RESEARCH ARTICLE
Does the Arcto-Tertiary Biogeographic
Hypothesis Explain the Disjunct Distribution
of Northern Hemisphere Herbaceous Plants?
The Case of Meehania (Lamiaceae)
Tao Deng1,2,3, Ze-Long Nie4, Bryan T. Drew5, Sergei Volis2, Changkyun Kim2,
Chun-Lei Xiang2, Jian-Wen Zhang2, Yue-Hua Wang1*, Hang Sun2*
a11111
1 School of Life Science, Yunnan University, Kunming, Yunnan, China, 2 Key Laboratory for Plant Diversity
and Biogeography of East Asia, Chinese Academy of Sciences, Kunming, Yunnan, China, 3 University of
Chinese Academy of Sciences, Beijing, China, 4 Key Laboratory of Plant Resources Conservation and
Utilization, College of Biology and Environmental Sciences, Jishou University, Jishou, Hunan, China,
5 Department of Biology, University of Nebraska at Kearney, Kearney, Nebraska, United States of America
* sunhang@mail.kib.ac.cn (HS); wangyh58212@126.com (YHW)
OPEN ACCESS
Citation: Deng T, Nie Z-L, Drew BT, Volis S, Kim C,
Xiang C-L, et al. (2015) Does the Arcto-Tertiary
Biogeographic Hypothesis Explain the Disjunct
Distribution of Northern Hemisphere Herbaceous
Plants? The Case of Meehania (Lamiaceae). PLoS
ONE 10(2): e0117171. doi:10.1371/journal.
pone.0117171
Academic Editor: Qi Wang, Institute of Botany,
CHINA
Received: July 7, 2014
Accepted: December 18, 2014
Published: February 6, 2015
Copyright: This is an open access article, free of all
copyright, and may be freely reproduced, distributed,
transmitted, modified, built upon, or otherwise used
by anyone for any lawful purpose. The work is made
available under the Creative Commons CCO public
domain dedication.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Funding: This study was supported by grants-in-aid
from the Strategic Priority Research Program of the
Chinese Academy of Sciences (XDB03030106),
NSFC-Yunnan Natural Science Foundation United
Project (Grant no. U1136601) and The CAS/SAFEA
International Partnership Program for Creative
Research Teams, Hundred Talents Program of the
Chinese Academy of Sciences (2011312D11022).
The funders had no role in study design, data
Abstract
Despite considerable progress, many details regarding the evolution of the Arcto-Tertiary
flora, including the timing, direction, and relative importance of migration routes in the evolution of woody and herbaceous taxa of the Northern Hemisphere, remain poorly understood.
Meehania (Lamiaceae) comprises seven species and five subspecies of annual or perennial herbs, and is one of the few Lamiaceae genera known to have an exclusively disjunct distribution between eastern Asia and eastern North America. We analyzed the phylogeny and
biogeographical history of Meehania to explore how the Arcto-Tertiary biogeographic hypothesis and two possible migration routes explain the disjunct distribution of Northern
Hemisphere herbaceous plants. Parsimony and Bayesian inference were used for phylogenetic analyses based on five plastid sequences (rbcL, rps16, rpl32-trnH, psbA-trnH, and
trnL-F) and two nuclear (ITS and ETS) gene regions. Divergence times and biogeographic
inferences were performed using Bayesian methods as implemented in BEAST and
S-DIVA, respectively. Analyses including 11 of the 12 known Meehania taxa revealed incongruence between the chloroplast and nuclear trees, particularly in the positions of Glechoma and Meehania cordata, possibly indicating allopolyploidy with chloroplast capture in
the late Miocene. Based on nrDNA, Meehania is monophyletic, and the North American
species M. cordata is sister to a clade containing the eastern Asian species. The divergence time between the North American M. cordata and the eastern Asian species occurred about 9.81 Mya according to the Bayesian relaxed clock methods applied to the
combined nuclear data. Biogeographic analyses suggest a primary role of the Arcto-Tertiary
flora in the study taxa distribution, with a northeast Asian origin of Meehania. Our results
suggest an Arcto-Tertiary origin of Meehania, with its present distribution most probably
being a result of vicariance and southward migrations of populations during climatic
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
1 / 18
Biogeographical Evolution of Meehania
collection and analysis, decision to publish, or
preparation of the manuscript.
oscillations in the middle Miocene with subsequent migration into eastern North America via
the Bering land bridge in the late Miocene.
Competing Interests: The authors have declared
that no competing interests exist.
Introduction
The biogeographic history of intercontinental disjunctions between eastern Asia and eastern
North America has long fascinated botanists and biogeographers [1–3], but until the inception
of molecular phylogenetics and the accompanying advance of complex analytical approaches,
these disjunctions were generally poorly understood. During the past two decades, however,
the phylogenetic relationships between disjunct lineages, the timing of these disjunctions, and
putative migration pathways for many disjunct taxa have been elucidated using molecular
data and new analytical techniques [4–6]. Most of these studies have focused on woody plants,
but several studies have examined the evolution of these disjunct patterns in terrestrial herbs
[7–11].
The primary hypothesis put forth for explaining patterns of East Asian/eastern North
American floristic disjunctions has been that a once continuous Arcto-Tertiary flora existed in
the Northern Hemisphere during the late Cretaceous and Palaeogene that was fragmented by
extinction due to global climatic cooling during the Neogene and Quaternary [3,12–14]. However, the wide range of divergence times estimated from molecular dating among disjunct taxa
between eastern Asia and North America suggests multiple and complex origins of the disjunctions in the Northern Hemisphere [15]. Based on 98 lineages with disjunct distributions between the two regions, Wen et al. [6] hypothesized that most of these lineages originated in
eastern Asia and subsequently moved to North America, but also postulated that some have
migrated in the opposite direction. At the same time, several groups present a distinct pattern,
such as Triosteum L. (Carprifoliaceae), Viburnum L. (Adoxaceae), Astilbe Buch.-Ham. ex
D. Don (Saxifragaceae), and Meehania Britt. ex Small et Vaill. (Lamiaceae), with the Tertiary
Arctic being the putative center of origin for these taxa [7,16,17]. The Arcto-Tertiary flora once
occupied wide areas of northern high latitudes in Cretaceous and early Paleogene time [18,19],
and this vegetation subsequently migrated southward to middle latitudes in Eurasia and North
America [20]. During such movements in space and time, many taxa became extinct or restricted to central and southern China and/or eastern/western North America. However, the
Arcto-Tertiary biogeographic hypothesis alone cannot explain the disjunct distribution of
many taxa because of plant migration during more recent times. Two migration routes, the Bering land bridge (BLB) and the North Atlantic land bridge (NALB), are crucial in interpreting
Northern Hemisphere floristic disjunctions [21–24]. Paleontological and molecular data suggest that the BLB was used mostly by temperate taxa prior to the late Miocene (<10 Mya)
[6,13,15], while the NALB has been viewed as a crucial route for the spread of subtropical and
tropical taxa in the early Paleogene [13,23,25]. Recently, the transoceanic long distance dispersal (LDD) has been proposed for taxa for which no land migration route existed at the time of
migration, e.g. Kelloggia Torrey ex Benth. & J. D. Hooker of Rubiaceae [9] and Leibnitzia Cass.
of Asteraceae [26].
Meehania is a small genus of annual and perennial herbaceous plants consisting of seven
species and five subspecies [27]. Meehania has an unevenly disjunct distribution between eastern Asia (11 taxa) and eastern North America (1 taxon; Fig. 1). Perhaps in part due to its disjunct distribution, Meehania species were previously assigned to distant genera such as
Dracocephalum L., Cedronella Moench, and Glechoma L. [27]. To date, the taxonomy of the
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
2 / 18
Biogeographical Evolution of Meehania
Fig 1. The Bayesian 50% majority-rule consensus tree of Meehania and closely related taxa inferred from analyses using (right) combined nuclear
ribosomal DNA regions (ITS and ETS) and (left) combined chloroplast DNA regions (rbcL, rps16, trnL-F, rpl32-trnL and psbA-trnH). Numbers above
the nodes are Bayesian posterior probabilities and below the nodes are bootstrap values obtained from MP analysis.
doi:10.1371/journal.pone.0117171.g001
genus, particularly the eastern Asian species, has only been assessed based on morphology.
