Saar, Dayle .
Red and White Mulberries (Morus rubra and M. alba: Moraceae) and Their Interspecific Hybrids: the "Real" Red Mulberry is not as Previously Thought.
Morus rubra (Red Mulberry) is the only mulberry native to eastern North America; only two species are native to this continent. M. alba (White Mulberry) is naturalized from Asia and is widespread throughout the United States, as a result of escapes from cultivation, both as a street planting and from unsuccessful attempts to establish a silk industry in this country (leaves used to feed larvae of the silkworm, Bombyx mori). Both species produce leaves of similar size and shape, and fruits are often the same color. For well over a century, plant keys and other literature have distinguished the two species based almost exclusively on the abundance (or lack of) and location leaf pubescence. The two species readily hybridize, and the fairly common trait of intermediate pubescence has been the presumed result. Results of this study with DNA-identified individuals demonstrate that leaf pubescence is not a reliable character for field identification of these two species. Further, hybrids are quite common and are often cryptic when judged on pubescence. M. alba and interspecific hybrids have been located in relatively undisturbed habitats, misidentified by current morphological criteria, but confirmed by molecular data. M. alba appears to be more cold-hardy, and this trait has been imparted on the hybrids. Based on our preliminary data, present maps show an inflated geographic range for M. rubra, including states where the "true" M. rubra probably does not exist. In at least one of these states, it appears that individuals of M. alba, misidentified as M. rubra, have been declared "threatened" in that state. Currently, DNA identifications are being compared with trees in an effort to discover more reliable morphological characters for field identification. Leaf vein patterns appear to be much more reliable than pubescence, and more testing is underway to confirm this. Reliable identifications based on morphology are imperative for field botanists and conservation personnel, particularly where M. rubra is an imperiled species.
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1 - Murray State University, Department of Biological Sciences, Biology Building 1112D, Murray, KY, 42071, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Waterman Room/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 2:00 PM