A new species of Argentina (Rosaceae, Potentilleae) from Southeast Tibet, with reference to the taxonomic status of the genus

Abstract

Argentina songzhuensis, a new species of tribe Potentilleae (Rosaceae) from Southeast Tibet, is described and illustrated. Placement of this species within Argentina was assessed based on morphological comparisons with related species and on phylogenetic analyses of nuclear ITS and plastid trnL-F sequences. The new species is similar to A. glabriuscula, but can be easily distinguished by its densely hairy leaflets, number of stamens (ca.10-12) and decurrent bases of the uppermost pair of leaflets. Our results support the generic status of Argentina and suggest that ventral stipular auricles may be a good synapomorphy for the genus. The recent transfer to Argentina of several Sibbaldia species as well as the genera Piletophyllum and Tylosperma is also confirmed by our molecular phylogenetic analyses. A taxonomic key to A. songzhuensis and other Argentina species in Tibet is provided.

Full text

ORIGINAL ARTICLE
A new species of Argentina (Rosaceae, Potentilleae)
from Southeast Tibet, with reference to the taxonomic status
of the genus
Tao Feng
•
Michael J. Moore
•
Yanxia Sun
•
Aiping Meng
•
Haijia Chu
•
Jianqiang Li
•
Hengchang Wang
Received: 8 January 2014 / Accepted: 7 July 2014
 Springer-Verlag Wien 2014
Abstract Argentina songzhuensis, a new species of tribe
Potentilleae (Rosaceae) from Southeast Tibet, is described
and illustrated. Placement of this species within Argentina
was assessed based on morphological comparisons with
related species and on phylogenetic analyses of nuclear ITS
and plastid trnL-F sequences. The new species is similar to
A. glabriuscula, but can be easily distinguished by its
densely hairy leaflets, number of stamens (ca.10–12) and
decurrent bases of the uppermost pair of leaflets. Our
results support the generic status of Argentina and suggest
that ventral stipular auricles may be a good synapomorphy
for the genus. The recent transfer to Argentina of several
Sibbaldia species as well as the genera Piletophyllum and
Tylosperma is also confirmed by our molecular phyloge-
netic analyses. A taxonomic key to A. songzhuensis and
other Argentina species in Tibet is provided.
Keywords Argentina  Potentilla  Molecular
phylogeny  trnL-F  ITS  Tibet
Introduction
Argentina Hill is a genus of Potentilleae (Rosaceae) with a
long and complicated taxonomic history. It was first sep-
arated from Potentilla L. by Hill (1756), although it was
not until Rydberg’s (1898, 1908) studies that the morpho-
logical basis for the genus was clearly established. Since
then, the taxonomic circumscription and rank of Argentina
have changed frequently (Soja
´
k 1985, 1994, 2004, 2008),
with most authors treating it as an infrageneric unit of
Potentilla, e.g., as subsect. Leptostylae (Wolf 1908) or sect.
Leptostylae (Yu
¨
and Li 1980, 1985; Li et al. 2003). Soja
´
k
(1994) recognized 54 species within sect. Anserina
(= sect.
Leptostylae), whereas Ikeda and Ohba (1999) treated sect.
Leptostylae as a Himalayan group of 24 species. Recently,
Soja
´
k elevated Argentina to a genus comprising over 60
species, mainly distributed in and around the Himalayas
and New Guinea (Soja
´
k 2010, 2012a, b).
Many species of Argentina have long resided within
other genera of Potentilleae, such as Sibbaldia L., Pileto-
phyllum Soja
´
k and Tylosperma Botsch. (Soja
´
k 2008).
Among these, Piletophyllum and Tylosperma are mono-
typic and were included within Argentina by Soja
´
k(2010).
Sibbaldia has presented its own taxonomic problems (Dixit
and Panigrahi 1981; Rajput et al. 1997; Soja
´
k 2008; Paule
and Soja
´
k 2009). Historically, Sibbaldia comprised 17
north temperate and alpine species (including 2 subspecies)
with a center of diversity in the Himalayas (Dixit and
Panigrahi 1981;Yu
¨
and Li 1981; Rajput et al. 1997;
Dikshit and Panigrahi 1998; Li et al. 2003). It has been
commonly separated from Potentilla based on its lower
number of stamens, though this feature also occurs in
Potentilla. However, more recent taxonomic work indi-
cates that Sibbaldia is a heterogenous conglomerate of
species from different evolutionary branches of the tribe
T. Feng  Y. Sun  A. Meng  H. Chu  J. Li (&) 
H. Wang (&)
Key Laboratory of Plant Germplasm Enhancement and Specialty
Agriculture, Wuhan Botanical Garden, Chinese Academy
of Sciences, Wuhan 430074, China
e-mail: lijq@wbgcas.cn
H. Wang
e-mail: hcwang@wbgcas.cn
T. Feng  Y. Sun
University of Chinese Academy of Sciences, Beijing, China
M. J. Moore
Department of Biology, Oberlin College, Oberlin, OH, USA
123
Plant Syst Evol
DOI 10.1007/s00606-014-1125-6

Potentilleae (Soja
´
k 2008; Dobes
ˇ
and Paule 2010). Soja
´
k
(2008) proposed that the species having anthers with two
thecae should be extracted from Sibbaldia, leaving only six
species in the genus, all characterized by a single theca.
