APOMIXIS, HYBRIDIZATION, AND TAXONOMIC COMPLEXITY IN EASTERN NORTH-AMERICAN AMELANCHIER (ROSACEAE)

Apomixis and hybridization together contribute to taxonomic complexity in Amelanchier. Hybridization combines genetically divergent genomes and spawns new forms that apomixis perpetuates. Apomixis is aposporous , facultative, and pseudogamous in the genus, and apomicts are general ly polyploid, pollen fertile, and pollinated by generalists. That gene flow actually occurs is empirically evident. As apomixis is genetical ly dominant over sexuality, hybrids involving at least one apomictic p arent are apomictic. Clonal reproduction may thus perpetuate Fl indivi duals and generate agamospecies. Alternatively hybrids may interbreed and backcross to create hybrid swarms or cross with species other than the parents. In eastern North America, the abundance of published nam es and general taxonomic confusion in the genus doubtless result at le ast in part from this interplay of apomixis and hybridization. The rol es of apomixis and hybridization in diversification within Amelanchier are examined in light of new data about breeding system of an apomict ic, hybrid microspecies, informally named A. ''erecta'' and its format ion of a hybrid swarm with another Amelanchier apomict, A. laevis.