INVESTIGADORES
BARREDA Viviana Dora
congresos y reuniones científicas
Título:
Radiation of basal Asteraceae and allied families during the Oligocene and Miocene in the Gondwanan continents
Autor/es:
BARREDA, V.; PALAZZESI, L.; TELLERÍA, M.C.; KATINAS, L.; CRISCI, J.V.
Lugar:
Mar del Plata
Reunión:
Simposio; XIV Simposio Argentino de Paleobotánica y Palinología; 2009
Resumen:
The evolutionary radiation of the Asteraceae and their closest relatives is one
of the most important and yet unresolved questions in today's botanical research
because unequivocal fossil evidence is scarce for the development of reliable
hypotheses. This issue is now becoming progressively more realistic thanks to
the increasing fossil findings from southern Africa, Australia, New Zealand, and
southern South America (Patagonia). Unequivocally assigned morphotaxa from
accurately dated sediments have permitted for the first time a comprehensive
review of the past distribution of the most important core of the sunflower
alliance of families (Menyanthaceae, Goodeniaceae, Calyceraceae and Asteraceae).
Several taxa, which today are restricted to isolated geographic regions, were
widespread in the Southern Hemisphere during Paleogene times. Menyanthaceae,
Goodeniaceae and Mutisioideae (Asteraceae), for example, had a wider
distribution in Gondwanan landmasses by the Oligocene and are now drastically
reduced in their geographic range. This broad distribution pattern during the
Oligocene supports previous assumptions of an Eocene origin of the clade. Early
Neogene records, in contrast, suggest diversification and extinction events that
progressively led to the present day configuration. In broad terms, the
distribution of Miocene fossils assigned to this clade agrees with that of today
(Barnadesioideae, Nassauvieae, Calyceraceae). Southern Hemisphere continents,
and particularly Patagonia, are unique by having the highest diversity of
sunflower-related fossils of any region. The major floristic turnovers coincided
with the final isolation of Antarctica, leading to cooler, drier, and more
seasonal climates that forced the evolution and distribution in space of all
these Gondwanan elements.