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A Taxonomic Nightmare Comes True: Phylogeny and Biogeography of Glassworts (Salicornia L., Chenopodiaceae)

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In this study we analysed ETS sequence data of 164 accessions belonging to 31 taxa of Salicornia, a widespread, hygrohalophytic genus of succulent, annual herbs of Chenopodiaceae subfam. Salicornioideae, to investigate phylogenetic and biogeographical patterns and hypothesise about the processes that shaped them. Furthermore, our aim was to understand the reasons for the notorious taxonomic difficulties in Salicornia. Salicornia probably originated during the Miocene somewhere between the Mediterranean and Central Asia from within the perennial Sarcocornia and started to diversify during Late Pliocene/Early Pleistocene. The climatic deterioration and landscape-evolution caused by orogenetic processes probably favoured the evolution and initial diversification of this annual, strongly inbreeding lineage from the perennial Sarcocornia that shows only very limited frost tolerance. The further diversification of Salicornia was promoted by at least five intercontinental dispersal events (2× to South Africa, at least 3× to North America) and at least two independentpolyploidization events resulting in rapidly expanding tetraploid lineages, both of which are able to grow in lower belts of the saltmarshes than their diploid relatives. The diploid lineages of Salicornia also show rapid and effective range expansion resulting in both widespread genotypes and multiple genotypes in a given area. Reproductive isolation through geographical isolation after dispersal, inbreeding, and comparatively young age might be responsible for the large number of only weakly differentiated lineages. The sequence data show that the taxonomic confusion in Salicornia has two major reasons: (1) in the absence of a global revision and the presence of high phenotypic plasticity, the same widespread genotypes having been given different names in different regions, and (2) striking morphological parallelism and weak morphological differentiation led to the misapplication of the same name to different genotypes in one region.
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Kadereit & al. • Phylogeny and biogeography of SalicorniaTAXO N 56 (4) • November 2007: 1143–1170
INTRODUCTION
Among botanists in temperate regions of the northern
hemisphere, Salicornia L. (glasswort, saltwort, samphire)
is well-known for two reasons: firstly, because of its unu-
sual appearance with succulent, apparently articulated
and leafless stems and branches (Fig. 1) and flowers ag-
gregated in dense terminal, spike-like thyrses (Fig. 2), and
secondly because of its notoriously difficult taxonomy
which makes it almost impossible for non-specialists to
determine most species, not to mention microspecies,
subspecies, varieties and putative hybrids. Frequently
the names Salicornia europaea or S. herbacaea are used
in a very broad sense to include most of the species in
the genus. This greatly complicates the assignment of
published information to taxa of the genus.
According to a molecular phylogenetic study by
Kade reit & al. (2006), Salicornia is monophyletic and
nested within the morphologically and ecologically
closely related Sarcocornia. Salicornia and Sarcocornia
differ from all other Salicornioideae by seeds that lack
perisperm (Ulbrich, 1934; Shepherd & al., 2005). Sali-
cornia split from Sarcocornia during the Middle Miocene
(14.2– 9.4 mya), but its extant lineages started to diversify
only in the Early Pleistocene (1.4–1.8 mya; Kadereit & al.,
2006). The genus is distinguishable from Sarcocornia by
two characters. These are the annual life form of Salicor-
nia versus the perennial life form of Sarcocornia, and the
A taxonomic nightmare comes true: phylogeny and biogeography of
glassworts (Salicornia L., Chenopodiaceae)
Gudrun Kadereit1*, Peter Ball2, Svetlana Beer3, Ladislav Mucina4, Dmitry Sokoloff
5, Patrick
Teege1, Ahmet E. Yaprak5 & Helmut Freitag6
1 Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, 55099
Mainz, Germany
2 Biology Department, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6, Canada
3 Higher Plants Department, Moscow State University, 119992 Moscow, Russia
4 Dept. of Botany & Zoology, Evolutionary Plant Biology & Conservation Group, Stellenbosch University,
7602 Matieland, South Africa
5 Ankara University, Science Faculty, Department of Biology, Besevler/Ankara, Turkey
6 Arbeitsgruppe Systematik und Morphologie der Pf lanzen, Universität Kassel, 34109 Kassel, Germany
* Author for correspondence (clausing@uni-mainz.de)
In this study we analysed ETS sequence data of 164 accessions belonging to 31 taxa of Salicornia, a wide-
spread, hygrohalophytic genus of succulent, annual herbs of Chenopodiaceae subfam. Salicornioideae, to
investigate phylogenetic and biogeographical patterns and hypothesise about the processes that shaped them.
Furthermore, our aim was to understand the reasons for the notorious taxonomic difficulties in Salicornia.
Salicornia probably originated during the Miocene somewhere between the Mediterranean and Central Asia
from within the perennial Sarcocornia and started to diversify during Late Pliocene/Early Pleistocene. The
climatic deterioration and landscape-evolution caused by orogenetic processes probably favoured the evolution
and initial diversification of this annual, strongly inbreeding lineage from the perennial Sarcocornia that
shows only very limited f rost tolerance. The further diversification of Salicornia was pr omote d by a t leas t five
intercontinental dispersal events (2× to South Africa, at least 3× to North America) and at least two independent
polyploidization events resulting in rapidly expanding tetraploid lineages, both of which are able to grow in
lower belts of the saltmarshes than their diploid relatives. The diploid lineages of Salicornia also show rapid
and effective range expansion resulting in both widespread genotypes and multiple genotypes in a given area.
Reproductive isolation through geographical isolation after dispersal, inbreeding, and comparatively young
age might be responsible for the large number of only weakly differentiated lineages. The sequence data show
that the taxonomic confusion in Salicornia has two major reasons: (1) in the absence of a global revision and
the presence of high phenotypic plasticity, the same widespread genotypes having been given different names
in different regions, and (2) striking morphological parallelism and weak morphological differentiation led to
the misapplication of the same name to different genotypes in one region.
KEYWORDS: annual habit, diversification, ecological and morphological parallelism, inbreeding,
Miocene, Pleistocene, polyploidization
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flowers forming a characteristic triangle with a larger cen-
tral and two smaller lateral f lowers in Salicornia versus
being arranged in a horizontal row in Sarcocornia.
Salicornia grows in periodically wet saline coastal
and inland habitats such as salt marshes, salt lake shores,
mud flats and salt pans (Fig. 1). The genus currently com-
prises ca. 25 to 30 species (Table 1). This is a rough esti-
mate because no general agreement exists on the number
of accepted species. Salicornia is widely distributed in
boreal, temperate and subtropical regions of the northern
Fig. 1. Photo plate illustrating different habitats and species of Salicornia. A, B, Salicornia meyeriana, South Africa, Western
Cape, Overberg, Cape inland salt pans (photo L. Mucina, 5 Apr. 2006); C, D, S. aff. perennans (chen 865), West Kazakhstan,
Kambash lake 30 km E of Small Aral lake (photo W. Wucherer, Oct. 2004); E, F, S. pojarkovae, Norway, East Finnmark,
Porsanger, Caskilnjarga (photo M. Piirainen, 15 Jul. 1989); G, H, S. europaea, Sweden, Gotland, Burgsviken, Näsudden, type
loc alit y (photo M. Piirainen, 16. Sep. 1999); I, S. dolichostachya comm., Germany, Lower Saxony, Jadebusen, foreland of dike
near Varel (photo H. Freitag, Sep. 1996); J, S. procumbens (right) with the short-spiked S. ramosissima (left), other data as in
I; K, L, S. emerici, Southeast Turkey, Seyhan prov., lagoon Ömer Gölü, ca. 35 km SE Adana (photo H. Freitag, Oct. 1997).
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Kadereit & al. • Phylogeny and biogeography of SalicorniaTAXO N 56 (4) • November 2007: 1143–1170
hemisphere and in South Africa (Figs. 1, 3). It is consid-
ered as absent from South America and Australia.
In their treatment of Salicornia for Flora Europaea,
Ball & Akeroyd (1993) pointed out that local accounts can
not be correlated either taxonomically or nomenclaturally,
even in NW Europe. These taxonomic difficulties have
five main reasons:
(1) Paucity of morphological characters. —
Sali -
cornia has a greatly simplified morphology (Figs. 1, 2).
The plants have green, succulent, articulated stems when
young, and the leaves and bracts are reduced to small,
scarious rims (Fig. 2B–E). Flowers consist of 3–4 fused
tepals, (0–)1–2 stamens, an ovary with one ovule and
a style that is apically divided into 23 stigmatic lobes
(Fig. 2A, E). The flowers are sessile and mostly arranged
in 3-flowered cymes per bract. The bracts are opposite,
connate and the flowers are tightly embedded in cavities
of the main axis and partly hidden by the bracts (Fig.
2B–E).
Further fusions within the inflorescence can be ob-
served in the recently described Salicornia heterantha.
