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Abstract Detail

The Role of Boundaries in Plant Diversification

Tectonic, Climatic, and Mass Extinction Boundaries and the Paleo-Patagonian Diaspora Flora of Australasia, Southeast Asia, and the Neotropics.

A wealth of new paleobotanical discoveries is emerging from the early Paleogene fossil biotas of Laguna del Hunco and other well-dated sites in Patagonian Argentina. These assemblages provide novel data from the terminal phase of Gondwana, coinciding with early Paleogene warmth that allowed diverse, mesic rainforest vegetation to flourish across the Antarctic. Today, the fossils’ far-flung diaspora of living relatives is frequently still associated, primarily in mesothermic, lower montane rainforest environments of Australasia and SE Asia and to a much lesser extent in the Neotropics. Sumatran orangutans feed on genera known as Eocene fossils at 15,000 km modern distance. Boundaries of many types and scales shaped these remarkable modern distributions. The Cretaceous-Paleogene boundary extinction (K-Pg) set the stage for all subsequent biogeographic history, and accumulating evidence suggests greater survival of Mesozoic lineages in Gondwana than in the Northern Hemisphere. The extant distributions can then be understood in terms of ecological conservativism and habitat tracking through the Cenozoic to meet edaphic requirements (boundaries). Many of the Patagonian fossil lineages are restricted today to everwet environments, and several of the fossil podocarps even preserve the extremely drought-sensitive foliar transfusion tissues seen in their living relatives. The first-order boundaries set by plate tectonics, climate, and sea-level change determined the changing distributions of suitable moist habitats through time that the plants followed. After the final separation of Antarctica from Australia and South America starting in the middle Eocene, Australia’s northward movement sheltered many formerly trans-Antarctic lineages from Cenozoic cooling (i.e., Ceratopetalum, Eucalyptus, Araucaria Section Eutacta) and sourced the diversification of many on smaller, sometimes emergent land masses. Subsequently, Australia collided with SE Asia beginning ca. 25 million years ago and delivered diaspora taxa that diversified in Wallacea (i.e., Agathis, bird-dispersed Dacrycarpus, Gymnostoma). Whereas Australia acted as museum and life raft, Patagonia became a death trap of environmental restrictions. Regional extinction of the ancient rainforest flora came from a combination of increasing aridity and cooling, marine incursions, and the barriers to northward escape posed by the persistent subtropical arid zone and Neotropical heat and insolation regimes. The Miocene principal onset of Andean uplift eventually provided suitable mesic rainforest habitats, many millions of years too late but for a few survivors (e.g., Podocarpus, Retrophyllum, Physalis). Thus, the paleo-Patagonian diaspora flora responded to changing boundary conditions through massive range shifts and diversification in new areas but suffered drastic extinctions in South America, especially in Patagonia itself.

1 - Penn State Univ., 537 Deike Bldg., UNIVERSITY PARK, PA, 16802, USA

Keywords:
Patagonia
Gondwana
biogeography
Asia
Podocarpaceae
Paleoclimate
leaf physiology
Niche conservatism
Rainforests
Cenozoic
Paleobotany.

Presentation Type: Symposium Presentation
Session: SY7, The Role of Boundaries in Plant Diversification - with Presentation of Pelton Award to Dr. Shirley Tucker
Location: Sundance 3/Omni Hotel
Date: Wednesday, June 28th, 2017
Time: 1:45 PM
Number: SY7002
Abstract ID:175
Candidate for Awards:None