Geographical Patterns of Morphological, Cytotype and cpDNA Haplotype Variation of Turnera sidoides L. Complex (Passifloraceae, Turneroideae): Evolutionary and Biogeographical Implications

GUILLERMO SEIJO; SOLIS NEFFA V.G.; LAURA CHALUP; MORENO E.M.S.

Foz do Iguacu

Conferencia; 21st International Chromosome Conference (ICC); 2016

International Chromosome and Genome Society

Turnera sidoides (x = 7) is an excellent model to study the actionof evolutionary processes in the Chaco Domain. This complexof perennial, rhizomatous herbs ranges across southern Bolivia,Paraguay and Brazil, Uruguay and Argentina, reaching 39°S. Fivesubspecies and 7 morphotypes were recognized in the complex.Additionally, it shows diploid to autooctoploid cytotypes. Here, weanalyze the geographical distribution of morphological and genetic(cytotype and cpDNA haplotypes) variation to interpret the currentpatterns of diversification of the complex. Our survey revealed2 main centers of species diversification. Most taxa have diploidand polyploid cytotypes. Within the taxa, both exclusive andshared cpDNA haplotypes were found in diploid and polyploidpopulations. The main concentration of diploids is located in thenorthwestern center. Their frequency regularly decreases along anorth-south gradient up to 30°S, and from higher to lower altitudes.In the eastern center, a few isolated diploid populations of 4different subspecies were detected. Tetraploids are by far the mostwidespread and occupy almost the entire species range, whereasthe frequency of higher ploidy levels increases to the western andeastern species boundaries, in regions with the wettest and driestregimes, respectively. T. sidoides diversification would occur at2.11 MYBP. The finding of the ancestral haplotype in diploids andpolyploids occurring at the higher regions, together with the resultsof ancestral area reconstruction suggest that during Pleistocenegeomorphological and climatic changes, the highlands alongthe Peripampasic arc and the adjacent lowlands represented putativecenters of diversification of the complex. Our comprehensiveanalysis further yields evidence of the dispersal pathways of the T.sidoides taxa that led to the present species boundaries by meansof polyploids. The Peripampasic arc would provide suitable conditionsfor diploids to survive and differentiate in allopatry and themain rivers as dispersal pathways toward the Chaco-Pampeanplain.