This species shows a total fusion of the tepals of the cen-
tral flower with the main axis of the inf lorescence (Fig.
2C; Beer & Demina, 2005). Reduction of the inflores-
cence to one flower per cyme can be observed occasion-
ally in a few species (P. Ball, S. Beer, pers. obs.), but
this character seems to be genetically fixed in Salicornia
pusilla (probably identical with S. disarticulata (Moss,
1912), S. uniflora (Tölken, 1967) and in an unpublished
taxon preliminarily called S. “knysnaensis” (L. Mucina
& G. Kadereit, unpulished data).
This highly reduced leaf and flower morphology
provides relatively few taxonomic characters. Some of
these are quantitative and applicable only to “well”-grown
individuals. Characters traditionally used to delimitate
Salicornia species are growth form, angle of branching,
shape of sterile and fertile segments, length of the in-
florescence, shape of bracts, size relation of central and
lateral flowers, shape of central flower, anther length and
anther dehiscence and occurrence of spirally thickened
cells in the cortex (e.g., Ball, 1964; Géhu, 1989; Ball &
Akeroyd, 1993; Iberite, 1996; Davy & al., 2001; Ball,
2003; Lahondère, 2004).
(2) Inadequacy of dried material for taxonomic
studies. —
The difficulties caused by scarcity of diag-
nostic characters and the importance of quantitative and
growth form characters are aggravated by the inadequacy
of dried and pressed plant material to represent the de-
tails of the succulent growth form of Salicornia (Davy
& al., 2001; Ball, 2003). In herbarium specimens, some
of the diagnostic characters, such as segment shape and
length, bract shape and length, relation of central flower
to lateral flowers and shape of central flower and anther
length are no longer reliably measurable. Fortunately,
most Salicornia species were described on the basis of
fresh material while few Salicornia taxonomists worked
with herbarium material only. A critical example of the
latter is S. borysthenica which was described by Tzve-
lev (1993) on the basis of only one herbarium specimen
(Russia, Prov. Cherson, Aleschki, 1901, N. Egorov s.n.,
LE). The only difference between S. borysthenica and
S. dolichostachya is the length of the anthers. Measure-
ments of this, however, are not strictly comparable in
dried and fresh material and anther size is quite variable
in S. dolichostachya even on one plant and certainly in
one population.
If identification keys were based on fresh material,
the identification of dried specimens can be very difficult
if not impossible. Already Ball & Tutin (1959) stated that
to key out Salicornia it is necessary to take a sample of t en
Fig. 2. A, central flower of S. pojarkovae with simultaneously emerging anther and stigma, cultivated at Botanical Garden
(BG) Mainz (photo P. Teege); B, inflorescence of S. pojarkovae, cultivated at BG Mainz (photo P. Teege); C, inflorescence of
S. heterantha, cultivated at BG Mainz (photo P. Teege); D, inflorescence of S. bigelovii (chen 896), U.S.A., Massachusetts,
South Wellfleet (photo P. Teege); E, inflorescence of S. perennans (photo S. Beer).
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TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
to twelve individuals from a (homogeneous) population,
excluding any damaged or apparently abnormal plants.
(3) Phenotypic plasticity. —
The habitats of
Salicornia are characterized by diurnal and/or seasonal
dynamics where duration of submergence, tidal scour,
waterlogging and salinity vary locally as well as within
or bet ween season s. Especially salinit y fluctuates g reatly
due to different factors such as tidal cycles, evapotranspi-
ration, precipitation and availability of fresh groundwater.
These fluctuations require high physiological plasticity
and cause strong phenotypic variation. The latter is also
caused by differences in soil texture and nutrient supply
(e.g.,nig, 1960).
It has been indicated that considerable phenotypic
plasticity exists in Salicornia and that the genetic basis
of diagnostic characters has to be tested experimentally
(Dalby, 1955; Ball & Tutin, 1959; Langlois & Ungar, 1976;
Rozema & al., 1987). Morphometric studies using all
phenotypic differences available irrespective of whether
they have a genetic basis or not could not reveal distinct
taxa even on a small regional scale (Ingrouille & Pear-
son, 1987; Ingrouille & al., 1990). The density of popula-
tions also is important and can vary greatly (Dalby, 1955;
Ungar & al., 1979; Jefferies & al., 1981; Beeftink, 1985;
Ungar, 1987; Davy & al., 2001). Salicornia seeds may ac-
cu mulate in depression s, below algal mats or around silted
mother plants, or remain attached to the buried stems of
the mother plants. In dense populations, Salicornia – like
most plant species – tends to be less branched, remains
smaller, has fewer and smaller inflorescences and some-
times larger numbers of sterile segments especially in
the shaded, basal branches (G. Kadereit & P. Teege, pers.
obs.). In contrast, in open stands and particularly on nu-
trient-rich places plants tend to be larger, with a more
elaborate branching pattern and root system.
Disentangling phenotypic plasticity and genetically
determined morphological differences is most difficult
without experimental approaches or long-term observa-
tions. For example, some diag nostic features such as pros-
trate growth may disappear in cultivation (Dalby, 1955;
Ball & Tutin, 1959). However, transplantation experiments
have shown that transplanted individuals normally retain
their specific morphology (Jefferies & al., 1981; Davy &
Smith, 1985, 1988; Smith, 1985; A. Davy, pers. comm.;
H. Freitag, pers. obs.; P. Teege, G. Kadereit & J. Kadereit,
unpublished data) indicating the genetic distinctness of
certain morphotypes.
However, the identification of stable and genetically
determined morphotypes does not automatically imply
that these belong to one evolutionary unit. They may well
represent several lineages that show morphological paral-
lelism.
(4) Breeding system and hybridization. —
In-
breeding seems to play a dominant role in the reproduc-
tion of Salicornia (Dalby, 1962; Ferguson, 1964). This
is more evident in the diploid species studied so far as
their anthers usually dehisce before they are exserted, and
several individuals in a population have been observed
to be entirely cleistogamous (Ball & Tutin, 1959; Ball,
1960, 1964; P. Teege, pers. obs.). In contrast, anthers of
tetraploid species normally dehisce after they have been
exserted but stigmatic lobes and anthers are always in
close contact which makes inbreeding also very likely
(Fig. 2A; P. Teege, pers. obs.). Potentially there is a small
chance of outbreeding by wind-pollination at least in the
slightly protogynous tetraploid taxa (Dalby, 1962; Davy
& al., 2001) and maybe through pistillate flowers which
can for example be observed in the diploid Salicornia
ramosissima (P. Ball, pers. obs.).
Population genetic studies using isozymes found in-
dividuals of diploid populations to be homozygous while
in individuals of tetraploid populations a homozygous
and fixed heterozygotic profile has been observed. For
both ploidy levels genetic differentiation was observed
between groups of populations (Jefferies & Gottlieb,
1982; Wolff & Jefferies, 1987b). In their RFLP analysis
of 38 maternal plants and 2,112 F1 progeny, Noble & al.
(1992) found no instance of genetic divergence between
parent and offspring. These molecular results imply near
100% inbreeding in Salicornia which certainly contrib-
utes greatly to the taxonomic difficulties in the group
by resulting in inbreedings lines with minute but fixed
phenotypic differences.
Although the strong inbreeding seems to preclude hy-
bridization, several putative hybrids have been described
(e.g., Tölken, 1967; Dalby, 1975; Lahondère, 2004). A
prominent example may be S. pusilla × S. ramosissima
which can be identified with some certainty by the oc-
currence of one, two and three f lowers per cyme in one
individual and which occurs together with the parents
(Dalby, 1975). In no case has the existence of hybrids
been clearly verified by molecular evidence. So far two
molecular studies (Murakeözy & al., 2007; M. Kaligaric,
B. Bohanec, B. Simonovik & N. Sajna, unpublished data)
found some molecular evidence for reticulate evolution in
Salicornia (see below). Probably mainly due to technical
problems nobody has succeeded in producing definite
hybrids experimentally in Salicornia (although two of
us, P. Ball and P. Teege, tried hard). However, in many
places two or even more species of Salicornia grow sym-
patrically, and often patches of plants or individual plants
look odd and seem to represent intermediate morphotypes
which can not be clearly assigned to any of the species
present.
(5)
Regional treatments. —
Possibly caused by
the difficulties outlined above, a cosmopolitan revision
of Salicornia has never been published. The large number
of regional treatments and flora accounts (Table 1) offer
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conflicting information, or by accepting only one or two
polymorphic species evade the problematic taxonomy of
the genus. In most cases the treatments are not compa-
rable because of the inconsistency of the few diagnostic
characters available, and uncertainties about the identity
of the respective taxa. Additional confusion was caused
by authors who are famous for outstanding knowledge
of their regional Salicornia species, but did not always
pay due attention to the rules of botanical nomenclature
(e.g., König, 1960; Lahondère, 2004). Therefore, also the
attempts to treat the genus over larger areas, as in Flora
Europaea (Ball & Akeroyd, 1993) could not solve the
taxonomic problems. An example to illustrate this prob-
lem is material from the English Channel. Depending on
which of the keys is considered one ends up with different
names for the same specimen. One specimen (P. Teege
chen 968, MJG) collected at La Gran Vey (Normandie,
France), for example, is keyed out as S. europaea subsp.
europaea (Rothmaler, 2002), S. europaea (Stace, 1997),
S. brachystachya (König, 1960; Lahondère, 2004) and S.
ramosissima (Ball & Akeroyd, 1993).
