The tribal position of Fockea and Cibirhiza
(Apocynaceae: Asclepiadoideae): evidence from pollinium structure and cpDNA
sequence data
Rudolf
L .Verhoeven , Sigrid Liede & Mary E. Endress
Abstract: The pollinium morphology of the two members of
the Asclepiadoideae, tribe Fockeeae, Fockea
Endl. and Cibirhiza
Bruyns, has been studied in detail and compared with that of eight genera of
Marsdenieae, the tribe in which Fockea
and Cibirhiza
were previously accommodated and thus their putative closest relatives, as well
as nine genera of Asclepiadeae. Both Fockea
and Cibirhiza
have several morphological characteristics in common, the most important of
which is the absence of well-developed caudicula, which distinguishes them from
all other genera of Asclepiadoideae known. The pollinium structure of these two
genera, however, differs significantly. Whereas the pollinium of Cibirhiza consists
of single pollen grains and is covered by a pollinium wall, as is typical for
other Asclepiadoideae, the pollinium of Fockea
consists of tetrads and is not covered by a pollinium wall, a condition
otherwise typical of Secamonoideae. Fockea,
however, has only two pollinia per anther, as does Cibirhiza and all other Asclepiadoideae,
whereas the Secamonoideae have four pollinia per anther. Sequence data from two
intergenic spacers, trnT-L
and trnL-F
and the trnL
intron of cpDNA was analyzed. The ingroup included three species of Fockea and one
species of Cibirhiza.
The outgroup taxa consisted of three representatives each of Periplocoideae,
and Secamonoideae and 24 species of Asclepiadoideae, including representatives
of all tribes, of which eight genera belong to Marsdenieae, as outgroups. The
results of the DNA analysis provide strong support for Fockeeae as a
monophyletic tribe, distinct from Marsdenieae and, to the rest of the
Asclepiadoideae. With the exception of pollen data, all morphological and
molecular evidence clearly support recognition of the tribe Fockeeae. The
occurrence of two such significantly different types of pollinia structure -
characters elsewhere in the family used to distinguish subfamilies - within the
small tribe Fockeeae was unexpected, and can perhaps best be understood as yet
another attestment to the basal position of the Fockeeae in the nascence of the
Asclepiadoideae.
View Matrix
(cpDNA spacer)
goto TreeBASE (Study accession number = 715, Matrix accession number = M1140, M1141)