Biogeog, Sobero 2007

Why are scientists increasingly estimating ecological niches?

Scientists increasingly estimate ecological niches to predict and map species distributional areas.

How are species distributions generally represented?

Species distributions are generally represented as maps.

Why are maps considered abstractions of species distributions?

Maps simplify complex ecological and spatial patterns into generalized representations.

What three major factors determine species distribution patterns?

Dispersal capacity, spatial distribution of favourable environmental conditions, and biotic interactions such as competition, predation, and pathogens.

What does the concept of a species distribution area include besides geographic presence?

It also includes the probability of observing the species.

What is meant by niche as a habitat?

Niche as a habitat refers to the environmental conditions where a species lives.

What is meant by niche as a function?

Niche as a function refers to the ecological role or interactions of a species.

Why must local and broad-scale niches be distinguished?

Local niches relate to behaviour and physiology of individuals or populations, whereas broad-scale niches involve species distribution limits.

What are the two major types of niche variables?

Resource variables and environmental condition variables.

What are bionomic niche variables?

Bionomic variables are resources that can be consumed and competed for.

What are scenopoetic variables?

Scenopoetic variables are environmental conditions not affected by competition.

What characterizes Grinnellian niche variables?

They are mainly non-interactive abiotic environmental conditions.

What characterizes Eltonian niche variables?

They involve biotic interactions such as competition, predation, and resource-consumer relationships.

What three components influence population growth rate?

Scenopoetic environmental conditions, biotic interactions, and immigration or propagule input.

What is the fundamental Grinnellian niche?

The set of all abiotic environmental conditions that would allow a species to survive indefinitely.

What is the realized Grinnellian niche?

The portion of the fundamental niche actually occupied after biotic interactions restrict distribution.

How can competition reduce a species’ realized niche?

Competition can restrict where a species can persist and reproduce.

Why is competition difficult to apply directly to Grinnellian niches?

Because Grinnellian niches are based on non-competitive abiotic conditions.

Through what mechanism can realized Grinnellian niches become reduced?

Through Eltonian niche processes such as competition and predation.

How can the fundamental Eltonian niche be reduced?

Through interactions with competitors, predators, or pathogens.

What third factor strongly affects relationships between niches and distributions?

Dispersal and movement ability.

What is the main basis of the Grinnellian niche?

Broad-scale abiotic conditions such as climate, temperature, and rainfall.

What is the main basis of the Eltonian niche?

Local-scale biotic interactions and resource use.

Why are Grinnellian niches easier to model?

Environmental variables such as climate are widely available and measurable.

Why are Eltonian niches harder to quantify?

Biotic interactions are dynamic, complex, and occur at fine spatial scales.

What three main factors determine species distributions?

Environmental suitability, biotic interactions, and dispersal ability.

What is an occupied distribution?

The area that a species actually inhabits.

What is a source-sink distribution?

A situation where species persist temporarily in unsuitable areas due to immigration from source populations.

Why do abiotic factors matter more at broader spatial scales?

Climate and large-scale environmental conditions shape broad geographic distributions.

Why do biotic interactions matter more at local scales?

Local competition, predation, and resource dynamics strongly influence local persistence.

What is an ecological niche?

The set of environmental conditions and ecological interactions allowing a species to survive and reproduce.

What is the difference between the fundamental and realized niche?

The fundamental niche includes all suitable conditions, while the realized niche is restricted by biotic interactions and dispersal limits.

How do propagules influence species distributions?

Availability of propagules affects the ability of species to colonize suitable habitats.

Why is dispersal important in understanding species distributions?

Species may fail to occupy suitable environments if they cannot disperse there.

What role do predators and pathogens play in species distributions?

They can limit survival and reduce the realized niche of a species.

How do resources differ from environmental conditions in niche theory?

Resources can be depleted and competed for, whereas environmental conditions cannot.

What type of variables are temperature and rainfall considered in niche theory?

They are scenopoetic variables.

What type of variables are prey availability and food resources considered?

They are bionomic variables.

Why are niche models important in ecology?

They help predict species distributions and responses to environmental change.