There are three regional studies of Salicornia that
were based on molecular data (Papini & al., 2004;
Murakeözy & al., 2007; M. Kaligaric, B. Bohanec, B.
Simonovik & N. Sajna, unpublished data). Papini &
al. (2004) found that diploid and tetraploid accessions
of Salicornia resolved as sister clades. The study was
based on ITS sequences of twelve samples of Salicornia
(all but one from Italy) representing four species (three
tetraploid, one diploid). Another regional study was done
by Murakeözy & al. (2007) investigating Salicornia na-
tive to the Atlantic coast of France. The 28 populations
included were carefully identified as eight different spe-
cies according to Lahondère (2004) and analysed using
sequence data (ITS, cp trnL-F, cp matK) and RAPD
fingerprints. Here also diploid and tetraploid accessions
were found to belong to sister clades in the ITS tree. The
cp DNA tree, however, showed a conf licting result for
two tetraploid accessions (referred to as S. fragilis) which
were placed among the diploid accessions. Murakeözy &
al. (2007) offer hybridization and allopolyploidisation
as likely explanation for the conf licting topologies. A
similar incongruency between nuclear and cp trees was
found in Salicornia populations from the Gulf of Trieste
(M. Kaligaric, B. Bohanec, B. Simonovik & N. Sajna, un-
published data). This study was based on 14 populations
(seven tetraploid, seven diploid), relative nuclear DNA
content measured by flow cytometry, a morphometric
survey as well as ITS and cp trnT-trnL spacer sequences.
As in the previous two studies, ITS sequences separated
the populations according to ploidy level. In this study,
however, two diploid samples (referred to as S. patula)
showed the same trnT-trnL spacer sequences as the tetra-
ploid samples again indicating hybridization, albeit with
a tetraploid mother.
Aims of this study. —
The taxonomic difficulties
hamper the formulation of testable hypotheses about
phylogenetic relationships and the biogeography of Sali-
cornia. The aim of this study is to identify evolutionary
units within Salicornia using External Transcribed Spacer
(ETS) sequence data, to understand the patterns of mor-
phological and geographical diversification, and perhaps
to identify the main reasons for the taxonomic difficulties
in the genus.
Fig. 3: Distribution map of Salicornia with location of accessions included in the ETS analysis.
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MATERIAL AND METHODS
Plant material. —
Altogether, 164 accessions of
Salicornia were sampled. The accessions are located
throughout the distribution area of Salicornia except for
North Africa and South Asia (Fig. 3). They include 23
out of a total of ca. 30 recognized taxa, and about 8 puta-
tive new species. Some areas are more densely sampled
than others, thus reflecting the availability of material.
We tried to handle the identification problems by using
the most recent treatments of the specific regions (Table
1) as far as they appear to be taxonomically reliable, and
our own knowledge which is still fragmentary. It must
be emphasised that in many cases the naming remains
tentative. Then, we simply added “aff.” to the respec-
tive species name, or—in case of putative new taxa—by
giving them working names which are set in quotation
marks. The sampled plant material was of different qual-
ity, ranging from living specimens to relatively old her-
barium vouchers.
The ingroup sampling also included 17 species of
Sarcocornia representing the major clades of the genus
as found by Kadereit & al. (2006) and two species of the
Australian Salicornieae (Halosarcia indica and Tecticor-
nia australasica) which are sister to the Salicornia/Sarco-
cornia lineage. Microcnemum coralloides and Arthrocne-
mum macrostachyum served as outgroup (all according
to Kadereit & al., 2006).
The taxa sampled, their voucher information and
GenBank accession numbers are listed in the Appendix.
DNA isolation, amplification, and sequencing.
Total DNAs were isolated either from fresh parts of
the plants (stem and/or inflorescence), with 50–100 mg
samples preserved in saturated NaCl-CTAB solution sup-
plemented with 200 mM sodium ascorbate (Thomson,
2002), or silica gel dried material, or herbarium material
using ca. 20–50 mg. The plant material was in most cases
ground in mortars using liquid nitrogen only rarely with
sand directly in the Eppendorf tubes. For DNA extrac-
tion the NucleoSpin plant DNA extraction kit (Macherey-
Nagel) or DNeasy Plant Mini Kit (QIAGEN) was used
following the manufacturers’ specifications.
The Internal and External Transcribed Spacers (ITS
and ETS) are part of the 18S-5.8S-26S region of the nu-
clear ribosomal DNA. ETS was choosen in this study be-
cause it is known to evolve faster than ITS (e.g., Baldwin
& Markos, 1998; Markos & Baldwin, 2002; Linder & al.,
2000; Álvarez & Wendel, 2003; Vander Stappen & al.,
2003). The resolution within Salicornia gained by ITS is
rather limited (Papini & al., 2004; Kadereit & al., 2006;
Murakeözy & al., 2007). For Salicornia, ETS shows ca.
thrice as many informative sites as ITS.
The entire IGS (Intergenic Spacer) was amplified with
the 18S-II rev (5-CTC TAA CTG ATT TAA TGA GCC
ATT CGC A-3) and the 26S-II for (5-TGC AGA CGA
CTT AAA TAC GCG ACG GGG T-3) primers (Ochs-
mann, 2000) for a few representatives of Salicornia. The
25 µl PCR reaction contained the following: 10x Buffer
(supplied with the Taq polymerase), 2.25 mM MgCl2, 50
pmol forward and reverse primers, 0.6 U Taq polymerase.
A PTC-100 cycler (MJ Research, Inc., MA, U.S.A.) was
program med as follows: 9C for 4 min; 30 cycles of 9C
for 30 s, 50.5°C for 45 s, 72°C for 4 min; 50.5°C for 1.2
min, 72°C for 8 min; 4°C forever. With a five-fold diluted
18S-II rev-primer ca. 800 bp of the 3 ETS-region were
sequenced (sequencing reaction and alignment see be-
low). To determine the correctness of the obtained ETS se-
quences, these were initially aligned to the overlapping 5
end of the18S rDNA of Celosia argentea (A maranthaceae,
GenBank accession AF206883). The ETS region ended
after ca. 550 bp. One new internal primer was designed
specifically to amplify and sequence the 3 ETS region
of the IGS, namely, ETS-Salicornia-5-GTC CCT ATT
GTG TAG ATT TCA T-3. Successive amplifications of
the 3 ETS were done using the primer combination ETS-
Salicornia and 18S-II rev.
Reactions for the amplification of the 3 ETS fragment
were prepared in 25 µl aliquots containing 10x Buffer
(supplied with the Taq polymerase), 2.25 mM MgCl2, 50
pmol forward and reverse primers, 0.6 U Taq polymerase
and 4% DMSO. A PTC-100 cycler (MJ Research, Inc.,
MA, U.S.A.) or a Biometra
®
T gradient thermocycler was
used according to the following protocol for the 3’ ETS,
9C for 3 min; 30 cycles of 95°C for 30 s, 50.5°C for
45 s, 72°C for 2 min; 72°C for 8 min. PCR products were
subse quently v isualized on a 0.8% agarose gel, then puri-
fied using a PCR extraction kit (QiaGen GmbH, Hilden,
Germany).
Sequencing reactions were prepared using ABI’s Big
Dye Terminator Kit following the manufacturer’s proto-
col. Sequences were obtained using an ABI 373A DNA
Sequencer. DNA chromatograms were edited and aligned
using Sequencher. The alignment was straightforward.
Phylogeny inference.
The ETS data matrix
was analyzed using the Maximum Likelihood (ML) and
Maximum Parsimony (MP) implemented in PAUP*4.10b
(Swofford, 2002) for Apple Computers. Heuristic search
settings were set to 100 (MP) and 10 (ML) random addi-
tion of taxa and tree-bisection-reconnection (TBR) branch
swapping.
Furthermore, we used Bayesian inference with
Markov chain Monte Carlo simulation implemented
in MrBayes v.3 (Ronquist & Huelsenbeck, 2003) for
phylogenetic reconstructions. The nucleotide sequence
evolution model needed for this analysis was identified
using Modeltest (Posada & Crandall, 1998). Maximum
likelihood analysis was performed using the GTR + G
(general time reversal) model of sequence evolution. The
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Table 1. Important treatments of Salicornia, ploidy levels, synonymy, and distribution.
