INVESTIGADORES
BARREDA Viviana Dora
congresos y reuniones científicas
Título:
Early diversification of Asteraceae from Patagonia: fossil pollen grains related to some basal groups
Autor/es:
TELLERÍA, M.C.; BARREDA, V.; PALAZZESI, L.; KATINAS, L.
Lugar:
Bonn
Reunión:
Congreso; 12th International Palynological Congress; 2008
Resumen:
The Oligocene-Miocene interval is considered as one of the most important times
in the early evolution of the sunflower family. Worldwide fossil records of
Asteraceae indicate that Mutisiinae (Mutisieae) is the oldest tribe recorded so
far (Africa, Australia, New Zealand, South America). In this contribution we
present a chronological scheme of fossil Asteracean records from Patagonia,
based on previous reports of Mutisiinae and Gochnatiinae subtribes and a new
record of pollen type comparable to those of Cardueae. Four pollen types were
identified on the basis of their exine features (sculpture, structure, and
thickness). Morphotype 1 -Mutisiapollis sp.- (Late Oligocene), have spines with
swollen bases, internal cavities and endosexine three times thicker than
ectosexine; it appears to be closely allied to Serratula type (Cardueae) and, to
Gongylolepis type (Mutisiinae from the Guayana group). Morphotype 2
-Mutisiapollis viteauensis (Barreda) Barreda- (latest Oligocene-Early Miocene),
characterized by having microspines, with microperforated tectum, ecto- and
endosexine equally thickened. This morphotype is close to Cnicothamnus type
(Gochnatiinae). Morphotype 3 -Mutisiapollis sp.- (Late Miocene), with
conspicuous microspines, comparable to Quelchia type (Gochnatiinae from the
Guyana Group). Morphotype 4 Mutisiapollis patersonii Macphail and Hill- (Late
Miocene), with miscrospines hardly distinguishable and exine very thickened at
the equatorial level; it is close to some species of Chaetanthera and Mutisia
(Mutisiinae). Some of extant members of Mutisieae (the Guayana group) are
palynologically linked. The nearest living relatives of the fossil morphotypes
here presented are no longer recorded in southeastern Patagonia. Most of them
occur in northern South America (Guyana) or in the high altitudes of the Andes.