Biogeography & Biodiversity (6)

What is biogeography?

The study of organismal diversity across space and time.

What determines observed biodiversity?

The spatial scale at which biodiversity is measured.

What does global biogeography focus on?

The influence of geological history, extinction, speciation, dispersal, and climate on biodiversity gradients.

What does regional biogeography focus on?

How immigration and local extinction determine equilibrium diversity.

What does local biogeography focus on?

How physical conditions and species interactions determine alpha diversity.

What is vicariance?

Evolutionary separation of species due to barriers such as continental drift.

What factor explains maple (Acer) distribution?

Continental drift causing geological separation of land masses.

What three factors combine to determine global biodiversity patterns?

Geological history, global climate patterns, and extinction plus evolution.

What is a major global biodiversity gradient?

Species diversity increases toward the equator.

Why might diversity increase toward the equator?

Lower extinction rates, higher speciation rates, and higher productivity.

How does elevation affect diversity?

Diversity decreases with elevation.

How does precipitation affect diversity?

Diversity increases with precipitation.

How do harsh environments affect richness?

Harsher conditions support fewer species.

How does productivity influence diversity?

Higher productivity supports more species.

What is the relationship between regional and local diversity?

Local diversity increases as regional species pool increases.

What are the six major biogeographic regions?

Nearctic, Neotropical, Palearctic, Ethiopian, Oriental, Australasian.

What is a species–area relationship?

Species richness increases with area.

What mechanisms explain species–area patterns?

Random distribution of individuals and habitat heterogeneity.

What does habitat heterogeneity do?

Increases niche variety and supports more species.

What is the species–area equation?

S = zA + c.

In the species–area equation, what is S?

Species richness.

In the species–area equation, what is A?

Area surveyed.

In the species–area equation, what is c?

The intercept representing baseline diversity.

In the species–area equation, what is z?

The slope describing how richness increases with area.

What does a steeper z value indicate?

A faster increase in richness with area.

What does a higher c value indicate?

A higher baseline richness.

What is island biogeography?

A theory explaining island richness through immigration and extinction.

What determines biodiversity on islands?

The balance between immigration and extinction rates.

Which islands have higher immigration rates?

Near islands.

Which islands have lower extinction rates?

Large islands.

Where else can island biogeography apply?

Fragments, lakes, mountaintops, isolated habitats.

What are ecological filters?

Constraints that determine which regional species enter the local community.

What is the dispersal filter?

Species must arrive at the site.

What is the environmental filter?

Species must tolerate local physical conditions.

What is the biotic filter?

Species must survive interactions with existing community members.

Which niche concept matches the environmental filter?

Fundamental niche.

Which niche concept matches the biotic filter?

Realized niche.

What is limiting similarity?

The idea that species too similar in resource use cannot coexist.

What does competitive exclusion predict?

Species using identical resources cannot coexist long-term.

How do species avoid competitive exclusion?

By differentiating their niches.

Example of niche differentiation

Warbler species using different parts of the same tree.

What determines whether similar species can coexist?

The degree of resource overlap and resource abundance.

What is an alternate stable state (MSE)?

A system that can exist in multiple different stable community configurations.

What drives alternate stable states?

Positive feedback loops and strong ecological interactions.

What is hysteresis?

Forward and reverse transitions occur at different thresholds.

What observational evidence supports MSE?

Rapid shifts, bimodality, and differing driver–response relationships.

What experimental evidence supports MSE?

Different starting states lead to different final states; disturbances produce shifts; hysteresis is present.

What is a smooth community transition?

A gradual shift toward or away from optimal conditions.

What is a threshold transition?

A sudden shift when physiological or competitive limits are crossed.

What causes global climate variation?

Tectonic plate movement, subduction zones, and mid-ocean spreading.

What is alpha diversity?

Local species richness.

What is gamma diversity?

Total richness across multiple sites.

What is beta diversity?

Difference in species composition among sites; increases with heterogeneity.

What determines local community composition?

Competition and resource availability.

How does competition influence coexistence?

It sets limits on how similar species can be and still coexist.