The number of flowering stems for 82 species on a transect 2 x 400 m was counted twice weekly during 1978 at Tucker Prairie, Callaway County, Missouri, USA, a tall—grass prairie remnant. Phenological curves (number of flowering stems vs. day of the year) are narrower (smaller standard deviations) for wind—pollinated species than for insect—pollinated species. Symmetry (g1) does not differ significantly for wind— and insect—pollinated species. The curves are largely either symmetric or begin abruptly and end gradually (right—skewed). Overlap, measured as the fraction of the area under the curves occupied by two or more species, does not differ significantly for wind— and insect—pollinated species, among 20 groups of five randomly drawn species. Dates of peak flowering are distributed randomly over the season (May to November 1978) and their distributions do not differ for wind— and insect—pollinated species. Dates of peak flowering are also randomly distributed for grasses, legumes, and composites considered separately. Thus, although species with different pollination modes show different shapes for phenological curves, the species aggregated into the community do not have ensemble patterns of temporal dispersion or overlap and cannot be distinguished from a random collection.

Sparse species have chronically small local population sizes, even though they occur in several habitats over a wide geographic range. Greenhouse de Wit replacement series with seven species of sparse and common perennial grasses of tallgrass prairie were performed with seedlings and tiller fragments for 5, 10, and 15, mo. As younger and older seedlings, sparse grasses overyielded and were advantaged by the interaction with common grasses. The common grasses underyielded and were disadvantaged in mixture with sparse grasses. As tillers, the interaction was less antagonistic, and both common and sparse grasses either overyielded or were unaffected by the interaction. Seedlings of sparse species were largest when planted in low proportion, surrounded by individuals of a common grass. Because the sparse species are not disadvantaged by interactions with their common neighbors, their competitive abilities are not implicated as a cause of their local rarity. Rather, the good competitive abilities of these sparse grasses are best viewed as a mechanism that offsets the hazards of low density and makes local persistence more likely.

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Seven grass species on an abundance continuum from common to sparse on a Missouri tallgrass prairie were examined for two diaspore traits (morphology and weight), for three dispersal traits (terminal velocity, and mean and maximum lateral movement propagules released in still air from a height of I m), and for two parental traits (culm biomass at maturity and culm height at dispersal). Dispersal ability, measured in the laboratory as the lateral movement ofpropagules in the upper 5% (right tail) of the distribution of distances, is inversely correlated (r, = -0.94) with biomass abundance. Under constant conditions, seeds of sparse species travel farther than seeds of common species. Dispersal ability is more closely related to a populational attribute (abundance) than to a more proximate characteristic (diaspore weight). Diaspore weight is closely related (r s = 0.97) to culm biomass of the parent, in apparently simple allometry, and more weakly related (r s = 0.71) to biomass abundance. Large parents make large seeds. The sparsest species, which is small in stature, has light (0.08 to 0.19 mg), flattened diaspores with low terminal velocities (82 to 87 cm sec-I) and achieves lateral movement (up to 460 mm) by tumbling and gliding. Species of intermediate abundance have intermediate stature and diaspore weight (1.0 to 1.8 mg), unornamented propagules, high terminal velocities (191 to 209 cm sec ") and intermediate dispersal ability (up to 388 mm). The three most common species have heavy propagules (2.2 to 2.8 mg), ornamented with long hairs. Although the ornamentation slows fall (96 to 194 cm sec "), it acts as a "guide parachute," orienting the propagule so that it falls nearly straight downward. The common species, which morphologically appear adapted to longer dispersal, achieve little lateral movement (up to 235 mm) under laboratory conditions. Terminal velocity is a misleading descriptor of dispersal because diaspores with similar terminal velocities have differing movement patterns. When diaspores of two species (one tall common species and one short sparse species) are released in still air from their natural height, differences in maximum fall distance observed under constant height of release are lost. When dispersal is observed in the field by means of sticky seed traps, the slopes of the dispersal curves (regression coefficient of In-transformed number of seeds caught on distance from the clump) do not differ from common and sparse species, despite the fact that seeds of the common species are released from greater heights. The orderly differences in dispersal behavior among species due to subtleties of morphology observed under laboratory conditions are masked in nature.SEED DISPERSAL of higher plants has been studied extensively on an observational (Guppy

We observed colonization and mortality of plants in small (26 m2) artificial soil disturbances and undisturbed controls in a tall‐grass prairie from 1977–1980. This paper examines the dynamics of colonists based on mode of origin (seedlings and shoots) and broad taxonomic affinity (forbs and graminoids). Few seedlings colonized either disturbances or controls the first year, probably due to a severe drought in 1976 when few seeds were produced. Graminoid shoots were more abundant in disturbed sites than in controls the first year, probably due to the “edge effect” of cutting roots and rhizomes and stimulating new growth. For each year following the first, the number of current residents peaked early in the season and then declined, with the decline more precipitous for seedlings than for shoots. The population fluctuations of seedlings were very predictable, and separate years resembled each other. In contrast to seedling populations, graminoid shoot populations generally were accumulating throughout the study. Populations of forb shoots rose and fell, but the years did not resemble each other. Neither seedlings nor forb shoots showed a response to the new uncolonized soil resource of the artificial disturbances compared to controls, but graminoid shoots were more common on disturbed sites. These results suggest a nonequilibrium dynamic among colonizers of small‐scale microsites.