Among the former Sino-Himalayan Sibbaldia, two species
are now treated as Argentina—A. glabriuscula and A. mi-
cropetala (Soja
´
k 2010).
Argentina was initially distinguished from Potentilla by
the presence of lateral style insertion (Rydberg 1898,
1908). However, the difference between subterminal and
lateral style insertion is sometimes small and difficult to
discern in some Argentina species, and more than ten
species (e.g., A. microphylla, A. commutata, A. turfosa,
A. vittata, A. tatsienluensis) possess more or less subter-
minal styles (Soja
´
k 2008). Although stylar differences do
not appear to differentiate the two genera, recent work by
Soja
´
k(2010) demonstrates that the basal leaves of all
Argentina species possess ventral stipular auricles, whereas
stipular auricles of basal leaves in Potentilla are lateral.
Soja
´
k’s separation of Argentina from Potentilla has
been supported by several molecular phylogenetic studies
(Eriksson et al. 2003; Dobes
ˇ
and Paule 2010;To
¨
pel et al.
2011). In their study of Rosoideae, Eriksson et al. (2003)
recovered a clade comprising P. anserina, P. stenophylla
and P. peduncularis (all three of which are currently
treated as Argentina
) as sister to the remainder of Poten-
tilla. Using three chloroplast loci and more extensive taxon
sampling (including 14 species of subtribe Fragariinae
together with more than 80 species of subtribe Potentilli-
nae), Dobes
ˇ
and Paule (2010) found similar, strongly
supported sister clades within Potentillinae. The first of
these clades comprised Potentilla, including members of
American genera Ivesia and Horkelia, while the second
clade consisted of Argentina anserina, Piletophyllum,
Potentilla leuconota, and Tylosperma, all of which were
merged into an expanded Argentina by Soja
´
k(2010). To
¨
pel
et al. (2011) identified six major well-supported clades in
Potentilla s.l., including the ‘‘Anserina clade’’ (= Argen-
tina), although the position of this clade was inconsistent
between nuclear and cpDNA. However, the generic status
of Argentina does not conflict with its uncertain phylogenic
position in this study.
During a field excursion in 2012 to collect Himalayan
Sibbaldia, an unusual isolated population of Potentilleae
was discovered in southeast Tibet. Due to its reduced
number of stamens, we initially considered the population
as a putatively undescribed species of Sibbaldia. After
closer scrutiny, however, all the individuals examined
possess anthers with two thecae and ventral stipular auri-
cles, which are characteristic of Argentina. Several char-
acters of this new taxon, such as the lack of stolons, the
number of cauline leaves (1or 2), and the reduced number
of stamens suggest an affinity of the new species to
Argentina series Microphylla [recognized by Ikeda and
Ohba (1999) in sect. Leptostylae before Soja
´
k reestablished
Argentina based on sect. Leptostylae]. The species is
morphologically most similar to A. glabriuscula, with
which it shares several characters that differentiate the two
from the remaining species of series Microphylla, includ-
ing a reduced number of stamens, lateral styles, and a
single stipular auricle. Despite the similarities with A.
glabriuscula and its close relatives, it is clear that this
population represents an undescribed species of Argentina
based on a suite of vegetative and stamen character states.
In this study, we describe and illustrate this new species
as Argentina songzhuensis, and we use molecular phylo-
genetic tools and morphological data to clarify the place-
ment of several taxa currently or formerly treated in
Sibbaldia, and to further investigate the taxonomic status of
Argentina.
Materials and methods
Taxon sampling
For morphological analyses, we scored seven vegetative
and two floral characters for Argentina songzhuensis and
six closely related taxa; characters, and character states are
listed in Table 1. Floral characters were difficult to observe
in older herbarium materials, and in these cases we
extracted the relevant character state data from Ikeda and
Ohba (1999) and Li et al. (2003). A total of 12 individuals
of Argentina songzhuensis collected from the type locality
were examined. In addition, individuals from four addi-
tional Argentina taxa, selected because of their clear
morphological similarity to A. songzhuensis, were scored
for morphological characters. These include collections in
the field of 36 individuals of A. glabriuscula from five
populations in Tibet (two from Milin, two from Motuo, and
one from Bomi), as well as five individuals of A. micro-
phylla from Bomi, Tibet and eight individuals of A. turfosa
from Bomi, Tibet. Herbarium accessions of A. glabrius-
cula, A. microphylla, A. commutata, and A. turfosa from
PE and KUN (acronyms follow Holmgren et al. 1990) were
also examined. In addition, we scored the same characters
for A. leuconota and A. peduncularis (Table 1), which we
found to be closely related phylogenetically to A. songzh-
uensis (Fig. 1), using information in Ikeda and Ohba
(1999) and Li et al. (2003). Herbarium accessions used in
morphological analyses are listed in Table 2.
