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The evolution of increased competitive ability (EICA) hypothesis predicts that invasive plant species may escape their specialized natural enemies in their introduced range and subsequently evolve with a decrease in investment in anti-herbivore chemical defenses relative to native conspecifics. We compared the chemical profile of 10 populations of US native and 20 populations of European invasive Solidago gigantea. To test for differences in inducibility between native and invasive populations, we measured secondary chemistry in both damaged and undamaged plants. We also performed bioassays with three specialist and two generalist insect herbivores from four different feeding guilds. There was no evidence that invasive populations had reduced concentrations of sesquiterpenes, diterpenes, or short-chain hydrocarbons (SCH), although significant variation among populations was detected. Sesquiterpene and diterpene concentrations were not influenced by damage to the host plant, whereas SCH concentrations were decreased by damage for both native and invasive plants. Performance of the three specialist insects was not affected by the continental origin of the host plant. However, larval mass of the generalist caterpillar Spodoptera exigua was 37% lower on native plants compared to invasive plants. The other generalist insect, a xylem-tapping spittlebug that occurs on both continents, performed equally well on native and invasive plants. These results offer partial support for the defense predictions of the EICA hypothesis: the better growth of Spodoptera caterpillars on European plants shows that some defenses have been lost in the introduced range, even though our measures of secondary chemistry did not detect differences between continents. Our results show significant variation in chemical defenses and herbivore performance across populations on both continents and emphasize the need for analysis across a broad spatial scale and the use of multiple herbivores.

Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650 μl l and two levels of soil nutrition. In the high nutrient treatment, increasing CO led to a doubling of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by changes in carbon allocation to shoot mass alone. Growth under CO enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO and low nutrient availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient limitation slightly reduced the C/N balance among the high-CO plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content.

Seed- and clonally-propagated plants of Big Sagebrush (Artemisia tridentata var.tridentata) were grown under atmospheric carbon dioxide regimes of 270, 350 and 650 μl l and fed toMelanoplus differentialis andM. sanguinipes grasshoppers. Total shrub biomass significantly increased as carbon dioxide levels increased, as did the weight and area of individual leaves. Plants grown from seed collected in a single population exhibited a 3-5 fold variation in the concentration of leaf volatile mono- and sesquiterpenes, guaianolide sesquiterpene lactones, coumarins and flavones within each CO treatment. The concentration of leaf allelochemicals did not differ significantly among CO treatments for these seed-propagated plants. Further, when genotypic variation was controlled by vegetative propagation, allelochemical concentrations also did not differ among carbon dioxide treatments. On the other hand, overall leaf nitrogen concentration declined significantly with elevated CO. Carbon accumulation was seen to dilute leaf nitrogen as the balance of leaf carbon versus nitrogen progressively increased as CO growth concentration increased. Grasshopper feeding was highest on sagebrush leaves grown under 270 and 650 μl l CO, but varied widely within treatments. Leaf nitrogen concentration was an important positive factor in grasshopper relative growth but had no overall effect on consumption. Potential compensatory consumption by these generalist grasshoppers was apparently limited by the sagebrush allelochemicals. Insects with a greater ability to feed on chemically defended host plants under carbon dioxide enrichment may ultimately consume leaves with a lower nitrogen concentration but the same concentration of allelochemicals. Compensatory feeding may potentially increase the amount of dietary allelochemicals ingested for each unit of nitrogen consumed.