Morphological variation within Meehania is chiefly observed in inflorescences, calyx characters, and especially leaf morphology [27–29]. According to our field investigations and specimen examinations, however, leaf morphology is highly variable in different populations.
The genus Meehania is characterized by having stolons, cordate-ovate to lanceolate leaves,
thyrsoid, terminal cymes, a pedunculate or sessile inflorescence with larger flowers (ca. 1–2.5
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
3 / 18
Biogeographical Evolution of Meehania
cm long), a tubular calyx, a strongly 2-lipped and 5-lobed (3/2) corolla, and parallel antherthecae [27,31]. Cytological analyses based on two species of Meehania, M. urticifolia (Miq.)
Makino and M. montis-koyae Ohwi, indicated that the genus is diploid, 2n = 18 [30]. Meehania,
together with 12 other extant genera, belongs to subtribe Nepetinae, tribe Mentheae, but its systematic position within the subtribe is uncertain [31]. Although significant progress has been
made in Lamiaceae phylogenetics at the tribal and generic levels [32–38], the genus Meehania
has been underrepresented in molecular systematic studies. Thus far, only two molecular phylogenetic studies have included Meehania species [34,39]. In their study on tribe Mentheae, Meehania was included as a member of the subtribe Nepetinae by Drew and Sytsma [34]. They
suggested that Meehania was polyphyletic because of the inclusion of the Eurasian genus Glechoma and Chinese endemic Heterolamium C. Y. Wu. However, their sampling was limited as
their study only included two species of Meehania and one species of Glechoma. Furthermore,
the voucher specimen for Heterolamium debile (Hemsl.) C. Y. Wu (Zhiduan, 960093) used in
their study was subsequently found to be misidentified by the first author of this paper, and is in
fact M. henryi (Hemsl.) Sun ex C. Y. Wu. Therefore, a comprehensive species sampling of both
Meehania and Glechoma is vital for resolving relationships within and between the two genera.
Although Meehania is not especially species-rich compared with some other well-known
Nepetoideae genera (e.g. Salvia L., Nepeta L.), its East Asian/North American disjunct distribution makes it well suitable for testing the hypothesis that Arctic latitudes in the Tertiary were a
major center of origin for taxa currently occurring in East Asia and elsewhere in the North
Hemisphere. It is noteworthy that of the ~12 genera of subtribe Nepetinae, 3 possess analogous
East Asian/North American disjunct distributions, suggesting common migration routes and
similar evolutionary processes in these genera. Meehania species typically occur in temperate
to subtropical forests in the Northern Hemisphere. In eastern Asia, M. urticifolia and M. montis-koyae are both restricted to northeastern China and Japan in temperate areas [27,28,40],
while the other four species, M. faberi (Hemsl.) C. Y. Wu, M. pinfaensis (H. Lév.) Sun ex
C. Y. Wu, M. fargesii and M. henryi, are widespread in areas to the south of the Yangtze River
in China [27,40]. In these southerly areas, Meehania taxa inhabit mesic sheltered microhabitats
within coniferous or mixed evergreen broad-leaved forests in moist alpine areas and along valley streams. The perennial M. cordata (Nutt.) Britt. is endemic to eastern North America, and
ranges from Southwest Pennsylvania in the north to North Carolina in the south, and is found
as far west as southern Illinois. Few mints exhibiting a primarily East Asian-eastern North
American disjunction pattern have been the primary focus of phylogenetic or biogeographic
studies. Thus, Meehania offers an excellent opportunity to study biogeography and diversification of an East Asian/North American disjunct group distributed across the temperate and subtropical regions of two continents.
In order to test the hypothesis of an Arcto-Tertiary origin of Meehania and subsequent migration southward to south-central China and south-eastern North America, we collected accessions of Meehania throughout its range and employed DNA sequence data from both the
nuclear ribosomal and chloroplast genomic regions to address the following specific questions:
(1) Is Meehania monophyletic, and how is it related to Glechoma and other genera of Nepetinae? (2) When and where did Meehania evolve? and (3) what was the likely mechanism or
route that facilitated the East Asian/eastern North American disjunction within the genus?
Materials and Methods
Ethics Statement
The authors have studied herbarium materials from the herbaria KUN and PE. No special permits were required for this study because all samples were collected by researchers with
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
4 / 18
Biogeographical Evolution of Meehania
introduction letters of KIB (Kunming Institute of Botany, Chinese Academy of Sciences) in
Kunming. Voucher specimens were deposited in the Herbarium, Kunming Institute of Botany,
CAS (KUN). The plant materials did not involve endangered or protected species.
Taxon sampling
A total of 19 accessions belonging to 11 of the 12 currently recognized taxa of Meehania were
included in this study (Table 1). Only M. pinfaensis (Levl.) Sun ex C. Y. Wu, a narrow endemic
from Guizhou Province of southwestern China, was not sampled. Our sampling of Meehania
covered the whole geographic range of the genus from southern and northern East Asia and
eastern North America. All samples of Meehania in this study were wild collected and dried
with silica-gel except for two accessions of M. urticifolia obtained from herbarium specimens
(Table 1). As recent phylogenetic studies of Mentheae show that Glechoma is the closest relative to Meehania [34,39], 10 accessions of Glechoma were included in this study (Table 1). Sequences of two Meehania and five Glechoma accessions from GenBank were also included in
our analyses (S1 Appendix).
Based on previous phylogenetic studies of the tribe Mentheae [34,39], Agastache Clayt.,
Cedronella Moench, Dracocephalum, Drepanocaryum Pojark., Hymenocrater Fisch. & C.A.
Mey., Hyssopus L., Lallemantia Fisch. et Mey., Lophanthus Adans., Marmoritis Benth., and
Nepeta L. from subtribe Nepetinae were also included in this study, and Lycopus L. was used as
an outgroup for our phylogenetic analyses.
In addition to the taxon sampling above, we also sampled across the Nepetoideae for our divergence time analyses (see below). Voucher information and GenBank accession numbers for
all specimens used in this study are listed in Table 1, as well as S1 Appendix.
DNA extractions, amplification, and sequencing
Total genomic DNA was isolated from silica gel-dried leaf material using a Universal Genomic
DNA Extraction Kit (Takara, Dalian, China). Five chloroplast (rbcL; the rps16 intron; the
trnL-F region; the rpl32-trnL and psbA-trnH intergenic spacers) and two nuclear ribosomal regions (ITS and ETS) were selected for phylogenetic inference. Primers used for amplification
and sequencing were Z1 and 1204R for rbcL [41], F and 2R for the rps16 intron [42], and tabc
and tabf [43] for the trnL-F region. The rpl32-trnL and psbA-trnH spacers were amplified using
the primers as described by Shaw et al. [44] and Sang et al. [45], respectively. ITS was amplified
and sequenced using the primers ITS1 and ITS4 [46], and ETS was amplified and sequenced as
described in Drew and Sytsma [39]. Amplified DNA samples were analyzed by electrophoresis
on 1.4% agarose gel, run in a 0.5 × TBE buffer and detected by ethidium bromide staining. The
PCR products were then purified using a QiaQuick gel extraction kit (Qiagen, Inc., Valencia,
California, USA) and directly sequenced in both directions using the amplification primers on
an the ABI 3730 automated sequencer (Applied Biosystems, Forster City, California, USA).
Sequence alignment and phylogenetic analyses
DNA Baser v.3 (http://www.DnaBaser.com) was used to evaluate the chromatograms for base
confirmation and to edit contiguous sequences. Multiple-sequence alignment was performed
by MAFFT v.6 [47], using the default alignment parameters followed by manual adjustment in
Se-Al v2.0a11 (http://tree.bio.ed.ac.uk/software/seal/), and gaps were treated as missing data.
Phylogenetic trees were constructed using maximum-parsimony (MP) and Bayesian inference (BI). The MP analyses were conducted using PAUP version 4.0b10 [48]. All characters
were weighted equally and unordered. Most parsimonious trees were searched with a heuristic
algorithm comprising tree bisection-reconnection, branch swapping, MULPARS, and the
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
5 / 18
Biogeographical Evolution of Meehania
Table 1. List of species/taxa with voucher information (Herbarium), location, GenBank accession for sequences of species used in this study.
Taxa
Voucher
ITS
ETS
trnL-F
rpl32-trnL
psbA-trnH
rbcL
rps16
Eriophyton wallichii Bentham
SNJ Exped.
