MOLECULAR ANALYSIS OF SOLIDASTER CV. LEMORE, A HYBRID GOLDENROD (ASTERACEAE)

2008·18.6 MB·English

by  Edward E Schilling

MOLECULAR
OF LEMORE,
SOLIDASTER
ANALYSIS
CV.
A GOLDENROD
HYBRID (ASTERACEAE)
James
Edward Beck
Schilling
B.
E.
and
went
of Ecology Evolutionary Biology
ungton
63130,
issouri U.S.A.
and
Garden
author correspondence Missouri Botanical
for ([email protected]
Missouri 631
St. Louis, 36, U.S.A.
Department
of Biology
address:
irrent
Durham U
North
Carolina 27708,
versity,
L
Randall Small
Patrick Calie
J.
artment of
Biological Scier
Kentucky
'astern University
)mond, Kentucky
40475,
U..
placement
of the generic o
ase pair polymorphisms. Cloning experiments recovered two different individual ITS sequences, one identi
L
^
^;^ unships within the genus
s
g
WoL
SoUa
ETS, phylogeny
CT Asteraceae, Astereae, Solidaster, ITS, hybrid,
go,
:
RESUMEN
un ETS
e realize analisis con los datos de las secuencias del ITS y nuclear ribos6mic o para evaluar las relacione
un un un
olidaster Lemore, cultivar que durante tiempo se creyo que era hlbri<io intergenerico (Solidago
cv.
>
de datos combinado de secuencias de ITS ET!Smostroquehayunrespalc
las los y
>
INTRODUCTION
Journal of the Botanical Research Institute of Texas 2(1)
8
phenomenon numerous documented examples Grant but there are
with 1980),
in plants, clearly still
(e.g.,
between
Of
perhaps hybridization
questions regarding evolutionary significance. greatest interest is
its
species of lineages that have diverged morphologically to the point of being recognized as distinct genera.
which normally considered
This represents potentially dramatic reversal of the process of evolution, is
a
on
and based phylogeny. thus
be divergent, also presents a challenge to systematic classification It is
to
it
be
of considerable interest examine closely possible cases of intergeneric hybridization to able to assess
to
how phenomenon
frequently occurs.
this
common
A
myth and perhaps even pervasive within
hybridization
persistent that intergeneric
is
is
Robinson and King and Robinson invoke intergeneric hybridiza-
Asteraceae. For example, (1983) (1987)
and
an explanation discordant distribution of morphological characters in Liabeae Eupatorieae,
tion as for
A
documented
however, few well cases of natural intergeneric
search of the reveals
respectively. literature,
documented by
been
have
Naturally occurring intergeneric hybrids recently
hybridization in Asteraceae.
made
been
some hybrids have
McKenzie and In intergeneric
(2004) Saito (2006). cases, artificial
et et
al. al.
between and
and have found incongruence nuclear
successfully Powell 1985; Carr 2003), studies
(e.g.,
&
chloroplast markers suggestive of past wide hybridization (Schilling Panero 1996; Fehrer et al. 2007).
most remains This prompted us undertake
documentation hybrids groups to
But of intergeneric in elusive.
within
a detailed study of a putative case of intergeneric hybridization the Astereae.
name known Lemore presumed
The
of the horticultural plant as Solidaster cv. (Fig. 1) reflects its
unknown
between and Aster The plant in the wild, but
hybrid origin as a cross species of Solidago L. L. is
North America (Nesom an
appeared in European gardens the import of plants from 1993). Its status as
after
Upland
intergeneric hybrid depends in part, however, on the classification of one of its putative parents, the
and The Upland White
White Aster, which has been variously placed in Aster, Solidago, Oligoneuron Small.
&
puzzlement
been taxonomists.
ptarmicoides (Torrey A. Gray) Boivin, has long a source of for
Aster, B.
