American Journal of Botany Eocene Araucaria Sect. Eutacta from Patagonia and floral turnover during the initial isolation of South America --Manuscript Draft-- Manuscript Number: AJB-D-19-00445R2 Full Title: Eocene Araucaria Sect. Eutacta from Patagonia and floral turnover during the initial isolation of South America Short Title: ROSSETTO-HARRIS ET AL. — PATAGONIAN ARAUCARIA SECT. EUTACTA FOSSILS Article Type: Research Article Section/Category: Paleobotany Corresponding Author: Gabriella Rossetto-Harris, M.S. Pennsylvania State University University Park, PA UNITED STATES Corresponding Author E-Mail: [email protected] First Author: Gabriella Rossetto-Harris, M.S. Order of Authors: Gabriella Rossetto-Harris, M.S. Peter Wilf Ignacio H. Escapa Ana Andruchow-Colombo Abstract: PREMISE OF THE STUDY— Eocene floras of Patagonia document biotic response to the final separation of Gondwana. The conifer genus Araucaria, distributed worldwide during the Mesozoic, has a disjunct extant distribution between South America and Australasia. Fossils assigned to Australasian Araucaria Sect. Eutacta usually are represented by isolated organs, making diagnosis difficult. Araucaria pichileufensis Berry, from the middle Eocene Río Pichileufú (RP) site in Argentine Patagonia, was originally placed in Sect. Eutacta and later reported from the early Eocene Laguna del Hunco (LH) locality. However, the relationship of A. pichileufensis to Sect. Eutacta and the conspecificity of the Araucaria material among these Patagonian floras have not been tested using modern methods. METHODS— We review the type material of A. pichileufensis alongside large (n = 192) new fossil collections of Araucaria from LH and RP, including multi-organ preservation of leafy branches, ovuliferous complexes, and pollen cones. We use a total evidence phylogenetic analysis to analyze relationships of the fossils to Sect. Eutacta. KEY RESULTS— We describe Araucaria huncoensis sp. nov. from LH and improve the whole-plant concept for Araucaria pichileufensis from RP. The two species respectively resolve in the crown and stem of Sect. Eutacta. CONCLUSIONS— Our results confirm the presence and indicate the survival of Sect. Eutacta in South America during early Antarctic separation. The exceptionally complete fossils significantly predate several molecular age estimates for crown Eutacta. The differentiation of two Araucaria species demonstrates conifer turnover during climate change and initial South American isolation from the early to middle Eocene. Keywords: Araucariaceae; biogeography; conifers; early Eocene climatic optimum; Gondwana; Laguna del Hunco; Patagonia; rainforest; Río Pichileufú; total evidence phylogeny Funding Information: National Science Foundation Dr. Peter Wilf (DEB-1556666) National Science Foundation Dr. Peter Wilf (EAR-1925755) National Science Foundation Dr. Peter Wilf (DEB-0919071) National Science Foundation Dr. Peter Wilf (DEB-0345750) Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Botanical Society of America Mrs. Gabriella Rossetto-Harris (Graduate Student Research Grant) Geological Society of America Mrs. Gabriella Rossetto-Harris (Graduate Student Research Grant) Graduate School, Pennsylvania State Mrs. Gabriella Rossetto-Harris University (Penn State Geosciences Charles E. Knopf, Sr., Memorial Scholarship; and a Penn State Geosciences Paul D. Krynine Scholarship) Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Manuscript Click here to access/download;Manuscript;MS Rossetto Harris Revision 2_2.docx 1 1 Eocene Araucaria Sect. Eutacta from Patagonia and floral turnover during the 2 initial isolation of South America1 3 4 Gabriella Rossetto-Harris2,4, Peter Wilf2, Ignacio H. Escapa3, and Ana Andruchow-Colombo3 5 6 1Manuscript received _________2019; revision accepted _________. 7 2Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 8 16802 USA; and 9 3Museo Paleontológico Egidio Feruglio, Consejo Nacional de Investigaciones Científicas y 10 Técnicas, Trelew 9100, Chubut, Argentina 11 4Author for correspondence (e-mail: [email protected]) 12 13 ROSSETTO-HARRIS ET AL. — PATAGONIAN ARAUCARIA SECT. EUTACTA FOSSILS 14 15 PREMISE OF THE STUDY — Eocene floras of Patagonia document biotic response to the 16 final separation of Gondwana. The conifer genus Araucaria, distributed worldwide during the 17 Mesozoic, has a disjunct extant distribution between South America and Australasia. Fossils 18 assigned to Australasian Araucaria Sect. Eutacta usually are represented by isolated organs, 19 making diagnosis difficult. Araucaria pichileufensis Berry, from the middle Eocene Río 20 Pichileufú (RP) site in Argentine Patagonia, was originally placed in Sect. Eutacta and later 2 21 reported from the early Eocene Laguna del Hunco (LH) locality. However, the relationship of A. 22 pichileufensis to Sect. Eutacta and the conspecificity of the Araucaria material among these 23 Patagonian floras have not been tested using modern methods. 