LAVIN, MATT*, MARTIN F. WOJCIECHOWSKI, MICHAEL J. SANDERSON, AND ADAM RICHMAN. Department of Plant Sciences, Montana State University, Bozeman, MT 59717, and Section of Evolution and Ecology, University of California, Davis, CA 95616. - Molecular biogeography of temperate and tropical legumes in North America.
Temperate deciduous forests have been the focus of northern hemisphere
biogeographical studies, yet the origins of the floristic elements in
these forests stem in part from tropical deciduous forests that
pervaded northern latitudes during the early Tertiary. The legume
family Fabaceae may provide some insight into the fate of the early
elements in North American deciduous forests. Most did not radiate
into the temperate deciduous forests, but rather remained in the
seasonally deciduous tropical forests that migrated southward with the
global cooling of the late Tertiary. Most of the temperate largely
herbaceous diversity in legumes seems to have migrated in from the Old
World during the late Tertiary rather than have evolved in situ in
North America from tropical, woody ancestors. We illustrate the early
Tertiary North American pattern with tropical legume groups including
Robinia and close relatives, as well as the dalbergioid legumes. The
late Tertiary to Quaternary North American pattern is illustrated with
temperate legumes including Hologalegina and Gleditsia. For tropical
lineages, a molecular clock based on nuclear rDNA ITS/5.8S sequences
is calibrated with an early Tertiary Caribbean vicariance event for
the endemic Greater Antillenan radiations Poitea and Pictetia.
Key words: Fabaceae, molecular biogeography, North America, Tertiary