ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. III. CHROMATOGRAPHIC VARIATION

Four widespread grasses, Andropogon scoparius Michx., A. gerardi Vitman, Sorghastrum nutans (Nash) Hitchc. and Panicum virgatum L., have been studied behaviorally and morphologically. In the present comparison characteristic flavonoid patterns were shown whereby the four grass taxa can be separated at the generic and specific level. The greatest similarity was shown by the two Andropogon species. Panicum was most dissimilar. Although intrapopulational and interpopuilational variation was demonstrated within each of the four taxa, both in transplanted material and in native plants of the original transplant site, there was no decisive correlation of biochemical variation with geographic origin, vegetative characteristics or maturity pattern. Early-flowering clones with short flowering culms and glabrous leaves, originating in northern and western areas, were essentially similar biochemically to later-flowering clones with tall flowering culms and extremely pubescent leaves, originating in southeastern areas. Blade samples collected in late fall, 1963, and in early spring, 1964, from the same transplanted clones were similar in flavonoid pattern. In P. virgatum, individual clonal patterns were characteristic of ramets grown under various daylength-thermoperiod conditions. Although biochemical markers for ecotypes would be useful eco logical tools, partially replacing their cultivation in transplant gardens, geographically correlated patterns were not revealed in this study. However, this study supports the present systematic position of the various morphologically and behaviorally diverse populations within the four taxa. A BROAD RANGE of ecological variation has been demonstrated within the four widespread prairie grasses. Under transplanted conditions those of northern and western origin in each species were early flowering and those of southern origin were late flowering. Height variation among the transplanted clones included tallest flowering culms among those of southern origin. Leaf variation included dense pubescence among clones of southeastern origin (Bragg and McMillan, 1962; Mc\1illan, 1964, 1965). The possible correlation of morphological and behavioral variation with biochemical variation was studied by a chromatographic comparison within each of the four grass species. Native and transplanted clones, largely of diverse origin in Texas, were compared for possible correlations with ecotypic differentiation and for determination of the constancy of a biochemical pattern under different environmental conditions. Individual clones were evaluated under controlled climates for further information on environmental influence on biochemical patterns. Although studies involving chromatographic evaluation have suggested the usefulness of flavonoid patterns in systematics (Alston and Turner, 1963; Smith and Levin, 1963; Harney and Grant, I Received for publication October 8, 1965. This study was aided by National Science Foundation Grants 0-14909 and GB-1459. The authors are grateful to Dr. Ralph E. Alston for the use of his chromatographic facilities. 2 Permanent address: Department of Biology, Arlington State College, Arlington, Texas. 1964), their correlation with ecotypic differentiation needed investigation. A convenient biochemical marking of an ecotype would greatly facilitate the recognit on of ecological variation within species, particularly if the biochemical pattern of an ecotype was relatively constant under diverse environmental conditions. While only the flavonoid constituents were examined in the present investigation, other biochemical markers may show greater relation to ecotypic differentiation. MATERIALS AND METHODS-The four taxa invest gated are among the most widespread and most complex of the prairie grasses. Andropogon scoparius Michx. is comprised of several varieties. Western Texas plants are referred to as var. neomexicanus (Nash) Hitchc., characterized by a copiously villous and straight rachis. Plants of this variety range northward in western localities of central North America. Their leaf blades and sheaths vary from barely to extremely glaucous. Populations of central Texas, including extremely glaucous plants, are included in var. frequens Hubb., which has a more flexuous rachis. Variety frequens includes populations extending north and eastward from central Texas. Variety divergens has included the densely pubescent plants with unreduced pedicellate spikelets in eastern Texas, and adjacent Arkansas and Louisiana. Gulf Coast plants of southern Texas and Mexico have been referred to as var. littoralis (Nash) Hitchc. They are morphologically similar to coastal plants from Virginia to New Jersey which have