20110814032 (KUN)
KM886719
KM886684
KM886612
KM886814
—
—
—
Glechoma biondiana var.
angustituba C. Y. Wu & C. Chen
D. G. Zhang 4583
(KUN)
KM886720
KM886685
KM886613
KM886815
KM886752
KM886782
KM886652
G. longituba (Nakai) Kuprianova
dt 178 (KUN)
KM886721
KM886686
KM886614
KM886816
KM886753
KM886783
KM886653
G. longituba (Nakai) Kuprianova
T. Deng 415 (KUN)
KM886722
KM886687
KM886615
KM886817
KM886754
KM886784
KM886654
G. longituba (Nakai) Kuprianova
T. Deng 416 (KUN)
KM886723
KM886688
KM886616
KM886818
KM886755
KM886785
KM886655
G. longituba (Nakai) Kuprianova
T. Deng 433 (KUN)
KM886724
KM886689
KM886617
KM886819
KM886756
KM886786
KM886656
G. longituba (Nakai) Kuprianova
dt167 (AJOU)
KM886725
KM886690
KM886618
KM886820
KM886757
KM886787
KM886657
Glechoma biondiana (Diels)
C. Y. Wu & C. Chen
D. G. Zhang 4731
(KUN)
KM886726
KM886691
KM886619
KM886821
KM886758
KM886788
KM886658
Glechoma biondiana (Diels)
C. Y. Wu & C. Chen
SNJ Exped.
20110604058 (KUN)
KM886727
KM886692
KM886620
KM886822
KM886759
KM886789
KM886659
Glechoma biondiana (Diels)
C. Y. Wu & C. Chen
D. G. Zhang 4446
(KUN)
KM886728
KM886693
KM886621
KM886823
KM886760
KM886790
KM886660
Glechoma biondiana (Diels)
C. Y. Wu & C. Chen
D. G. Zhang 6076
(KUN)
KM886729
KM886694
KM886622
KM886824
KM886761
KM886791
KM886661
Hyptis laniflora Benth.
B. Drew 41 (WIS)
—
—
KM886623
KM886825
—
—
—
Isodon dawoensis (Hand.-Mazz.)
H. Hara
Erskine et al., 392
(UC)
—
—
KM886624
KM886826
—
—
—
Lavandula angustifolia Mill.
J. Walker 2565 (WIS)
—
—
KM886625
KM886827
—
—
—
Lycopus cavaleriei H.Lév.
SNJ Exped.
20110807071 (KUN)
KM886730
KM886695
KM886626
KM886828
KM886762
KM886792
KM886662
Marmoritis complanata (Dunn)
A. L. Budantzev
T. Deng 2359 (KUN)
KM886731
KM886696
KM886627
KM886829
KM886763
KM886793
KM886663
Meehania cordata (Nutt.) Britton
dt 101 (KUN)
KM886732
KM886697
KM886628
KM886830
KM886764
KM886794
KM886664
Meehania faberi (Hemsl.) C.Y.Wu
T. Deng 438 (KUN)
KM886733
KM886698
KM886629
KM886831
KM886765
KM886795
KM886665
Meehania fargesii var. fargesii (H.
Léveillé) C. Y. Wu
C. L. Xiang 057
(KUN)
KM886734
KM886699
KM886630
KM886832
KM886766
KM886796
KM886666
Meehania fargesii var. pedunculata
(Hemsley) C. Y. Wu
D. G. Zhang 6091
(KUN)
KM886735
KM886700
KM886631
KM886833
KM886767
KM886797
KM886667
Meehania fargesii var. pedunculata
(Hemsley) C. Y. Wu
D. G. Zhang 6391
(KUN)
KM886736
KM886701
KM886632
KM886834
KM886768
KM886798
KM886668
Meehania fargesii var. pinetorum
(Handel-Mazzetti) C. Y. Wu
C. L.Xiang 056 (KUN)
KM886737
KM886702
KM886633
KM886835
KM886769
KM886799
KM886669
Meehania fargesii var. pinetorum
(Handel-Mazzetti) C. Y. Wu
C. L.Xiang 357 (KUN)
KM886738
KM886703
KM886634
KM886836
KM886770
KM886800
KM886670
Meehania fargesii var. radicans
D. G. Zhang 6502
(KUN)
KM886739
KM886704
KM886635
KM886837
KM886771
KM886801
KM886671
Meehania henryi (Hemsl.)
Y. Z. Sun ex C. Y. Wu
D. G. Zhang 4596
(KUN)
KM886740
KM886705
KM886636
KM886838
—
KM886802
KM886672
Meehania henryi (Hemsl.)
Y. Z. Sun ex C. Y. Wu
D. G. Zhang 6235
(KUN)
—
KM886706
KM886637
KM886839
KM886772
KM886803
KM886673
Meehania henryi (Hemsl.)
Y. Z. Sun ex C.Y.Wu
D. G. Zhang 4606
(KUN)
—
KM886707
KM886638
KM886840
KM886773
KM886804
KM886674
Meehania henryi var. kaitcheensis
(H. Léveillé) C. Y. Wu
D. G. Zhang &L. Xu
109 (KUN)
KM886741
KM886708
KM886639
KM886841
KM886774
KM886805
KM886675
Meehania henryi var. stachydifolia
(H. Léveillé) C. Y. Wu
T. Deng 2358 (KUN)
KM886742
KM886709
KM886640
—
—
KM886806
KM886676
Meehania montis-koyae Ohwi
G. H. Xia 215 (KUN)
KM886743
KM886710
KM886641
KM886842
KM886775
KM886807
KM886677
Meehania montis-koyae Ohwi
T. Deng 2356 (KUN)
KM886744
—
KM886642
—
KM886776
KM886808
KM886678
(Continued)
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
6 / 18
Biogeographical Evolution of Meehania
Table 1. (Continued)
Taxa
Voucher
ITS
ETS
trnL-F
rpl32-trnL
psbA-trnH
rbcL
rps16
Meehania montis-koyae Ohwi
T. Deng 2357 (KUN)
KM886745
KM886711
KM886643
KM886843
KM886777
KM886809
KM886679
Meehania sp.
Qiu & Su 20091002
(KUN)
KM886746
KM886712
KM886644
KM886844
KM886778
KM886810
KM886680
Meehania urticifolia (Miq.) Makino
# 39114 (AJOU)
KM886747
KM886713
KM886645
KM886845
KM886779
KM886811
KM886681
Meehania urticifolia (Miq.) Makino
# 42845 (AJOU)
—
KM886714
—
KM886846
KM886780
KM886812
KM886682
Melissa axillaris (Bentham)
Bakhuizen f.
SNJ Exped.
20110809081 (KUN)
KM886748
KM886715
KM886646
KM886847
—
—
—
Ocimum basilicum L.
J. Walker 2557 (WIS)
—
—
KM886647
KM886848
—
—
—
Plectranthus cremnus B.J. Conn
H. Forbes s.n. (UC)
—
—
KM886648
KM886849
—
—
—
Prunella vulgaris L.
SNJ Exped.
20110719005 (KUN)
KM886749
KM886716
KM886649
KM886850
KM886781
KM886813
KM886683
Salvia maximowicziana Hemsley
SNJ Exped.
20110719092 (KUN)
KM886750
KM886717
KM886650
KM886851
—
—
—
Salvia scapiformis Hance
SNJ Exped.
20110606022 (KUN)
KM886751
KM886718
KM886651
KM886852
—
—
—
doi:10.1371/journal.pone.0117171.t001
alternative character state. A strict consensus tree was constructed from the most parsimonious
trees. Bootstrap analyses (BP; 1000 pseudoreplicates) were conducted to examine the relative
level of support for individual clades on the cladograms of each search [49].
Nucleotide substitution model parameters were determined for cpDNA and nrDNA data
sets using MrModeltest version 2.3 [50,51]. Bayesian inference was conducted using MrBayes
version 3.2.1 [38,52] with the model parameters determined from MrModeltest. For the chloroplast DNA partitions MrModeltest suggested the K81uf+ G (rps16, psbA-trnH and trnL-F)
and TVM+ G (rbcL and rpl32-trnL spacer) models. For the nrDNA partitions, MrModeltest
suggested the TVM+ G model for ETS and GTR+ I+ G for ITS. The Markov chain Monte
Carlo (MCMC) algorithm was run for 3,000,000 generations with one cold and three heated
chains, starting from random trees and sampling one out of every 300 generations. Runs were
repeated twice to test the convergence of the results. The burn-in and convergence diagnostics
were graphically assessed using AWTY [53]. After discarding the trees saved prior to the burnin point (ca. 15%), the remaining trees were imported into PAUP and a 50% majority-rule consensus tree was produced to obtain posterior probabilities (PP) of the clades. The incongruence
length difference (ILD) test [54] was used to evaluate congruence between the chloroplast and
the nuclear data sets. For all ILD tests, 100 replications were performed using PAUP. As the
ILD test (P < 0.01) suggested incongruence between the two data sets, and the topologies also
exhibited discordance, we performed separate analyses for the cpDNA and the nrDNA data.
