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bolanderi
due to recent information which has shown it to be morphologically
and genetically distinct (Oliveri and Jain 1977; Rieseberg et al. 1988; Jain et
al. 1992). Third, the species name
H
.
pauciflorus
has priority over
H
.
rigidus
and is treated accordingly herein. Fourth,
Viguiera porteri
has been
transferred to
Helianthus porteri
(Pruski 1998; Schilling et al. 1998). Fifth,
Helianthus verticillatus
has recently been rediscovered and redescribed, and
is now recognized as a species (Matthews et al. 2002). Sixth,
Helianthus
niveus
ssp.
canescens
has been transferred to
Helianthus petiolaris
ssp.
canescens
(Schilling 2006).
In the past, phylogenetic relationships of the perennial species and
polyploidy hybrids have been particularly difficult to resolve. Using the
external transcribed spacer region of the nucleus 18S-26S rDNA region,
Timme et al. (2007) revealed a highly resolved gene tree for
Helianthus
.
Phylogenetic analysis allowed for the determination of monophyletic annual
H.
section
Helianthus
, a two-lineage polyphyletic
H
. section
Ciliares,
and the
monotypic
H
. section
Agrestis
, all of which were nested within the large
perennial and polyphyletic
H
. section
Divaricati
. The distribution of
perennial polyploids and known annual diploid hybrids on this phylogeny
suggested that multiple independent hybrid speciation events gave rise to
at least four polyploids and three diploid hybrids. Also provided by this
phylogeny was evidence for homoploid hybrid speciation outside of
H
.
section
Helianthus
.
Anashchenko (1979) proposed the first phylogeny for
Helianthus
on the
basis of different chromosome sets: the protogenome A for the perennial
forms (
Atrorubentes
) of the west coast of North America, the genome B for the
annual forms, C for the
Ciliares
, and the protogenome S for perennial shrubs
of South America (
Viguiera
). The
Ciliares
group was therefore regarded as a
separate group in
Helianthus
. The genome organization in
Helianthus
is
therefore still questionable. Chandler (1991) reviewed sunflower genomic
relationships and came to the conclusion that there is little evidence of the
existence of distinct genomes in
Helianthus
.
Sossey-Alaoui et al. (1998) using RAPD technology proposed a
phylogeny of 36
Helianthus
species based on 33 fragments common to all the
Helianthus
species. Fifty-six were unique to perennial species of sections
Atrorubentes
and
Ciliares
, 24 were unique to section
Atrorubentes
, and 29
were unique to section
Helianthus
, whereas none were unique to section
Ciliares
. Each set of common or specific fragments was assumed to belong to
a genome: (1) the
C
genome carrying the fragments common to all species of
the three sections, (2) the
H
genome unique to section
Helianthus
, (3) the
P
genome common to perennial species sections
Atrorubentes
and
Ciliares
, (4)
the
A
genome unique to section Atrorubentes. The genomic structure was
therefore
HC
for section
Helianthus
,
CPA
for section Atrorubentes, and
CP?
for section
Ciliares
. They also concluded that molecular hybridization with
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