INIBIOMA   20415
INSTITUTO DE INVESTIGACIONES EN BIODIVERSIDAD Y MEDIOAMBIENTE
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Origin and biogeography of subgenus Podocarpus
Autor/es:
PAULA QUIROGA; PAULA MATHIASEN; ANDREA PREMOLI; ARI IGLESIAS
Lugar:
Mendoza
Reunión:
Congreso; 4th International Paleontological Congress,; 2014
Institución organizadora:
IANIGLA CCT CONICET Mendoza
Resumen:
The genus Podocarpus widely
distributed in the Southern Hemisphere provides a great opportunity to contrast
biogeographical hypotheses. Given that Podocarpus reaches tropical
latitudes, it offers the chance to analyze divergence between disjunct forests
within South America and even more among
continents. The genus Podocarpus consists of two subgenera, Foliolatus
found in Asia and Oceania, and Podocarpus (Eupodocarpus) present
in Australia, Africa, New Zealand, New Caledonia,
Madagascar, and tropical and
temperate South America, with 50 species
approximately each one. We present the phylogenetic relationships specially
among South American Podocarpus species using nuclear and chloroplast
DNA regions, estimate the divergence time of clades within Eupodocarpus subgenus,
and finally propose reviewing the subgeneric classification. The phylogeny
includes new sequences of species from South America not included in previous
studies; the first record of macrofossil of Podocarpus from Patagonia with age constrained fossil data, which comes
from precise isotope geochronology or can be well correlated to a specific
geological frame.
The phylogenetic hypotheses suggest a strong
geographical association within Eupodocarpus clades. The Austral
subclade includes species from southern landmasses. The other clade is composed
by two subclades, including species of tropical and subtropical distribution in
the Americas and Africa. The African species are sister to subtropical
South American species, and the tropical species from America are
included in an independent subclade. The molecular dating suggests a minimal
age of 87 (63.35 - 117.84) My for the minimum age of the genus Podocarpus.
Our results suggest that disjunctions among clades in southern continents are
the product of vicariance events due to continental drifting. In addition,
disjunctions within South America are
associated to vicariance after specifical geographic and climatic episodes
occurred during the Paleogene and Neogene times. The differentiation between
tropical-subtropical and southern South American species is probably associated
with an ancient presence of an extended and persistent arid barrier that
impeded the migration between both areas. Finally, as a strong evidence of molecular and morfological monophyly of each
subgenera, we propose revisiting the subgeneric classification and rise the
subgenera Podocarpus and Foliolatus to the genus level.