INVESTIGADORES
URDAMPILLETA Juan Domingo
congresos y reuniones científicas
Título:
Scape anatomy, fruit dehiscence, and chromosome numbers support polyphyly of Neomarica (Iridiaceae) and parallel evolution of the leaf-like scape
Autor/es:
GIL, A. S. B.; TRAD, R. J.; URDAMPILLETA, J. D.; BITTRICH, V.; AMARAL, M. C. E.
Lugar:
Melbourne
Reunión:
Congreso; XVIII International Botanical Congress; 2011
Institución organizadora:
University of Melbourne
Resumen:
The family Iridaceae Juss. is composed of ca. 66 genera
and 2,030 species. The neotropical tribe Trimezieae Rav.
is probably monophyletic, but the delimitation of its
currently accepted four genera is still uncertain.
Neomarica Sprague is the largest genus of this tribe with
ca. 24 species. It is characterized mainly by the broadly
flattened scape, morphologically very similar to the
leaves, formerly considered a synapomorphy of the
genus. Recent studies on fruit morphology, chromosome
numbers and phylogeny using DNA sequence data,
however, pointed to the possibility that the genus is
polyphyletic and its species belong to three not closely
related clades. This suggests that the characteristic kind
of scape might have evolved three times in the tribe and
is a false synapomorphy for the genus. We therefore
investigated the anatomy of the scapes to verify if
anatomical data would support the idea of parallel
evolution of a broadly flattened scape in the groups of
Neomarica. Anatomical sections of the scapes of 12
species of Neomarica belonging to the three clades and
of 5 species of Trimezia were made by hand and stained
with safranine /astra blue. The sections were immersed in
glycerin jelly and on the following day studied and
photographed in a microscope. We found two different
types of scape anatomy agreeing with the findings of
different and not closely groups of Neomarica based on
the phylogenetic analysis of DNA sequence data, capsule
morphology and chromosome number. One type is
characterized by an abrupt constriction of the peripheral
parts of the scape into two wings, which may be short or
elongated. In most species, this wing formation is
correlated with a thick peripheral sclerenchymatic ring in
the scape closed in the region where the wings are
located. The wings of these scapes are very thin and
mainly build of sclerenchyma and vascular bundles. The
chromosome number of the plants with this anatomy is
2n=32 and the dehiscence of the fruits occurs only at the
apex. In the second type, the peripheral parts of the scape
narrow gradually to form elongated wings and the
sclerenchymatic ring is open at exactly these regions.
The wings of these scapes are build of parenchyma with
scattered vascular bundles. The chromosome number of
these plants is 2n=18 and the fruit dehisces, so far as
known, completely down to the base. The first type is
typical for Neomarica spp. belonging to the group
presumably sister to the genus Trimezia and for N.
rupestris, which is more closely related to the genus
Pseudotrimezia. The scape of Trimezia spp. is either
completely wingless or presents only very short wings.
The sclerenchymatic ring here is always closed, which
probably represents the plesiomorphic scape anatomy in
the tribe. The second type characterizes species of
Neomarica s.s. Our study once more demonstrates that
phylogenies obtained from molecular data may provoke
interesting character re-evaluations of morphoanatomical
characters.