GEOG20009 Lecture 2: Lecture 2 Detailed Notes Landscapes & Diversity GEOG 20009
15 May 2018
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Department
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Professor
LECTURE 2: REGIONAL V LOCAL POOLS
INTRODUCTION TO FIRST 3RD OF LECTURES – ECOLOGICAL
BIOGEOGRAPHY
• Ecological Biogeography: examines ecological theories that explain the proximate (operating now) drivers of
diversity in time and space
• Proximate drivers of species diversity: focus on first 3rd
Proximate vs Distal Factors
• Distal (historical) Factors: happened in the past but those events explain patterns we still
see today
• Proximate (modern-day) Factors: can explain changes in species diversity happening now
or the recent past
• One is not more important than the other – both required for comprehensive
understanding
REGIONAL V LOCAL POOLS
Species Richness: the number of species in an area or locality
Species Diversity: captures the relative abundances of species as well as the total number of species (variety of
mathematical indicies for expressing it)
• Shannon-Weiner index most common
Regional Diversity: total number of species determined by evolution, dispersal + extinction (historical events)
• Larger scale, region is defined by the scientist, usually a bigger area
Local sites or habitat patch diversity: numbers of species determined by regional richness plus local effects, such as
species interactions
• Smaller scale, also defined by the scientist
Relations between regional + local richness
Gamma (γ) diversity: total number (or diversity) of species in a region
Alpha (α) diversity: number of species in a locality
Beta (β) diversity: component of diversity resulting from differences between
localities, includes:
• Turnover: species present at one site are absent from another site but are replaced by species absent from the first
site
• Nestedness: species present at one site are absent from another site but are not replaced by other species
• Calculating: 1 divided by number of sites occupied by a species
Lecture Questions
1. How can we measure
diversity across
landscapes?
2. What are the relations
between regional + local
diversity?
3. Are communities
saturated with species?
Alpha & beta diversity allow us to
understand drivers of gamma diversity
Gamma (γ) diversity = mean alpha diversity (α) x mean beta (β) diversity x number of localities
Document Summary
Introduction to first 3rd of lectures ecological. Ecological biogeography: examines ecological theories that explain the proximate (operating now) drivers of diversity in time and space. Proximate drivers of species diversity: focus on first 3rd. Proximate vs distal factors: distal (historical) factors: happened in the past but those events explain patterns we still see today. Species richness: the number of species in an area or locality. Species diversity: captures the relative abundances of species as well as the total number of species (variety of mathematical indicies for expressing it) Regional diversity: total number of species determined by evolution, dispersal + extinction (historical events) Local sites or habitat patch diversity: numbers of species determined by regional richness plus local effects, such as species interactions. Larger scale, region is defined by the scientist, usually a bigger area. Alpha & beta diversity allow us to understand drivers of gamma diversity. Gamma ( ) diversity: total number (or diversity) of species in a region.
