Study Notes on Species Abundance and Biodiversity

Species Abundance and Biodiversity

Introduction

  • Key Concepts
    • Definition of a species.
    • Quantification of species.
    • Ecological niche and its significance.
    • Species diversity and community evenness.
    • Importance and application of biological diversity in ecosystems.

What is Biodiversity?

  • Definition:
    • "Biodiversity - diversity of plant and animal life, as represented by the number of extant species"
    • Ricklefs & Miller: Biodiversity includes varying levels of variation in the natural world: genetic diversity, species diversity, and ecosystem diversity.
    • Begon et al.: "The term may be used to describe the number of species, the amount of genetic variation or the number of community types present in an area."

Key Terminology Related to Biodiversity

  • Abundance:
    • Definition: Total number of organisms in an area.
    • Note: This does not take biodiversity into account.
  • Species Richness:
    • Definition: Total number of different species in an area.
    • Note: This does not take abundance into account.
  • Diversity:
    • Definition: Incorporates both the total number of species and the evenness of their abundances.
  • Community:
    • Definition: A group of populations occupying the same geographical area at the same time.

Index of Species Diversity

  • Formula:
    • D=N(N−1)Σn(n−1)D = \frac{N(N-1)}{\Sigma n(n-1)}
    • Steps to Calculate:
    • Step one: Calculate N (total number of individuals).
    • Step two: Calculate N(N − 1).
    • Step three: Calculate each individual species count, represented as n.
    • Step four: Calculate Σn(n−1)\Sigma n(n - 1).
    • Step five: Divide the results of step two by step four to determine D.

Measuring Abundance

  • Whale Counting:
    • Challenges: Locating whales in Earth's vast oceans.
    • Technologies Used:
    • Saildrones: Autonomous technology collecting data on whale behavior over extended periods.
    • Passive Acoustic Recorders: These devices allow for 24/7 recording of whale presence across a range of conditions.
    • Satellite Tags: Help in tracking population densities, migratory routes, and dive aggregations, offering a predictive model, differing from ship-based observations.
  • Deep Learning Techniques:
    • Recent studies using CNN-based systems for detecting whales in satellite and aerial imagery, achieving 94% accuracy in counting whales (Guirado et al., 2019).

Biological Species Concept

  • Definition:
    • "Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups."

Understanding Species Distributions

  • Driving Factors:
    • All species have tolerance limits for environmental factors beyond which they cannot survive, grow, or reproduce.
    • Critical Factors Influencing Species Distribution:
    • Sunlight
    • Temperature
    • Precipitation
    • Wind
    • Latitude
    • Altitude
    • Fire frequency
    • Soil characteristics
    • Water currents
    • Dissolved nutrient concentrations
    • Suspended solids
    • Habitat connectivity

Ecological Niche

  • Concept:
    • Represents the range of ecological resources for each species, including habitat, substratum, food, and environmental variation.
  • Types of Niches:
    • Fundamental Niche: Full range of theoretical environmental conditions/resources an organism can occupy.
    • Realized Niche: The organism typically occupies a narrower niche due to biotic interactions (Krebs, 2009).
  • Stability of Niches: Realized niches can shift over time due to changes in biotic interactions.

Competition in Niche Partitioning

  • Concept of Niche Partitioning:
    • Example: Two species of barnacles competing for the same resource within rocky intertidal zones leads to realized niches based on physiological limits and competition.
  • Types of Interference Competition: Dominance of certain species can slow growth and impact reproduction in coral reefs, thus defining community organization.

Measuring Biodiversity

  • Species Richness vs. Diversity:
    • Species Richness: Number of different species present in an area.
    • Species Diversity: Incorporates both the number of species and their abundance (evenness).
  • Example:
    • Site A may have 10 species with equal high numbers, while Site B may also have 10 species but with one dominant species. Thus, Site A is more diverse despite equal richness.
  • Shannon-Wiener Index:
    • Quantitative measure of biodiversity defined as:
    • H′=−Σ(p<em>i⋅ln⁡p</em>i)H' = -\Sigma (p<em>i \cdot \ln p</em>i)
    • Where pip_i is the proportion of each species.
  • Ecological Value: Application of the index helps in ecological assessments.

Effects of Latitude on Species Richness

  • Species richness is generally greater in low-latitude communities than in high-latitude communities due to climatic conditions.
  • As environmental stress increases, species richness tends to decrease, with more stable conditions closer to the equator supporting more species.