Area,
reference Listed species
Ploidy
level
2n =
Synonyms, as given by
the authors (selected)
Species names ac-
cepted in this account
(partly provisional) Distribution
Europe
(Fl. Eur. 1,
ed. 2; Ball
& Akeroyd,
1993)
S. europaea L.
S. obscura P.W. Ball
& Tutin
S. prostrata Pall.
S. pusilla Woo ds
S. ramosissima
Woods
S. dolichostachya
Moss subsp. dolicho-
stachya
subsp. strictissima
(Gram) P.W. Ball
S. fragilis P.W. Ball
& Tutin
S. nitens P.W. Ball &
Tut in
18
18
18
18
18
36
36
36
36
S. stricta Dumort., S.
patula Duval-Jouve, S.
brachystachya (G.F.W.
Meyer) D. König, S.
simonkaiana (Soó) Soó
S. oliveri Moss,
S. pojarkovae Semenova
S. strictissima Gram
S. emerici Duval-Jouve,
S. stricta subsp. decum-
bens Aellen (S. stricta
subsp. procumbens sensu
D. König), S. veneta
Pignatti & Lausi, S. lute-
scens P.W. Ball & Tutin
S. europaea L.
S. obscura P.W. B a ll
& Tutin
S. perennans Willd.
S. pusilla Woods
S. ramosissima
Woods
S. dolichostachya
Moss
S. procumbens Sm.
in Sowerby
S. emerici Duval-
Jouve
S. nitens P.W. Ball
& Tutin
NW Europe
W Europe
SE & E Europe, ? Siberia
N & NW France,
S Britain, S Ireland
W Europe, W Medi-ter-
ranean,
N Europe (except Baltic
Sea)
North Sea, Baltic Sea
W & S Europe
W Europe
Scandinavia
(Fl. Nord.
1; Pii rainen,
2001)
S. europaea L.
S. dolichostachya
Moss subsp. dolicho-
stachya
subsp. pojarkovae
(Semenova) Piirainen
subsp. strictissima
(Gram) P.W. Ball
18
36
S. herbacea L.,
S. ramosissima Woods ,
S. brachystachya (G.F.W.
Meyer) D. König
S. pojarkovae Semenova
S. strictissima Gram,
S. leiosperma Gram
S. europaea L.
S. dolichostachya
Moss
S. pojarkovae
Semenova
S. procumbens Sm.
in Sowerby
Coasts up to 70°
W Denmark
N Norway
Denmark, SW Sweden,
S Norway
British Isles
(Davy & al.,
2001)
S. europaea L.
S. obscura P.W. B a ll
& Tutin
S. pusilla Woo ds
S. ramosissima
Woo ds
S. dolichostachya
Moss
18
18
18
18
36
(? var. of S. europaea L.)
(? var. of S. europaea L.)
S. europaea L.
S. obscura P.W. B a ll
& Tutin
S. pusilla Woods
S. ramosissima Moss
S. dolichostachya P.W.
Ball & Tutin
All coasts up to 54°
(scat t ered)
Up to 55°30
All coasts
All coasts
Up to 56°
1150
TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
Table 1. Important treatments of Salicornia, ploidy levels, synonymy, and distribution.
Area,
reference Listed species
Ploidy
level
2n =
Synonyms, as given by
the authors (selected)
Species names ac-
cepted in this account
(partly provisional) Distribution
S. fragilis P.W. Ball
& Tutin
S. nitens P.W. Bal l
& Tutin
36
36
S. fragilis P.W. Ba l l
& Tutin
S. nitens P.W. Bal l
& Tutin
Up to 55°40
Up to 55°30 (scat tered)
France
(Lahondère,
2004)
S. brachystachya D.
König
S. disarticulata Moss
S. obscura P.W. Ba l l
& Tutin
S. patula Duval-Jouve
S. ramosissima
Woods
S. dolichostachya
Moss
S. emerici Duval-
Jouve
S. fragilis P.W. Ball
& Tutin
18
18
18
18
18
36
36
36
S. pusilla Moss,
S. stricta Dumort.
S. pusilla Woods
S. stricta (G.F.W. Meyer)
D. König p.p., etc.
S. procumbens Sm. in
Sowerby, S. appressa
Dumort.
S. procumbens Sm. in
Sowerby var. stricta
S. nitens P.W. Ball &
Tut i n, S. veneta Pignatti
& Lausi
S. lutescens P.W. Ball &
Tut in
S. ramosissima
Woods
S. disarticulata Moss
S. obscura P.W. Ball
& Tutin
S. patula Duval-Jouve
S. ramosissima
Woods
S. dolichostachya
Moss
?
S. emerici Duval-
Jouve
S. fragilis P.W. Ball &
Tut in
N coast up to Bretagne
N & W coasts
W & N coasts
S coast, Corse
W and N coasts, Corse
W and N coasts
S coast, W coast up to
Bretagne
W and N coasts
Mediterranean
Region
(Greuter & al.,
1984)
S. europaea L.
S. prostrata Pall.
S. pusilla Woo ds
S. ramosissima Woo ds
S. procumbens Sm. in
Sowerby
? S. emerici Duval-
Jouve
? S. nitens P.W. B a ll
& Tutin
? S. oliveri Moss
? S. veneta Pignatti &
Lausi
S. deserticola A.
Cheval.
S. brachystachya
(G.F.W. Meyer)
D. Kön ig, S. europaea
subsp. duvalii (A. Chev.)
Maire, S. obscura (P.W.
Ball & Tutin, S. patula
Duval-Jouve, S. stricta
Dumort., S. appressa
Dumort., S. fragilis P. W.
Ball & Tutin, S. lutes-
cens P.W. Ball & Tutin
S. disarticulata C.E.
Moss
S. patula Duval-Jouve,
and ?
S. perennans Willd.
S. pusilla Woods
?
?
S. emerici Duval-Jouve
S. nitens P.W. Ball &
Tut in
?
S. veneta Pignatti &
Lausi
S. deserticola A.
Cheval.
Around the
Mediterranean except
from Algeria to Sinai
Bulgaria, Asian Turkey
France
Spain to Italy, Bulgaria
Portugal, France, Italy,
Asian Turkey
France
Portugal
France
Italy
Algeria (N Sahara)
Table 1. Continued.
1151
Kadereit & al. • Phylogeny and biogeography of SalicorniaTAXO N 56 (4) • November 2007: 1143–1170
Table 1. Important treatments of Salicornia, ploidy levels, synonymy, and distribution.
Area,
reference Listed species
Ploidy
level
2n =
Synonyms, as given by
the authors (selected)
Species names ac-
cepted in this account
(partly provisional) Distribution
Iberian Pen.
(Fl. Ib 2;
Valdés &
Castroviejo,
1990)
S. ramosissima
Woods
S. emerici Duval-
Jouve
S. dolichostachya
Moss
18
36
36
S. nitens sensu Franco S. ramosissima Woo ds
(? also S. patula
Duval-Jouve)
S. emerici Duval-Jouve
S. dolichostachya
Moss
All coasts incl. Balearic
Isl., more rarely inland
Coasts of NE Spain and
S France
Coasts of N Spain
Iberian Pen.
(Rivas-
Martinez
& Herrera,
1996)
S. obscura P.W. Ba l l
& Tutin
S. patula Duval-
Jouve
S. ramosissima
Woods
S. dolichostachya
Moss
S. lutescens P.W. B al l
& Tutin
S. emerici Duval-
Jouve s.l.
18
18
18
36
36
36
S. decumbens (Aellen)
Rivas-Mart. (? S. pro-
cumbens Sm.)
S. appressa Dumort.
S. stricta sensu D. König
S. fragilis P.W. Ball &
Tut in
S. veneta Pignatti &
Lausi, S. vicensis J.
Duvign., S. nitens P.W.
Ball & Tutin,
? S. obscura P.W. B a ll
& Tutin
S. patula Duval-Jouve
S. ramosissima Moss
S. dolichostachya
Moss
S. nitens P.W. Ball &
Tut in
S. emerici Duval-
Jouve
Coats from S Scandi-
navia to N Spain
Strait of Gibraltar,
Medit. coasts and inland
Spain
S England to Portugal
(Algarve)
Coasts from Britain to
S Portugal, probably also
along NW Morocco and
SE Spain
Atlantic coasts
Atlantic and Medit.
coasts from Britain to
Corse and Sardinia
Italy
(Iberite, 1996)
S. patula Duval-
Jouve
S. emerici Duval-
Jouve
S. dolichostachya
Moss
S. veneta Pignatti &
Lausi
18
36
36
36
S. patula Duval-Jouve
S. emerici Duval-
Jouve
S. dolichostachya
Moss
S. veneta Pignatti &
Lausi
All Italian coasts, incl.
islands
All Italian coasts, incl.
