Evolution of Hypochaeris (Asteraceae) in South America

This proposal seeks support for continued studies on phylogeny, biogeography and speciation in the flora of southern South America. The genus Hypochaeris (Compositae) remains the principal focus of this grant phase, which consists of c. 40 species in the continent. The genus in South America is ideally suited for evolutionary studies due to its low chromosome number (n = 4), large chromosomes (208 m), herbaceous habit, wide distribution in the southern portion of the continent, diversity of ecological tolerances, and very recent evolution (the entire complex having evolved within approximately the last one million years). Phylogenetic results on Hypochaeris in South America from nuclear and chloroplast DNA sequences in the previous grant phases show the group to be clearly monophyletic. Different lines of parallel evolution have developed, giving rise to a pattern of morphological adaptive radiation, but genetic divergence among the lines is low. AFLP analyses have been developed in the previous grant phase to provide a good yardstick by which to identify closely related species complexes. Molecular cytogenetic studies have also revealed species groups that to a large extent correlate with AFLP groupings. Phylogeographic patterns based on AFLP data reveal isolation by distance along the Andean chain as well as suggesting the hypothesis of a Pleistocene refugium in the Coastal Range in Chile. More extensive sampling of outgroup genera for DNA sequence analysis has shown that the European sections of Hypochaeris relate most closely to the genus Leontodon (although the former still remains monophyletic), but the latter is clearly biphyletic with subg. Oporinia requiring elevation to generic status (as Scorzoneroides). The focus of this new proposal on Hypochaeris is to build upon information gained in the first grant phases and to: (1) test hypotheses of phylogenetic relationships established by AFLP and cytogenetic data by low-copy DNA sequences and morphological data; (2) investigate cases of known hybridization among diploid species using morphology, cytogenetics and molecular data to learn the dynamics of interspecific crossing plus possibilities for gene flow; and (3) examine the biogeographic and evolutionary import of genetic variation (AFLPs and cpPCR- RFLPs) among populations between the Coastal Range and main Andean Cordillera in Chile, testing the hypothesis that the former served as a refugium during Pleistocene glaciation. These studies are significant in focusing on basic questions in the flora of southern South America of genetic divergence, dynamics of interspecific hybridization, and biogeographic patterns in relation to Pleistocene glaciation.

This proposal seeks support for continued studies on phylogeny, biogeography and speciation in the flora of southern South America. The genus Hypochaeris (Compositae) remains the principal focus of this grant phase, which consists of c. 40 species in the continent. The genus in South America is ideally suited for evolutionary studies due to its low chromosome number (n = 4), large chromosomes (208 m), herbaceous habit, wide distribution in the southern portion of the continent, diversity of ecological tolerances, and very recent evolution (the entire complex having evolved within approximately the last one million years). Phylogenetic results on Hypochaeris in South America from nuclear and chloroplast DNA sequences in the previous grant phases show the group to be clearly monophyletic. Different lines of parallel evolution have developed, giving rise to a pattern of morphological adaptive radiation, but genetic divergence among the lines is low. AFLP analyses have been developed in the previous grant phase to provide a good yardstick by which to identify closely related species complexes. Molecular cytogenetic studies have also revealed species groups that to a large extent correlate with AFLP groupings. Phylogeographic patterns based on AFLP data reveal isolation by distance along the Andean chain as well as suggesting the hypothesis of a Pleistocene refugium in the Coastal Range in Chile. More extensive sampling of outgroup genera for DNA sequence analysis has shown that the European sections of Hypochaeris relate most closely to the genus Leontodon (although the former still remains monophyletic), but the latter is clearly biphyletic with subg. Oporinia requiring elevation to generic status (as Scorzoneroides). The focus of this new proposal on Hypochaeris is to build upon information gained in the first grant phases and to: (1) test hypotheses of phylogenetic relationships established by AFLP and cytogenetic data by low-copy DNA sequences and morphological data; (2) investigate cases of known hybridization among diploid species using morphology, cytogenetics and molecular data to learn the dynamics of interspecific crossing plus possibilities for gene flow; and (3) examine the biogeographic and evolutionary import of genetic variation (AFLPs and cpPCR- RFLPs) among populations between the Coastal Range and main Andean Cordillera in Chile, testing the hypothesis that the former served as a refugium during Pleistocene glaciation. These studies are significant in focusing on basic questions in the flora of southern South America of genetic divergence, dynamics of interspecific hybridization, and biogeographic patterns in relation to Pleistocene glaciation.