PHYLOGENETIC RELATIONSHIPS OF EPHEDRA CANTERATA IN SOUTH AMERICA

PUEBLA, GABRIELA; GOMEZ. MARIA; VENTO, BARBARA; PRAMPARO, MERCEDES

Buenos Aires, Virtual

Congreso; XII Congreso de la Asociacion Paleontologia Argentina; 2021

Asociacion Paleontologica Argentina

The gymnosperm genus Ephedra contains about 68 extantspecies distributed in semiarid and arid areas of most continents. In e lasttwo decades, numerous macrofossils and mesofossils of Ephedra or Ephedra-typehave been found, mostly from the Early Cretaceous, around the world. La CanteraFormation (upper Aptian) is located in the San Luis Basin, central-western ofArgentina. This unit provided a rich paleontological association (fishes,insects, palynomorphs, plants) including Ephedra canterata, which has beenpreviously described and published. Ephedra canterata and Ephedra verticillatafrom the Anfiteatro de Ticó Formation (upper Aptian), Patagonia, are the onlytwo species found in southern South America. In this work, we attempt tounderstand the phylogenetic relationships among representatives of the familyEphedraceae in South America. Our goal is to analyze the phylogenetic positionof Ephedra canterata and discuss its relationships with fossil and extantspecies. We also tested the monophyly of the South American clade of Ephedra.We coded a set of 35 morphological characters from 16 taxa to construct amatrix. The phylogenetic analysis included both fossil and living taxa of thegenus Ephedra from South America. Fossilspecimens of E. verticillata are housed at Museo de Ciencias Naturales?Bernardino Rivadavia?, Buenos Aires and E. canterata at the Museo Interactivode Ciencias of the Universidad Nacional de San Luis, San Luis Province. Wechoose two outgroups: Gnetum and Welwitschia mirabilis. We performed twoanalyses and selected our evolutionary hypothesis based on the currentlimitations of each method and considering the congruence with the morphologicalevidence. The relationships among taxa in both analyses were the same. Wetested the phylogenetic placement of fossils using the traditional parsimonyanalysis under equal weight and we also used the implied weighting analysis.The equal analysis resulted in three most parsimonious trees of 63 steps and apolytomy was observed. The implied weight analysis resulted in one tree from K=3 and the monophyly corresponding to representatives of the genus Ephedra iscorroborated. A close relationship between fossil and extant species is observed.The fossil taxon Ephedra canterata appears closely related to Ephedraverticillata and several living species such as Ephedra trifurcata, Ephedra multiflora,and Ephedra boelckei. Ephedra canterata represents one of the best preservedrecords until now and together with Ephedra verticillata are the oldest recordsfound in South America. The close relationship among the fossil taxa would indicatethat they probably evolved from a common ancestor. This research is a contributionto improve our knowledge of the evolutionary history of the genus Ephedra.