Title: Biogeographical Relationships of North American Tertiary Floras
Abstract:Comparisons of Tertiary floras of North America with those of Europe and Asia document a long history of floristic interc hange.The stratigraphic and geographic ranges of selected conifer and angiospe...Comparisons of Tertiary floras of North America with those of Europe and Asia document a long history of floristic interc hange.The stratigraphic and geographic ranges of selected conifer and angiosperm genera that are easily recognized in the fossil record provide a basis for discerning patterns in the routes and timings of intercontinental dispersals through the Tertiary.The origin of the extant flora and vegetation of North America has been the subject of much interest and debate ever since the floristic similarities between North America and Asia were first documented.Many of the woody genera comprising North America's present-day forests have excellent fossil records that can be traced through the Tertiary in North America and other continents of the Northern Hemisphere (Wolfe, 1975; Graham, 1993; Tiffney, 1985a, b; Mai, 1995).In addition, many genera that are no longer native to North America have well-documented Tertiary records.Patterns of geographic disjunction among extinct and extant genera provide important clues to the history of North American flora and the former continuity of Tertiary forests in the Northern Hemisphere.By comparing the stratigraphic records of genera shared among two or more continents it is possible to consider the pathways and timing of plant interchange through the Tertiary.Many ideas have been published on the paleobotanical origins and development of extant flora ; Latham & Ricklefs, 1993; 5; Akhmetiev, 1996).In the attempt to be as comprehensive as possible, investigators have sometimes relied uncritically upon genera reported in the literature.Closer scrutiny reveals many erroneous generic determinations (Dilcher, 1974).Read More