Evol Ecol Res 6: 33-48 (2004)     Full PDF if your library subscribes.

Structure of the North American vegetation gradient during the late Paleocene/early Eocene warm climate

Guy J. Harrington*

Department of Paleobiology, Smithsonian Institution, 10th and Constitution Avenue NW, Washington, DC 20560-0121, USA


e-mail: g.j.harrington@bham.ac.uk

ABSTRACT

Late Paleocene/early Eocene pollen and spore data taken from the US Gulf Coast (paleolatitude 32°N), western interior basins (Wyoming, North Dakota; paleolatitude 44–47°N) and Canadian Arctic (paleolatitude > 68°N) represent a vegetation proxy for ancient paratropical, subtropical and temperate biomes. These data provide information on the latitudinal diversity gradient of plants during an ancient greenhouse climate with non-freezing winters at polar latitudes. Comparing pollen data from the early Paleogene with a pollen data set compiled at the same latitudes from the late Holocene (3000 years B.P. to present) reveals that the diversity gradient between middle to high latitudes was steeper than today at the same sampling intensity. The gradient is a step-like decrease of about 50% in taxonomic diversity with increasing latitude between regions. The diversity gradient is formed by the ‘spillover’ of paratropical taxa into other regions of North America, which reflects the modern pattern of plant ranges. Taxa present in the Arctic, therefore, have great geographic ranges with endemism greatest in the paratropical biome. Paleogene diversity gradients show that decreasing diversity with increasing latitude is ancient and not dependent upon freezing temperatures.

Keywords: Eocene, latitudinal diversity gradient, North America, Paleocene, palynology, vegetation.

DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.

 

        © 2004 Guy J. Harrington. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.