Sierra Nevada Aquatic Research Laboratory

15 Jun, 11 AM - 30 Jun, 05 AM

Very few studies have studied the effects of floral herbivory on plant populations, and even fewer studies have investigated plant resistance to floral herbivory. (Euler and Baldwin 1996) showed that damage to both leaves and corolla tissue in N. attenuata increased nicotine levels in the corolla, although the ecological effects on pollinators and floral herbivores was not investigated. The evolutionary consequences of resistance to floral herbivory are particularly interesting, since resistance may also negatively affect pollinators. During the 2002 field season, I tested if foliar damage can reduce floral or fruit herbivory through induced resistance in two N. attenuata populations near the Sierra Nevada Aquatic Research Laboratory (SNARL). I damaged 30% of the leaves (both cauline and basal) on 40 plants in two populations, leaving 40 plants in each population as controls. I also recorded the amount of foliar damage, floral damage, fruit damage, and presence of seed predators in these populations over two months. I found that, in one population, artificial foliar damage decreased the number of flowers damaged by insects relative to the control plants (Wilcoxon rank sum test, P=0.052), although there was no difference between the treatments in the other population. There were also significant negative correlations between percent foliar herbivory and percent fruit damage in both populations, suggesting that induced defense may operate in fruits as well as in flowers. In 2003 I would like to repeat the induced resistance experiments I performed in 2002. I will induce a set of N. attenuata plants with methyl jasmonate, and another set by damaging the basal leaves with a pattern wheel (this induces defense but does not decrease leaf area). A control set of plants will be handled, but no damage or chemicals will be applied. The treatments will be applied to 60 plants at SNARL and just outside the reserve boundaries (if I can find 60). I will record the number of fruit damaged per plant, the numbers of flowers and damaged flowers per plant, and the number of floral visitors per plant. I would also like to collect nectar from the plants in order to determine if nectar nicotine levels are affected by foliar damage. During dawn and dusk hours I will observe the plants in order to quantify pollinator activity. Lastly, if funds are available, I would like to estimate outcrossing rates for both damaged and undamaged plants by running allozymes on leaf tissue. I will also treat at least two populations near Benton Crossing Road, on BLM land. The population at SNARL is especially important to my study, since two of my populations on BLM land were destroyed late in the 2002 season by motor vehicles. Although I will be treating a large majority of N. attenuata plants at SNARL, I will not be collecting seed, so the long-term population dynamics of the plant should not be affected greatly. I would like to stay at SNARL, if possible, during the project's duration. Works Cited: Euler, M., and I. T. Baldwin. 1996. The chemistry of defense and apparency in the corollas of Nicotiana attenuata. Oecologia 107:102-112.

Visit #723 @Sierra Nevada Aquatic Research Laboratory

Approved

Under Project # 665 | Research

University of California, Davis - Section of Evolution and Ecology

faculty - Denison University

Reservation Members(s)

Andrew McCall Jun 15 - 30, 2003 (16 days)
Andrew McCall Jun 15 - 30, 2003 (16 days)

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Q8 2 Jun 15 - 30, 2003