Lecture 23 - Community Ecology 15 - Biodiversity Drivers - 11/12/2025

Introduction to Biodiversity and Final Paper Instructions

  • Continuing Themes

    • Patterns of biodiversity

    • Explanations for those patterns

  • Final Paper Instructions

    • Document: "final paper instructions one"

    • Detailed rubric will be provided after Thanksgiving break

    • Final paper worth 80 points, replacing the final exam

    • Due: Wednesday, December 10

    • Available for questions until December 15

Purpose of the Final Paper

  • Objective:

    • Explore a topic of personal interest

    • Demonstrate understanding of scientific concepts and the ability to utilize empirical evidence

  • Use of Empirical Literature:

    • Support arguments with articles that either confirm or elaborate on chosen topic

    • Experience in writing a scientific review paper

Scientific vs. Review Papers

  • Empirical Papers:

    • Involve original research, hypothesis-testing, data collection, and analysis

    • Outcomes either support or challenge initial hypotheses

  • Review Papers:

    • Compile existing research on a topic

    • Organize and summarize primary literature

    • Analyze previous findings and present a coherent narrative

Selecting a Topic

  • Choosing a Topic:

    • Ensure there is sufficient literature available

    • Example: De-extinction might be too contentious with limited sources

    • Students should contextualize their topics with appropriate background

  • Paper Structure:

    • Introduction: Define key concepts and framework

    • Contextualize your topic

    • State your motivation

    • Core of the Paper:

    • Detail three minimum (more encouraged) empirical articles

    • Summarize main results without going deep into statistical analysis or methods

    • Conclusion:

    • Reflect on the current state of knowledge regarding the topic

    • Include personal insights

Writing Guidelines

  • Word Count:

    • Aim for 2,500 to 3,500 words (not including references)

  • Avoid AI Assistance:

    • Originality in writing is expected

  • Title and Abstract:

    • Include a relevant title

    • Write a concise abstract (200 words) after the paper is complete, summarizing main points

  • References:

    • Use APA format for citations

    • Include a list of references at the end of the paper

Important Considerations

  • Implicit Expectations:

    • Clarity in writing (grammar and structure)

    • Use primary sources from the literature, rather than lecture citations

Recap of Biodiversity Gradient Concepts

  • Gradient of Biodiversity:

    • More species closer to the equator

    • Two main explanations: productivity and temperature

Productivity

  • Theory: More light near the equator leads to higher productivity and thus higher diversity

  • Critical Consideration:

    • Productivity must correlate with available resources for increased diversity

Temperature

  • As temperature increases, metabolic rates rise, facilitating speciation and reducing extinction rates

  • Temperature effects on biodiversity are more complex than those of productivity

Empirical Evidence for Biodiversity Patterns

  • Figure Discussion:

    • Net primary productivity vs. temperature show positive correlations with species richness. These figures typically illustrate scatter plots where the X-axis represents either net primary productivity or temperature, and the Y-axis represents the number of species (species richness). An upward trend in these plots indicates that as productivity or temperature increases, species richness generally tends to increase as well, supporting the proposed theories.

    • The data reflects leaky correlations but generally adheres to expected global biodiversity patterns. A "leaky correlation" implies that while a general positive trend exists, there can be significant scatter or outliers in the data. This means that for any given level of productivity or temperature, there might be a range of observed species richness values, and the relationship is not perfectly linear or deterministic. However, despite these variations, the overall pattern across different geographical regions or ecosystems still aligns with the expectation of higher biodiversity in more productive or warmer areas, particularly towards the equator.

Exceptions to the Biodiversity-Productivity Link

  • Examples:

    • High biodiversity in subtropical gyres despite low productivity

    • Deep ocean ecosystems showcase high biodiversity without traditional light-driven productivity

Disturbance and Biodiversity

  • Investigating the role of environmental stability in biodiversity patterns

  • Environmental stability appears to affect biodiversity across temporal scales

  • Important Study Findings:

    • Climatic conditions and their effect on forest distribution suggest that regions with climatic stability support higher biodiversity

Disturbance Hypothesis

  • Intermediate disturbance hypothesis suggests a non-linear relationship exists between productivity and species richness (humped pattern):

    • High productivity leads to competitive exclusion of less efficient species

    • Increased disturbance allows coexistence of diverse species

Future Discussions

  • Transition to local processes explaining biodiversity

  • Explore ecological succession in the next class

Conclusion

  • Biodiversity patterns are influenced by a myriad of factors including productivity, temperature, and disturbance

  • Understand the implications of these factors on local and global scales as we progress through the course.