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Título:
Multiple, polytopic replacement of diploids by tetraploids in the Patagonian and Subantarctic plant Hypochaeris incana (Asteraceae, Cichorieae) as an adaptive response to post-glacial aridification?.
Autor/es:
K. TREMETSBERGER; E. URTUBEY; A. TERRAB; C. M. BAEZA; M. A. ORTIZ; M. TALAVERA; C. KONIG; TEMSCH; S. TALAVERA; T. F. STUESSY
Lugar:
Fribourg
Reunión:
Simposio; Symposium Polyploidization, plant fitness and trophic interactions. University of Fribourg Switzerland.; 2009
Institución organizadora:
University of Fribourg Switzerland.
Resumen:
We ask how tetraploids are distributed in relation to diploids in the Patagonian and Subantarctic plant
Hypochaeris incana endemic to southeastern South America and how polyploids have spread and
expanded their range in relation to the diploids. We applied AFLP and chloroplast DNA (cpDNA)
analysis to 28 resp. 32 populations throughout the distributional range of H. incana and assessed
ploidy levels using flow cytometry. While cpDNA data suggest repeated or simultaneous parallel
colonization of Patagonia and Tierra del Fuego by several haplotypes and/or hybridization, AFLPs
reveal three clusters corresponding to geographic regions. The central and northern Patagonian
clusters (~38-51° S), which are closer to the outgroup, contain mainly tetraploid, isolated and highly
differentiated populations with low genetic diversity. To the contrary, the southern Patagonian and
Fuegian cluster (~51-55° S) contains mainly diploid populations with high genetic diversity and
connected by high levels of gene flow. The data suggest that H. incana originated at the diploid level
in central or northern Patagonia, from where it migrated south. All three areas, northern, central and
southern, have similar levels of rare and private AFLP bands, suggesting that all three served as
refugia for H. incana during glacial times. In southern Patagonia and Tierra del Fuego, the mainly
diploid populations seem to have expanded their population system in post-glacial times, when the
climate became warmer and more humid. In central and northern Patagonia, the populations seem to
have become restricted to favourable sites with increasing temperature and decreasing moisture. For
this region, we infer a multiple, polytopic replacement of diploids by tetraploids, i.e., a parallel
replacement in local populations, thus challenging the traditional view that polyploids spread by
extending the range of their diploid progenitors. The most common mechanism of polyploid evolution
is via unreduced gamete formation, which can be affected by environmental conditions. Our results
allow us to hypothesize that polyploidization in H. incana occurred as an adaptive response to postglacial
climate warming and aridification in Patagonia. This hypothesis needs to be tested via explicit
assessment of cytotype fitness in different environments.....ver PDF