03241nas a2200169   4500008004100000020001400041245009600055210006900151260000800220300001200228490000700240520266200247653001502909100002002924700001702944856011002961       2010                        eng d  a0021-890100aBottom-up control of water hyacinth weevil populations: do the plants regulate the insects?0 aBottomup control of water hyacinth weevil populations do the pla  cApr  a329-3370 v473 a1. Nutrient availability varies widely in aquatic systems and is likely to profoundly affect the outcomes of plant-herbivore interactions in aquatic environments. This has implications in programmes aimed at the biological control of water weeds. We hypothesized that nutrient flux seasonally affects ovarian development of two specialist weevil species, Neochetina eichhorniae and Neochetina bruchi, thereby influencing population growth on the floating plant Eichhornia crassipes. 2. We also hypothesized that the weevils differed in their sensitivities to nutritional quality and interacted differently depending on host quality. 3. To test these hypotheses, we cultured E. crassipes plants under 20 fertilizer regimens then introduced reproductively dormant, over-wintering female weevils as single or mixed species populations. They were later retrieved and dissected to ascertain ovarian status. F1 progeny was extracted biweekly to compare fecundity with population growth. 4. Ovaries regained functionality and the reproductive proportion of the population increased with fertilizer rate as did the fecundity of reproductive individuals. F1 progeny increased exponentially from 7 to over 300 weevils tank-1 in the highest fertilizer treatment. 5. Mixed species treatments produced more offspring under high fertilizer rates than single species treatments (236 [plus or minus] 32 mixed vs. 155 [plus or minus] 25 N. bruchi or 170 [plus or minus] 33 N. eichhorniae pure). Neochetina eichhorniae was more productive throughout than N. bruchi, but N. bruchi performed nearly as well in high fertilizer treatments. 6. Ratios of the two species remained consistent whether in single or mixed species populations suggesting a lack of interspecific interference. However, N. eichhorniae seemed more adaptable to a wider range of plant quality and more tolerant of lower nutritional circumstances. 7. Synthesis and applications. The coupling of reproductive status of the parental generation with the population response of the F1 generation indicates that plant quality drives population growth of both weevil species, demonstrating bottom-up regulation. This largely explains the variable performance of these weevils as biological control agents. These results emphasize the importance of considering bottom-up regulation in evaluating host range trials, predicting efficacy and in post-release evaluations. In addition, they suggest that partial herbicide treatments to accomplish phased removal of infestations could enhance the quality of the remaining plants, thereby better integrating biological control into current E. crassipes management systems.10aNeochetina1 aCenter, Ted, D.1 aDray, F., A.  uhttps://weevil.myspecies.info/bottom-control-water-hyacinth-weevil-populations-do-plants-regulate-insects02699nas a2200169   4500008004100000020001400041245012500055210006900180260000800249300001200257490000700269520206600276653001502342100002002357700001702377856013502394       2010                        eng d  a0015-404000aEFFECTS OF HOST QUALITY ON FLIGHT MUSCLE DEVELOPMENT IN NEOCHETINA EICHHORNIAE AND N. BRUCHI (COLEOPTERA: CURCULIONIDAE)0 aEFFECTS OF HOST QUALITY ON FLIGHT MUSCLE DEVELOPMENT IN NEOCHETI  cJun  a161-1660 v933 aNeochetina eichhorniae Warner and N. bruchi Hustache, biological control agents of Eichhornia crassipes (Martius) Solms-Laubach, are usually incapable of flight but occasionally develop indirect flight muscles enabling dispersal. This reportedly alternates with oogenesis and is reversible. We examined host quality as a possible explanation for the transitions between these 2 states by allowing populations of the 2 species to develop on plants differing in nutritive quality and then examining the status of their ovaries and flight muscle development. The leaf nitrogen content of the plants increased directly with fertilizer treatment levels but herbivory by the weevils changed the pattern of variation. Neochetina eichhorniae suppressed overall nutritive quality while still enabling tissue nitrogen levels to increase with fertilizer treatments. Neochetina bruchi, however, negated these effects and tissue nitrogen levels failed to correlate with fertilizer treatments. As a result, herbivore intensity (the number of weevils per plant) and the proportion of the populations that responded in one way or the other (either oogenesis or flight muscle development) differed between the 2 species. Very few N eichhorniae responded in the lowest fertilizer treatment and none produced flight muscles. This increased in the intermediate treatments to about an 80% response with most individuals reproductive. At higher levels, the overall response declined somewhat with an increasing proportion becoming dispersive. Very few N bruchi developed flight muscles except in the highest fertilizer treatment. The frequency of reproductive N bruchi varied little across fertilizer treatments, tracking host quality instead. We conclude that transitions from reproduction to dispersal in these 2 species are not in response to low nutritive quality of the plant tissue and require adequate nutrition to occur. Host quality, however, is affected by a multitude of factors, including the intensity of herbivory, which complicates interpretation of nuanced responses.10aNeochetina1 aCenter, Ted, D.1 aDray, F., A.  uhttps://weevil.myspecies.info/effects-host-quality-flight-muscle-development-neochetina-eichhorniae-and-n-bruchi-coleoptera-curcul