IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
artículos
Título:
Molecular evidence of ice-age refugia in the Patagonia steppe and post-glacial colonisation of the Andes slopes: insights from the endemic species Calceolaria polyrhiza (Calceolariaceae)
Autor/es:
COSACOV, A.; SÉRSIC, A.; SOSA, V.; JOHNSON, L.; COCUCCI A. A.
Revista:
JOURNAL OF BIOGEOGRAPHY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2010 vol. 37 p. 1463 - 1477
ISSN:
0305-0270
Resumen:
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ABSTRACT
Aim We perform a phylogeographical study of an endemic Patagonian
herbaceous plant to assess whether geographical patterns of genetic variation
correspond to in situ Pleistocene survival or to glacial retreat and post-glacial
expansion. We also seek to determine the locations of potential glacial refugia and
post-glacial colonization routes.
Location Southern Andes and Patagonian steppe.
Methods We used Calceolaria polyrhiza, a widely distributed Patagonian
herbaceous plant that occurs mainly in the understorey of Nothofagus rain
forests and in the arid Patagonian steppe, as our model system. The chloroplast
intergenic spacer trnHpsbA was sequenced for 590 individuals from 68
populations. Sequence data were analysed using phylogenetic (maximum
parsimony, maximum likelihood and Bayesian inference) and population
genetic (spatial analyses of molecular variance, mismatch distributions and
neutrality tests) methods. Nested clade phylogeographic analyses, and divergence
time estimates using a calibrated molecular clock, were also conducted.
Results A total of 27 haplotypes identified in the present study clustered into
four primary genealogical lineages, revealing three significant latitudinal
phylogeographical breaks. The two high Andean lineages probably split first,
during the late Miocene, and the Patagonian lineage split around 4 Ma,
coincident with the establishment of the Patagonian steppe. Within each
haplogroup, major diversification occurred in the Pleistocene. The Patagonian
groups show a pattern consistent with a rapid post-glacial expansion and
colonization of the Andean flanks, achieved independently by four lineages. The
highest haplotype diversity was found along a longitudinal transect that is
remarkably congruent with the limit of the ice-sheet extension during the
Greatest Patagonian Glaciation. A north-east expansion is evident, which is
probably associated with the Arid Diagonal fluctuations.
Main conclusions Glacial climate fluctuations had a substantial impact on the
diversification, distribution and demography of the study species. A scenario of
multiple periglacial Pleistocene refugia and subsequent multiple recolonization
routes, from eastern Patagonia to the Andean flanks, may explain the
phylogeographical patterns observed. However, current genetic structure also
preserves the imprints of older events that probably occurred in the Miocene and
Pliocene, providing evidence that multiple processes, operating at different spatial
and temporal scales, have moulded biodiversity in Patagonia.