Abstract
Artificial hybridization experiments involving 25 taxa ofRuellia had as one objective to determine the possibility of any genetic relationships between North American temperate species and certain widespread tropical American taxa. The results confirm a close morpho-genetic link betweenR. caroliniensis-R. pedunculata and the Caribbean species R.geminiflora and betweenR. nudiflora and the pantropical R.tuberosa. A second objective was to test the genetic basis for the present generic concept ofRuellia. The results of hybridizations among species representatives of six proposed segregate genera were measured by relative seed-set in crosses. The results support the view that the present circumscription of the genus is unnatural and that some taxa presently classified inRuellia bear little if any morphological or genetic relationship toRuellia. When the ecotype concept is applied to the genus, natural, closely related species groups can be identified by hybridization experiments. This approach can lead to an accurate, precise delimitation ofRuellia and may be applicable in other large genera of Acanthaceae.
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Research supported by grants GB-35231 and GB-1026 from the National Science Foundation. I thank C. P. Sreemadhavan, Martha Meagher, and Suzanne Todd, who served as assistants.
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Long, R.W. Artificial interspecific hybridization in temperate and tropical species of ruellia (acanthaceae). Brittonia 27, 289–296 (1975). https://doi.org/10.2307/2805899
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DOI: https://doi.org/10.2307/2805899