A biosystematic study of the Chloris cucullata-chloris verticillata complex

Abstract

An investigation was undertaken to determine the taxonomic relationships of the Chloris-cucullata-C. verticillata complex and the variation patterns within these populations apparently resulting from hybridization. As delimited by Hitchock the taxa of the complex are: Chloris verticillata, C. cucullata, C. andropogonoides, C. texensis, C. latisquamea, and C. subdolichostachya. Of special concern were the aneuploid plants, presumably of hybrid origin, referable to C. verticillata and C. subdolichostachya, including those of C. latisquamea as interpreted by Hitchock. The study involved investigation of anatomical, cytological, and reproductive characteristics coupled with morphological data from mass collections of native populations form the Post Oak Savannah, the South Texas Plains, Gulf Prairies and Marshes, and the Edwards Plateau of Texas. Intensive and detailed population and cytological studies were made in the Bryan-College Station are, Brazos County, and the Welder Wildlife Refuge, San Patricio County. Gross morphology, involving mass collections, herbarium specimens, and cytological voucher specimens, provided the most useful characters for delimiting the taxa of the complex. The characters found to be of most value were: length of the longest inflorescence branch, greatest distance between spikelets at the base of this branch, shape of the apex of the spikelet rudiment, rudiment width, lower floret length, color of mature spikelet, and length of awn of the lower (fertile) floret. Based on data obtained in this investigation, five taxa were recognized in the complex, namely: Chloris verticillata, C. cucullata, C. andropogonoides, C. texensis, and C. subdolichostachya. ...