Urban Insect Biodiversity: Effects of Drought-Tolerant Plants

Project Overview

This project statistical examines how drought-tolerant landscaping affects insect diversity in urban Los Angeles, using data from 30 sites sampled monthly across 2014.

Scientific Hypothesis

Research Question:

1. Do drought-tolerant plants increase insect species richness in urban Los Angeles?

2. Do drought-tolerant plants and local temperature interact to affect insect species richness in urban Los Angeles?

Hypothesis:

Sites with drought-tolerant plants have higher insect species richness than sites without drought-tolerant plants, after accounting for temperature and Urban Type.

Justification:

Drought-tolerant plants are better adapted to Los Angeles's naturally arid climate and may provide more suitable habitat for local insect species compared to non-native ornamental plants that require frequent watering.

Statistical Model

Response Variable:

• CorRichne = Insect species richness (count per site type)

Model Family:

• Negative Binomial (handles overdispersion in count data)

Model Structure:

$$ \begin{align}
&\text{Richness} \sim \text{Negative Binomial},(\mu, \sigma) \ &log(\mu) = \beta_{0} + \beta_{1}, \text{Drought-tolerant Plants} + \beta_{2}, \text{Mean Temperature} + \beta_{3} , \text{Urban Type(Moderate)} + \beta_{4}\text{Urban Type (High)}\ \end{align} $$ Link Function:

log link (because we're modeling counts)

Statistical Hypotheses

Primary Hypothesis (Drought-Tolerant Plants Effect):

H₀: β₁ = 0 (Drought-tolerant plants have no effect on species richness)

Hᴀ: β₁ \> 0 (Drought-tolerant plants increase species richness)

Data Description

• Source: Adams et al. (2020) - Los Angeles urban biodiversity study
• Samples: 360 observations (30 sites × 12 months)
• Response: Species richness per trap day
• Key predictors: Drought-tolerant plants, urbanization, temperature

Repository Structure

├── data
│   ├── Adams_et_al_Ecological_Applications_data.xlsx
│   └── InsectData.csv
├── EDS-222-Final-Project.Rproj
├── fig4_combined_exploratory.png
├── Insect_Diversity.html
├── Insect_Diversity.qmd
├── LICENSE
├── README.html
└── README.md

References

Adams, B. J., et al. (2020). Local- and landscape-scale variables shape insect diversity in an urban biodiversity hot spot. Ecological Applications, 30(4), e02089.