S.
open corymbose and heads
outward appearance, capitulescence relatively large
especially
superficial
its
Its
and
and seems an conceived, reflected
with white rays disk flowers, clearly that of aster, as traditionally is
common
name. Despite considerable evidence has suggested a closer affinity to the goldenrods,
in this,
its
including the observation of abundant natural hybrids with species of Solidago (Boivin 1972), considerations
&
DNA
and
phytogeography and technical features of morphology (Brouillet Semple 1981), a chloroplast
of
widely
restriction site study placing within Solidago L. (Semple et al. 1999). Nevertheless, it is still referred
it
genus
an Aster Another, somewhat different interpretation involves segregation of the Oligoneuron as
to as
s.l.
from Nesom which would include the Upland White Aster as well as five other
distinct Solidago 1993),
(e.g.,
been be
Although the second parent of Solidaster has generally considered to a Solidago, particularly
species.
&
Nesom on morphology was more
Semple suggested based
(1993) that
canadensis (Brouillet 1981), it
S.
be Euthamia
Nutt.
likely to graminijolia (L.)
The taxonomic Upland White ptarmicoides, has been reviewed by Brouillet
history of the Aster, Solidago
and Semple and only summary will be presented here. Not only the generic placement but
(1981), a brief
where
also species epithet has varied. The plant was originally described by Nuttall in Inula L., it received
its
When
the appropriate epithet alba for white rays and disk flowers. transferred to either Aster or Solidago
its
resemblance
and (from
proved be already occupied, the alternative ptarmicoides to Achillea
this epithet to its
When
was by
proposed Nees. placed in
widely garden Fernald 1950)
ptarmica a cultivated plant; still
L.,
Nesom Over taxonomic
another genus, such as Oligoneuron 1993), reverts to the epithet album. its
(e.g., it
&
Cook
the species has been placed in nine separate genera by various authors (Semple 2006).
history,
&
Cook
Although
The taxonomic treatment of Solidago has been notoriously difficult (Semple 2006).
number North America, no morphological
clearcut
there are large of relatively similar species in eastern
a
apomorphy has been discovered unequivocally defines the genus. Similarly, delimitation of infrageneric
that
many
which
groups has been elusive as has recognition and identification of individual species, of differ
The
from one another by minute details of inflorescence form or pubescence. situation is further compli-
Some
and
by occurrence both hybridization polyploidy. representatives
cated the frequent of interspecific
Lemore
Schilling et Molecular analysis of Solidaster cv.
al.,
nd
dominants during
are particularly significant as early
where components model system
successional stages of old fields, se:vveeral are of a well studied ecological
Abrahamson become
2005). Addi Solidago taxa have invasive in Europe (Weber 2001)
et
(e.g., al. lly,
and (Dong and and
Asia 2006), are and the general evolution ecology
et
al.
&
(Van Kleunen Schmidt Jakobs 2004; Meyer The abundanc
2003; 2005).
et et
al. al.
:s
make
and importance sound taxonomy highly
ecological of Solidago therefore a desirable.
A
number
problems
of studies have applied molecular data the resolution of systematic in Astereae
to
& & &
Simpson Morgan Simpson Lane Zhang Noyes
(Suh 1990; 1992; 1996; 1996; Rieseberg 1999;
et
al.
&
body
Roberts Urbatsch 2003; Urbatsch 2003; Beck 2004), so a considerable of molecular data
et et
al. al.
DNA
has begun to accumulate for the tribe. Other than a chloroplast restriction site analysis (Zhang 1996;
DNA
Semple has been no sequence on although few
et 1999), there focus as yet for analysis Solidago, a
al.
we
sequences are available from other work. As part of an initial survey for suitable molecular markers,
analyzed ITS and ETS sequence variation several samples of Solidago that represented the major subunits
for
Cook
by Semple and Although
of the genus, as delimited (2006). the lack of suitable variation in these
make we
markers led us to abandon any attempt to a complete survey of the genus, one of the species that
sampled was ptarmicoides, and sufficient data have been acquired to allow for an assessment of generic
5. its
we
which
placement, as well as to clarify the parentage of its hybrid offspring, Solidaster cv. Lemore, report
Plant Material
A
sample Lemore was grown from material obtained commercially (Bluestone
of Solidaster
cv. (Fig.
