Ecosystem engineers often have cascading impacts on the ecosystems in which they occur. Understanding the factors that contribute to their habitat selection can provide valuable information on how ecosystems function. Our study investigates the habitat distribution of desert woodrats (Neotoma lepida) in the Eastern Mojave Desert. We show that there is a difference in desert woodrat abundance among habitats, and found that specific aspects of these environments are associated with woodrats. These aspects include grass...

Ant-aphid mutualisms play important ecological roles in many ecosystems. While Formica ants are well studied model organisms, pine-specialist Cinara aphids remain understudied. Moreover, there is little research on ant-aphid mutualism in subalpine ecosystems. We investigated multiple species of Formica ants and their mutualistic interactions with Cinara aphids on the limber pine Pinus flexilis in a subalpine ecosystem. Cinara apini colonies were found tended to by silver, black, and red Formica ants, and they occupy older...

Recent changes in global climate are causing many species to shift their ranges towards higher elevations. The rate at which species can shift their ranges may determine whether or not they will be able to persist in light of such rapid environmental change. In this study, we examined the effect of elevation on recruitment, mortality, and intraspecific competition in Great Basin bristlecone pines (Pinus longaeva, BC), a long-lived subalpine species whose upper limit is often...

Alpine ecosystems are a harsh environment with little nutrients and the abiotic effect that the soil has on the plant community is relatively unknown. The focus of this study is to illuminate the role that soils play in the plant diversity of alpine wet meadows. In doing so we investigated the function of clay and root content, organic matter, pH and soil moisture in determining plant diversity in three meadows in the White Mountains, California....

At the edges of its range in the Colorado Desert, jojoba (Simmondsia chinensis) has been known to exhibit local morphological adaptations not found elsewhere in its distribution. In this study, we expand upon jojoba’s known sexually dimorphic adaptations and examine its behavioral adaptations to a xeric environment. Specifically, we investigate how jojoba avoids intense solar radiation through leaf orientation. We found that jojoba does not exhibit paraheliotropic leaf tracking but instead orients its leaves to...

Pollinators are essential to worldwide biodiversity. This study focuses on pollinator communities on Isocoma acradenia, a late blooming shrub in the Colorado desert. We hypothesize that late in the flowering season, exotic honey bees and native pollinators experience increased competition for floral resources. We surveyed pollinator species richness, abundance, and competitive interactions. Our results reveal that honey bee presence does not have effects, competitive or otherwise, on native pollinators. Continuing to research exotic and native...

Optimal foraging theory states that foragers maximize their energy intake by minimizing the energy expended to collect their food. The harvester ant, Messor pergandei, provides a model system to study foraging energy expenditure due to their dependable group foraging behavior. Exploring seed preference could give us further insight into how their harvesting affects the surrounding vegetation and ecosystem as a whole. Choice trials were conducted on M. pergandei using three native seeds and one non-native...

Forest tree communities are shifting as a result of changes in regional climate and human management, which has cascading effects on other members of the community such as epiphytic bryophytes. Epiphytic bryophytes play important roles in ecosystem function, and their distribution is highly dependent on the characteristics of their substrate. To see how epiphytic substrate characteristics affect bryophyte abundance, we measured bark thickness, pH, and water holding capacity as it varied with bryophyte coverage on...

In the age of fire suppression, a major killer of coniferous forests has shifted from wildfires to beetle infestations and drought stress. We examined a conifer forest in the Eastern Sierra Nevada to obtain demographic data on the area and to determine the factors affecting conifer mortality. We found a positive relationship between the number of boreholes and mortality across tree species. Bark beetle tree mortality in lodgepole pine (Pinus contorta) was related to density,...

Hypotheses such as the plant stress hypothesis, apparency theory, and the resource availability hypothesis provide contrasting predictions to how plants respond to abiotic stress and their interactions with herbivores. In this paper we examined the effects of a water availability gradient on the morphological characteristics and herbivory of Lupinus latifolius var. columbianus. We measured the abundance of the leaf beetle, Galeruca rudis, and Aphididae as well as the amount of leaf herbivory damage on lupine...

Woodrats are ecosystem engineers that can increase biodiversity by physically changing the environment. In doing so, they alter landscapes and increase the number of microhabitats for other organisms. In order to better understand woodrats’ role in their ecosystem, we surveyed big-eared woodrat (Neotoma macrotis) houses in Hastings Natural History Reservation located in Monterey County, California. For each house, we determined its usability and measured its size. We found a 26 percent increase in population density...

Secondary metabolites are volatile compounds produced by plants that can be used as defense mechanisms for reducing stressors such as herbivory and competition. Leaves, roots, and stems of California bay trees (Umbellularia californica) get their notable aroma from secondary metabolites called monoterpenes, which are allelopathic constituents in many other plants, such as eucalyptus. In this study, we investigated the potential allelopathic and anti-herbivory effects of California bay trees by examining their understory composition, germination rates...

In seasonally dry areas, artificial water sources become a gathering place for a variety of avian species, leading to interactions between birds whose niches otherwise do not overlap. To maximize water use while reducing negative costs associated with conflict and predation, birds adopt anti-predation behaviors and engage in differing levels of tolerant and conflict interactions. In order to better understand how birds interact and behave at artificial water resources, we examined whether species and flock...

Climate change has increased the frequency of wildfires globally. This increase in wildfires causes many animals to adjust their behaviors in order to cope with the more regular disturbances occurring in their habitats. It is often thought that birds are less affected by disturbances such as fire because of their ability to easily relocate by flying, but species with high levels of territoriality, such as acorn woodpeckers (Melanerpes formicivorus), may be more greatly affected by...

California coastal dune ecosystems are prime targets for conservation and restoration efforts due to their high native plant diversity and rates of endemism. Invasive dune species such as European sea rocket (Cakile maritima) may disrupt key ecosystem processes by altering dune physical processes and outcompeting native species, decreasing the success of the endangered species beach layia (Layia carnosa) and Tidestrom's lupine (Lupinus tidestromii) at Point Reyes National Seashore in Marin County, California. We investigated potential...

Many mechanisms of biodiversity exist in nature. Temporal niche partitioning is an overlooked mechanism that could explain how species coexist in the same space. We hypothesized that different vertebrate communities would be using a shared habitat space (rock bars) at different times of day. To test this hypothesis, we surveyed the total number of vertebrates present on six different rock bars during morning, midday, and night. We documented strong differences between vertebrate communities by time...

The process of succession can be a major driving force in sculpting ecological communities over time. Decomposers play a crucial role in forest succession, recycling nutrients from fallen logs back into the ecosystem. In this study, we examined the community of plants, fungi, and invertebrates living in fallen log microhabitats across decomposition stages in a mixed conifer forest. We predicted there would be a shift in species composition among decomposer communities in Douglas fir logs...

Abiotic stress and heavy competition each limit the assemblages of plant communities, defining their composition as well as their boundaries. One plant community governed by stress and another by competition may abut one another, forming a biotic gradient called an ecotone. In California’s White Mountains, this gradient occurs across the meeting point between a calcareous (dolomite) and non-calcareous (quartzite) soil types. In this study, we tested the effects of this gradient on plant community compositions...