Sicily & Sardinia
Tyrrhenian coast
(S Latium)
NW Adriatic coast,
endemic
Tu rk ey
(Fl. Turk. 2;
Ball, 1967)
S. europaea L.
S. prostrata Pall.
S. fragilis P.W. Ba l l
& Tutin
S. stricta Dumort.
S. ramosissima auct.
S. stricta auct., S. lute-
scens P.W. Ball & Tutin
?
S. perennans Willd.
S. patula Duval-Jouve
?
Inland Turkey
Coastal W Turkey
Egypt
(Boulos, 1999)
S. europaea L. s.l. S. obscura P.W. Ball &
Tut in
? N & C Egypt, Sinai
Arabian Pen.
(Boulos, 1996) S. europaea L. ? Arabian Gulf: Kuwait to
Bahrein
Table 1. Continued.
1152
TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
Table 1. Important treatments of Salicornia, ploidy levels, synonymy, and distribution.
Area,
reference Listed species
Ploidy
level
2n =
Synonyms, as given by
the authors (selected)
Species names ac-
cepted in this account
(partly provisional) Distribution
Libanon/Syria
(Mouterde,
1966)
S. europaea L. ? SW Syria (near
Damascus), NE Syria
(Lake Khatouniye)
Iraq (Aellen &
Hillcoat, 1964)
S. herbacea L. s.l. ? Iraq (Western Desert)
Middle East
(Fl. Ir. 172,
Hedge, 1997)
(de scr ibed
afterwards)
S. europaea L. s.l.
S. persica Akhani 36
S. prostrata Pall. ?
S. persica Akhani
N & C Iran, Turkmeni-
stan, NE Afghanistan
C Iran
East Europe
(Fl. Eur. Or. 9;
Tzvelev, 1996)
S. europaea L.
S. perennans Willd.
? S. ramosissima
Woods
S. borysthenica
Tzvelev
S. pojarkovae
Semenova
18
18
36
36
S. acetaria Pall.
S. prostrata Pall
S. herbacea L. subsp.
pojarkovae ( Semenova)
V.G . Se r gi e nk o , S. doli-
chostachya Moss subsp.
pojarkovae (Semenova)
Piirainen
S. europaea L.
S. perennans Willd.
?
S. borysthenica
Tzvelev
S. pojarkovae
Semenova
White Sea coast, Baltic
Sea coast
S Ukraine, SE European
Russia
S Crimea and S Russia
(Rostov prov.)
Black Sea coast near
lower Dnepr river
Northern European
Russia: White Sea coast
Former
U.S.S.R
(Cze repa nov,
1995)
(de scr ibed
afterwards)
S. europaea L.
S. perennans Willd.
S. borysthenica
Tzvelev
S. pojarkovae
Semenova
S. heterantha S.S.
Beer & Demina
S. prostrata Pall.
S. dolichostachya auct.
S. europaea L.
S. perennans Willd.
S. borysthenica
Tzvelev
S. pojarkovae
Semenova
S. heterantha S.S.
Beer & Demina
European Russia (north-
ern)
Widespread
European Russia (south-
ern)
European Russia (north-
ern)
SE European Russia
Siberia (Fl.
Sib. 5; Lomo-
nosova, 1992)
(de scr ibed
afterwards)
S. europaea L.
S. altaica Lomon.
?
S. altaica Lomon.
W, C & E Siberia
S Siberia (Altai)
Central Asia
(Pl. Centr.
Asia 2;
Grubov, 2000)
S. europaea L.
subsp. acetaria Pall.
subsp. prostrata Pall.
?
S. perennans Willd.
(p.p.)
Mongolia, W China
Table 1. Continued.
1153
Kadereit & al. • Phylogeny and biogeography of SalicorniaTAXO N 56 (4) • November 2007: 1143–1170
Table 1. Important treatments of Salicornia, ploidy levels, synonymy, and distribution.
Area,
reference Listed species
Ploidy
level
2n =
Synonyms, as given by
the authors (selected)
Species names ac-
cepted in this account
(partly provisional) Distribution
China (Fl.
China 5; Zhu
Gelin, 2003)
S. europaea L. Prob. S. prostrata Pall. ? W, C and NE China,
coastal China down to
31° N
North America
(Fl. North Am.
4; Ball, 2003)
S. maritima S.L.
Wolff & Jefferies
S. rubra A. Nelson
S. bigelovii Torrey
S. depressa Standl.
18
18
36
36
S. prostrata sensu
Standl.
S. borealis S.L. Wolff &
Jefferies
S. virginica L.
? S. maritima S.L.
Wolff & Jefferies
? S. rubra A. Nelson,
? S. borealis S.L.
Wolff & Jefferies
S. bigelovii Torr.
S. depressa Stando.
Coastal SE Canada,
northeastern U.S.A.,
S Alaska
Central U.S.A. and
Canada, Subarctic
Canada
Gulf of Mexico, Atlantic
coast up to Maine,
S California
Pacific coast from
Alaska to California,
Atlantic coast from
Canada to S Carolina
Wes ter n
Trop. Africa
(Brenan,
1954, 1966)
S. praecox A. Chev.
S. senegalensis A.
Chev.
S. praecox A. Chev.
S. senegalensis A.
Chev.
W Senegal
W Senegal
Eastern Trop.
Africa (Fl.
Zamb. 9;
Brenan, 1988)
S. perrieri A. Chev.
S. pachystachya
Bunge ex Ungern-
Sternb.
S. pachystachya sensu
Toelken p.p.
S. perrieri A. Chev.
S. pachystachya
Bunge ex Ungern-
Sternb.
E African coast:
Mozambique to Natal,
Madagascar, poss.
Tanzania and Zanzibar
E African coast: S Kenia
to Natal, Madagascar
South Africa
(Tölken,
1967)
S. meyeriana Moss
S. pachystachya
Bunge ex Ungern-
Sternb.
S. uniflora Toel ke n
Incl. S. perrieri A. Chev. S. meyeriana Moss
S. pachystachya
Bunge ex Ungern-
Sternb.
S. uniflora Toel ke n
S African coasts,
Vanrhy n s dort to D urba n
E African coast to Natal
SW Namibia (Lüderitz),
Northwest S Africa
(Darling)
South Asia
(Rev. Handb.
Ceylon 9;
Boulos, 1995)
S. brachiata Roxb. S. brachiata Roxb. Coastal Ceylon, E coast
of India up to Bengal
Table 1. Continued.
1154
TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
detailed ML settings were: base frequencies A = 0.3235,
C = 0.2886, G = 0.1969, T = 0.1910, γ-shape parameter:
0.7555, rate matrix: 0.534, 2.989, 1.327, 0.224, 2.989. A
total of 10,000,000 generations were simulated, sampling
the chain every 100 generations. The first 4,000 trees were
discarded in the burn-in phase and the remaining 16,000
were used to estimate Bayesian posterior probabilities.
The posterior probabilities derived from the Bayesian in-
ference served as measure of support.
RESULTS
The ETS data matrix comprises 185 individuals and
507 characters. Of these, 279 are invariable, 76 are parsi-
mony uninformative and 152 (30%) parsimony informa-
tive. Within Salicornia (164 individuals), 431 characters
are invariable, 22 are parsimony uninformative and 54
(10.7%) parsimony informative.
In the MP analysis a total of 3,937 shortest trees of 437
steps were found on one island with a consistency index
(CI) of 0.705 and a retention index (RI) of 0.936. Figure
4 shows the ML tree with number of character changes
above branches and posterior probabilities resulting from
the Bayesian analysis below branches. The strict consensus
tree derived from the parsimony analysis and the cladogram
derived from the Bayesian inference were identical.
DISCUSSION
Origin of Salicornia. —
The ETS tree clearly re-
solves Salicornia as monophyletic (Fig. 4A). This supports
the results of previous studies (Kadereit & al., 2006; Mu-
rakeözy & al., 2007) which were based on a much smaller
sample of ITS and atpB-rbcL spacer sequences (Kadereit
& al., 2006) and ITS, matK, trnL/F (Murakeözy & al.,
2007), respectively.
The annual habit and the size difference between
larger central and smaller lateral f lowers together forming
a triangle (Fig. 2A–E) which were used by Scott (1977) as
diagnostic characters to delimit Salicornia from Sarco-
cornia thus prove to be autapomorphies of the genus. The
latter character, however, needs to be qualified: In most
species of Sarcocornia the lateral flowers are also slightly
smaller than the central f lower (comparable to some tetra-
ploid Salicornia, especially Salicornia freitagii ”) and in
a few species of Sarcocornia lateral flowers are distinctly
Fig. 4A–C. Maximum likelihood tree based on 185 ETS sequences; 164 sequences represent the genus Salicornia ; number of
character changes above branches, posterior probabilities ( > 75) resulting from the Bayesian analysis below branches.