Divergence time estimation
For our divergence time estimation, we analyzed the Meehania clade within a broad phylogenetic framework of Lamiaceae to enable multiple fossil calibrations. We included 79 taxa from
Nepetoideae in our nrDNA dataset and 74 Nepetoideae taxa for the cpDNA dataset, of which
59 were obtained from GenBank (S1 Appendix). Eriophyton wallichii Benth. from the Lamioideae served as an outgroup.
Like most plant groups, the fossil record of Lamiaceae is fairly sparse [31], but there are several described fossils that are useful for calibration points. Hexacolpate pollen is a synapomorphy for subfamily Nepetoideae [31], but is otherwise very rare within angiosperms. Kar [55]
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
7 / 18
Biogeographical Evolution of Meehania
identified a middle Eocene hexacolpate pollen sample as Ocimum L., which is within the Ocimeae tribe of Nepetoideae. However, based upon the comments of Harley et al. [31], we followed the methodology employed by Drew and Sytsma [34] and placed the fossil calibration at
the crown of Nepetoideae as opposed to elsewhere (crown of the Ocimeae). Following the procedure of Drew and Sytsma [34], for both the nrDNA and cpDNA datasets the Nepetoideae
crown was constrained with a lognormal prior having an offset of 49 million years (Mya), a
mean of 2.6, and a standard deviation (SD) of 0.5. In both datasets we also constrained the
most recent common ancestor of Melissa L. and Lepechinia Willd. with a log-normal distribution having an offset of 28.4 Mya, a mean of 1.5, and a SD of 0.5. The offset was based on a fossil fruit of Melissa from the early-middle Oligocene [56,57]. Additionally, Lepechinia and
Melissa were constrained to be monophyletic in both the nrDNA and cpDNA analyses. To prevent the root of the tree from “running away” [58], the root of both the nrDNA and cpDNA
trees was constrained using a uniform prior distribution with a minimum of 49 Mya and a
maximum of 84 Mya. The maximum age corresponded to the upper age estimate (from the
95% HPD) obtained for the family Lamiaceae in Drew and Sytsma [34]. Since the oldest crown
date for the order Lamiales is 107 Mya [34,59], and the Lamiaceae is nested deeply within the
Lamiales, the 84 Mya maximum age for Lamiaceae used here is conservative.
Bayesian dating based on a relaxed-clock model [60] was used to estimate the divergence
times of the main clades in Meehania using the program BEAST version 1.8.0 [61]. BEAST employs a Bayesian MCMC approach to co-estimate topology, substitution rates and node ages
[62]. Based on the results from Modeltest, the nrDNA analyses were performed using the GTR
model of nucleotide substitution with a G and invariant sites distribution with six rate categories, while for the cpDNA data the TVM + G model was employed. The tree prior model (Yule)
was implemented in the analysis, with rate variation across branches assumed to be uncorrelated and lognormally distributed [60]. Posterior distributions of parameters were approximated
using two independent MCMC analyses of 30,000,000 generations (sampling once every 5000
generations). Samples from the two chains, which yielded similar results, were combined after
a 10% burn-in for each. Convergence of the chains was checked using the program Tracer 1.5
[63], and the effective sample size (ESS) was well over 200 for all categories.
Biogeographic analyses
Analysis of potential ancestral distribution areas of clades and taxa in Meehania was conducted
using RASP 2.1b [64], which implements the S-DIVA (statistical dispersal-vicariance analysis)
method [65]. The input file for RASP consisted of the 10,800 post-burn-in trees from our
nrDNA BEAST analyses. Three areas of endemism were defined for the biogeographical analysis based on the extant distribution of the genus and the geological history: A, northeastern
Asia; B, southeastern Asia; C, eastern North America. Because there were no species in our
studied taxa distributed in more than two areas, the maximum range size was constrained to
2 in our analyses.
Results
Phylogenetic analyses
The combined nrDNA data matrix had 1144 characters, 519 of which were variable and 339
were potentially parsimony-informative. The parsimony strict consensus tree was largely congruent with the Bayesian consensus tree, especially concerning the backbone of the Meehania
phylogeny. The Bayesian consensus tree with PP and BP values is shown in Fig. 1 (right). The
combined chloroplast DNA (rbcL, rps16, trnL-F, rpl32-trnL and psbA-trnH) matrix consisted
4727 of characters, of which 914 were variable and 426 potentially parsimony-informative.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
8 / 18
Biogeographical Evolution of Meehania
Topologies from the parsimony strict consensus tree and the Bayesian tree are largely congruent, and the Bayesian tree with PP value and BP support is shown in Fig. 1 (left).
Phylogenetic analysis based on the nrDNA data supported the monophyly of Meehania
(Fig. 1). In the nrDNA tree, all Glechoma taxa formed a clade sister to a clade of Meehania species with strong support (Fig. 1, BP = 100, PP = 1.00). By contrast, in the cpDNA tree, Glechoma was nested within (instead of sister to) the Meehania clade, and was sister to the
southeastern Asian Meehania clade, but this relationship received weak Bayesian support
(PP = 0.67) and no parsimony support (Fig. 1).
Within Meehania, four lineages were well recognized in both the nuclear and chloroplast
datasets: M. cordata (North America), M. montis-koyae (Japan and East China), the M. urticifolia (Northeast Asia), and a clade including the remaining species from southeastern Asia.
The phylogenies resulting from the cpDNA analysis showed that M. montis-koyae diverged
first, whereas in the nuclear data analysis, M. cordata was the first-diverging lineage. Both nuclear and chloroplast results indicated phylogenetic relationships among M. henryi, M. fargesii,
and M. faberi are uncertain.
Biogeographic analysis
The chronogram and results of divergence-time estimation based on the nrDNA are shown in
Fig. 2. The divergence age between Meehania and its sister Glechoma was estimated at 11.88
Mya with 95% highest posterior density (HPD) of 8.40–16.10 Mya (node 1, Fig. 2). The crown
age of Meehania (node 2, Fig. 2), indicating the disjunction of Meehania between eastern Asia
and North America, was estimated at 9.81 Mya in the Miocene (95% HPD 6.70–13.07 Mya).
The split between the southeastern Asian Meehania lineage from its northern relatives (node 3,
Fig. 2) was estimated at 6.12 Mya (95%HPD: 4.17–8.67 Mya). Divergence time estimates based
on the cpDNA generated very similar divergence time as those from nrDNA. The crown age of
Meehania (including Glechoma) was estimated to be 11.7 Mya (95%HPD: 7.69–16.72; S1 Fig.).
The disjunction between eastern North American M. cordata and eastern Asian species was estimated to be 7.58 Mya (95%HPD: 4.90–10.86; S1 Fig.).
In Fig. 3 we illustrate the results obtained from S-DIVA, as well as migration or dispersal
routes. The results of the biogeographic inference indicated that the crown node of Meehania
unequivocally originated in the northern part of eastern Asia. Following the crown divergence,
the genus was found to have had two diversification routes: one is an early split from northeastern Asia to eastern North America between M. cordata and the remaining Meehania species;
another is a north to south migration within eastern Asia (Fig. 3).
Discussion
A reticulate evolutionary history of Meehania-Glechoma with chloroplast
capture
The chloroplast and nuclear phylogenetic analyses produced conflicting results with respect to
generic relationships in the subtribe Nepetinae (Fig. 1). The most striking difference between
the two topologies is in the position of Glechoma and Meehania cordata. In the chloroplast
DNA tree, species of Glechoma formed a well-supported clade embedded within Meehania
(Fig. 1; BP = 78, PP = 1.0), and sister to the south clade (Fig. 1; PP = 0.66), the pattern found
also by Drew and Sytsma [34,39] using chloroplast data and limited sampling of these two genera. In contrast, the nuclear topology clustered all members of Meehania as a single moderately-supported clade (Fig. 1; BP = 56, PP = 0.98) and separated the Glechoma clade from
Meehania with high support (Fig. 1; BP = 100, PP = 1.0).