1)
Perennials, Ohio, USA). Samples of Solidago (Appendix) were either collected in the or obtained from
field
member
herbarium specimens. Sampling was designed include one of each of the currently rec-
to at least
&
Cook
ognized and genus (Semple To
sections subsections of the 2006). evaluate intraspecific variability,
and an
multiple accessions of four species canadensis, ptarmicoides, nitidd) as well as
(S. S. riddellii, S. S.
we
most
additional sample of Brintonia discoidea were analyzed. Note that have elected to follow the recent
&
Cook which
treatment of Solidago (Semple 2006), deviates from nomenclature used in our earlier paper
10 Journal of the Botanical Research Institute of Texas 2(1)
from
(Beck 2004) by including Oligoneuron within Solidago but recognizing Brintonia as separate the
et it;
al.
North America
treatments.
classification of related genera also follows the Flora of
Methods
Molecular
DNA
and
made procedure Doyle
Preparations of from fresh (0.5-2.0 leaves generally followed the of
total g)
Dneasy
Doyle and those from herbarium material 0.1 were performed with the Plant Minikit
(1987), (ca. g)
DNA
(Qiagen, Valencia CA). The crude extracts of some samples required further purification using the
DNA
Methods and sequencing were
Wizard (Promega, Madison, Wisconsin). amplification
Kit protocol for
Schmidt and Amplification and sequencing reactions the ITS region
described in Schilling (2000). for
as
and
were both performed using primers "ITS-4" and "ITS-5" (White 1990). Amplification sequencing
et
al.
&
ETS region were performed using primers Ast-1 (Markos Baldwin 2001) and 18-S-ETS
reactions for the
&
PCR was
Sequencing
(Baldwin Markos 1998). All products were checked by agarose gel electrophoresis.
Dye
ABI Prism Terminator
done the University of Tennessee Automated Sequencing Facility, utilizing the
at
DNA
Cycle Sequencing reaction on an ABI 373 or ABI 3100 sequencer (Perkin-Elmer Inc. Foster City,
kit
same
The were comparison with the data displayed in
CA). sequence data text edited following
initial files
Sequence alignment was performed using the Clustal
four-color electropherograms before further analysis.
X
(Thompson
program
(version 1994).
et
1.6) al.
sample Lemore was undertaken confirm ITS poly-
Cloning of the ITS region for the of Solidaster cv. to
pGEM-T
PCR
morphisms from sequencing. The purified products were ligatedinto (Promega,
inferred direct
Competent ToplO San
Madison, Wisconsin) according the manufacturer's instructions. F' (Invitrogen,
to
and were screened
Diego, California) were transformed via electroporation the resulting colonies for
cells
PCR
were from
plasmids with by using the original amplification primers. Plasmids isolated single
inserts
(Sambrook Sequences
recombinant colonies using an alkaline lysis/PEG precipitation protocol et 1989).
al.
were obtained ten independent clones.
for
GenBank,
Data additional ITS and ETS sequences for Solidago were obtained from as well as for
for
Two
same Beck "Clade data
of the samples placed in the clade as Solidago in et (2004; III"). sets
all s.s. al.
were which ITS sequences from broad sampling of with samples
analyzed, the of utilized a Solidago,
first
The second both ITS and ETS data with broader sampling
of Brintonia discoidea as outgroups. utilized a
and
genera (Appendix) assess the placement of Solidago ptarmicoides of Oligoneuron relative to
of related to
and were added outgroups
and samples gramineus as
other of Sericocarpus Cuniculotinus
Solidago, tortifolius
maximum
were analyzed using both parsimony and Bayesian
Phylogenetic relationships
for this analysis.
PAUP*
with
Parsimony was implemented using 4.0bl0 (Swofford 2003), gaps treated as
approaches. analysis
TBR
random and with branch swapping.
missing using search with ,000 addition replicates
data, a heuristic
1
FASTSTEP
was performed with 10,000 using the search
Bootstrap analysis (Felsenstein 1985) replicates
&
MRBAYES
run
was implemented 3.0B4 (Huelsenbeck Ronquist 2001)
Bayesian in for
option. analysis
number
The
with chains and saved every 100 generations. of
ten million generations four separate trees
run and
was by sampled throughout the
discard "burn-in" assessed plotting likelihoods of trees
trees to as
An
10%
were
discarding trees prior to the stable likelihood plateau (in both analyses the first discarded).
all
maximum Time model
model sequence (GTR+I+G; General Reversible
evolution
appropriate likelihood of
gamma was
chosen
with a proportion of invariant sites and distributed rates) for the Bayesian analysis for
&
both analyses using Modeltest (Posada Crandall 1998).
