Quiz 5 - Biological Inquiries

The effects of Habitat fragmentation

Fragmentation has genetic impacts (inbreeding & the

ability to adapt), ecological impacts (a reordering of the

whole community) and can alter processes (e.g., how

nutrients flow through the system)

How does habitat loss occur?

clear cutting, agriculture, housing, roads

What is a habitat?

The range of environmental conditions (biotic and abiotic) that a species needs

• Unique to each species

• Not a geographic location

• Habitat generalists & specialists

Traits of a population that maintains genetic diversity:

I. Large population size

• Mutations occur

• Drift is minimized

II. Even sex ratios

III. Random mating

• Avoids inbreeding, inbreeding depression (ID)

IV. Migration between populations

What is a bottleneck event?

an event that drastically reduces the size of a population, leading to a significant decrease in genetic diversity within that population, often caused by a natural disaster or human activity that drastically limits the number of surviving individuals

What is mtDNA

mtDNA is passed down from a person's mother to their children

What are three factors that drive population decline?

1. Environmental stochasticity

2. Demographic stochasticity

3. Genetic stochasticity

What is an extinction vortex?

Each time a population dips to low numbers, it incurs a heavier genetic disadvantage and the population stays small for longer and longer periods of time (even when conditions are favorable) and this increases the risk of extinction via environmental and demographic factors

What is the most basic need for all species?

Land/ Area

• when you lose habitat you lose species

Species-Area Relationship (SAR)

S = c × Az

S = # of spp

c = constant, equal to the # of spp in the smallest sampling unit

(aka: y intercept)

A = area

z = rate at which new species accumulate (aka: slope on log-log scale)

Oceanic Islands

Never attached to mainland

• Only species there are those that made their way across an ocean by themselves

• Species with great dispersal abilities

• Islands are species-poor ... in specific ways:

• few mammals

• few top predators (mesopredators become apex

predators)

Land bridge islands

• Once attached to mainland, become separated sloooowly

• Contain more species per unit area than oceanic island of same size

• Have species that could never have made it to island on their own (e.g., moose, bears, top predators)

Faunal relaxation:

it takes a while for species to be lost once a land bridge or habitat fragment forms. what you see immediately following the creation of an island is not good indication of the long-term outcome

Extinction Debt

species ‘committed to extinction’ owing to habitat loss and reduced population size but not yet extinct

trophic cascade:

indirect affects of one species on another thats at least one trophic level removed

→ refers to indirect interaction

What is the SLOSS Debate

Should you choose to save a Single Large reserve or Several Small reserves?

Benefits of Saving several Small

• if you try and save the small you can have less richness loss

• they are better protected against disaters

Benefits of saving one Large

• less edge effect

• more connectivity (less imbreading and more genetic diversity)

• larger populations less prone to extinction/ declines

Perfectly nested

• A high degree in which two patches have species in common

• identical species

Partially-nested patches

the patches have half of their species in common

Non-nested patches

no species in common

Are oceanic islands nested or non-nested

non-nested

Are landbrige islands nested or non-nested

Nested

Habitat islands - Nested or non-nested?

Non-nested

What causes oceanic islands to be largely non-nested

Priority effects: If early colonists are able to

preempt the habitat, the random order of

arrival of species will drive higher richness

• Extinctions: If the same spp always disappear

from small habitat patches, then only large

isolates can will contain those spp ...

• But, if extinctions are random, then small

isolates will vary in composition & cumulative

diversity of multiple small islands will be high

What causes land fragments to be largely non-nested?

Extinctions: If the same spp always disappear

from small habitat patches, then only large

isolates can will contain those spp ...

• But, if extinctions are random, then small

isolates will vary in composition & cumulative

diversity of multiple small islands will be high

What was the question the madsen paper was trying to answer?

do genetic factors contribute to population decline

How did they know that the increase in births was due to the introduced males?

• there was more generically variablity

• the rate of stillborn offspring was lower after the introduction of the new males

What is “genetic rescue”?

rescuing a population by introducing more genetic variability by adding more mating partners