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
9 / 18
Biogeographical Evolution of Meehania
Fig 2. The results of BEAST analysis based on combined nrITS and nrETS data. Gray bars represent the 95% highest posterior density intervals for
node ages. Numerals 1–3 are nodes of interests as discussed in the text, and fossil calibrations are marked with black stars.
doi:10.1371/journal.pone.0117171.g002
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
10 / 18
Biogeographical Evolution of Meehania
Fig 3. The results of RASP ancestral area reconstruction analysis based on combined nrITS and nrETS data. Three areas of endemism are defined:
A (green), north of eastern Asia; B (yellow), south of eastern Asia; C (red), eastern North America. Pie charts show probabilities of ancestral
area reconstructions.
doi:10.1371/journal.pone.0117171.g003
Discordance between nuclear and cytoplasmic data is common in plants [66–69]. One possible explanation for the conflicts has invoked introgression of the cytoplasmic genome from
one species into the nuclear background of another (or vice versa) by interspecific hybridization [67,70], in which case the incongruent trees represent the different histories of cp- and
nrDNA. Another possible cause is intra-individual polymorphism of nrDNA, which may arise
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
11 / 18
Biogeographical Evolution of Meehania
through incomplete concerted evolution, and can cause paralogy problems or incomplete lineage sorting of nrDNA [71].
Morphological data can often be employed in explaining the conflicts between nrDNA and
cpDNA topologies [72,73]. The morphological evidence from Meehania and Glechoma is congruent with their phylogenetic relationships based on the nuclear data. Numerous morphological synapomorphies support Glechoma as a separate genus distinguished from Meehania in
having small flowers (ca. 1–2.5 cm long) in the axils of the middle and upper leaves, an indistinctly 2-lipped calyx, and anther-thecae divaricate at 90° [27, 30]. Since the chloroplast-based
phylogeny does not accurately reflect their morphological relationships, the discordance between nrDNA and chloroplast data may be explained by chloroplast capture [66,74]. This inference is common for the mint family [35,72,75], and is specifically shown in such genera as
Phlomis L. [76], Sideritis L. [77], Bystropogon L’Hér. [72], Chelonopsis Miq. [78], Conradina
A. Gray [79,80], Dicerandra Benth. [81] and Mentha L. [82]. Ancient hybridizations with chloroplast introgression may have occurred among ancestors of these isolated taxa.
Phylogenetic relationships
Based on nrDNA results, two well-supported lineages were recognized within Meehania: one
clade consists of the single species from eastern North America and the other contains all eastern Asian taxa (Fig. 1). Within the eastern Asian group, the geographically isolated M. montiskoyae is sister to the remaining species. Meehania montis-koyae is endemic to Japan and
known only from the type locality in Mt. Koya in Kii Peninsula, Wakayama Prefecture. A suite
of morphological characters found in M. montis-koyae, such as an erect and herbaceous habit,
a height of 10–20 cm, abaxial leaves purple, a violet tubular calyx, and an arrangement of flowers in axillary pairs are quite unique within Meehania. Recently, Xia and Li [83] reported that
M. montis-koyae is also found in eastern China and occurs on slopes within or at the edge of
mixed forests. This plant was previously unknown from China and bridges the two distribution
areas between China and Japan. The M. montis-koyae individual from China is closely related
to the two Japanese individuals as inferred by our molecular data with high support (Fig. 1; BP
= 100, PP = 1.0). The current disjunction of M. montis-koyae between eastern China and Japan
might be remant populations left over from a previously existing continuous distribution.
Except for Meehania montis-koyae and M. urticifolia, all the species from southeastern Asia
form a well-supported south clade (Fig. 1; BP = 80, PP = 1.0). Phylogenetic relationships of the
three species complexes among the south clade remained unresolved (Fig. 1), possibly due to
the recent evolutionary radiation of this group. However, taxa from this clade exhibit a wide
range of morphological and ecological variations. Meehania faberi is a distinct species based on
its annual life history, morphological traits such as ovate and fleshy leaves and short inflorescences, and a geographically isolated distribution [27]. The two geographically widespread species complexes, Meehania henryi and M. fargesii, were found to be polyphyletic (Fig. 1). The
Meehania henryi complex is endemic to a small area of Central China and is characterized by
an erect habit, a height of ca. 30–60 cm, large leaves, a narrowly tubular calyx, and verticillasters in terminal and lateral racemes [27,40]. The Meehania fargesii complex is characterized
by having slender stems, a prostrate or stoloniferous habit, a height of 10–20 cm, a tubular
calyx, and 2-flowered verticillasters inserted in the leaf axils of the upper 2 or 3 leaf pairs of the
stem [27,40]. Subtle differences in verticillaster flower number, stem branching pattern and
leaf shape were used previously to delimit subspecies within the complex [27]. Ecologically, the
M. henryi complex is distributed in evergreen broad-leaved and mixed forests from 300–700 m
in elevation, whereas the M. fargesii complex is distributed from temperate mixed forests to coniferous forests at a higher elevation from 700 to 3500 m.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
12 / 18
Biogeographical Evolution of Meehania
Historical biogeography and divergence times
Glechoma, the sister group of Meehania, occurs in north temperate areas in Eurasia, and the
basal lineages of Meehania (M. montis-koyae and M. urticifolia) are also largely restricted to
northeastern Asia (i.e., Japan, East China, and South Korea) [27,28], making the high latitude
area of Eurasia a plausible ancestral area for Meehania (Fig. 3). Ancestral area reconstruction
with RASP based on our nrDNA phylogeny supported this view, suggesting a Meehania origin
in the high latitude area of Eurasia, especially northeastern Asia (Fig. 3). This evidence agrees
well with the Arcto-Tertiary origin hypotheses, which has been extensively documented
[18,84,85]. Subsequently, the decrease of annual mean temperature at northern latitudes provided opportunities for biota dispersal and subdivision [86]. The present distribution of Meehania in eastern North America and northeastern and southeastern Asia could result from
vicariance of south-migrating populations during climatic oscillation and further fragmentation and dispersal of these populations. This inference is robustly supported by our molecular
phylogenetic results, viz. a sister relationship between North American M. cordata and the
clade of East Asian Meehania (the latter comprising the two subclades within this area; Fig. 1).
Similar cases are found in Astilbe Buch.-Ham. ex D. Don, Cedrus Trew, Maianthemum Web.
and Triosteum L. in which the southeastern Asian species were found to have their origin in
Arcto-Tertiary geofloras [7,17,87,88]. Zhu et al. [7] suggested Astilbe had its origin in Japan
and subsequently migrated independently to eastern North America, continental Asia, and
even to southeastern Asian islands. Based on fossils and molecular data, Qiao et al. [88] suggested an origin of Cedrus in high latitudes of Eurasia, and its present distribution in the Mediterranean and Himalayas could result from vicariance of a southward migration during
climatic oscillations in the Tertiary.
The estimated divergence times between the Meehania lineages from isolated regions
completely overlap the timing of Miocene cooling and drying. In the Miocene, a significant
global cooling transition occurred at approximately 15–10 Mya [89–91]. This cooling event
was proposed to cause southward invasions and displacements of organisms [92]. As a result,
four Meehania species occur today in the southernmost areas of eastern Asia (Fig. 3). We estimated the divergence of the southern clade (between the northern M. urticifolia and other
southern Asian taxa) at 4.17–8.67 Mya in the late Miocene. Another Miocene climate change
emphasized by Savage [92] caused enhanced aridity at middle latitudes of the Northern Hemisphere. In the interior of Eurasia, a drying event occurred at about 8–7 Mya [93,94] that may
have caused isolation between Meehania in northern and southern East Asia. Extant M. urticifolia and M. montis-koyae show preferences to cool and moist habitats [27,95], and are probably relicts that previously inhabited northern regions. This distribution pattern has also been
reported for other taxa, such as Parthenocissus Planch. [96], Mitchella L. [8] and Astilbe Buch.Ham. ex D. Don [7].
The ancestor of eastern North American Meehania might have reached North America in
the late Miocene, which is supported by our estimation of ca. 9.81 Mya for the divergence between the North American M. cordata and the East Asian clade (Fig. 2). The North Atlantic
land bridge, which largely contributed to the dispersal of more tropical elements, ceased to
exist in the middle Miocene [13], and was apparently less suitable for Meehania interchange.
