NATR 2100 Exam 3

How to assess a species’ extinctions risk?

• Geographic + landscape structure & changes

• Dispersal ability

• Demography (birth + death rates)

Reduction in total habitat area.

Habitat loss

Increased patch numbers, smaller patches, and greater isolation.

Fragmentation

What is the exception to greater isolation?

Fine-scale fragmentation — restoration in some places; can reduce isolation.

What patch size is more likely to be occupied by a species?

Larger patches

What is patch isolation influenced by?

• Distance

• Species’ dispersal ability

• Matrix hostility

Enhances population success.

Complementation

Organism use several similar substitute resource patches.

Supplementation

How much of the Cerulean warbler birds’ population been lost?

83%

Why did the Cerulean warbler population decline?

• Loss of hardwood forest habitats on breeding grounds in eastern North America.

• Loss of montane forest wintering grounds in the Andes.

Models how species use habitats by relating species occurrence to environmental variables.

Resource-selection functions

Use species occurrence data with environmental variables to estimate where suitable habitats exist.

Ecological niche models

Full potential range of environmental conditions.

Fundamental niche

The subset actually occupied.

Realized niche

Link species distributions to temperature and precipitation.

Climate envelope models

Uses four key factors to determine population size changes over time.

Basic population growth model

A collection of spatially separated populations (subpopulations).

Metapopulation

Examines the balance between colonization and extinction.

Classical metapopulation models

A large, persistent mainland population acts as a continual source of colonists for smaller “island” populations.

Mainland-island modification

High-quality areas with surplus individuals that export emigrants.

Source patches

poor-quality areas where deaths exceed births.

Sink patches

What are the 6 stages of invasion?

• Introduction

• Colonziation

• Establishment

• Dispersal

• Spatially distributed populations

• Invasive spread

The minimum amount of habitat or distance condition required for population spread.

Invasion threshold

Small, isolated colonies located ahead of the main invasion front.

Satellite populations