For molecular phylogenetic analyses, a total of 33
accessions representing 27 species and eight genera from
the tribe Potentilleae sensu Eriksson et al. (2003) were
included in molecular phylogenetic analyses. According to
a preliminary molecular phylogenetic study of Sibbaldia
T. Feng et al.
123

that we are undertaking that includes 19 taxa (including
two subspecies) historically treated in the genus, three
species currently or recently treated as Sibbaldia (S.
phanerophlebia, S. micropetala, and S. glabriuscula) are
nested within Argentina. Hence, we have included all three
of these taxa in our phylogenetic analyses. We also
included eight species of Potentilla (including Horkelia
and Ivesia), representing four of the five major clades
recognized by To
¨
pel et al. (2011). A single accession each
of Rosa majalis and Sanguisorba officinalis served as
outgroups. Of the 33 internal transcribed spacer (ITS)
sequences and 31 trnL-F sequences used in the analyses, 12
and 10 (respectively) were newly sequenced, and all others
were downloaded from GenBank. Taxon names, voucher
information, and GenBank accession numbers are given in
Table 3.
Phylogenetic analyses
Total genomic DNA was extracted from silica-gel-dried
leaf tissue using the procedure of Doyle and Dolye (1987)
with the following modifications: 10–15 mg of dry leaf
tissue was ground in 2.0 mL tubes using a mini-beadbeater
(Biospec, Beijing, China), and the DNA pellet was washed
twice with 75 % ethanol.
The internal transcribed spacer regions of the 18S–26S
nuclear ribosomal cistron, including the 5.8S subunit, were
amplified and sequenced using the primer pair ITS4 and
ITS5 (White et al. 1990). The spacer between the plastid
trnL-UAA and trnF-GAA genes and the trnL-UAA intron
were amplified and sequenced using primers c and f of
Taberlet et al. (1991). PCRs of 25 lL were set up by
mixing 1.5 units (U) Taq DNA polymerase (Tiangen Bio-
tech, Beijing, China), 19 PCR reaction buffer, 1.5 mM
MgCl
2
, 0.2 mM of each dNTP, 0.2 lM each of forward
and reverse primers, 1.0 lL of total DNA, and ddH
2
O. The
following thermocycler program was used for all PCRs:
initial denaturation for 5 min at 94 C, followed by 30
cycles of 94 C denaturation for 30 s, annealing at 55 C
for 30 s, and extension of amplification products at 72  C
for 90 s. A final extension was performed at 72 C for
7 min. PCR products were checked for length and con-
centrations on 2 % agarose gels and sent to Sangon
(Shanghai, China) for commercial sequencing. Cycle
sequencing was performed on both strands. Runs resulting
in sequences of low quality were repeated. The sequences
were aligned using CLUSTALX (Thompson et al. 1997)
and then adjusted by hand.