We favor a hypothesis based on a migration scenario across the Bering land bridge in the late
Miocene. North America and Asia were repeatedly connected via the Bering Bridge, with biotic
interchange moderated mainly by climatic factors [97]. The Bering land bridge supported exchanges of temperate floras [3], but was ultimately disrupted by a sharp decrease in average
temperatures from the Oligocene to the present [91]. In the late Miocene and Pliocene, the
colder climate restricted Beringian interchange to mostly cold-adapted species. Decreasing
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
13 / 18
Biogeographical Evolution of Meehania
temperatures could have prohibited subsequent interchange of warm adapted taxa, including
Meehania, between eastern Asia and eastern North America.
Meehania, like other taxa from tribe Mentheae, possess mericarps for dispersal. The dispersal ability of these nutlets is usually limited (reviewed by [56,98]), and long distance dispersal
between Asia and North America in Meehania is highly unlikely. Consequently, as a result of
geographic and ecological isolation, diverged Meehania lineages likely formed within each
aforementioned isolated region after these climatic change events. These results suggest that vicariance played an important role in the evolution of herbaceous plants between eastern Asia
and North America.
Conclusions
Two important conclusions stem from this study. First, we show that Arctic latitudes were a
major center of origin for taxa currently occurring in East Asia and elsewhere in the North
Hemisphere. Secondly, the current disjunct distribution of some herbs with a putative ArctoTertiary origin is probably a result of vicariance and subsequent southward migration of populations during climatic oscillations in the middle Miocene with subsequent migration into eastern North America via the Bering land bridge in the late Miocene.
Supporting Information
S1 Fig. BEAST chronogram based on trnL-F and trnL-rpl32 data. Gray bars represent the
95% highest posterior density intervals for node ages.
(TIF)
S1 Appendix. List of taxa with accession numbers obtained from GenBank.
(DOC)
Acknowledgments
We thank Daigui Zhang, Xiaojie Li and Guohua Xia for collecting leaf materials. We also appreciate Prof. Philip Cantino and Prof. Jin Murata for providing some DNA samples. The
study represents part of Tao Deng’s dissertation research.
Author Contributions
Conceived and designed the experiments: HS TD YHW. Performed the experiments: TD CK.
Analyzed the data: TD ZLN BTD. Contributed reagents/materials/analysis tools: CLX JWZ
TD. Wrote the paper: TD HS SV. Revised the draft: SV BTD CLX.
References
1.
Thorne RF (1972) Major disjunctions in the geographic ranges of seed plants. The Quarterly Review of
Biology 47: 365–411.
2.
Tiffney BH (2008) Phylogeography, fossils, and Northern Hemisphere biogeography: The role of physiological uniformitarianism. Annals of the Missouri Botanical Garden 95: 135–143.
3.
Wen J (1999) Evolution of eastern Asian and eastern North American disjunct distributions in flowering
plants. Annual Review of Ecology and Systematics 30: 421–455.
4.
Donoghue MJ, Smith SA (2004) Patterns in the assembly of temperate forests around the Northern
Hemisphere. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences
359: 1633–1644. PMID: 15519978
5.
Wen J, Xiang QY, Qian H, Li JH, Wang XQ, et al. (2009) Intercontinental and intracontinental biogeography-patterns and methods. Journal of Systematics and Evolution 47: 327–329.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
14 / 18
Biogeographical Evolution of Meehania
6.
Wen J, Ickert-Bond SM, Nie ZL, Li R (2010) Timing and modes of evolution of eastern Asian—North
American biogeographic disjunctions in seed plants. In: Long M, Gu H, Zhou Z, editors. Darwin’s Heritage Today: Proceedings of the Darwin 200 Beijing International Conference. Beijing: Higher Education Press. pp. 252–269. doi: 10.1136/bmjopen-2014-007247 PMID: 25596202
7.
Zhu WD, Nie ZL, Wen J, Sun H (2013) Molecular phylogeny and biogeography of Astilbe (Saxifragaceae) in Asia and eastern North America. Botanical Journal of the Linnean Society 171: 377–394.
8.
Huang WP, Sun H, Deng T, Razafimandimbison SG, Nie ZL, et al. (2013) Molecular phylogenetics and
biogeography of the eastern Asian—eastern North American disjunct Mitchella and its close relative
Damnacanthus (Rubiaceae, Mitchelleae). Botanical Journal of the Linnean Society 171: 395–412.
9.
Nie ZL, Wen J, Sun H, Bartholomew B (2005) Monophyly of Kelloggia Torrey ex Benth.(Rubiaceae)
and evolution of its intercontinental disjunction between western North America and eastern Asia.
American Journal of Botany 92: 642–652. doi: 10.3732/ajb.92.4.642 PMID: 21652442
10.
Xu X, Walters C, Antolin MF, Alexander ML, Lutz S, et al. (2010) Phylogeny and biogeography of the
eastern Asian—North American disjunct wild-rice genus (Zizania L., Poaceae). Molecular Phylogenetics and Evolution 55: 1008–1017. doi: 10.1016/j.ympev.2009.11.018 PMID: 19944174
11.
Xie L, Wagner WL, Ree RH, Berry PE, Wen J (2009) Molecular phylogeny, divergence time estimates,
and historical biogeography of Circaea (Onagraceae) in the Northern Hemisphere. Molecular Phylogenetics and Evolution 53: 995–1009. doi: 10.1016/j.ympev.2009.09.009 PMID: 19751838
12.
Tiffney BH (1985) Perspectives on the origin of the floristic similarity between eastern Asia and eastern
North America. Journal of the Arnold Arboretum 66: 73–94.
13.
Tiffney BH, Manchester SR (2001) The use of geological and paleontological evidence in evaluating
plant phylogeographic hypotheses in the Northern Hemisphere Tertiary. International Journal of Plant
Sciences 162: S3–S17.
14.
Milne RI, Abbott RJ (2002) The origin and evolution of tertiary relict floras. Advances in Botanical Research 38: 281–314.
15.
Xiang Q-Y, Soltis DE, Soltis PS, Manchester SR, Crawford DJ (2000) Timing the eastern Asian-Eastern
North American floristic disjunction: molecular clock corroborates paleontological estimates. Molecular
Phylogenetics and Evolution 15: 462–472. PMID: 10860654
16.
Sun H (2002) Evolution of Arctic-Tertiary flora in Himalayan-Hengduan mountains. Acta Botanica Yunnanica 24: 671–688.
17.
Gould KR, Donoghue MJ (2000) Phylogeny and biogeography of Triosteum (Caprifoliaceae). Harvard
Papers in Botany 5: 157–166.
18.
Mai DH (1991) Palaeofloristic change in Europe and the confirmation of Arctotertiary-Palaeotropical
geofloral concept. Review of Palaeobotany and Palynology 68: 29–36.
19.
Chaney RW (1947) Tertiary centers and migration routes. Ecological Monographs 17: 139–148.
20.
Sakai A (1971) Freezing resistance of relicts from Arcto-Tertiary Flora. New Phytologist 70:
1199–1205.
21.
Hopkins D (1967) The Bering land bridge. Palo Alto: Stanford University Press.
22.
McKenna MC (1983) Holarctic landmass rearrangement, cosmic events, and cenozoic terrestrial organisms. Annals of the Missouri Botanical Garden 70: 459–489.
23.
Tiffney BH (1985) The Eocene North Atlantic land bridge: its importance in tertiary and modern phytogeography of the Northern Hemisphere. Journal of the Arnold Arboretum 66: 243–273.
24.
Budantsev LY (1992) Early stages of formation and dispersal of the temperate flora in the Boreal region.
Botanical Review 58: 1–48.
25.
Wolfe JA (1975) Some aspects of plant geography of the Northern Hemisphere during the late Cretaceous and Tertiary. Annals of the Missouri Botanical Garden 62: 264–279.
26.
Baird KE, Funk VA, Wen J, Weeks A (2010) Molecular phylogenetic analysis of Leibnitzia Cass. (Asteraceae: Mutisieae: Gerbera-complex), an Asian-North American disjunct genus. Journal of Systematics
and Evolution 48: 161–174.
27.
Li XW, Hedge IC (1994) Meehania Britton. In: Wu ZY, Raven PH, editors. Flora of China. Beijing/
St. Louis: Science Press/ Missouri Botanical Garden. pp. 122–124.
