The importance of herbivorous insects for plant demography and fitness is still controversial. The fact that their effect has not be fully evaluated within the context of the complete plant life cycle contributes to this controversy. This study is the first to test directly the influence of flower and seed consumption by a guild of inflorescence—feeding insects on the demography and fitness of a native plant over its whole life cycle within its natural environment. First, we discuss the evidence required to assess the effect of inflorescence—feeding on sequential stages in the plant life cycle. Then, we present the detailed results of two experiments that quantify the effect of inflorescence—feeding insects on seeds, seedlings, juveniles, and subsequent flowering progeny of Cirsium canescens (Platte thistle), a native, monocapic perennial species of Sandhills prairie, Nebraska. Exclusion of inflorescence—feeding insects by insecticide had four main effects. Total seed output increased (P < 0.0005 in both experiments), indicating that resource were not limiting seed production. Flower heads produced later in the season contributed to the seed pool when insects were reduced (P < 0.01), suggesting that insect feeding restricted the phenology of flowering and pollination. The density of seedling increased around plants protected from florescences—feeding insects (P < 0.0005), showing that safe sites were not limiting. Finally, the increase in seedlings led to higher numbers of flowering adults (P < 0.009), demonstrating that inflorescence—feeding insects significantly reduced lifetime fitness. Neither individual compensation for seed loss, nor density—dependent compensation for increased plant population densities, was observed when insects were excluded. Thus, we conclude that the inflorescence—feeding insect herbivores limited seed production, seedling recruitment, plant density, and maternal fitness of this plant under natural conditions. This outcome challenges current theoretical models of the effect of insects on plant population dynamics. We predict that our result will be general for short—lived perennial plants with life histories in which persistence is tightly linked to regeneration from current seed, such as for fugitive perennials with transient seed banks.

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Workforce homogeneity limits creativity, discovery, and job satisfaction; nonetheless, the vast majority of university faculty in science, technology, engineering, and mathematics (STEM) fields are men. We conducted a randomized and controlled three-step faculty search intervention based in self-determination theory aimed at increasing the number of women faculty in STEM at one US university where increasing diversity had historically proved elusive. Results show that the numbers of women candidates considered for and offered tenure-track positions were significantly higher in the intervention groups compared with those in controls. Searches in the intervention were 6.3 times more likely to make an offer to a woman candidate, and women who were made an offer were 5.8 times more likely to accept the offer from an intervention search. Although the focus was on increasing women faculty within STEM, the intervention can be adapted to other scientific and academic communities to advance diversity along any dimension.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 144.122.ABSTRACT.-This study examines the effect of differential survival of seedlings on the distribution of native grasses along topographic gradients in the Nebraska Sandhills. In 1981, seeds of three ridge species (Andropogon hallii, Sorghastrum nutans, Panicum virgatum) were planted into rototilled, irrigated, rototilled and irrigated, or untreated soils on three sites: one ridge site (ridge) and two valley sites (valley and lowland). The three sites represented a gradient of topography and soil moisture-holding capacity. For all species, seedling survival was greatest (86%) in the rototilled and irrigated treatment on the lowland site. No seedlings survived in untreated plots along the gradient.In 1982 and 1983, seeds of a ridge species (Andropogon hallii) and a valley species (Bouteloua gracilis) were planted in replicated ridge and valley plots. Seeds were planted into either untreated plots, or plots where plants received weekly clipping treatments around seedlings. Although clipping significantly increased survival of both species in both sites, it had a significantly greater effect in valley sites. In untreated plots, seedling survival was greatest (20%) in ridge sites in a year of average precipitation (1982) and in valley sites (49%) in a year that was exceptionally wet (1983). In 1983, soil moisture explained 98% of the variation in the survival of A. hallii seedlings and 82% in B. gracilis seedlings.Competition from existing vegetation severely limited the probability of seedling establishment. The distribution pattern of ridge species likely results from differential survival of juveniles and adults along the gradient, rather than the ability of seedlings to have higher establishment success on ridge sites. Significant establishment of the valley species (Bouteloua gracilis) occurred only during an exceptionally wet year when the pattern of survival of seedlings reflected the distribution pattern of adult plants. Establishment of prairie grass seedlings appears to depend on the availability of soil moisture, which may only be adequate in relatively large disturbance areas (> 1 m2), or in years of higher than normal precipitation. POTVIN: GRASS SEEDLING ESTABLISHMENT 249

End of season components of biomass and litter were measured on a Nebraska Sandhills prairie site to follow vegetation changes during the first 4 years following the cessation of intense livestock grazing. The 1977-1980 mean annual end of season biomass at Arapaho Prairie, a Sandhills prairie site, was 109 g/m2. Summer grazing on Arapaho Prairie was terminated in 1977, and as a result, significant increases in the biomass of the deep-rooted, palatable warm-season (Cd) grasses, sand bluestem, little bluestem and switchgrass, have occurred since then. The biomass of the shallowly rooted C4 grama grasses for the I-year period was significantly correlated with growing season precipitation. Significant decreases in end of season biomass of the cool-season (CS) grasses during the same 4-year period were highly correlated with yearly decreases in May precipitation. Following the removal of grazing, litter increased from 40 to 127 g/m* from 1977 to 1980. A nonsignificant yearly increase in litter production occurred in the third year after grazing as a steady state of litter production and decomDosition was auuroached.