A molecular phylogeny of Calenduleae (Asteraceae) supports the transfer of Dimorphotheca polyptera DC. to Osteospermum L.
Author
Sadler, Robert
Author
Parker, Thaabiet
Author
Verboom, George Anthony
Author
Ellis, Allan G.
Author
Jackson, Mariëtte
Author
van Zyl, Juanita
Author
Manning, John
Author
Bergh, Nicola G.
text
South African Journal of Botany
2022
2022-12-31
151
234
245
http://dx.doi.org/10.1016/j.sajb.2022.09.001
journal article
10.1016/j.sajb.2022.09.001
1727-9321
10496950
4.3.
Osteospermum
Our phylogeny is consistent with the enlarged circumscription of
Osteospermum
sensu (
Manning and Goldblatt, 2012
)
, since all sampled members of
Osteospermum
,
Chrysanthemoides
,
Tripteris
, and other subsequently segregated genera fall into clade C. We also demonstrate the monophyly of
Osteospermum sect. Calendula
based on a sample of ca. two-thirds of the species, confirming that it is embedded within clade C where it shares a common ancestor with several
Osteospermum
species
(node H). This placement of the former genus
Calendula
was first demonstrated by
Nordenstam (1994a)
and later confirmed using DNA sequence data from both plastid (Nordenstam et al., 2006) and nuclear partitions (Nordenstam and K allersj € € o, 2009). The names
Calendula
and
Osteospermum
were published simultaneously (
Linnaeus, 1753
) and thus compete for priority. Understandably, Nordenstam and colleagues were reluctant to lose the name
Calendula
, since members of the genus, particularly
C. of
fi
cionalis
, have a long and ongoing history of medical, culinary, pharmacological, cosmetic and religious uses in the Northern Hemisphere (e.g. https://en. wikipedia.org/wiki/
Calendula
). They were equally reluctant to lose the name
Osteospermum
, since synonymising this large genus would result in many new combinations. Instead,
Nordenstam (1994a
,
b, 1996
, 2006), Nordenstam et al. (2006), and Nordenstam and K€ allersj€ o (2009) attempted to maintain the monophyly of
Osteospermum
by dividing it into numerous smaller, monophyletic genera. The largest of these was
Tripteris
(
Nordenstam, 1994a
)
, but as indicated in
Fig. 4
, the fruit
type
defining this genus has arisen at least twice, and possibly three times, even though we included only four of the ca. 20 species. This non-monophyly may have underpinned (Nordenstam’ s, 2006) subsequent segregation of
Tripteris
into the smaller genera
Monoculus
,
Norlindhia
, and
Inuloides
. Of these four genera, we have representatives of only
Tripteris
and
Monoculus
in our tree. The molecular phylogeny presented by Nordenstam and K€ allersj€ o (2009) resolved representatives of genera
Gibbaria
(2 species),
Inuloides
(1 species),
Nephrotheca
(1 species),
Norlindhia
(3 species), and
Oligocarpus
(2 species), with high support inside a clade that corresponds to our
Osteospermum sensu amplo
clade. However, we were unable to obtain material or sequences of species from these genera, and clearly, the phylogenetic relationships of many more species of
Osteospermum sensu amplo
need to be resolved.
In addition to species from the former genus
Tripteris
, many other
Osteospermum
species
have fruits in which the angles are developed to a lesser or greater extent into wings, although they lack the air cavity. These species were placed by
Norlindh (1943)
in sections
Trialatae
and
Spinosae
of subgenus
Osteospermum
, the latter unfortunately with no representatives in our tree, since it contains the
type
species of
Osteospermum
,
O. spinosum
L.
Greater sampling, of both taxa and of genetic partitions, will be required to properly elucidate relationships within
Osteospermum sensu amplo
. However, phylogenetic evidence from this and from past studies indicates that the circumscription within, and relationship amongst, the clades defining
Garuleum
,
Dimorphotheca
, and
Osteospermum
sect.
Calendula
, are unlikely to change with future phylogenetic discoveries. Also, since the publication of
Manning and Goldblatt (2012)
resulted in the prioritisation of
Osteospermum
over
Calendula
(Turland et. al. 2018, Art. 11.5), and since all phylogenetic evidence to date indicates that
Osteospermum sensu amplo
is monophyletic, the enlarged circumscription of
Osteospermum
is likely be the most stable.