28.
Murata G, Yamazaki T (1993) Meehania Britton. In: Iwatsuki K, Yamazaki T, Boufford DE, Ohba H, editors. Flora of Japan. Tokyo: Kodansha. pp. 289–290.
29.
Wu CY, Li HW (1977) Meehania. In: Wu CY, Li XW, editors. Flora Reipublicae Popularis Sinicae. Beijing: Science Press. pp. 334–344.
30.
Funamoto T, Tanabe T, Nakamura T (2000) A karyomorphological comparison of two species of Japanese Meehania, Lamiaceae (Labiatae). Chromosome Research: 107–109.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
15 / 18
Biogeographical Evolution of Meehania
31.
Harley RM, Atkins S, Budantsev AL, Cantino PD, Conn BJ, et al. (2004) Labiatae. In: Kubitzki K, editor.
The Families and Genera of Vasular Plants. Berlin: Springer. pp. 167–275.
32.
Agostini G, Echeverrigaray S, Souza-Chies TT (2012) A preliminary phylogeny of the genus Cunila
D. Royen ex L. (Lamiaceae) based on ITS rDNA and trnL-F regions. Molecular Phylogenetics and Evolution 65: 739–747. doi: 10.1016/j.ympev.2012.07.030 PMID: 22877642
33.
Conn BJ, Streiber N, Brown EA, Heywood MJ, Olmstead RG (2009) Infrageneric phylogeny of
Chloantheae (Lamiaceae) based on chloroplast ndhF and nuclear ITS sequence data. Australian Journal of Botany 22: 243–256.
34.
Drew BT, Sytsma KJ (2012) Phylogenetics, biogeography, and staminal evolution in the tribe Mentheae
(Lamiaceae). American Journal of Botany 99: 933–953. doi: 10.3732/ajb.1100549 PMID: 22539517
35.
Drew BT, Sytsma KJ (2013) The South American radiation of Lepechinia (Lamiaceae): phylogenetics,
divergence times and evolution of dioecy. Botanical Journal of the Linnean Society 171: 171–190.
36.
Lindqvist C, Scheen AC, Bendiksby M, Ryding O, Mathiesen C, et al. (2010) Molecular phylogenetics,
character evolution, and suprageneric classification of Lamioideae (Lamiaceae). Annals of the Missouri
Botanical Garden 97: 191–217.
37.
Ryding O (2007) Amount of calyx fibers in Lamiaceae, relation to calyx structure, phylogeny and ecology. Plant Systematics and Evolution 268: 45–58.
38.
Ronquist F, Huelsenbeck JP (2003) MRBAYES 3: Bayesian phylogenetic inference under mixed models. Bioinformatics 19: 1572–1574. PMID: 12912839
39.
Drew BT, Sytsma KJ (2011) Testing the monophyly and placement of Lepechinia in the tribe Mentheae
(Lamiaceae). Systematic Botany 36: 1038–1049.
40.
Wu CY (1959) Revisio Labiatarum sinensium. Acta Phytotaxonomica Sinica 8: 3–20.
41.
Zurawski G, Perrot B, Bottomley W, Paul RW (1981) The structure of the gene for the large subunit of
ribulose 1,5-bisphosphate carboxylase from spinach chloroplast DNA. Nucleic Acids Research 9:
3251–3270. PMID: 6269077
42.
Oxelman B, Liden M, Berglund D (1997) Chloroplast rps16 intron phylogeny of the tribe Sileneae
(Caryophyllaceae). Plant Systematics and Evolution 206: 393–410.
43.
Taberlet P, Gielly L, Pautou G, Bouvet J (1991) Universal primers for amplification of three non-coding
regions of chloroplast DNA. Plant Molecular Biology 17: 1105–1109. PMID: 1932684
44.
Shaw J, Lickey EB, Schilling EE, Small RL (2007) Comparison of whole chloroplast genome sequences
to choose noncoding regions for phylogenetic studies in angiosperms: The tortoise and the hare III.
American Journal of Botany 94: 275–288. doi: 10.3732/ajb.94.3.275 PMID: 21636401
45.
Sang T, Crawford DJ, Stuessy TF (1997) Chloroplast DNA phylogeny, reticulate evolution, and biogeography of Paeonia (Paeoniaceae). American Journal of Botany 84: 1120–1136. PMID: 21708667
46.
White TJ, Bruns T, Lee S, Taylor J (1990) Amplification and direct sequencing of fungal ribosomal RNA
genes for phylogenetics. In: Innis MA, Gelfand DH, Shinsky JJ, White TJ, editors. PCR Protocols: A
Guide to Methods and Applications. San Diego: Academic Press. pp. 315–322.
47.
Katoh K, Toh H (2008) Recent developments in the MAFFT multiple sequence alignment program.
Briefings in Bioinformatics 9: 286–298. doi: 10.1093/bib/bbn013 PMID: 18372315
48.
Swofford DL (2002) PAUP*: Phylogenetic analysis using parsimony (*and other methods), version
4.0b10. Sunderland, Massachusetts: Sinauer Associates.
49.
Felsenstein J (1985) Confidence limits on phylogenies: an approach using the bootstrap. Evolution 39:
783–791.
50.
Nylander JAA (2004) MrModeltest V2.3 Program distributed by the author, Evolutionary Biology Centre, Uppsala University. PMID: 25057686
51.
Posada D, Buckley TR (2004) Model selection and model averaging in phylogenetics: advantages of
the AIC and Bayesian approaches over likelihood ratio tests. Systematic Biology 53: 793–808. PMID:
15545256
52.
Huelsenbeck JP, Ronquist F (2001) MRBAYES: Bayesian inference of phylogeny. Bioinformatics 17:
754–755. PMID: 11524383
53.
Nylander JAA, Olsson U, Alstrom P, Sanmartin I (2008) Accounting for phylogenetic uncertainty in biogeography: a Bayesian approach to dispersal-vicariance analysis of the thrushes (Aves: Turdus). Systematic Biology 57: 257–268. doi: 10.1080/10635150802044003 PMID: 18425716
54.
Farris JS, Källersjö M, Kluge AG, Bult C (1994) Testing significance of incongruence. Cladistics 10:
315–319.
55.
Kar RK (1996) On the Indian origin of Ocimum (Lamiaceae): A palynological approach. Palaeobotanist
43.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
16 / 18
Biogeographical Evolution of Meehania
56.
Martinez-Millan M (2010) Fossil record and age of the Asteridae. Botanical Review 76: 83–135.
57.
Reid EM, Chandler MEJ (1926) Catalogue of Cainzoic plants in the department of geology. The Brembridge flora. London: British Museum (Natural History).
58.
Sytsma KJ, Spalink D, Berger B (2014) Calibrated chronograms, fossils, outgroup relationships, and
root priors: re-examining the historical biogeography of Geraniales. Biological Journal of the Linnean
Society In Press.
59.
Janssens SB, Knox EB, Huysmans S, Smets EF, Merckx VSFT (2009) Rapid radiation of Impatiens
(Balsaminaceae) during Pliocene and Pleistocene: Result of a global climate change. Molecular Phylogenetics and Evolution 52: 806–824. doi: 10.1016/j.ympev.2009.04.013 PMID: 19398024
60.
Drummond AJ, Ho SY, Phillips MJ, Rambaut A (2006) Relaxed phylogenetics and dating with confidence. PLoS Biology 4: e88. PMID: 16683862
61.
Drummond AJ, Rambaut A (2007) BEAST: Bayesian evolutionary analysis by sampling trees. BMC
Evolutionary Biology 7: 214. PMID: 17996036
62.
Drummond AJ, Nicholls GK, Rodrigo AG, Solomon W (2002) Estimating mutation parameters, population history and genealogy simultaneously from temporally spaced sequence data. Genetics 161:
1307–1320. PMID: 12136032
63.
Rambaut A, Drummond AJ (2007) Tracer v1.4, Available from http://beast.bio.ed.ac.uk/Tracer.
64.
Yu Y, Harris AJ, He XJ (2013) RASP (Reconstruct Ancestral State in Phylogenies) 2.1 beta. Available
at http://mnhscueducn/soft/blog/RASP. doi: 10.1007/s13197-013-0993-z PMID: 25593984
65.
