regions （amphitropical range）. Great heterogeneity in the substitution rates of Gnetales （Ephedra, Gnetum, and Welwitschia） has made it difficult to infer the ages of the major divergence events in Ephedra, such as the timing of the Beringian disjunction in the genus and the entry into South America. Here, we use data from as many Gnetales species and genes as available from GenBank and from a recent study to investigate the timing of the major divergence events. Because of the tradeoff between the amount of missing data and taxon/gene sampling, we reduced the initial matrix of 265 accessions and 12 loci to 95 accessions and 10 loci, and further to 42 species （and 7736 aligned nucleotides） to achieve stationary distributions in the Bayesian molecular clock runs. Results from a relaxed clock with an uncorrelated rates model and fossil-based calibration reveal that New World species are monophyletic and diverged from their mostly Asian sister clade some 30 mya, fitting with many other Beringian disjunctions. The split between the single North American and the single South American clade occurred approximately 25 mya, well before the closure of the Panamanian Isthmus. Overall, the biogeographic history of Ephedra appears dominated by long-distance dispersal, but finer-scale studies are needed to test this hypothesis.     

Northern hemisphere biogeography of Cerastium (Caryophyllaceae): insights from phylogenetic analysis of noncoding plastidnucleotide sequences

Phylogenetic relationships and biogeography of the genus Cerastium were studied using sequences of three noncoding plastid DNA regions (trnL intron, trnL-trnF spacer, and psbA-trnH spacer). A total of 57 Cerastium taxa was analyzed using two species of the putative sister genus Stellaria as outgroups. Maximum parsimony analyses identified four clades that largely corresponded to previously recognized infrageneric groups. The results suggest an Old World origin and at least two migration events into North America from the Old World. The first event possibly took place across the Bering land bridge during the Miocene. Subsequent colonization of South America occurred after the North and South American continents joined during the Pliocene. A more recent migration event into North America probably across the northern Atlantic took place during the Quaternary, resulting in the current circumpolar distribution of the Arctic species. Molecular clock dating of major biogeographic events was internally consistent on the phylogenetic trees. The arctic high-polyploid species form a polytomy together with some boreal and temperate species of the C. tomentosum group and the C. arvense group. Lack of genetic variation among the arctic species probably indicates a recent origin. The annual life form is shown to be of polyphyletic origin.     

Sexual mass allocation in species with inflorescences as pollination units: a comparison between Arum italicum and Arisaema (Araceae)

Sex allocation models predict that cosexuality is stabilized by high allocation to attractive structures in pollen-limited species or by high allocation to shared structures that contribute to both genders. High investment in unilateral fixed costs favor the evolution of dioecy or gender change. With these predictions in mind, I studied sexual mass allocation at flowering in the monoecious Arum italicum (Araceae) and compared it with information available for its sex labile relative Arisaema dracontium. In A. italicum, 68% of biomass was allocated to structures believed to be involved in pollinator attraction and capture. This allocation pattern contrasts with that of Arisaema dracontium, in which 70% of biomass was allocated to scape, considered to be a unilateral fixed cost. The importance of attractive structures in A. italicum was further supported by a disproportionate increased allocation, in larger inflorescences, to the appendix (an attractive structure) compared to fertile flowers. In addition, an increase in inflorescence mass involved a disproportionate increase in mass allocation to male, rather than female, flowers. This pattern also contrasts with a size-related gender change from male to female in Arisaema species. These findings were consistent with sex allocation model predictions and shed light on the evolution of sex lability in Arisaema species.     

ORIGIN AND BIOGEOGRAPHY OF AESCULUS L. (HIPPOCASTANACEAE): A MOLECULAR PHYLOGENETIC PERSPECTIVE

Sequences of chloroplast gene matK and internal transcribed spacers of nuclear ribosomal RNA genes were used for phylogenetic analyses of Aesculus, a genus currently distributed in eastern Asia, eastern and western North America, and southeastern Europe. Phylogenetic relationships inferred from these molecular data are highly correlated with the geographic distributions of species. The identified lineages closely correspond to the five sections previously recognized on the basis of morphology. Ancestral character-state reconstruction, a molecular clock, and fossil evidence were used to infer the origin and biogeographic history of the genus within a phylogenetic framework. Based on the molecular phylogenetic reconstruction of the genus, sequence divergence, and paleontological evidence, we infer that the genus originated during the transition from the Cretaceous to the Tertiary (~65 M.Y.B.P.) at a high latitude in eastern Asia and spread into North America and Europe as an element of the “boreotropical flora”; the current disjunct distribution of the genus resulted from geological and climatic changes during the Tertiary.     

