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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #247093
Title: Effects of host quality on flight muscle development in Neochetina eichhornia and N bruchi (Coleoptera: Curculionidae)

Author
item Center, Ted
item Dray, F Allen

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2009
Publication Date: 6/10/2010
Citation: Center, T.D., Dray Jr, F.A. 2010. Effects of host quality on flight muscle development in Neochetina eichhornia and N bruchi (Coleoptera: Curculionidae). Florida Entomologist. 93(2): 161-166.

Interpretive Summary: Water hyacinth is arguably the world’s worst weed affecting nearly all conceivable uses of water resource. It causes severe hardships in developing countries where local peoples depend on access to lakes, rivers, and canals for transport, fishing, and irrigation. Two South American weevils were introduced into the US in the early 1970s in an attempt to control this plant with a great deal of success but results have been inconsistent. We suspect that a much of this inconsistency is attributable to variation in the fertility of the water body supporting the weed populations. This study confirms this and shows that the weevils do not do well, either in terms of their ability to disperse or to reproduce when the plants are supplied with low fertilizer levels. The weevils need good nutritive quality plants to provide energy for reproduction or dispersal but the response towards one or the other varies between the weevils species and with the fertilizer supply.

Technical Abstract: Neochetina eichhorniae Warner and N. bruchi Hustache, biological control agents of waterhyacinth. are usually incapable of flight but occasionally develop flight muscles enabling dispersal. We examined host quality as a possible explanation for the transitions between these two states by allowing populations of the two species to develop on plants differing in nutritive quality then examining the status of their ovaries and flight muscle development. The leaf nitrogen content increased with fertilizer treatment levels but herbivory by the weevils changed the pattern of variation. N. eichhorniae suppressed overall nutritive quality while still enabling tissue N levels to increase with fertilizer treatments. N. bruchi, however, negated these effects so tissue N levels failed to correlate with fertilizer treatments. As a result, herbivore intensity and the proportion of the populations that responded through either oögenesis or flight muscle development differed between the two 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 two 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.