Phenological Variation within Seven Transplanted Grassland Community Fractions from Texas and New Mexico

Community fractions, consisting of population samples of Andropogon scoparius Michx., A. gerardii Vitman, Panicum virgatum L., and Sorghastrum nutans (L.) Nash, were transplanted to Austin, Texas, from six sites in Texas and one site in New Mexico. A behavioral gradient among the transplanted community fractions was correlated with the length of the growing period (over 300 to less than 200 days) and altitude (sea level to near 2,800 m) of origin. Late maturity characterized the populations from shorter growing periods and higher altitude. The population samples of 10 clones were compared in time of initial flowering with earlier samples of three clones taken from the same geographic area. Despite variations in site and year the gradient of mean flowering time was similar. The uniformity of flowering time and morphology within certain population samples of A. gerardii and P. virgatum suggested vegetative replication. Local differentiation was show in P. virgatum, caespitose (tetraploid) plants from a river bottom being later flowering than rhizomatous (octoploid) plants from an adjacent sandhill area. During an extended summer drought, the community fraction originating in central Texas showed selective superiority in the central Texas transplant habitat.