Bayesian and maximum likelihood (ML) analyses
were used to reconstruct phylogenies for both ITS and
trnL-F. Applying the Akaike Information Criterion, as
implemented in jModeltest (Posada 2008), the TIM2?G
model was selected as best fitting the sequence data for ITS
Table 1 Morphological comparisons between Argentina songzhuensis and closely related species
Character A. songzhuensis A. glabriuscula A. microphylla A. commutata A. turfosa
a
A. leuconota
a
A. peduncularis
Life form Rhizomatous Rhizomatous Rhizomatous Rosette Rosette Rosette Rhizomatous
Number of
stamens
10–12 5–8(–10) 20 10–14(–20) 20 20 20
Inflorescence 1–3 flowers Solitary 1–2 flowers Solitary Solitary Umbel-like Cymes
Insertion of styles Lateral Lateral Subterminal Subterminal Subterminal Lateral Lateral
Stipular auricles
of basal leaves
1, apex acute 1, apex round 2, apex round 1, apex round 2, apex acute 2, connate from the
base to the middle
1, apex round
Leaflet number 5–11 pairs 3–7 pairs 2–10 pairs 5–15 pairs 3–8 pairs 6–18 pairs 10–15 pairs
Teeth number in
terminal leaflet
5–7 3–5 3–9 7–12 7–18 10–25 10–15
Cauline leaves Simple Simple Simple Simple Simple With 3–10 pairs of
leaflets
With 1–2 pairs of leaflets
Leaflet
indumentum
Leaflets sparse above,
densely hairy on midrib,
lateral veins, and near
apices of teeth
Leaflets (except the midrib)
glabrous beneath, rarely
hairy on lateral veins or
near apices of teeth
Leaflets strigose or
hirsute beneath
Leaflets, including the
surface between
veins, densely hairy
beneath
Leaflets
strigose
beneath
Leaflets sericeous
beneath
Leaflets sericeous or strigose,
especially on veins beneath
a
Data according to Ikeda and Ohba (1999) and Li et al. (2003)
A new species of Argentina (Rosaceae, Potentilleae)
123

Sibbaldia procumbens
Sanguisorba officinalis
Rosa majalis
Chamaerhodos erecta
Drymoccallis glutinosa
Dasiphora parvifolia
Sibbaldianthe adpressa
Sibbaldianthe bifurca
Sibbaldia cuneata
Fragaria chiloensi
A. glabriuscula 53
A. glabriuscula 57
A. glabriuscula 67
A. songzhuensis
A. peduncularis
A. leuconota
A. stenophylla
A. turfosa var. gracilescens
A. tapetodes
A. microphylla
Sibbaldia phanerophlebia
A. micropetala
A. lignosa
A. anserina T52
A. anserina 116
Horkelia bolanderi
Ivesia kingii
Potentilla argentea
Potentilla chinensis
Potentilla reptans
Potentilla erecta
Potentilla biflora
Potentilla articulata
100/1
62/0.66
86/1
95/1
82/0.77
66/0.86
71/1
88/1
97/1
100/1
--/0.72
68/0.83
100/1
99/1
90/1
100/1
99/1
93/1
100/1
55/0.85
98/1
97/1
64/0.71
100/1
100/1
100/1
1
99/1
99/1
97/1
100/1
91/1
89/1
100/1
100/1
100/1
100/1
85/1
100/1
99/1
100/0.97
65/0.81
100/1
75/0.97
77/1
93/0.84
99/1
100/1
96/1
--/0.52
86/0.98
97/1
1
Fragariinae
Potentilla
(a) nuclear
(b) plastid
Argentina
Outgroup
Potentilleae
Fig. 1 a Bayesian consensus tree of Potentilleae based on nuclear
ITS data. b Bayesian consensus tree of Potentilleae based on plastid
trnL-F data. Numbers above branches are ML bootstrap values/
Bayesian posterior probabilities. Argentina is indicated within the
gray rectangle and the new species is shown in bold. Numbers
following names are accession numbers (Table 3). The circle
indicates the species referred to Piletophyllum, whereas the triangle
indicates the species referred to Tylosperma (Soja
´
k 2008)
Table 2 Herbarium accessions used in morphological analyses
Taxa Herbarium accessions
A. songzhuensis (12)
a
China, Tibet, Bomi County, Guxiang, alpine grasslands in Songzhu Mountains. 2950
0
16
00
N, 9529
0
57
00
E, elev. 3,310 m
(Feng 5801, 5 Aug. 2012, HIB).
A. microphylla (8) China, Tibet, Nyingchi County, Segrila Pass (Li and Cheng 6134, 4 Aug. 1983, PE); China, Tibet, Nyingchi County, Pai
(Li, Cheng and Ni 05868, 26 Jul. 1983, PE); China, Tibet, Galong Pass (Cheng and Li 00013, 14 Aug. 1982, PE);
China, Tibet, Segrila Pass (Ecology-High Mts. Team 15603, 17 Sep. 1980, PE);
a
China, Tibet, Dingqing, Butuo-
Cuoqing Lake 4,733 m (Feng 93, 30 Aug. 2012, HIB).
A. glabriuscula (14) China, Yunnan, Nushan (Mekong-Salwin Divide), 3,800 m (Yu
¨
22265, 10 Aug. 1938, PE); China, Tibet, Zayu County,
4,200 m (Qingzang Expedition 73-1127, 13 Aug. 1973, PE); China, Tibet, Motuo County, 3,800 m (Qingzang
Expedition 74-3893, 1 Aug. 1974, PE); China, Tibet, Motuo, north of Jinzhula (Ecology-High Mts. Team 14765, 2 Sep.
1980, PE);
a
China, Tibet, Milin, Duoxiong Pass 4,100 m (Feng 50, 30 July 2012, HIB);
a
China, Tibet, Milin, Duoxiong
Pass 3932 (Feng 51, 1 Aug. 2012, HIB);
a
China, Tibet, Bomi, Mt. Songzhu 3,301 m (Feng 57, 5 Aug. 2012, HIB);
a
China, Tibet, Bomi, Galong la, 4,127 m (Feng 60, 6 Aug. 2012, HIB).
