Ecotypic Differentiation Within Four North American Prairie Grasses. Ii. Behavioral Variation Within Transplanted Community Fractions

Ecotypic differentiation in transplanted clones of Andropogon scoparius Michx., A. gerardi Vitman, Panicum virgatum L. and Sorghastrum nutans (L.) Nash showed north‐south correlations. In Austin, Texas, during 1959–1962, southern populations had earliest spring activity, latest flowering and latest dormancy. Northern community fractions from Massachusetts to North Dakota showed early flowering and a short span separating initial anthesis among the species‐populations. Community fractions from Virginia to Nebraska had initial anthesis over a longer period than in more northern or more southern samples. Community fractions from South Carolina to eastern Texas had late flowering over a short period. Western community fractions, latitudinally and altitudinally diverse, were behaviorally uniform. The length of the growing period and its recurrent selection have sorted out ecological variants in harmony with the habitat gradients. Whether they are of the predominant physiognomic types, as in the true prairie region, or understory plants in the pine forests, the 4 grass taxa are in the climax matrix.