Understanding the Influences of Invasion on Native Species

Abundances in California

Tara Alvarez-Salazar, Julisa Garnica , Breanna Hernandez, Berenice Rosales
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Biological invasions pose a significant threat to many natural ecosystems worldwide and have negative impacts on the native biodiversity and functions of an ecosystem. These invasions are expected to increase due to climate change. The biotic resistance hypothesis states that as native biodiversity in an ecosystem increases, the vulnerability to invasion decreases. However, other research has found that if the environment is suitable, both native and invasive species have the ability to increase in abundance, regardless of native biodiversity. The objective of this project was to understand how an ecosystem’s biodiversity affects the likelihood of invasive species taking over habitat. We hypothesized that native species richness and abundance will be highly correlated with invasive species richness and abundance, especially because many CA invasive species are opportunists. We compared plant diversity data collected by NEON scientists in three sites in the Sierra National Forest that describes the estimated number of plant species found in different plots. Our results indicate that invasive species abundance is negatively correlated with native abundance, but invasive richness is positively correlated with native richness. Thus, the biodiversity of these ecosystems seems to not affect the likelihood of invasive species taking over, highlighting the complexity of ecological interactions. Understanding these dynamics is crucial for effective conservation and management strategies, as it provides valuable insights into how biodiversity influences the prevalence of invasive species in natural habitats.

Space use in small mammals.

Aidan Daley, Emely Ellis, Rachael Gaytan Perez,  Gema Torres-Navarro, 

Understanding the spatial ecology of different populations can offer valuable insight into wildlife conservation efforts, animal behavior, and population dynamics. Here, we study the relationship between home range size, sex, and population density in deer mice (Peromyscus maniculatus). We used over a decade of mammal trap data across the 47 National Ecological Observatory Network (NEON) terrestrial field sites. We found that home range size is inversely correlated with population density. This supports our hypothesis that individual deer mice will be more motivated to expand their home range size if there is increased competition for food and shelter. We also found that males have larger home range sizes compared to females. Although the difference in home range size by sex is significant, we were surprised to find that the magnitude of this difference is quite small. Future research can investigate if there is an interaction effect between sex and population density, with males having larger home range sizes at low population density due to mate-seeking behavior. Future research can also investigate how the relationship between home range size and sex is impacted by disturbances, such as fire, and if there is seasonal variation in home range size. 

Ground Beetle Community Characteristics Across North American

​​Forests 

Kelli Hailey, Asher Holloway, Claudia Iraheta

The community of trees within a forest determines aspects of the environment including what resources are available and what microhabitats are created. Ground beetles comprise a large number of species belonging to a variety of functional groups within the forest habitat and may respond differently to different litterfall quantities and qualities based on the vegetative forest structure. We tested whether forest structure, broadly categorized as either deciduous or evergreen forests, and litterfall quantity proxies, such as plant cover and plant species richness, significantly affect ground beetle density, diversity and species richness. With data from the National Ecological Observatory Network (NEON), we used Wilcoxon tests to compare deciduous and evergreen forest types to see if there was a relationship between forest type and beetle density, diversity and beetle species richness across all North American forested NEON sites. We also used Spearman’s rank test to test for significant correlations between plant cover and plant species richness and beetle density, diversity, and species richness in 3 forest sites in the Pacific Southwest Domain. We found that deciduous forests support denser, more diverse, and more speciose beetle populations than evergreen forests across all NEON forested sites. When evaluating beetle populations based on litterfall proxies at the 3 terrestrial sites in the Pacific Southwest Domain, we only found a significant, positive relationship between plant cover and plant species richness and beetle species richness. The results demonstrate forest type and plant community characteristics influence ground beetle communities in forested ecosystems. The difference in beetle community characteristics by forest type was expected based on a prior study and the faster rate of abscission and decomposition in deciduous leaves, distributing nutrients to the forest floor habitat. The results indicate that habitats created by leaf litter do not strongly determine the density of beetles in a community, rather it influences the number of beetle species present while broader forest structure does affect the density, diversity and species richness of ground beetles. It would be worth investigating in what ways deciduous and evergreen leaf litter support the habitats they create. While abundant deciduous leaf fall disperses nutrients, less abundant evergreen leaf fall breaks down less easily and could potentially support a community of organisms as a living habitat for longer. The two types of leaf litter could be compared seasonally and may reveal relationships between the species that live in or feed on leaf litter, and climate change’s impact to phenology and weather could affect this relationship. Because forest type and litterfall qualities significantly affect the community of beetles in forests, this indicates that there must be care taken when modifying forest environments. There is the implication that the removal of deciduous forest environment or plant cover and species number causes harm to the location’s beetle community, and a forest losing its trees and plants would expect a decline in beetle abundance, diversity, and richness.