A. turfosa (8) China, Tibet, Bomi, 4,200 m (Ying and Hong 1180, PE); China, Yunnan, Gongshan, 3600 m (Yu
¨
22231, 8 Aug. 1938,
PE); China, Yunnan, Taron-Taru Divide, Valley of Bucahwang, 2,600 m (Yu
¨
20099, 3 Sep. 1938, PE);
a
China, Tibet,
Milin, Mt. Duoxiong 3,900 m (Feng 55, 1 Aug. 2012, HIB).
A. commutata (6) China, Sichuan, Jiulong County, Jichougou (Tang et al. 233, 8 July 1982 PE); Nepal, Bhyundar Valley, near HemKund
temple (F. Billiet et al. J. Leonard 6617, 17 Aug. 1975, PE); China, Sichuan, Kangding Tapaoshan (Harry Smith 11479,
22 Aug. 1934, PE).
a
Indicates materials that were collected for the present study. The number of individuals examined is indicated in parentheses after the taxon
name. Herbarium acronyms follow Holmgren et al. (1990)
T. Feng et al.
123

and TPM1uf?G for trnL-F. ML analyses, including 1,000
bootstrap replicates, were conducted in RAxML 7.0.3
(Stamatakis 2006) using the following commands: ‘‘rax-
mlHPC -# 1000 -n ITS-f a -m GTRGAMMA –x 12345 -p
12345 -s ITS.phy’’ for the ITS dataset, and ‘‘raxmlHPC -#
1000 -n trnL-F -f a -m GTRGAMMA -x 12345 -p 12345 -s
trnL-F.phy’’ for the trnL-F dataset. Bayesian analyses
employed MrBayes3.1.2 (Huelsenbeck and Ronquist
Table 3 List of taxa used in
molecular phylogenetic
analyses, including voucher
information and GenBank
accession numbers
a
Eriksson et al. (1998)
b
Eriksson et al. (2003)
c
Gehrke et al. (2008)
d
Lundberg et al. (2009)
e
To
¨
pel et al. (2011)
Taxa Voucher GenBank accession
ITS trnL-F
Argentina anserina (L.) Rydb. 116 Feng 11601 (HIB) KF954772 KJ020644
Argentina anserina (L.) Rydb. T52 Eriksson T. 644(GH, S) U90788
a
Eriksson T. TE#153 FN561752
e
Argentina glabriuscula (Yu
¨
and Li) Soja
´
k
53
Feng 5301 (HIB) KF954763 KJ020639
Argentina glabriuscula (Yu
¨
and Li) Soja
´
k
57
Feng 5701 (HIB) KF954764 KJ020640
Argentina glabriuscula (Yu
¨
and Li)
Soja
´
k67
Feng 6701 (HIB) KF954765 KJ020637
Argentina micropetala (D. Don) Soja
´
k Feng 801 (HIB) KF954771 KJ020641
Argentina leuconota (D. Don) Soja
´
k Feng 10801 (HIB) KF954767 KJ020643
Argentina lignose (Willd. in D. F. K.
Schltdl.) Soja
´
k
M. To
¨
pel MA132 (GB) FJ356171
d
FJ422299
d
Argentina microphylla (D. Don) Soja
´
k MA 144 (GB) FN430809
e
FN556412
e
Argentina tapetodes (Soja
´
k) Soja
´
k Feng 9301 (HIB) KF954769 Missing
Argentina peduncularis (D. Don) Soja
´
k MA 173 (GB) FN430820
e
FN561742
e
Argentina songzhuensis T. Feng and H.
Wang
Feng 5801 (HIB) KF954766 KJ020638
Argentina stenophylla (Franch.) Soja
´
k T. Eriksson and Vretblad
TE763 (SBT)
AJ511780
b
AJ512240
b
Argentina turfosa var. gracilescens (Soja
´
k)
