Masters Thesis

Effects of Nitrogen Availability and Climate on Hermes Copper Butterfly (Lycaena hermes) Habitat in Southern California

As environmental conditions continue to change, phytophagous insects are under increasing selective pressure when identifying and choosing quality host plants. The Hermes copper butterfly (Lycaena hermes) is a rare species endemic to San Diego County and parts of northern Baja California. The small butterfly population is a fascinating topic since the host plant, Rhamnus crocea, extends well beyond the range of the insect. Based on what is known about plant herbivore interactions it is possible that variation in plant chemistry is contributing to small population sizes and a limited distribution. Plant tissue chemistry is affected by environmental variations, such as chronic nitrogen deposition, temperature, and precipitation. We hypothesized that plant secondary compounds are likely to vary significantly within and outside of the Hermes copper butterfly range, trends in secondary compounds will be affected by variations in climate, such as temperature and precipitation, and spatial variations in plant secondary compounds will be affected by N availability. Leaf tissue from current and historical Hermes copper habitat sites were analyzed and plant secondary compounds classes were identified. Soil samples were collected in May 2018 to measure extractable N, soil moisture, total N and C, and pH. N availability did not have a significant effect on plant secondary compounds within and outside of the range of the butterfly. However, it was found that climate conditions did have a significant effect on these compounds. The lack of a N effect on plant secondary compounds in the host plant suggests that allocation of resources within the plant may not be significantly influenced by changes in N availability, but may be affected by changes in temperature and precipitation.

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