The Carpinus caroliniana Complex in North America. II. Systematics

Abstract

The Carpinus caroliniana complex consists of a series of geographical races ranging north and south through the deciduous forest zone of eastern temperate North America and the mountains of Mexico and northern Central America. All of these races are morphologically variable and difficult to distinguish on the basis of independent characters. Nevertheless, each possesses a broadly distinctive set of features related to a particular ecological situation. Published records of Pleistocene and post-Pleistocene pollen floras suggest that Carpinus survived Wisconsin glaciations throughout much of its present range in unglaciated eastern North America, both east and west of the Appalachian Mountains, and geological and paleobotanical evidence supports the hypothesis of pre-Pleistocene western introduction of the genus into Mexico. The complex is divided to form two species. The northern C. caroliniana consists of subsp. caroliniana of the Atlantic and Gulf Coastal Plains of the southeastern United States and subsp. virginiana of the Appalachian Mountains and northern interior regions to the west. The Latin American C. tropicalis is separated into subsp. tropicalis of the deciduous forest zone of the highlands of southern Mexico and northern Central America and subsp. mexicana of the cool humid zone of mountains in northeastern Mexico and the trans-Mexican volcanic belt.