Soja
´
k
Feng 5501 (HIB) KF954768 Missing
Chamaerhodo serecta (L.) Bunge Lackschewitz 11453 (GH) U90794
a
Norlindh & Ahti 10161A (S) AJ512219
b
Dasiphora parvifolia (Fisch. ex Lehm.) Juz. Feng 11901 (HIB) KF954762 KJ020646
Drymocallis glutinosa Rydb. M. Lundberg 5 (S) FJ356162
d
FJ422291
d
Fragaria chiloensis (L.) Mill. M. Lundberg 14 (S) FJ356164
d
FJ422293
d
Horkelia bolanderi A. Gray Eriksson s.n. (SBT) FN430789
e
FN556395
e
Ivesia kingii S. Watson J. L. Reveal et al. #4782 (GB) FN430787
e
FN561735
e
Potentilla argentea L. MA 143 (GB) FN430808
e
FN561750
e
Potentilla articulate Franch KGB 324 (GB) FN555611
e
FN666414
e
Potentilla biflora Willd. ex Schltdl. Viereck 5042 (S) FN430826
e
FN561749
e
Potentilla chinensis Ser. Eriksson s.n. (SBT) FN430825
e
FN561748
e
Potentilla reptans L. T. Eriksson 650 (GH, S) U90784
a
T. Eriksson 822(SBT) AJ512241
b
Rosa majalis Herrm. T. Eriksson 641 (GH, S) U90801
a
AJ512229
b
Sanguisorba officinalis L. T. Eriksson s.n. (GH) U90797
a
T. Eriksson 804 (S) AJ416465
b
Sibbaldia cuneata Hornem Gehrke/BG-K413(ZH) EU072592
c
EU072679
c
Sibbaldia procumbens L. Gehrke/BG-S397(ZH) EU072593
c
EU072680
c
Sibbaldia phanerophlebia Yu
¨
and Li Feng 603 (HIB) KF954770 KJ020642
Sibbaldianthe adpressa (Bunge) Juz. V. A. Gusev 391(S) FJ356176
d
FJ422304
d
Sibbaldianthe bifurca (L.) Kurtto and
T. Erikss.
Feng 11301 (HIB) KF954761 KJ020645
A new species of Argentina (Rosaceae, Potentilleae)
123

2001), using two independent Markov chain Monte Carlo
(MCMC) runs of four chains (three hot, one cold). Runs
were performed for 3 million generations for ITS and 1
million generations for trnL-F, sampling every 100 gen-
erations. When the standard deviation of split frequencies
between the two independent runs fell below 0.01, a con-
sensus tree was calculated after omitting the first 25 % of
trees as burn-in.
Results
The aligned ITS dataset contained 638 characters, of which
406 were constant, 48 were variable but parsimony-unin-
formative, and 184 were parsimony-informative. The trnL-F
alignment contained 1,035 characters, including 770
constant, 120 variable but uninformative, and 145 infor-
mative characters. The ML and Bayesian analyses pro-
duced trees with similar topologies and only the Bayesian
phylogram is shown in Fig. 1, with ML bootstrap (BS)
proportions and Bayesian posterior probabilities (BPP)
indicated.
Three major clades were identified with strong to
moderate support in both ITS and trnL-F phylogenetic
trees (Fig. 1): (1) subtribe Fragariinae (consisting of six
genera), (2) Argentina, and (3) Potentilla (including
Horkelia and Ivesia). Argentina was sister to Fragariinae
in the ITS tree (BS = 97; BPP = 1; henceforth, numbers
in parentheses refer to BS and BPP values, respectively),
whereas it was sister to Potentilla in the trnL-F tree
(97/1). Relationships within Argentina were not well
resolved in the ITS tree and were not completely con-
gruent between the two datasets. For example, A. pe-
duncularis was sister to A. leuconota in the ITS tree (66/
0.86) but was sister to A. microphylla in the trnL-F tree
(91/1). In both trees, Argentina micropetala [previously
treated as Piletophyllum (Soja
´
k 2008)] was nested within
Argentina and was sister to Sibbaldia phanerophlebia
with strong support. The new species A. songzhuensis was
closely associated with A. glabriuscula in both trees: in
the ITS tree, A. songzhuensis was sister to a clade com-
prising the three accessions of A. glabriuscula with
moderate support values (82/0.77), whereas in the trnL-
F tree A. songzhuensis formed a polytomy with the
accessions of A. glabriuscula.
All Argentina species examined shared many mor-
phological character states, including slender styles, gla-
brous ovaries (very rarely hairy), and stipular auricles of
basal leaves borne on the adaxial side of the petiole, in
contrast to Potentilla. Compared to its closest relatives in
Argentina, A. songzhuensis was characterized by the fol-
lowing suite of character states: (1) leaflets with dense
pubescence on the midrib, lateral veins and near apices of
the teeth, (2) relatively reduced number of stamens
(10–12), (3) a single auricle with an entire margin, and
(4) decurrent bases in the uppermost pair of leaflets
(Table 1).
Discussion
Our phylogenetic results are generally consistent with
those from previous molecular studies of tribe Potentilleae
(Eriksson et al. 2003; Dobes
ˇ
and Paule 2010;To
¨
pel et al.
2011). For example, our plastid trees found Argentina as a
well-supported sister clade to Potentilla (97/1), which is
congruent with results of Dobes
ˇ
and Paule (2010) and
To
¨
pel et al. (2011), which were based on multiple spacer
regions. However, our ITS analyses, which included more
species of Argentina than all previous analyses, obtained
much stronger support values (97/1) for a sister relationship
between Argentina and Fragariinae than in the combined
ITS and ETS analyses of To
¨
pel et al. (2011), which
recovered the same relationship.
