Chapter 22 - Biogeography

what does habitat heterogeneity mean

the variety and patchiness of environmental conditions and resources within a given area

examples of habitat heterogeneity

• a forest with a variety of tree ages and species that provide different nesting and feeding opportunities

• managed grazing or fire that results in a mix of grazed, ungrazed, and burned areas

how does habitat heterogeneity increase species richness

creating a greater number of ecological niches, which allows for more species to coexist.

what is legacy effect

the persistent impact of past conditions on current ecological processes

3 examples of legacy effect

• deforestation for agriculture, creates lasting changes to ecosystems even after the land use has stopped.

• greenhouse gases emitted from the burning of fossil fuels remain in the atmosphere and results in further warming

• eskers the linear formation deposits left over from rivers that flowed under glaciers

alpha vs beta vs gamma diversity

alpha: the diversity within a single habitat

beta: the change in species composition between habitats

gamma: the total diversity across a larger region encompassing multiple habitats.

how are alpha, beta and gamma diversity related

gamma is the overall diversity of a large landscape

alpha is the diversity in one of its small habitats

beta measures how different the habitats are from each other. 

what is the species area relationship

the number of species in a given area increases as the area size increases.

3 things that could cause the species area relationship

• Larger areas typically encompass a greater variety of habitats

• Larger areas can support larger population sizes for each species.

• Larger areas act as bigger "targets" for colonizing individuals and species.

what changes occur with habitat fragmentation

• total number of habitats decreases

• number of habitat patches increases

• average patch size decreases

• amount of edge habitats increase

• patch isolation increases

differences between forest edges and forest interior (light, heat, moisture)

forest edge

• light: Higher (more solar radiation penetration)

• heat: Warmer

• moisture: drier

forest interior

• light: lower

• heat: cooler

• moisture: wetter

why do forest edges have more species than a forest interior

create a mosaic of environmental conditions and resources, supporting both forest-dwelling and open-land species

how does the concept of nestedness related to the SLOSS debate

strongly nested species distribution supports the argument for a single large reserve as a large area is more likely to contain the habitat needed for the most species.

summarize the Equilibrium Theory of Island Biogeography

the number of species on an island is determined by a balance between immigration of new species and extinction of existing ones

which of two islands will have more species based on:

1. size

2. distance from the mainland

The island that is larger and closer to the mainland will have more species.

patterns of species richness in NA

follows a latitudinal gradient, with more species found in the tropics and fewer towards the poles.

how does glaciation history lead to differences in terrestrial diversity between 2 regions

the movement of continents via continental drift opens the door for changing opportunities for dispersal of species among the continents

SLOSS debate

Single Large or Several Small habitat reserves

two main factors affecting the dynamic equilibrium of island biogeography

• island size which affects extinction rates,

• isolation, which affects immigration rates.

alpha diversity is also known as the

local diversity

gamma diversity is also known as the

regional diversity

regional species pool

the collection of species that occur within a region

species sorting

process of sorting species in regional pools among localities according to their adaptions and interactions

an increase in beta diversity reflects

a greater difference in species between 2 habitats

what serves as a source of species for all the local sites within a region

regional species pool

what are stepping stones

small intervening habitat patches that dispersing organisms (ex. flying) can use to move between large favorable habitats

what habitats have the lowest ratio of edge to inner are? the highest ratio?

lowest: round habitats

highest: skinny rectangles or ovals

what is an unintended downside of corridors

facilitates movement of predators, pathogens, competitors

what is the risk of a single large habitat reserve

more likely for species to be destroyed be a natural disaster or disease

3 processes for the underlying diversity patterns in NA

1. ecological heterogeneity (more variation = more species)

2. solar energy and precipitation (more energy = higher abundance of species)

3. water temps