Phylogeny of magpies (genus Pica) inferred from mtDNA data

We investigated the phylogenetic relationships of species and subspecies of the cosmopolitan genus Pica using 813 bp of the mitochondrial genome (including portions of 16s rDNA, tRNA-Leu, and ND1). The phylogenetic relationships within the genus Pica revealed in our molecular analyses can be summarized as follows: (1). the Korean magpie (Pica pica sericea) appears basal within the genus Pica; (2). the European magpie (Pica pica pica) shows a close relationship to the Kamchatkan magpie (Pica pica camtschatica); (3). two North American species (Pica hudsonia and Pica nuttalli) shows a sister-group relationship; (4). most importantly, the European+Kamchatkan clade appears more closely related to the North American clade than to Korean magpies. Based on these results and genetic distance data, it is possible that members of an ancestral magpie lineage in East Asia initially moved north to form Kamchatkan magpies and then crossed the Bering land bridge to found North American taxa. At a later date, a group might have split off from Kamchatkan magpies and migrated west to form the Eurasian subspecies. The divergence between the two North American taxa appears to have happened no later than the divergence of Eurasian subspecies and both processes appear to have been relatively rapid. Rather than the formation of P. hudsonia by re-colonization from an Asian magpie ancestor, as suggested by, our data suggest a shared ancestry between P. hudsonia and P. nuttalli. Based on the above findings, including phylogenetic placement of P. hudsonia and P. nuttalli as nested within the larger Pica pica clade, and the lack of evidence suggesting reproductive isolation within the genus Pica, we believe that the current classification may be inaccurate. A more conservative classification would recognize one monophyletic species (i.e., P. pica) and treat P. nuttalli and P. hudsonia as subspecies (i.e., P. p. nuttalli and P. p. hudsonia). More extensive studies on the population genetics and biogeography of magpies should be conducted to better inform any taxonomic decisions.     

A phylogeny of the ITS and ETS for Montanoa (Asteraceae: Heliantheae)

A phylogeny of the genus Montanoa based on the internal transcribed spacer (ITS) and the external transcribed spacer (ETS) is presented. Each of the two clades revealed by the Bayesian and parsimony analyses has approximately half of the number of species in the genus. One lineage is composed mostly of central and southern Mexican species whereas the other lineage contains those species endemic to Mesoamerica and South America. The molecular phylogeny is compared to previous phylogenetic hypotheses based on morphological characters. Key features in the structure of the capitulum such as pale morphology, heavily used in the past to construct hypotheses of relationship within the genus, are viewed as of minimal value to circumscribe natural groups. The relationships of Montanoa to other genera in the Heliantheae are briefly discussed.     

Phylogenetics and biogeography of eastern Asian–North American disjunct genus Pachysandra (Buxaceae) inferred from nucleotide sequences

Abstract Pachysandra is an eastern Asian–North American disjunct genus with three species, two in eastern Asia (Pachysandra axillaris and Pachysandra terminalis) and one in eastern North America (Pachysandra procumbens). Although morphological and cytological studies suggest a close affinity of P. procumbens with P. axillaris, molecular data from nuclear and chloroplast DNA regions have provided conflicting signals. In this study, we tested previous phylogenetic hypotheses using sequences of nuclear ribosomal DNA internal transcribed spacers and chloroplast ndhF gene from multiple individuals of each of the three species. We also estimated the time of divergence between eastern Asia and eastern North America. Our results support the morphological and cytological conclusion that P. procumbens is more closely related to P. axillaris than to P. terminalis. The estimated time of divergence of P. axillaris and P. procumbens was 14.6±5.5 mya, consistent with estimates from many other eastern Asian–North American disjunct genera. The migration of Pachysandra populations from eastern Asia to North America might have occurred by way of the North Atlantic land bridge.