RESULTS
Newly Lemore and were consistent in length with
obtained ITS sequences Solidaster for Solidago
for cv.
among
any
was length
previous reports the genus. In particular, there extraordinarily variation in
for little
627-629
of the sampled members of the genus; individual sequence lengths varied from bp. Insertion of
single bp indels were required for five samples (three insertions and two deletions) to produce a completely
1
aligned matrix of length 631 bp for the entire ITS region. Similarly, there was little sequence length varia-
was
627-630 and matrix
with sequences varying from bp, the aligned of
tion in allied genera, individual
Lemore
Molecular of 11
Schilling etal., analysis Solidaster cv.
length 634. There was also only limited sequence variation between species of Solidago for the ITS region;
between
pairwise comparisons revealed sequence divergence of generally less than 1%, with total differences
more
samples of 1-10 bp. Samples of other genera were generally, although not always, divergent, with
1-3% and 7-19 The sample
pairwise divergence values of total differences of bp. of Sericocarpus
tortifolius
differed from all Solidago samples for at least 15 bp, but was still relatively similar, with overall divergence
23-29
values of 2-3%; the sample of Cuniculotinus gramineus was somewhat more divergent, differing by
bp from
(4% overall divergence) samples of Solidago. In the five species (S. canadensis, S. riddellii, S. nitida,
and where were examined was most one bp
multiple accessions there
ptarmicoides, Brintonia discoided) at
S.
among
and no nonmonophyly.
samples evidence
difference of
The ITS sequence Solidaster cv Lemore was very similar to other Solidago sequences, but displayed
for
bp polymorphisms the following positions: 18 (A/G), 106 (C/A); 514 (C/T), 611 (G/T), 612 (C/T),
(Fig. 2) at
bp polymorphisms would with com-
613 (A/G). Visual inspection revealed that this pattern of exactly a
fit
and Cloned ITS
bination of the ITS sequences characteristic of ptarmicoides canadensis (Fig repeats
5. S. 2.)
from Solidaster Lemore exhibited ITS sequences that matched closely either those of ptarmicoides or
cv. 5.
showed
comparison broad sampling
those of canadensis. Phylogenetic analysis in to a of Solidago that
5.
some
consensus sequences from the clones clustered with support with those from ptarmicoides
statistical S.
and canadensis which provided supporting evidence that the polymorphisms obtained from direct
(Fig.
S.
3),
sequencing could have originated from a combination of the sequences from these species. The ITS sequence
Nesom
of Euthamia proposed by (1993) as the second potential parent of Solidaster, has been
graminifolia,
shown and and
be from (Noyes Rieseberg reported ITS
to relatively divergent those of Solidago 1999), its
minimum
(GenBank AF046982) from by 4 32
sequence differs that of ptarmicoides indels as well as a of
S.
Lemore show any polymorphisms,
bp. Because the ITS sequence of Solidaster did not evidence of indel
cv.
and only few bp polymorphisms, Euthamia not one of parents.
a graminifolia is clearly its
ETS
Approximately 450 bp of the region were amplified for each sample of Solidago with the primer
18S-ETS and Removing poor sequence and uncertain alignment produced matrix
pair Ast-1. regions of a
among
with a total length of 444 bp, including 18 bp of 18S coding sequence. As with ITS, length variation
sequences was minimal among Solidago samples: only a single bp deletion in patula, and only a single
1 5.
bp and bp both outgroup and were
insertion in Stenotus 3 deletion in taxa, Cuniculotinus Sericocarpus,
1 a
ETS ETS
required for complete alignment of this portion of the region. Levels of sequence divergence for
among 0-1%
were similar to those for ITS, with pairwise divergence values Solidago samples of (0-4 bp)
maximum 4%
and among The ETS sequence Lemore was
samples reaching a of (17 bp). of Solidaster cv.
all
bp
although each sequence exhibited non-informative
basically identical that of ptarmicoides, a single,
to 5.
polymorphism (position 124 in Solidaster, 36 in ptarmicoides; both A/G). Other than the polymorphic
S.