Addendum to: Hull-Sanders HM, Johnson RH, Owen H, Meyer GA. Effects of polyploidy on secondary chemistry, physiology and performance of native and invasive genotypes of Solidago gigantea (Asteraceae). Am J Bot 2009; 96:762-70; DOI: 10.3732/ajb.0800200. H erbivores are sensitive to the genetic structure of plant populations, as genetics underlies plant phenotype and host quality. Polyploidy is a widespread feature of angiosperm genomes, yet few studies have examined how polyploidy influences herbivores. Introduction to new ranges, with consequent changes in selective regimes, can lead to evolution of changes in plant defensive characteristics and also affect herbivores. Here, we examine how insect herbivores respond to polyploidy in Solidago gigantea, using plants derived from both the native range (USA) and introduced range (Europe). S. gigantea has three cytotypes in the US, with two of these present in Europe. We performed bioassays with generalist (Spodoptera exigua) and specialist (Trirhabda virgata) leaf-feeding insects. Insects were reared on detached leaves (Spodoptera) or potted host plants (Trirhabda) and mortality and mass were measured. Trirhabda larvae showed little variation in survival or pupal mass attributable to either cytotype or plant origin. Spodoptera larvae were more sensitive to both cytotype and plant origin: they grew best on European tetraploids and poorly on US diploids (high mortality) and US tetraploids (low larval mass). These results show that both cytotype and plant origin influence insect herbi-vores, but that generalist and specialist insects may respond differently. Polyploidy, or the possession of more than two sets of homologous chromosomes, is a fundamental force in angiosperm evolution. 1,2 Many plant species or species complexes consist of multiple cytotypes that may occur sympatrically; 3 this is an important source of genetic structure in plant populations that is often overlooked. 4 Possession of multiple genomes may confer advantages to polyploid plants such as increased heterozygosity, a decreased probability of inbreeding depression, or a greater gene pool available for selection; these traits contribute to the widespread success of polyploids and may make them prone to invasive-ness. 5,6 In a recent article, 7 we examined the functional consequences of poly-ploidy for different cytotypes of Solidago gigantea Ait. (Asteraceae), collected from both its native range (North America) and its introduced range (Europe). In this addendum, we show how cytotype and continent of origin influence interactions of S. gigantea with insect herbi-vores. Interactions with herbivores are expected to vary with cytotype because of phenotypic changes associated with polyploidy, but this area has received little study (reviewed in refs. 8-11). Plant origin, from either the native range or an introduced range, should also influence herbivores. Plants may escape from their specialist natural enemies in the introduced range, thereby experiencing reduced herbivore pressure from an insect comm...

ABSTRACT. Fatal lead encephalopathy has disappeared and blood lead concentrations have decreased in US children, but approximately 25% still live in housing with deteriorated lead-based paint and are at risk of lead exposure with resulting cognitive impairment and other sequelae. Evidence continues to accrue that commonly encountered blood lead concentrations, even those less than 10 g/dL, may impair cognition, and there is no threshold yet identified for this effect. Most US children are at sufficient risk that they should have their blood lead concentration measured at least once. There is now evidence-based guidance available for managing children with increased lead exposure. Housing stabilization and repair can interrupt exposure in most cases. The focus in childhood lead-poisoning policy, however, should shift from case identification and management to primary prevention, with a goal of safe housing for all children.

This study tested the effectiveness of a rechargeable electric toothbrush, Interplak, in removing supragingival plaque and resolving gingivitis. Forty adults with gingivitis were randomly assigned to either a "manual" or "electric" group. Detailed oral hygiene instructions were given and a blind examiner assessed plaque scores before and after brushing, toothbrush abrasion, and gingival inflammation at baseline, 1, 2, and 4 weeks. Subjects using the electric brush had significantly lower (P less than 0.05) mean plaque and gingival inflammation scores. The electric group's plaque scores fell from 77% at baseline to 28% (before brushing) and 14% (after brushing) at 4 weeks; the manual group's dropped from 75% to 50% and 30% (before and after brushing, respectively). The mean G.I. for the electric group fell from 1.65 at baseline to 1.28 at 4 weeks, while the manual group's scores decreased from 1.65 to 1.43. The results suggest that the electric brush removed supragingival plaque and resolved gingivitis better than the manual brush over a 28-day period. However, a telephone survey conducted 6 months later indicated that most subjects were not using the device twice a day as they had during the study.