Abstract Detail

Paleobotany

DeVore, Melanie [1], Pigg, Kathleen B [2].

Alternative analogues for the evolutionary mechanisms that drive diversification of some upland Rosaceae.

The latest early Eocene Republic locality of Washington, in concert with those of the other Okanagon Highlands sites in British Columbia, provide a record of high elevation floras with temperate elements that is contemporaneous with tropical coastal forests of the Eocene thermal maximum. Well represented in these fossil floras is the Rosaceae, a family predominately distributed in temperate regions of the Northern Hemisphere today. However, their current distribution is not a good analogue for investigating the drivers of evolutionary mechanisms within Rosaceae. Instead, tropical highland floras in both the New and Old Worlds provide a better backdrop for interpreting the variation within fossil Rosaceae of the Pacific Northwest. Based on the autecology and breeding systems of taxa present within the floras of the Northern Andes and the Virunga Mountains of central eastern Africa, we see at least three interesting patterns within the family. First, floras of both continents have suites of Rubus populations actively hybridizing within high elevation vegetation zones today, a pattern that we have documented for the Okanogan Highlands. Secondly, the presence of Prunus africanus at high altitudes in the Virunga Mountains, suggests that it is a relictual element of a taxon known to be more widely distributed during the Paleogene. Finally, both the Northern Andes and Virungas host endemic, woody rosaceous taxa with compound leaves in montane ecosystems. In both the case of Hagenia (Africa) and Polylepis (Andes) these arborescent taxa originate from herbaceous ancestors. We see a similar pattern of highly dissected to compound leaves attributed to Rosaceae such as the extinct genus Stonebergia in the Eocene of western North America. These taxa also may represent endemic forms that descended from herbaceous ancestors. The mechanisms of diversification of this third group of Rosaceae lie in sharp contrast to such long-lived hybrid complexes as Rubus or taxa like Prunus, which persist because of their superb dispersal potential.

1 - Dept Of Biology & Env. Science, GC & SU Campus Box 81, MILLEDGEVILLE, GA, 31061-0001, USA
2 - Arizona State University, School of Life Sciences and BioKIC, PO Box 874501, Tempe, Arizona, 85287-4501, United States

Keywords:
Rosaceae
Okanagon Highlands
Eocene Floras
Biogeography.

Presentation Type: Oral Paper
Session: 28, Mesozoic to Pleistocene Paleobotany
Location: 102/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 2:45 PM
Number: 28006
Abstract ID:561
Candidate for Awards:None