Major taxonomic events in Oligocene-Miocene sunflower taxa of Patagonia: fossil pollen evidence

BARREDA, V.; PALAZZESI, L.; TELLERÍA, M.C.; KATINAS, L.

Prague

Congreso; European Paleobotanical and Palynological Conference; 2006

Prague University

The sunflower (Asteraceae) family constitutes the largest group of extant plants. Despite the great abundance and diversity of recent taxa, fossil record of Asteraceae is extremely sparse; thus the time and place of the family origin remain controversial. Recent fossil pollen discoveries from Patagonia (southern South America) allow outlining different stages of the evolution of Asteraceae from the Late Oligocene to the Late Miocene. Botanical affinity of most of morphotypes was made by using a pollen collection of living Asteraceae. On the basis of taxonomic affinity, abundance, and temporal distribution of the Patagonian fossil records, five major stages were identified: (1) Late Oligocene, first report of Asteraceae with a morphotype related to Mutisiinae (tribe Mutisieae); (2) Early Miocene, increasing of the Mutisiinae and appearance of Nassauviinae (Mutisieae); (3) latest Early Miocene, appearance of Astereae morphotypes; (4) Middle-Late Miocene, progressive dominance of the previous asteracean taxa, both in terms of diversity and abundance, and first record of  the subfamily Barnadesioideae; (5) Late Miocene, first appearance of Heliantheae morphotypes. Though boundaries of these stages may overlap slightly, they most probably represent each major asteracean turnovers. Recent phylogenetic trees based on molecular data are partly in agreement with the succession of appearance of these groups in the fossil record.