1155
Kadereit & al. • Phylogeny and biogeography of SalicorniaTAXO N 56 (4) • November 2007: 1143–1170
smaller (e.g., Sarcocornia freitagii S. Steffen, L. Mucina
& G. Kadereit, ined.). But the flowers in Sarcocornia are
always arranged in a row and the lateral flowers are never
in contact beneath the central flower as is usually the case
in Salicornia (but see Moss, 1912).
The ITS and atpB-rbcL spacer data for the Salicornia/
Sarcocornia lineage (Kadereit & al., 2006) and our find-
ings for ETS (Fig. 4A) congruently support three major
clades: (1) American/Eurasian Sarcocornia, (2) Salicor-
nia, and (3). South African/Australian Sarcocornia. Of
these, the former two are well-supported by molecular
data while the latter receives relatively low BS support
and is not resolved by atpB-rbcL spacer data. The mo-
lecular data are contradictory with respect to the position
of Salicornia. In the ETS tree, Salicornia is sister to a
clade comprising Eurasian and North American Sarco-
cornia (Fig. 4A), in the ITS tree it originates from within
South African/Australian Sarcocornia, and in the atpB-
rbcL spacer tree it originates from within the American/
Eurasian Sarcocornia. None of these topologies receives
convincing statistical support. The changing position of
Salicornia might be an artefact caused by its relatively
long branch in combination with short basal branches
within the Sarcocornia/Salicornia lineage. In addition
to the morphological differences between the two genera
(see above), these results substantiate the separation of
Salicornia and Sarcocornia though this eventual ly might
leave the latter genus paraphyletic.
The intrageneric topology of the ETS tree implies an
Eurasian origin of Salicornia because the early branching
Salicornia crassa” group is distributed in Eurasia, and
most American as well as the two South African lineages
originate from within Eurasian clades (Fig. 4B). This in
turn suggests that Salicornia is most closely related to
Eurasian/American Sarcocornia as found here. In Eura-
sia, Sarcocornia is restricted to the Mediterranean and
the Atlantic coast. Sarcocornia perennis, a species with
creeping branches, extends northwards up to the British
Channel with a few outposts in coastal South Ireland,
Wales and Scotland (Davy & al., 2006). The distribu-
tion area of Sarcocornia usually does not exceed the 1°C
January isotherm in the northern hemisphere (although
according to Davy & al., 2006 in case of the populations
on the British Isles its distribution corresponds more
closely with the July isotherm). Obviously Sarcocornia
is frost-susceptible, and its distribution also thins out in
the Northeast Mediterranean towards the Black Sea coast.
In North America only the erect growing Sarcocornia
ambigua reaches southern New England where mean low
temperatures reach –5°C. In severe winters the growth
of the current season dies back but the stouter woody
branches survive (P. Ball, pers. obs.). We deduce, there-
fore, that many local Sarcocornia lineages might have
gone extinct during the Pleistocene glaciations. Especially
in the northern hemisphere the genus is species-poor with
only two species in Eurasia and three to four species oc-
curring in North America. In contrast, the South African
and South American Sarcocornia lineages comprise 11
to 15 species (Kadereit & al., 2006) and 6 to 7 species
(Alonso & Crespo, in press). For South Africa this would
constitute an indirect corroboration of the hypothesis
that the climatically stable regions support and preserve
rich cladogenesis (Dynesius & Jansson, 2000; Jansson &
Dynesius, 2002).
Large-scale extinctions in northern Sarcocornia line-
ages might have also played a role in shaping the unre-
solved relationships among the major clades of Sarcocor-
nia and Salicornia, and they might explain the relatively
long and late diverging clades supporting the Eurasian and
American Sarcocornia species, in constrast to the early
and more extensively diverging South African clade.
The annual Salicornia species have a much wider dis-
tribution in the Northern hemisphere than Sarcocornia
(see Fig. 3). They extend into adjacent areas with severe
frost during winter, and even into the boreal and subarctic
zones. The northernmost species are Salicornia pojarkovae
which occurs at the White Sea (northern European Russia)
and at the Norwegian Sea (northern Norway) coasts in-
cluding the area beyond the Polar Circle (Semenova-Tyan-
Shanskaya, 1956; Piirainen, 2001) and S. borealis which
is distributed in North Canada (James Bay, Hudson Bay
and southern Yukon). This area expansion of Salicornia
in contrast to Sarcocornia indicates that likely the annual
life form was the key innovation which enabled Salicor-
nia to colonize hygro-halophytic habitats in environments
susceptible to severe frost. In warm temperate and Medi-
terranean climates, Salicornia and Sarcocornia grow in
close sympatry but in ecological respect they are usually
well separated. Salicornia often dominates coastal lagoons
and—most conspicuously—saline inland depressions of
the semiarid and arid parts of the Mediterranean region
which are flooded for weeks or months by the winter rains.
Therefore, the annual life form was possibly also a key in-
novation which enabled Salicornia to colonize less stable
and seasonally flooded habitats.
The annual life form in Salicornia arose some time
between the Middle Miocene and the beginning of the
Pleistocene (9.4–1.4 mya; Kadereit & al., 2006). Based on
the ecology and distribution of extant species of Eurasian
Sarcocornia and Salicornia two alternative hypotheses
can be formulated: (1) The annual life form evolved from
a perennial lineage in marginal habitats where probably
increasing frost was the driving selective force, possibly
through selection for shorter generation cycles as con-
sequence of reaction to cold stress. Simultaneously or
later it invaded suitable habitats in areas with warmer cli-
mates. (2) The annual life form evolved from an ancestral
Mediterranean perennial lineage under a warm-temper-
1156
TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
S. perennans. 720 - Russia, Rostov prov., Manych river
S. perennans. 448 - Ukraine, SE Crimnea, salt lake
S. perennans. 322, 323 - NW Kazakhstan, inland
S. aff. patula. 636 - Turkey, inland
S. perennans. 480, 481 - Russia, Rostov prov.
S. aff. perennans. 865 - shores of Lake Aral
S. aff. patula. 613 - C Turkey, inland
S. perennans. 445 - Ukraine, NE Crimea, salt lake
S. bigelovii. 896 - N America, E coast
S. bigelovii. 1428 - Mexico, W coast
S. depressa. 1115 - N America, E coast
S. depressa. 488 - N America, W coast
S. depressa. 898, 899, 900, 901, 1043 - N America, E coast
S. aff. perennans. 340 - Altai, inland
S. aff. perennans. 339 - Russia, S Siberia, inland
S. aff. perennans. 447, 467 - Tuva, inland
S. aff. perennans. 985a - Russia, Novosibirsk, inland
S. aff. perennans. 446 - Russia, E Siberia, inland
S. "sibirica". 468 - Tuva, inland
S. altaica. 454 - Russia, C Siberia, inland - decaploid
S. aff. europaea. 484 - Russia, Arkhangel’sk prov.
S. aff. perennans. 863 - shores of Lake Aral
S. aff. meyeriana. 587 - S Africa, inland
S. meyeriana.1007 - S Africa, W Cape
S. "macrocarpa". 459, 935 - S Africa, eastern S coast
S. "macrocarpa". 946 - S Africa, eastern S coast
S. meyeriana. 923 - S Africa, W Cape
S. uniflora. 1009 - Namibia, W coast
S. "dagmarae". 389, 1004, 1011, 1091 - S Africa, W Cape
S. meyeriana. 924 - S Africa, W Cape
S. "knysnaensis". 381 - S Africa, W Cape, Knysna lagoon
S. "narmanii". 616 - Turkey, inland
S. aff. perennans. 992a - China, Nei Menggu prov.
S. aff. perennans. 864 - shores of Lake Aral
S. europaea s.l. 854 - Japan
S. aff. perennans.1246 - Iran, inland
S. rubra. 1376 - U.S.A., Montana, inland
S. borealis. 1378 - Canada, Manitoba
S. borealis. 1048 - Canada, Yukon
S. rubra. 1041 - Canada, Quebec
S. rubra. 1417 - Canada, Ontario
S. rubra. 1419 - U.S.A., Michigan, inland
S. rubra. 1112 - U.S.A., California, inland
S. rubra. 1044 - U.S.A., Nevada, inland
S. rubra. 1436 - U.S.A., Nevada, inland
S. "crassa". 451 - Ukraine, N Crimea, Black Sea coast
S. "crassa". 610 - NE Turkey, inland
3
1
1
1
1
1
2
10 3
91
1
1
5
1
2
11
3
11
1
1
5
1
2
2
11
1
1
S. perennans. 379 - Romania, inland
S. aff. patula. 366 - Sicily, SE coast
S. aff. patula. 490 - Italy, W coast
S. aff. patula. 1252 - Italy, E coast
S. aff. perennans. 1359 - Austria, inland
S. patula. 635 - Turkey, W coast
S. patula. 1304 - Turkey
S. perennans. 395, 396 - Romania, inland
S. perennans. 472, 473 - Ukraine, W Crimea, salt lake
S. perennans. 359 - Hungary, inland
S. aff. patula. 987a - Italy, Adriatic coast
S. aff. patula. 365 - Sicily, SE coast
diploid III
(Salicornia
perennans
group)
diploid IV
(Salicornia sibirica
group)
Salicornia rubra group
Salicornia borealis group
Salicornia
meyeriana
clade
Salicornia altaica “clade”
Salicornia "crassa" group
diploid VII
diploid VI
North
American
tetraploids
4n
Fig. 4 continued
92
99
100
83 99
98
90
96
98
100
100
89
92
Fig. 4B. Monophyletic Salicornia lineage resolved in the ML tree based on ETS sequences (see Fig. 4A); numbers after spe-
cies names indicate different accessions from the same region (compare Appendix for exact localities of each sample);
colour labelling: yellow – American samples; orange – South African samples; samples without underlying colour are
from Eurasia; red bars – Baltic Sea; green bars – Lake Aral (both examples for multiple arrival of different ETS genotypes);
blue bars mark two samples where prostrate and erect growth forms were analysed from the same locality (see text for
further explanations).