Our phylogenetic analyses strongly support the generic
status of Argentina as proposed by Soja
´
k(2010). Soja
´
k’s
(2010) transfer of several species of Sibbaldia to Argen-
tina, as for example A.glabriuscula and A. micropetala,is
also confirmed (Fig. 1). Likewise, our results support the
transfer of the monotypic genera Piletophyllum and Tylo-
sperma to Argentina (Soja
´
k 2010; Fig. 1). This is congru-
ent with the cpDNA phylogeny of Potentilla in Dobes
ˇ
and
Paule (2010), in which Piletophyllum and Tylosperma were
resolved in a clade including two Argentina species. We
also found that the Chinese endemic species Sibbaldia
phanerophlebia should be included within Argentina. S.
phanerophlebia is strongly supported as sister to A. mi-
cropetala in both the ITS and trnL-F trees. In addition, it is
characterized by having anthers with two thecae, lateral
styles, and ventral stipular auricles, which are diagnostic
for Argentina. Hence, we make the following formal
transfer of this species to Argentina:
Argentina phanerophlebia (Yu
¨
and Li) T. Feng
and H. Wang, comb. nov.
Basionym: Sibbaldia phanerophlebia Yu
¨
and Li, Acta
Phytotax. Sinica. 19(4): 517. 1981.
Relationships within Argentina are incongruent
between nuclear and cpDNA data (Fig. 2), as detected in
previous studies (To
¨
pel et al. 2011). Species-level gene
tree incongruences have also been observed in some
other members of Rosaceae and have been considered
evidence of hybridization (e.g., Lundberg et al. 2009;
To
¨
pel et al. 2011), and many members of Fragariinae
(Fragaria, Alchemilla) and other closely related genera
(Rosa, Rubus, Potentilla) have been suggested to have a
hybrid origin (Schulze-Menz 1964). Chromosome counts
T. Feng et al.
123

in Argentina have revealed various ploidy levels in the
genus, including diploids (e.g., A.glabriuscula, A. leu-
conota, and A. commutata) and polyploids [e.g., A.
microphylla (2x, 4x), A. peduncularis (4x) and A.
anserina (4x, 5x, 6x)] (Ikeda and Ohba 1999;To
¨
pel
et al. 2011). The observed incongruence between nuclear
and cpDNA trees within Argentina and the widespread
polyploidy in the genus may reflect hybridization,
Fig. 2 Argentina songzhuensis T. Feng and H. Wang. a Alpine
habitat in southeast Tibet (3,310 m elevation), b flowers (in August),
c flower in front view, showing ca. 10–12 stamens, d flower in side
view showing dense pubescence on the pedicel, e upper surface of
basal leaves, showing leaflet number and teeth, f stipules of basal
leaves, showing the single auricle situated on the adaxial side of the
petiole, g petal, sepal, and episepal, h lower surface of basal leaves,
showing the dense pubescence on the midrib, lateral veins, and near
apices of teeth
A new species of Argentina (Rosaceae, Potentilleae)
123

perhaps including allopolyploid hybridization. However,
we cannot exclude other explanations for the gene tree
incongruence, such as incomplete lineage sorting.
Sequences of multiple low-copy nuclear sequences will
be necessary to resolve the causes of gene tree incon-
gruence within Argentina.
Description of A. songzhuensis
The morphological features (Table 1) and molecular phy-
logeny (Fig. 1) support the status of the Songzhu
Mountains population as a new species within Argentina
and suggest a close affinity of the new taxon with A.
glabriuscula. To confirm the morphological uniqueness of
A. songzhuensis, we have studied the holotypes of A.
glabriuscula (China, Yunnan, Nu Shan, Mekong-Salwin
Divide, 3,800 m, Yu
¨
22265, 10 Aug. 1938, PE) and
A.turfosa (China, Tibet, Bomi, 4200 m, Ying and Hong
1180, PE). For A. microphylla and A. commutata,we
obtained the photographs of the type specimens from BM
and K. We also checked collections of Argentina in several
Chinese herbaria (PE, KUN, WUK, HNWP, IBSC, and
Fig. 3 Argentina songzhuensis
T. Feng and H. Wang. a Habit
(perennial herb), b flower in
front view, c ovary with lateral
style, d basal leaves with ventral
stipular auricles, e petal, f sepal,
g episepal, h the lower surface
of leaflets showing the dense
pubescence on the midrib,
lateral veins, and near apices of
teeth. Drawing from the
holotype [T. Feng 5801 (HIB)]
courtesy of Jia Nan
T. Feng et al.
123

CDBI) and reviewed online images of Chinese Argentina
specimens at K, E, BM, A, NY, US, MO, P, W, and WU.
No materials belonging to A. songzhuensis have been
found.
Argentina songzhuensis T. Feng and H. Wang sp. nov.