ETS
from
positions, the sequence of canadensis differed those of ptarmicoides only a single position,
at
S.
S.
and was no polymorphism sequence Lemore
there evidence of in the of Solidaster this position.
cv. at
and
For phylogenetic analysis to assess the placement of ptarmicoides relative to Solidago, the ITS
S.
ETS sequence data were analyzed together, producing a combined matrix of 1078 bp in which there were
46 potentially parsimony-informative characters and 85 additional variable but parsimony-uninformative
The low
characters. results of phylogenetic analyses (Fig. 4) reflected the overall levels of divergence in
many
The
providing a poorly resolved tree with relatively low levels of support for branches. results of the
parsimony and Bayesian analyses were topologically consistent although the Bayesian tree was more resolved.
A
was
monophyletic group corresponding to clade III of Beck et al. (2004) defined relative to Cuniculotinus
LOO 100%
and and
gramineus Sericocarpus with posterior probability of (Bayesian) (bootstrap),
a
tortifolius
respectively. At the next level of branching there was a large polytomy in the strict consensus tree, within
which there was a strongly supported clade formed by the three species of Chrysothamnus, C. scopulorum,
and
and supported with
(LOO; 99%), a variably clade Petradoria Stenotus
C. stylosus, C. viscidiflorus (0.97;
57%), and strongly supported clade formed by Chrysoma, and Brintonia 76%). Within the
a Solidago, (1.00;
last clade, there was a Chrysoma + Brintonia clade (0.79; <50%) that was sister to a Solidago s.s. clade (LOO;
69%). Within the Solidago clade, there was resolution in the consensus tree, with the only bootstrap
little
s.s.
12 Journal of the Botanical Research Institute of Texas 2(1)
Icaacgcgt
gaat
tcat
tg
c a
ptarmicoides a
S.
tggtgtga
cgcgt
canadensis
c a
a~|
S.
|
tggtgtg
caacgcgt
Solidaster
AAMAAaaAM
80%
support greater than multispecific clades going strongly supported canadensis + gigantea
for to a S. S.
was
clade (1.00; 94%); weaker support provided to clades consisting of S. rigida + S. ohiensis (0.99; 64%), 5.
+ 64%), and arguta + patula <50%). The three samples of ptarmicoides
caesia S. riddellii (0.62; S. S. (0.50; S.
members
were placed in a large polytomy with other of the genus (Fig. Results of the Bayesian analysis
4).
50%
provided weak strong support clades that received than bootstrap support, including
also to for less
and consensus
with Solidago/Chrysoma/Brintonia clades not present in the
Petradoria/Stenotus (0.94) strict tree:
and and
Oreochrysum + Tonestus with sequential addition of Lorandersonia Eastwoodia
(0.52), (0.76),
(0.51),
clade combined with the three species of Chrysothamnus These results are completely congruent
this (0.60).
showing
with those presented by Urbatsch (2003) in placing Oligoneuron within Solidago as well as
et
al.
They
Chrysoma as a near outgroup to Solidago relative to Sericocarpus. also support the revised classification
Chrysothamnus and genera presented by Urbatsch
of related et (2005).
al.
DISCUSSION
showed Lemore an hybrid by providing evidence not
Molecular data that Solidaster not intergeneric
cv. is
members
show both placed
only to identify parents (Figs. 3) but to clearly that are accurately as of
its 2,
The and
Solidago (Figs. combination of Solidago ptarmicoides 5. canadensis as its progenitors fits well
3, 4).
&
known
with what of the origin of Solidaster, and has been proposed previously Brouillet Semple
is (e.g.,
was and
1981). has been clear based on morphology that ptarmicoides one of the parents, S. canadensis
5.