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ate (subtropical) climate. The annual habit enabled the
first Salicornias to colonize seasonally flooded habitats
in large parts of the Sarcocornia area and subsequently
it proved also to be an appropriate adaptation to habitats
exposed to severe frost. However, neither hypothesis can
be tested.
When the Salicornia lineage split from the Sarcocor-
nia lineages some time in the Middle or Late Miocene,
about 9.4–4.2 Mya (Kadereit & al., 2006), globally the
climate was much warmer, and large areas from Southeast
Europe across the Black Sea, the Caspian Sea and beyond
to the Aral Sea were covered by the Paratethys, a northern
remnant of the former Tethys Sea, which in the process of
the alpine orogenies stepwise disintegrated into isolated
basins still present today (see, e.g., Rögl & Steininger,
1983; Steininger & Rögl, 1984; Ricou, 1996; Dineley,
2004). Fossil evidence of Sarcocornia from the Paratethys
area is lacking, but the genus probably was present there
because many fossil terrestrial f loras from the Central and
Eastern Paratethys contain evergreen laurophyllous and
S. patula. 2002/1 - France, Mediterranean Sea coast, Camargue
S. ramosissima. 2002/13 - NE Spain, inland
S. ramosissima. 2002/19 - N Spain, Atlantic coast
S. ramosissima. 1248 - S Spain
S. ramosissima. 1249 - S Spain, inland
S. aff. europaea. 627 - SW Turkey, inland
S. aff. perennans. 357 - Hungary, inland
S. ramosissima. 955, Jerx.1, Arte.3 - Germany, inland
S. ramosissima. 393. Portugal, Algarve coast
S. europaea. 993a - Baltic Sea coast
S. aff. perennans. 455, 453 - Russia, Tuva, inland
S. aff. perennans. 450 - Russia, Chita, inland
S. aff. perennans. 602 - shores of Lake Aral
S. pachystachya. 384, 1395 - South Africa, E coast
S. persica.1243, 1244, 1245, 1247 - Iran, inland
S. "arabica". 991a, 999 - Arabian Gulf coast
S. aff. perennans. 617 - E Turkey, inland
S. aff. perennans. 990a - Dead Sea coast
S. aff. perennans. 601 - shores of Lake Aral
S. aff. borysthenica. 986a - Russia, Uralsk prov.
S. heterantha. 719 - Russia, Rostov prov.
S. aff. fragilis. 962, 963 - France, Atlantic coast
S. aff. fragilis. 2002/2 - France, Mediterranean Sea coast, Camarque
S. dolichostachya. 989b, 990b, Great Brittain
S. dolichostachya. 966, 957, 961, 958, 964 - France Atlantic coast
S. dolichostachya. 974 - North Sea coast
S. procumbens. 952, 953, 973, 975, HK19_1, HK13_2 - North Sea coast
S. aff. emerici. 988 - Italy, Adriatic coast
S. veneta. 989a - Italy, Adriatic coast
2
1
3
1
1
1
1
5
1
2
9
1
1
S. maritima. 897, 1379, 1046, 1049 - N America, E coast
S. europaea. 991 - Great Brittain, S coast
S. europaea. HK A_20 - North Sea coast
S. pusilla. 574, 959, 960 - France, Atlantic coast
S. pusilla. 985b, 986b, 987b, 988 - Great Brittain, S coast
S. aff. ramosissima (brachystachya sensu Lahondère 2004). 956, 969, 971 - France, Atlantic coast
S. ramosissima. 2002_22. - N Spain, Atlantic coast
S. ramosissima. 965, 967, 968, 970 - France, Atlantic coast
S. ramosissima. 992b, 993b - Great Brittain, S coast
S. ramosissima. 951, 954 972, 976, 977, HK21_19 - North Sea
S. ramosissima. Grasw.3, Boinsw.1 - Baltic Sea coast
1S. ramosissima. 1250, 1251 - S Spain, inland
S. borysthenica. 449 - Ukraine, E Crimea
S. dolichostachya. 2002/5. E Spain, Mediterranean Sea
S. dolichostachya. 633 - Turkey, W coast
S. aff. emerici. 631 - Turkey, W coast
S. "freitagii". 611,1274 - NE Turkey, inland
S. pojarkovae. 478, 479. Russia, White Sea coast
S. sp. 482 - Russia, Astrakhan prov.
S. sp. 363 - Sicily, S coast
S. sp. 994. Greece, Peleponnes
diploid I
(Salicornia
ramosissima
clade)
diploid II
(Salicornia
europaea
group)
Eurasian
tetraploids
(Salicornia
dolichostachya
clade)
Salicornia persica clade
Salicornia pachystachya clade
Fig. 4 continued
diploid V
4n
4n?
100
83
98
94
100
75
99
95
98
Fig. 4C. Monophyletic Salicornia lineage resolved in the ML tree based on ETS sequences (see Fig. 4A); numbers after spe-
cies names indicate different accessions from the same region (compare Appendix for exact localities of each sample);
colour labelling: yellow – American samples; orange – South African samples; samples without underlying colour are
from Eurasia; red bars – Baltic Sea; green bars – Lake Aral (both examples for multiple arrival of different ETS genotypes);
blue bars mark two samples where prostrate and erect growth forms were analysed from the same locality (see text for
further explanations).
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sclerophyllous frost-sensitive trees and shrubs through
Ukraine and the Caucasus up to Turkmenia and West
Kazakhstan (Palamarev, 1989; Mai, 1995 and ref. therein),
and near to its arid easternmost section microfossils docu-
ment the formation of steppes and semideserts (see, e.g.,
Song & al., 1981 and ref. therein). The Paratethys area
with predominance of shallow coasts, absence of tides
and arid conditions in the eastern section probably offered
suitable conditions for the origin of Salicornia. The pres-
ence of the most ancestral Salicornia crassa” group just
near the northern and the southern shores of the Black Sea
which represents the residual of the Central Paratethys is
wel l in accordance wit h our opinion that Salicornia might
have originated somewhere between the East Mediter-
ranean and the eastern Paratethys.
In summary, the evolution of the annual habit (maybe
together with predominant inbreeding) was a key inno-
vation that enabled Salicornia to colonize cold temper-
ate and boreal regions as well as seasonally flooded and
highly dynamic habitats. Two main selective forces might
have driven the evolution of the annual life form, regular
severe frost and/or long-lasting flooding. Possibly, the
area of origin was located between the East Mediterranean
and the Central or eastern Paratethys.
Diversification within Salicornia. —
The tree to-
pology within Salicornia reveals the following overall
pattern (Fig. 4B, C): A basal split separates the S.crassa
group from the remainder of the genus. The latter shows a
large numb er of only wea kly differentiated line ages, most
of them having a Mediterranean and/or Eurasian distri-
bution. Five long branches (branches with five or more
character changes marked by bold lines in Fig. 4B, C) are
nested among these lineages. These long-branched line-
ages show either polyploidization or they are distributed
in geographically remote areas, or both. However, there
are two lineages in North America and two polyploid
lineages that do not have a long branch. Most likely, they
are of more recent origin. This topology shows that both
polyploidization and long-distance dispersal which often
were followed by radiation have played a major role in the
evolution of the genus.
Initial diversification. —
Diversification of extant
lineages probably started in the late Pliocene/early Pleis-
tocene, about 1.8–1.4 mya (Kadereit & al., 2006) with
the split of the S. crassa group (Fig. 4B). It consists of
two accessions, one from Crimea and one from North-
east Turkey. The plants were collected in areas where no
particular attention has been given to Salicornia so far.
The molecular data and also morphological differences,
the most prominent being the extremely robust appear-
ance of the specimens suggest that they likely represent
a new species which is awaiting a detailed study. From
their morphology we concluded that these two specimens
represent diploids. This and the distribution of tetraploid
clades within Salicornia (compare Fig. 4B, C) imply that
tetraploid and diploid Salicornia are not monophyletic
sister groups as suggested by previous studies (Papini
& al., 2004; Murakeözy & al., 2007) but that tetraploid
Salicornia originated more t han once from with in d iploid
Salicornia lineages.
