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:
QUIROGA MP; MATHIASEN, P.; PREMOLI, A.C.; IGLESIAS, A.
Reunión:
Congreso; 4th International Palaeontological Congress. International Paleontological Association-CONICET Mendoza; 2014
Resumen:
The
genus Podocarpus has a widespread
distribution and provides the opportunity to contrast hypotheses of
long-distance dispersal and vicariance in the Southern Hemisphere. These have
been traditionally tested among different land masses using, for example,
genera of austral origin as Nothofagus.
Given that Podocarpus reaches
tropical latitudes, it offers the chance to analyze divergence between disjunct
forests within all South America and even more within continents. The genus Podocarpus consists of two subgenera, Foliolatus
found in Asia and Oceania, and Podocarpus present in Australia, Africa,
New Zealand, New Caledonia, Madagascar, and tropical and temperate South
America. We hereby calibrated the phylogeny of genus Podocarpus,
using Bayesian analysis, including novel DNA sequences and fossil
records to unravel the biogeographical history within subgenus Podocarpus. Sequences of the chloroplast (rbcL and matK)
and two regions of the nuclear (ITS 1 and 2) were obtained by standard
sequencing methods. The outgroup consisted of one speceis of Araucaria
and also one species for each genus of the Podocarpaceae family. Our results
suggest that subgenus Podocarpus is organized into two well supported
and geographically differentiated clades. One includes Austral species,
including those from southern South America, Australia, New Zealand, and New
Caledonia. A second clade is composed of two subclades, including species of
tropical and subtropical distribution in the Americas and Africa. Surprisingly,
our data strongly suggest that those species distributed in subtropical South
America are closed affiliated to African species, remaining far differentiated
from other monophyletic tropical clade integrated by northern South America and
the Caribbean. The molecular dating suggests a minimal age of 87 My for the
origin of the genus Podocarpus, 30 My older than previously estimated
minimal origin. The analysis suggesting
disjunctions among southern continent clades are the result of vicariance
events due to continental drifting. Disjunctions within South America are associated
to vicariance after specifically geographic and climatic episodes happened in
Paleogene and Neogene times. The differentiation between tropical-subtropical
and southern South American species is probably associated with the presence of an extended and persistent arid barrier that impeded
the migration between areas since the Paleogene