Simultaneous effects of potassium, rutin and temperature on performance ofManduca sexta caterpillars |
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Authors: | N E Stamp |
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Institution: | (1) Department of Biological Sciences, Box 6000, Binghamton University, State University of New York, 13902-6000 Binghamton, NY, USA |
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Abstract: | the simultaneous effects on an insect herbivore (third instar tobacco hornwormManduca sexta (L.): Sphingidae) of temperature (daytime temperatures of 20 °C, 25 °C and 30 °C), a mineral that may play a role in plant
defense (potassium) and a common allelochemical (rutin) were examined in a factorial experiment. To manipulate potassium levels,
a modified diet with limited plant material was used as the base and KCl and rutin added. Temperature affected efficiency
of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), time to head-capsule slippage, stadium
duration, relative consumption rate (RCR) and relative growth rate (RGR) but not food consumed, biomass gained and approximate
digestibility (AD). Potassium concentration influenced all of the variables except AD, time to head-capsule slippage (HCS),
duration of the stadium and percent of stadium time to HCS. Rutin impacted negatively on all of the variables except food
consumed. Compared to larvae on the non-rutin diets, fewer larvae fed rutin survived through molt initiation to ecdysis and
fewer successfully completed ecdysis. Temperature and rutin had interactive effects for AD, ECD, RCR, RGR, time to HCS, and
percent of stadium required to reach HCS. Rutin and potassium had interactive effects for biomass gained, RCR, ECI, time to
HCS, duration of stadium, and percent of stadium required to reach HCS. Comparison of larval responses on an average potassium
concentration (3.1%) versus high concentration (6.1%) showed that at the low daytime temperature increasing potassium concentration
depressed biomass gained, but at the warmer temperatures potassium concentration had little effect unless rutin was present.
In addition, potassium concentration had little impact on ECI unless rutin was present. These results indicate that significant
interactive effects occur among temperature, potassium and rutin, and thus suggest that such interactive effects on larval
performance may be common under field conditions, which are characterized by varying temperature and different concentrations
of minerals and allelochemicals in hostplants. |
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Keywords: | potassium rutin temperature food utilization efficiencies molt nutritional ecology Manduca sexta |
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