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Rupert Barneby and his legume legacy

Baskin, Jerry M. [1], Baskin, Carol C. [1].

Ecology and life cycle biology of two geographically-restricted Astragalus species (Fabaceae): A. bibullatus Barneby & Bridges and A. tennesseensis A. Gray ex Chapman.

Astragalus bibullatus is endemic to limestone glades in the Central Basin of Tennessee. Except for one population in Illinois, A. tennesseensis is endemic to limestone glades in the Central Basin and in the Moulton Valley of Alabama. However, this species has been extirpated from several counties in Illinois and from its only known site in Indiana. A. bibullatus is closely related to the geographically-widespread Great Plains taxon A. crassicarpus var. crassicarpus, whereas A. tennesseensis is the only taxon in section Tennesseensis. Vegetative plants of A. bibullatus have lower genetic diversity than those of A. tennesseensis. However, genetic diversity of A. bibullatus seeds in the soil seed bank is higher than that of vegetative plants. Both species are shallow-rooted hemicryptophyte perennials, have no effective means of seed dispersal, form long-lived seed banks, do not reproduce vegetatively, have similar life cycle phenologies, and are intolerant of heavy shade. Additional information is available on the autecology of A. tennesseensis: (1) its primary habitat is the transition zone between open glades and glade woods, where physical environmental factors are intermediate between those of the adjacent zones; (2) seedling-juvenile survival is low; (3) plants flower first in their 2nd-5th year and only a few times before dying, are self-incompatible, respond to drought by shedding leaves and by accumulating large amounts of proline, and compete poorly; and (4) populations exhibit high fluctuations in number of individuals and have high turnover rates. Although maximum photosynthesis rates were higher for A. crassicarpus than for A. bibullatus, a greenhouse study did not identify any difference in the responses of these species to light or soil moisture that could account for the great difference in their geographic ranges. Thus, historical factors need to be considered along with the speciesí biology in explaining the narrow endemism of A. bibullatus.

1 - University of Kentucky, Department of Biology, 101 Morgan Bldg, Lexington, Kentucky, 40506, USA

geographical distribution
plant life history
soil seed bank
genetic diversity
narrow endemic.

Presentation Type: Symposium
Session: 19-10
Location: Magpie (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 4:30 PM
Abstract ID:144

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