colony collapse. This paper aims to understand how these different factors contribute to the decline of honeybee populations by using two separate approaches: data analysis and mathematical modeling. The data analysis examines the relative impacts of mites, pollen, mites, and viruses on honeybee populations and colony collapse. From the data, low initial bee populations lead to collapse in September while mites and viruses can lead to collapse in December. Feeding bee colonies also has a mixed effect, where it increases both bee and mite populations. For the model, we focus on the population dynamics of the honeybee-mite interaction. Using a system of delay differential equations with five population components, we find that bee colonies can collapse from mites, coexist with mites, and survive without them. As long as bees produce more pupa than the death rate of pupa and mites produce enough phoretic mites compared to their death rates, bees and mites can coexist. Thus, it is possible for honeybee colonies to withstand mites, but if the parasitism is too large, the colony will collapse. Provided
this equilibrium exists, the addition of mites leads to the colony moving to the interior equilibrium. Additionally, population oscillations are persistent if they occur and are connected to the interior equilibrium. Certain parameter values destabilize bee populations, leading to large
oscillations and even collapse. From these parameters, we can develop approaches that can help us prevent honeybee colony collapse before it occurs.
Aboveground-belowground relationships between vegetation and its associated soil biotic community play an important role in every terrestrial ecosystem for nutrient cycling and soil health maintenance. Deserts are especially sensitive to change and little is known about Sonoran Desert soil microbiota, while exotic herbaceous species are increasingly invading into the ecosystem with other harmful effects. In many other environments, soil communities have been associated with both plant species and plant functional type. The soil community food web depends on the sustenance brought by vegetation, and different soil community members are adapted to different diets. In this paper, we hypothesized that invasive plants would cause belowground soil communities to have greater abundance and lesser diversity than those under native, more locally established plants. To test this hypothesis, we selected four desert understory plant taxa: one native grass, one native forb, one invasive grass, and one invasive forb. We predicted that the invasive plants would be associated with a greater count of microarthropods per unit mass of soil but lesser microarthropod species diversity. The invasive plants were not statistically associated with a greater count of microarthropods per kilogram of soil nor lesser microarthropod species diversity. There was not a significant difference in abundance in the microarthropod categories between native and invasive plants, so the hypothesis was rejected. However, the invasive Erodium cicutarium was found to harbor high soil mite abundance, which warrants further study, and it is yet to be seen whether soil moisture and proximity to trees played a role in the data. The results of this study should help in generating more informed hypotheses regarding desert aboveground-belowground relationships.