24 METHODS — We review the type material of A. pichileufensis alongside large (n = 192) new 25 fossil collections of Araucaria from LH and RP, including multi-organ preservation of leafy 26 branches, ovuliferous complexes, and pollen cones. We use a total evidence phylogenetic 27 analysis to analyze relationships of the fossils to Sect. Eutacta. 28 KEY RESULTS — We describe Araucaria huncoensis sp. nov. from LH and improve the 29 whole-plant concept for Araucaria pichileufensis from RP. The two species respectively resolve 30 in the crown and stem of Sect. Eutacta. 31 CONCLUSIONS — Our results confirm the presence and indicate the survival of Sect. Eutacta 32 in South America during early Antarctic separation. T exceptionallyhe complete fossils 33 significantly predate several molecular age estimates for crown Eutacta. The differentiation of 34 two Araucaria species demonstrates conifer turnover during climate change and initial South 35 American isolation from the early to middle Eocene. 36 KEY WORDS —Araucariaceae; biogeography; conifers; early Eocene climatic optimum; 37 Gondwana; Laguna del Hunco; Patagonia; rainforest; Río Pichileufú; total evidence phylogeny 38 39 The final breakup of Gondwana had a profound influence on conifer evolution and biogeography 40 (McLoughlin, 2001; Leslie et al., 2012; Kooyman et al., 2014). Conifer taxa previously 41 described from the Eocene fossil caldera-lake deposits of Laguna del Hunco (~52.2 Ma), Chubut, 3 42 Argentina, and Río Pichileufú (~47.7 Ma), Río Negro, Argentina (Figure 1; Berry, 1938; Wilf et 43 al. 2009, 2014, 2017a; Wilf, 2012), illustrate a complex biogeographic history of Old World 44 (mostly Australasian/SE Asian) and New World survival patterns following the early Cenozoic 45 isolation of Antarctica and onset of global cooling (Zachos et al., 2001; Lauretano et al., 2018). 46 Laguna del Hunco preserves a highly diverse late Gondwanan flora (Wilf et al., 2003, 47 2013; Appendix S1; see Supplemental Data with this article) from the early Eocene climatic 48 optimum (EECO), the longest period of sustained warmth in the Cenozoic (~53-49 Ma; Zachos 49 et al., 2001; Lauretano et al., 2018). In that greenhouse world, the westernmost edge of a frost- 50 free, trans-Antarctic, mesothermal rainforest biome reached into southern South America via a 51 close connection between Patagonia and Antarctica (e.g., Hill 1995; Wilf et al. 2013; Kooyman 52 et al., 2014). The Río Pichileufú flora (Berry, 1938; Wilf et al., 2005) represents a period of 53 initial climatic cooling and drying following the EECO, as known from regional and global 54 records (Pearson et al., 2007; Hollis et al., 2012; Bijl et al., 2013; Dunn et al., 2015), from a time 55 when the earliest separation of South America and Antarctica was underway (e.g., Lawver et al., 56 2011). Comparison of the well-studied elements of the Laguna del Hunco and Río Pichileufú 57 floras (Appendix S1), yields evidence of turnover in the angiosperms, cycads, and ferns, 58 suggesting some extinction and a shift in the paleoenvironment (Wilf et al., 2013, 2019). 59 However, until now there has been no detection of a significant change in species composition of 60 the prevalent conifers between the two localities, and abundant Araucaria fossils at both sites are 61 considered to have affinities with A. Sect. Eutacta (e.g., Wilf et al. 2017a) but have not been 62 formally investigated since the 1940s (Berry 1938; Florin 1940). 63 The family Araucariaceae consists of the sister clades Araucaria Juss. and the agathioid 64 clade, comprised of the sister genera Agathis Salisb. and Wollemia W.G. Jones, K.D. Hill & J.M. 4 65 Allen (Gilmore and Hill, 1997; Stefanovic et al., 1998; Kunzmann, 2007; Liu et al., 2009; Leslie 66 et al., 2012; Escapa and Catalano, 2013; Escapa et al., 2018). Araucaria includes 20 extant 67 species within four sections that show a disjunct distribution: South American Section Araucaria 68 and Australasian Sects. Bunya, Eutacta, and Intermedia (Endlicher, 1847; Wilde and Eames, 69 1952; Farjon, 2010; Mill et al., 2017). Section Eutacta Endlicher (New Caledonia, New Guinea, 70 Australia) accounts for most of the extant diversity within Araucaria, encompassing 16 species 71 (Farjon, 2010; Mill et al., 2017). 72 Araucaria species are large, monoecious (rarely dioecious: Sect. Araucaria) evergreen 73 trees that are often recognized by their characteristic candelabra-shaped, pyramidal, or columnar 74 crowns (Farjon, 2010). Their leaves