It
where was
was one of the few goldenrod species naturalized near the nursery Solidaster discovered
first
(Nesom 1993). Although Solidaster does not show complete additivity in morphological features relative to
now
and (Nesom numerous well documented cases of hybrids
ptarmicoides canadensis 1993), there are
S. S.
more Note
exhibit one or seemingly characteristic of their progenitors (Rieseberg 1995).
failing to traits
and marketed
that these results apply specifically to the cultivar Lemore, other material as "Solidaster" (or
may common
may
shops which somewhat morphologies, not have
in florists as "Aster"), exhibit different a
Laureto and Barkmann comm.) present molecular-based evidence the hybrid origin
origin. (2005, pers. for
&
members
of another species, houghtonii Torr. A. Gray ex A. Gray, that involves of sect. Ptarmicoidei
S. (5.
show
and and morphology. Exclusion
similarly does not additivity in
Triplinerve gigantea),
sect.
riddellii)
(5.
ofEuthamiagraminifolia as a potential parent of Solidaster also refutes another potential intergeneric hybrid-
(Nesom
hypothesis
ization 1993).
Lemore
Schilling et Molecular analysis of Solidaster cv.
al.,
Copy
Solidaster
1
0.73/53
1*
ptarmicoides
S.
2*
ptarmicoides
S.
3*
ptarmicoides
S.
Copy
Solidaster 2
canadensis
S.
1
S
canadensis
2
1.00/94
canadensis
3
S.
gigantea
S.
S. fistuiosa
speciosa
S.
S. shortii
S. rigida*
arguta
S.
caesia
S.
patula
S.
1.00/99
-/59
virgaurea
S,
|
decunens
S.
1*
S. nitida
2*
S. nitida
3*
S. nitida
ohiensis*
$.
riddeiiiiV
S.
0.99 86
/
riddelHH*
S.
3*
S. riddeilii
simplex
S.
S, flexicauiis
juncea
S.
S. petioiaris
nemoralis
S.
Brintonia discoidea
1
id bootstrap greater than 50%) shown ab anches. Asterisks designate species of Solidago sect.
(if
Ptarmicoidea (Oligoneuron).
Journal of the Botanical Research Institute of Texas
2(1)
Solidago canadensis
Solidago gigantea
Solidago
fistuiosa
Soiidago sempervirens
Solidago
shortii
Solidago a*
id
rig
Solidago ohiensis*
Solidago arguta
Solidago patuia
Soiidago caesia
V
Solidago
riddel®
2*
Solidago
riddellii
3*
Solidago
riddellii
Solidago virgaurea
1*
Solidago
nitida
73/-
|
2*
Solidago
nitida
3*
Solidago
nitida
*
Solidago ptarmicoides
1
00/98
I
2*
Solidago ptarmicoides
cE
0/100
,0
Brintonia discoidea
1
m
2
Brintonia discoidea
Chtysoma
paucifloscufosa
Petradoria pumila
Stenotus
acautis
Columbiadoria
hallii
Oreochrysum
parryi
pygmaeus
Tonestus
Lorandersonia
iinifolia
Chrysothamnus scopulorvm
Chrysothamnus
stylosus
gramineus
Cuniculotinus
Sericocarpus
tortifolius
4. Phylogenetic placement of Solidago ptarmicoides relative to Solidago and related genera, based on combined analysis of ITS and ETS data. Shown
Fig. is
minimum
the tree produced by Bayesian analysis (the consensus of 408 length trees a single island, Cl=0.69, Rl=0.85, obtained from parsimony
strict in
analysis was topological^ similar although with less resolutii and Sericocarpus as outgroups. Support valuesfrom Bayesian
and bootstrap (if greater than 50%) shown above branches. Asterisks designate species of Solidago sect. Ptarmicoidea (Oligoneuron).
Lemore 15
Molecular analysis of Solidastercv.
Schilling etal.,
ETS
The major conclusion from phylogenetic analysis of ITS and sequence data is that there is strong
support the inclusion of ptarmicoides within Solidago. Phylogenetic analysis clearly placed in the clade
for 5. it
ETS
and combined) from
and sequence other
(ITS
corresponding differed in total
to Solidago s.s (Fig.
