活動備忘 Event Memo：
consisting of about 500 species, is mainly distributed in the tropical to
subtropical areas with a diversity center in tropical Asia. Elatostema
has long been a taxonomically difficult group due to frequent homoplasy of
morphological characters and numerous species with a wide distribution and
complex sexual systems. The circumstances of generic delimitation among Elatostema,
are quite controversial, and the infrageneric
grouping within Elatostema
is also uncertain. A comprehensive phylogenetic analysis, comprising Elatostema
and related Urticaceae
was conducted. The results showed
that Elatostema s.l.
can be divided into three well-supported genera:
Four strongly support subclades within Elatostema
can be recognized, including Weddellia
clade and core Elatostema
clade. Homoplasy amongst the morphological characters used in this study makes
it impossible to circumscribe genera using synapomorphies.
Combined suites of characters, however, do enable the morphological diagnosis
of Elatostema s.l. The
history of Elatostema s.a.
involves in a variety of biogeographical scenarios. Two
intercontinental dispersal events from Asia to Africa were identified, which
are probably correlated with two warm phases peaking during
Cenozoic Era, respectively. There
are at least five major dispersal events within core Elatostema
clade, including the two routes of origin from East Asia through Malesia to Australasia.
In addition, based on previous field observation, E. cyrtandrifolium,
E. oblongifolium and
only have female individuals or female-biased species and still can produce
seeds. In this study, these species are confirmed to be apomictic plants with
polyploidy. The results of flow cytometric seed screen and embryogenesis
further demonstrated that these species should belong to an infrequent case of
obligate autonomous apomixis.