التفاصيل البيبلوغرافية
| العنوان: |
AFLP trees versus scatterplots: evolution and phylogeography of the polyploid complex Achillea millefolium agg. (Asteraceae). |
| المؤلفون: |
Van-Ping Guo, Saukel, Johannes, Ehrendorfer, Friedrich |
| المصدر: |
Taxon; Feb2008, Vol. 57 Issue 1, p153-169, 17p, 4 Diagrams, 1 Chart |
| مصطلحات موضوعية: |
COMMON yarrow, POLYPLOIDY, SPECIES hybridization, GENETIC research, ASTERACEAE, PHYLOGEOGRAPHY |
| مصطلحات جغرافية: |
CAUCASUS, ASIA, UNITED States |
| مستخلص: |
Achillea millefolium agg. is an ecologically most diverse N Hemisphere polyploid complex. Because of ubiqui- tous hybridization and polyploidization, the aggregate is extremely polymorphic and notorious for its difficult taxonomy. AFLP analyses were applied to 61 populations representing most of the known taxa ofA. millefolium agg. Genetic distance methods ofpopulation pairwise FST and Neighbour Joining for tree constructions and the 2D^Euklid algorithm for scatter plots were used to evaluate the AFLP-matrix with 459, mostly polymorphic bands. The aggregate is monophyletic and sister to the subalpine relic A. latiloba-2x from NE Turkish and adjacent Georgian mountains. The seven 2x-species of A. millefolium agg. have differentiated vicariously in Europe/SW Asia and expanded into C and E Asia. Both, the NJ trees and the 2D^Euklid scatterplots demon- strate these 2x as genetically monophyletic and distinct; only A. roseoalba-2x, close to A. asplen~folia-2x, may be the product of hybrid introgression. The polyploids of the aggregate (about 20 taxa and cytotypes) exhibit various combinations of 2x AFLP bands, but in addition also 16.9% of exclusive bands, documenting new genetic variation. Whereas the ALFP trees suggest most of these polyploid taxa to be polyphyletic, the AFLP 2DEuklid scatterplots demonstrate their phyletic coherence. This conflicting evidence apparently is due to wide-spread secondary hybrid merging between sympatric populations ofdifferent polyploid taxa, resulting in geographic instead of phyletic clustering of their populations in the AFLP trees. Available data suggest several parallel reticulating and ascending polyploid lines and their eco-geographical radiations. This has resulted in the origin of eight taxa of 4x, four or five of 6x and three of 8x in Europe and the Caucasus. One of them, A. millefolium subsp. millefolium-6x, also occurs throughout Asia, where two more 4x taxa, one additional 6x and one 8x can be recognized. Finally, from ancestors close to A. asialica s.str.-4x, the A. borealis s.l. dade has originated in N America, where it has radiated with numerous 4x- and 6x-ecotypes into most diverse habitats. Thus, the polyploid complex A. millefolium agg., shaped by successive cycles of differentiation and hybridiza- tion + polyplodization, has expanded stepwise from Europe and SW Asia to E Asia, then to N America and finally world-wide with A. millefolium-6x as a weed. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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