4), it
members of Solidago by as little as a two bp differences (vs. S. shortii). There was also no support from sequence
represented in the data by of six species including ptarmicoides,
data to segregate Oligoneuron, set five its S.
as a distinct genus; the combined ITS and ETS data in fact placed one of the Oligoneuron species, S. riddellii,
with caesia from sect. Solidago, albeit with only weak support (Fig. 3, 4; see asterisks). The sequence data
5.
weak and Chrysoma,
exclude
did, however, provide support for restricting the limits of Solidago to Brintonia
although the group formed by inclusion of these genera with Solidago would be monophyletic. These results
on
by Zhang reproduced Semple 1999) based chloroplast
mirror those presented (1986; in et
largely al.
DNA
most and comprehensive taxonomic
and provide additional support for the recent
restriction data,
site
&
Cook
treatment of the abovementioned taxa (Semple 2006).
mem-
A among
ETS was
notable aspect of the ITS and sequence data the striking lack of divergence
bers of Solidago. By contrast, ITS divergence in Eupatorium L. another genus of Asteraceae with a similar
2-6%
bp
between (12-43
geographic range and occurrence in old habitats, species differences;
field is
&
from
Eutrochium
Schmidt Schilling 2000; Schilling 2007); Eupatorium further differentiated Raf.,
et is
al.
bp and
which are widely treated as congeners, by two indels (loss of a 13 region in Eupatorium addition of
8%
minimum
(33-61 should be noted
a 3 bp region in Eutrochium) in addition to a of bp) divergence. It
previous chloroplast RFLP analysis (Zhang 1996) reports a higher level of variation within Solidago,
that a
These
and the resulting phylogeny strongly supports certain previously hypothesized groups. contrasting
DNA
amount
by sequence scored each
of phylogenetic signal are best explained the relative of in
levels
kb
study Extrapolating from the values reported in Lane et (1996), approximately 2.5-3 of chloroplast
al.
was Zhang compared approximately kb ITS/ETS
sequence assessed variation in the study, to the 1.1
for
RFLP
work
dataset analyzed here. In addition, previous in Asteraceae indicates that chloroplast datasets
can be more informative those from ITS sequence (Morgan 1997). The most obvious possible
relative to
Other
source of the lack of ITS divergence in Solidago that species level divergence is very recent. possible
is
and homogenization
contributing factors include relatively large effective population sizes the potential for
through widespread hybridization followed by concerted evolution. Hybridization tradition-
interspecific is
viewed widespread within (Cronquist and homogenization via concerted evolution
as Solidago 1980),
ally
&
Mummenhoff
The
(Franzke lack of
potentially a rapid process following hybridization 1999). relative
is
which
ITS sequence between distantly related congeners, because of geographical
differentiation in relatively
primary
be hybridization network, suggests that the cause
considerations are unlikely to part of a larger is
may
between
species
recency of divergence. This suggests that the striking ecological differences Solidago
and phylogeny
have arisen during relatively short periods of time indicates that resolving the of Solidago
more and
will be a major challenge that will require markers evolving rapidly than ITS ETS.
Collections of Solidago and related genera sampled for molecular analyses, with collector and herbarium or literature refer-
and GenBank numbers
ence
ETS).
(ITS,
Solidago Lemore, 07-06 (TENN), EU1 25353, EU1 25374. Sect. Solidago, Subsect. Argutae, arguta
Solidaster Schilling
L. cv. 5.
Beck481 (MO), EU1 25354, EU eck482 (MO), EU1 25355, EU1 25376. Subsect. Glomeruliferae,
Aiton, S.
DQ005979. Subsect. Humiles, simplex Kunth,
Beck483 (MO), EU1 25356, Kress et 2005,
caesia L, El al. 5.
DQ005981 Subsect. Maritimae, sempervirens
Kress et 2005, DQ005982. Subsect. Juncea, S.juncea Aiton, Kress et 2005, 5.
al.
al.
.
Sub-
Urbatsch et 2003, AF477668, AF477732. Subsect. Nemorales, nemoralis Aiton, Estes 1521 (TENN), EU1 25357.
L, S.
al.
GenBank
Subsect.
Solidago, EU1 25358, EU1 25378; decurrens Record, EFT 03140.
sect. Lour.,
virg 5.
5.
)),
&
Noyes
Squarrosae, (TENN), EU 25359. Subsect. Thyrsiflorae, petiolaris Aiton, Rieseberg
specioi 5.