The polyploid clades. —
It has long been known
(e.g., König, 1939), that diploid (2n = 18) and tetr aploid
(2n = 36) kar yotypes occu r in Salicornia (see review
given by Shepherd & Yan, 2003), and recently a decaploid
species (S. altaica, 2n = 90) was discovered ( Lomonosova,
2005). Polyploidization marks at least three widespread,
long-branched clades within Salicornia, the Salicornia
dolichostachya, S. bigelovii and S. depressa clades (North
American tetraploids) with the latter two being sister to
each other and probably one short-branched clade, the
Salicornia persica clade (Fig. 4B, C).
Surprisingly, almost all known Eurasian tetraploids
(S. dolichostachya, S. emerici, S. fragilis, S. pojarkovae,
S. procumbens, and S. veneta [probably a synonym of S.
emerici]) together with a few species of unknown ploidy
level (S. borysthenica, S.freitagii ”, S. heterantha) form
a well-supported, monophyletic group (Salicornia doli-
chostachya clade) with very little variation among the
32 accessions included. Our sampling covers most of the
distribution area of these species (Fig. 5A) and represents
all recognized species except S. nitens which maybe is a
synonym of S. emerici (Lahondère, 2004), or a micro-
species of the latter (Rivas-Martinez & Herrera, 1996).
Only one species, S. persica (Akhani, 2003), represents
an independent Eurasian tetraploid lineage, its ITS se-
quence being identical to accessions from Turkey and the
Arabian Peninsula with unknown ploidy level (Fig. 4C).
The ETS tree suggests that both the S. dolichostachya
clade and the S. persica clade are most closely related to
Southwest and Central Asian diploids. We are lacking
suff icient material f rom SW Asia (except for Turkey), E ast
Asia and North Africa from where the occurrence and
distribution of tetraploid species is not known. Probably,
as can be judged from the illustration in Berhaut (1974:
302), also S. senegalensis from Senegal belongs to the
Salicornia dolichostachya clade, and likewise maybe S.
deserticola (Maire, 1962). An improved sampling might
reveal further origins of Eurasian polyploid lineages such
as the decaploid S. altaica.
The low genetic variation found within the Salicornia
dolichostachya clade points to a recent and rapid expan-
sion into its present day distribution area. The clade is
distributed more or less continuously along the sandy and
muddy coasts of Europe from Port ugal to South Scandina-
via and the Kattegat. It has a more scattered distribution
around North Norway up to the White Sea (S. pojarkovae),
along the coasts of the Mediterranean and the Black Sea,
from where sometimes it enters inland salt marshes. This
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Fig. 5. A, distribution of examined specimens of Eurasian tetraploid Salicornia species; B, distribution of the different
North American ETS genotypes; C, distribution map of the S. ramosissima clade; D, distribution map of the S. europaea
group; E, distribution of the S. perennans group; F, distribution of the S. sibirica group.
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TAXO N 56 (4) • November 2007: 1143–1170Kadereit & al. • Phylogeny and biogeography of Salicornia
shows that this lineage is able to tolerate a span of climatic
conditions ranging from the warm-temperate Mediterra-
nean to subarctic climates. Most species of the Salicornia
dolichostachya clade grow in the lower belts of intertidal
salt marshes which are exposed to daily flooding for sev-
eral hours while only a few grow in the middle salt marsh
that is not flooded for several weeks in summer.
Although the species of the Salicornia dolichostachya
clade are molecularly very uniform, at least some show
considerable morphological and ecological differentia-
tion. This applies in particular to S. pojarkovae, a dwarfed
subarctic species with a very short life cycle (Semenova-
Tyan-Shanskaya, 1956; Piirainen, 2001), S. heterantha
(Beer & Demina, 2005; Fig. 2C) in which the tissues of
the central flower tepals and the inflorescence axis are
completely fused, and S. freitagii ”, an i n land tet raploid
with conspicuous scarious leaf and bract margins and
subequal flowers in one cyme.
Most species of the S. dolichostachya clade (S. bo-
rysthenica, S. dolichostachya, S. emerici, S. fragilis, S.
nitens, S. procumbens, S. veneta), however, are more dif-
ficult to separate morphologically and ecologically. Sali-
cornia dolichostachya seems to be a low level pioneering
species of the Atlantic coast with high tidal amplitudes,
whereas S. emerici seems to be confined to coastal la-
goons of the Mediterranean with very weak tides. The
other species, however, are somewhat intermediate. Since
also their distribution ranges at least partly overlap, a more
detailed study of the S. dolichostachya clade is needed
to disentangle the phylogenetic relationships within this
group. An ongoing A FLP analysis of this cla de may resu lt
in better phylogenetic resolution and may show the genetic
distinctness of some species (S. Beer, A.E. Yaprak & G.
Kadereit, unpublished data).
Two North American tetraploids, S. depressa and S.
bigelovii, form a monophyletic group that includes two
long-branched tetraploid sister clades (Salicornia bigelovii
clade and Salicornia depressa clade, Fig. 4B). This clade
forms a polytomy with the decaploid S. altaica and seven
accessions from Central Asia of unknown ploidy level.
This relationship, however, received little statistical sup-
port (posterior probability 60; Fig. 4B).
In contrast to the Eurasian tetraploids, these two
North American tetraploid species are well separated.
When directly compared they show 13 base mutations
and two indels of 10 and 6 nucleotides, respectively. While
S. bigelovii is morphologically very distinct, S. depressa
could well be taken for an Eurasian tetraploid, e.g., S.
fragilis. The monophyly of the S. depressa/S. bigelovii
clade receives only weak support (Fig. 4B). Probably the
two species separated shortly after their arrival in North
America.
Salicornia bigelovii is distributed on the Atlantic and
Gulf of Mexico coasts of the U.S.A., the Caribbean and
the coast of South California and adjacent Mexico and can
be distinguished from all other species of Salicornia by
its acute and sharply mucronate leaf and bract tips (Ball,
2003). According to Flora of North America (Ball, 2003),
Salicornia depressa is widespread along the Atlantic and
Pacific coasts of North America. While the seven acces-
sions of S. depressa are identical in their ETS sequences,
the two accessions of S. bigelovii (one from the East and
one from the West coast) differ substantially. Salicornia
bigelovii and S. depressa grow—like the Eurasian tetra-
ploids—in more frequently flooded lower and middle
zones of salt marshes.
Apart from the karyotype, the decaploid Salicornia
altaica is distinct in that the spike length—as in S. po-
jarkovaeexceeds the sterile part of the stem, in growth
form and in ecology. It grows on solonchaks at 1800 m
above sea level (Lomonosova, 2005). Surprisingly, it
shows very little sequence divergence from some Central
Asian accessions which were provisionally identified as
S. aff. perennans and may contain hidden polyploids as
well. Chromosome counts and a more detailed sampling
in the distribution area of S. altaica might give a clearer
picture of its origin.
In conclusion, the polyploid lineages are very suc-
cessful in terms of range expansion. Like their diploid
relatives, the polyploid species were able to rapidly spread
along the coasts. Most polyploid species found their eco-
logical optimum in lower and middle belts of salt marshes
and occupy these habitats often in monospecific stands
under widely differing climatic conditions. Possibly more
polyploid lineages will be found when sampling is in-
creased.
The diploid Eurasian clades and groups. —
The
diploid Eurasian accessions fall into seven clades/groups
of more or le ss similar ETS ge notypes. Only some of these
clades/groups receive considerable statistical support and
the relationships among them remain largely unresolved.
All seven diploid Eurasian clades/groups are widespread
with overlapping distribution ranges (Figs. 4, 5C–F).
The Salicornia ramosissima clade (diploid I, Fig. 4C)
is a clearly monophyletic, well supported lineage of 33
accessions distributed in the West Mediterranean, the At-
lantic coasts of West, Northwest and Central Europe, the
westernmost Baltic Sea and in eastern North America (S.
maritima, see above, Fig. 5C). The Salicornia ramosis-
sima clade originates from within the Salicornia euro-
paea group. Except for the two accessions from the West
Mediterranean which represent S. patula and S. ramosis-
sima, the accessions of the Salicornia ramosissima clade
show identical ETS sequences although several species are
included, S. ramosissima (locally often called S. brachy-
stachya), S. europaea, S. pusilla and S. maritima.
The Salicornia europaea group (diploid II, Fig. 4C)
consists of 16 accessions wh ich form a poly tomy of similar
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ETS genotypes that show a wide geographical distribution
(Fig. 5D). Like the Salicornia ramosissima clade it com-
prises several species, viz. S. ramosissima, S. europaea
and S. aff. perennans. The latter is not represented in the
Salicornia ramosissima clade. The Salicornia europaea