Yu Y, Harris AJ, He X (2010) S-DIVA (Statistical Dispersal-Vicariance Analysis): A tool for inferring biogeographic histories. Molecular Phylogenetics and Evolution 56: 848–850. doi: 10.1016/j.ympev.2010.
04.011 PMID: 20399277
66.
Rieseberg LH, Soltis DE (1991) Phylogenetic consequences of cytoplasmic gene flow in plants. Evolutionary Trends in P1ants. 5: 65–84.
67.
Soltis DE, Kuzoff RK (1995) Discordance between nuclear and chloroplast phylogenies in the Heuchera group (Saxifragaceae). Evolution 49: 727–742.
68.
Guo YP, Ehrendorfer F, Samuel R (2004) Phylogeny and systematics of Achillea (AsteraceaeAnthemideae) inferred from nrITS and plastid trnL-F DNA sequences. Taxon 53: 657–672.
69.
Fehrer J, Gmeinholzer B, Chrtek J Jr., Bräutigam S (2007) Incongruent plastid and nuclear DNA phylogenies reveal ancient intergeneric hybridization in Pilosella hawkweeds (Hieracium, Cichorieae,
Asteraceae). Molecular Phylogenetics and Evolution 42: 347–361. PMID: 16949310
70.
Wendel JF, Doyle JJ (1998) Phylogenetic incongruence: window into genome history and molecular
evolution. Molecular systematics of plants II: Springer. pp. 265–296.
71.
Guggisberg A, Mansion G, Conti E (2009) Disentangling reticulate evolution in an arctic—alpine polyploid complex. Systematic Biology: syp010.
72.
Trusty JL, Olmstead RG, Bogler DJ, Santos-Guerra A, Francisco-Ortega J (2004) Using molecular data
to test a biogeographic connection of the macaronesian genus Bystropogon (Lamiaceae) to the New
World: A case of conflicting phylogenies. Systematic Botany 29: 702–715.
73.
Yuan YW, Olmstead RG (2008) A species-level phylogenetic study of the Verbena complex (Verbenaceae) indicates two independent intergeneric chloroplast transfers. Molecular Phylogenetics and Evolution 48: 23–33. doi: 10.1016/j.ympev.2008.04.004 PMID: 18495498
74.
Soltis DE, Johnson LA, Looney C (1996) Discordance between ITS and chloroplast topologies in the
Boykinia group (Saxifragaceae). Systematic Botany 21: 169–185.
75.
Moon HK, Smets E, Huysmans S (2010) Phylogeny of tribe Mentheae (Lamiaceae): The story of molecules and micromorphological characters. Taxon 59: 1065–1076. doi: 10.1016/j.metabol.2009.11.003
PMID: 20045154
76.
Albaladejo RG, Aguilar JF, Aparicio A, Feliner GN (2005) Contrasting nuclear-plastidial phylogenetic
patterns in the recently diverged Iberian Phlomis crinita and P. lychnitis lineages (Lamiaceae). Taxon
54: 987–998.
77.
Barber JC, Finch CC, Francisco-Ortega J, Santos-Guerra A, Jansen RK (2007) Hybridization in Macaronesian Sideritis (Lamiaceae): evidence from incongruence of multiple independent nuclear and chloroplast sequence datasets. Taxon 56: 74–88.
78.
Xiang C-L, Zhang Q, Scheen A-C, Cantino PD, Funamoto T, et al. (2013) Molecular phylogenetics of
Chelonopsis (Lamiaceae: Gomphostemmateae) as inferred from nuclear and plastid DNA and morphology. Taxon 62: 375–386.
79.
Edwards CE, Soltis DE, Soltis PS (2006) Molecular phylogeny of Conradina and other scrub mints
(Lamiaceae) from the southeastern USA: Evidence for hybridization in Pleistocene refugia? Systematic
Botany 31: 193–207.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
17 / 18
Biogeographical Evolution of Meehania
80.
Edwards CE, Lefkowitz D, Soltis DE, Soltis PS (2008) Phylogeny of Conradina and related southeastern scrub mints (Lamiaceae) based on GapC gene sequences. International Journal of Plant Sciences
169: 579–594.
81.
Oliveira LO, Huck RB, Gitzendanner MA, Judd WS, Soltis DE, et al. (2007) Molecular phylogeny, biogeography, and systematics of Dicerandra (Lamiaceae), a genus endemic to the southeastern United
States. American Journal of Botany 94: 1017–1027. doi: 10.3732/ajb.94.6.1017 PMID: 21636471
82.
Gobert V, Moja S, Taberlet P, Wink M (2006) Heterogeneity of three molecular data partition phylogenies of mints related to M. x piperita (Mentha; Lamiaceae). Plant Biology 8: 470–485 PMID: 16917980
83.
Xia G-H, Li G-Y (2011) Meehania montis-koyae, a new record of Lamiaceae from China. Guihaia 31:
581–583.
84.
Chaney RW (1947) Tertiary centers and migration routes. Ecological Monographs 17: 139–148.
85.
Takhtajan A (1969) Flowering plants origin and dispersal. Edinburgh: Oliver & Boyd.
86.
Manchester SR, Tiffney BH (2001) Integration of paleobotanical and neobotanical data in the assessment of phytogeographic history of holarctic angiosperm clades. International Journal of Plant Sciences
162: S19–S27.
87.
Meng Y, Wen J, Nie Z-L, Sun H, Yang YP (2008) Phylogeny and biogeographic diversification of
Maianthemum (Ruscaceae: Polygonatae). Molecular Phylogenetic and Evolution 49: 424–434. doi:
10.1016/j.ympev.2008.07.017 PMID: 18722539
88.
Chen CH, Huang JP, Tsai CC, Chaw SM (2009) Phylogeny of Calocedrus (Cupressaceae), an eastern
Asian and western North American disjunct gymnosperm genus, inferred from nuclear ribosomal nrITS
sequences. Botanical Studies 50: 425–433.
89.
Douglas RG, Woodruff F (1981) Deep sea benthic foraminifera. In: Emiliani C, editor. The Sea The
Oceanic Lithosphere. New York: Wiley-Interscience. pp. 1233–1327.
90.
Haq BU, Hardenbol J, Vail PR (1987) Chronology of fluctuating sea levels since the Triassic. Science
235: 1156–1167. PMID: 17818978
91.
Zachos J, Pagani M, Sloan L, Thomas E, Billups K (2001) Trends, rhythms, and aberrations in global
climate 65 Ma to present. Science 292: 686–693. PMID: 11326091
92.
Savage JM (1973) The geographic distribution of frogs: patterns and predictions. In: Vial JL, editor.
Evolutionary Biology of the Anurans. Columbia: University of Missouri Press. pp. 351–445.
93.
An Z, John EK, Warrwn LP, Stephen CP (2001) Evolution of Asian monsoons and phased uplift of the
Himalayan-Tibetan plateau since Late Miocene times. Nature 411: 62–66. PMID: 11333976
94.
An Z, Zhang P, Wang E, Wang S, Qiang X, et al. (2006) Changes of the monsoon-arid environment in
China and growth of the Tibetan Plateau since the Miocene. Quaternary Sciences 26: 678–693. PMID:
17357487
95.
Chen C (1979) On the Eurasian genus Glechoma Linn. and its relationship with allied genera. Acta Botanica Yunnanica 1: 81–89.
96.
Nie ZL, Sun H, Chen DA, Meng Y, Manchester SR, et al. (2010) Molecular phylogeny and biogeographic diversification of Parthenocissus (Vitaceae) disjunct between Asia and North America. American
Journal of Botany 97: 1342–1353. doi: 10.3732/ajb.1000085 PMID: 21616887
97.
Schönhofer AL, McCormack M, Tsurusaki N, Martens J, Hedin M (2013) Molecular phylogeny of the
harvestmen genus Sabacon (Arachnida: Opiliones: Dyspnoi) reveals multiple Eocene—Oligocene intercontinental dispersal events in the Holarctic. Molecular Phylogenetics and Evolution 66: 303–315.
doi: 10.1016/j.ympev.2012.10.001 PMID: 23085535
98.
Harley RM, Atkins S, Budantsev AL, Cantino PD, Conn BJ, et al. (2004) Flowering plants, dicotyledons.
In: Kubitzki K, editor. The families and genera of vascular plants. Berlin: Springer Verlag. pp. 167–275.
PLOS ONE | DOI:10.1371/journal.pone.0117171 February 6, 2015
18 / 18