5.
1
AF477665, AF477729; 3564 (TENN),
1999, AF046968. Subsect. Triplinerve, canadensis L, Urbatsch et 2003, Laferriere
S. al.
&
Beck509 EU125362, EU125379;
EU125360, -; Weidon 7/22/81 (TENN), EU125361; gigantea Aiton, (MO), shortiiTon. A.
5.
5.
1
Beck AY523854, Subsect. Venosae, Urbatsch et 2003, AF477666, AF477730. Sect.
Gray, et 2004, [submit]. 5. fistuiosa Mill, al.
al.
Ptarmacoidei (Oligoneuron), ptarmicoides (Torrey & A. Gray) Boivin, Brandt 2603 (MO), EU1 25363, EU1 25380; Dietrich 524
B.
S.
.
16 Journal of the Botanical Research Institute of Texas 2(1)
(MO), EU1 25364, EU1 25381 Anderson M0221, EU1 25365, EU1 25382; nitida Joney & A. Gray, Thomas 141724 (MO), EU1 25366,
5.
;
EU125383; Thomas 97470 (MO), EU125367, EU125384; Thomas EU125368, EU125385; 48497
138143, ohiensis Riddell, Krai
5.
(MO), EU125369, EU125386; Smith 3617 (MO), EU125370, EU125387; Vogt 506 (MO), EU125371, EU125388;
Frank,
riddeilii
5.
Luges (MO), EU1 25372, EU1 25389; Becket 2004, AY523851, EU1 25390. Brintonia Greene, discoidea
rigida L, (Elliott)
s.n. 5. al. B.
C
& Chrysoma
Greene, Roberts Urbatsch 2003, AY1 70930, AY1 69727; Anderson 20021 (MO), EU1 25373, EU1 25391. Nutt,
C
Chrysothamnus
AF47770
paucifloscuiosa (Michx.) Greene, Urbatsch et 2003, AF477637, Nutt., scopulorum (M.E. Jones)
al.
1
.
& C
&
Urbatsch, R.R Roberts Neubig, Roberts Urbatsch 2003, AY1 70956, AY1 69753; styiosus (Eastwood) Urbatsch, Roberts
R.P.
& & &
Neubig, Roberts Urbatsch 2003, AY1 70973, AY1 69770.C Nutt, Roberts Urbatsch 2003, AY1 70947, AY1 69744.
viscidiflorus
C
&
Columbiadoria G.L Nesom, Gray) G.L Nesom, Roberts Urbatsch 2003, AY1 70948, AY1 69745. Cuniculotinus
hallii (A.
C
& & &
Urbatsch, Roberts Neubig, gramineus M. Urbatsch, Roberts Neubig, Roberts Urbatsch 2003, AY1 70936,
(H. Hall) R.R
R.P.
Eastwoodia £ & Lorandersonia
AY1 69733. Brandegee, elegans Brandegee, Roberts Urbatsch 2003, AY1 70949, AY1 69746.
& & &
Urbatsch, R.R Roberts Neubig, L (Greene) Urbatsch, Roberts Neubig, Roberts Urbatsch 2003, AY1 70936,
tinifolia R.P.
Oreochrysum &
AY1 69737. Rydb., parryi Rydb., Roberts Urbatsch 2003, AY1 70958, AY1 69755. Petradoria Greene, P.pumila
O.
&
Greene, Roberts Urbatsch 2003, AY1 70959, AY1 69756. Sericocarpus Nees, Nees, Urbatsch 2003, AF477664,
et
tortifoiius
5. al.
& Tpygmaeus
AF477728. Stenotus Nutt, acaulis Nutt., Roberts Urbatsch 2003, AY1 70960, AY1 69757. Tonestus A. Nelson,
S.
&
Nelson, Roberts Urbatsch 2003, AY1 70972, AY1 69769.
A.
Nesom
The thank and and and Semple
authors G. Beattie, Heise, Miller for technical support, G. for
P.
J. J.
comments Fund
helpful on the manuscript. Financial support from the L.R. Hesler of the Department of
NIH
and award #P20 RR164841,
Botany, University of Tennessee, gratefully acknowledged.
is
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