(Figs. 2, 3)
Type: China. Tibet. Bomi County, Guxiang, alpine
grasslands in Songzhu Mountains. 2950
0
16
00
N, 9529’57
00
E,
elev. 3,310 m. 5 Aug. 2012. T. Feng 5801 (Holotype, HIB).
Etymology: the epithet of the new species refers to its
type locality in the Songzhu Mountains of southeastern
Tibet.
Low perennial herbs. Roots robust, terete; lateral roots
filiform. Flowering stems erect, 1–2.5 cm tall, pilose. Basal
leaves 1.5–5 cm, including petiole; stipules brown, mem-
branous, abaxially subglabrous, auricles connate from base
to apex, apex acute; petiole densely pubescent; leaf blade
pinnate with 5–11 pairs of leaflets; leaflets shortly petiol-
ulate or subsessile, oblong to narrowly obovate, 2–4 mm
(wide) 9 3–5 mm (long), pubescence sparse above, den-
sely hairy on midrib, lateral veins and near apices of teeth,
margin 3–7-serrate, apex acute; cauline leaves 1 (or 2), or
reduced and bract-like. Inflorescence 1–3 flowered,
6–12 mm in diameter. Sepals elliptic to ovate, apex roun-
ded; epicalyx segments oblong-lanceolate, nearly equaling
sepals, abaxially sparsely pubescent or subglabrous, apex
obtuse or acute. Petals yellow, oblong to elliptic, 3–5 mm
(wide) 9 6–8 mm (long), apex rounded. Stamens 10–12.
Styles lateral. Achenes oblong-globose, ca. 0.8 mm long,
dark brown when dry.
A. songzhuensis differs from A. glabriuscula by having
dense pubescence on the midrib, lateral veins, and near
apices of teeth [vs. leaflets (except the midrib) glabrous,
rarely hairy on lateral veins or near apices of teeth], stamens
10–12 (vs. 5–10), bases of uppermost pair of leaflets decur-
rent (vs. cuneate) and inflorescence 1–3 flowered (vs. flower
solitary). The distribution of A. songzhuensis and A. glabri-
uscula is given in Fig. 4. The newly discovered taxon is so far
known only from the type locality, where it is scattered on
moist rocks or in shady crevices below rocks, at elevations of
ca. 3,310 m. A. songzhuensis grows sympatrically with
A. glabriuscula, but no evidence of hybridization is apparent.
According to the last comprehensive systematic treat-
ments of Argentina (Ikeda and Ohba 1999; Li et al. 2003)a
total of 14 species of Argentina occur in Tibet, inclusive of
A. songzhuensis, A. micropetala, and A. phanerophlebia.
The following key, expanded from Li et al. (2003), allows
for the determination of all 14 of these species:
1. Plants with stolons……A. anserina
1. Plants without stolons……2
2. Cauline leaves more than 4……3
2. Cauline leaves 1–3……4
3. Auricles of stipules of basal leaves connate from base
to middle……A. festiva
3. Auricles of stipules of basal leaves free……A. lineata
Fig. 4 Geographical distribution of Argentina songzhuensis and A. glabriuscula in the Himalayas
A new species of Argentina (Rosaceae, Potentilleae)
123

4. Auricles of basal leaves 1……5
4. Auricles of basal leaves 2……9
5. Petals oblong-lanceolate, shorter than or equaling
sepals……6
5. Petals oblong to elliptic, longer than sepals……7
6. Flowering stems and petioles densely white-tomen-
tose, leaflets abaxially inconspicuously veined and
densely white-tomentose……A. micropetala
6. Flowering stems and petioles yellow-pilose and
white-tomentose, leaflets abaxially prominently
veined……A. phanerophlebia
7. Stamens ca. 20……A. peduncularis
7. Stamens 5–12……8
8. Stamens 10–12, leaflets sparse above, densely hairy
on midrib, lateral veins and near apices of
teeth……A. songzhuensis
8. Stamens 5–8(–10), leaflets (except the midrib) gla-
brous beneath, rarely hairy on lateral veins or near
apices of teeth……A. glabriuscula
9. Apical pair of leaflets sessile, but not decurrent at
base……10
9. Apical pair of leaflets decurrent at base…… 13
10. Smaller leaflets usually present between main
leaflets……A. turfosa
10. Smaller leaflets usually absent between main
leaflets……11
11. Rhizome with a few slender, elongate
roots……A. aristata
11. Rhizome without slender, elongate roots……12
12. Leaflets 2–4 mm……A. microphylla
12. Leaflets 5–15 mm……A. stenophylla
13. Inflorescence pseudoumbellate……A. leuconota
13. Inflorescence cymose……A. contigua
Acknowledgments This work was founded by National Science
Foundation of China grant 31070191.
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