Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Constance I. Millar
    Date: 1993
    Source: Annals of the Missouri Botanical Garden 80:471-498
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (2.5 MB)

    Description

    Pinus evolved in middle latitudes of the Northern Hemisphere in the middle Mesozoic. By the late Cretaceous pines had spread east and west throughout Laurasia, attaining high diversity in eastern Asia, the eastern United States, and western Europe, but having little representation at high northern latitudes. Changing climates in the early Tertiary established warm and humid tropical/subtropical conditions in a broad zone to 70°N throughout middle latitudes. Pines and their relatives disappeared from many middle-latitude areas during this time and were replaced by diverse angiosperm taxa of the boreotropical flora, which were adapted to the equable, tropical climate. The effect of this climate change and spread of boreotropical flora was to displace pines from their former habitats. A hypothesis is defended that pines shifted, during the three warm periods of the Eocene, into three major refugial areas in the Northern Hemisphere: high latitudes, low latitudes, and upland regions of middle latitudes, especially in western North America. Some of these refugial areas (e.g., Mexico/Central America) underwent active volcanism and mountainbuilding in the Eocene and became secondary centers of pine diversity. Many phylogenetic patterns within Pinus can be traced to this fragmentation, isolation, and evolution in Eocene refugia. Subsections Oocarpae and Sabinianae appear to have originated from refugia in Mexico and Central America. Older subsections such as Sylvestres, Ponderosae, Contortae, and Strobi were distributed over several refugia; subsections Leiophyllae, Australes, and Cernbroides evolved in southern refugia in North America; and Canarienses evolved in southern refugia along the Tethys seaway in Eurasia. Following the cooling and drying of the climate at the end of the Eocene, many angiosperm taxa of the boreotropical flora became extinct and pines recolonized middle latitudes, a zone they have occupied to the present. Migration out of refugia provided additional opportunities for hybridization and introgression, as formerly isolated lineages expanded and met.

    Publication Notes

    • You may send email to psw_communications@fs.fed.us to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Millar, Constance I. 1993. Impact of the eocene on the evolution of Pinus L. Annals of the Missouri Botanical Garden 80:471-498

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page
https://www.fs.usda.gov/treesearch/pubs/24277