habitat and fragmentation 1 - bio iq

what is habitat?

• the range of environmental (biotic and abiotic) that a species needs

• unique to each species

• not a geographical location

inhospitable matrix

where the fragments live

habitat loss comes in many forms

• clear cutting

• agriculture

• housing

• roads

changes that seem subtle are not subtle to _____

plants and animals

fragmentation has

• genetic impacts (inbreeding and the ability to adapt)

• ecological impacts (a reordering of the whole community)

• can alter processes (how nutrients flow through the system)

how does habitat loss and/or fragmentation lead to changes in genetic diversity and why does it matter?

• genetic diversity is good for individuals

• genetic diversity is required for adaptive evolution—especially important in an era of rapid climate change

traits of a population that maintains genetic diversity

• large population size

  • mutations occur

  • draft is minimized

• even sex ratios

• random mating

  • avoids inbreeding, inbreeding depression (ID)

• migration between populations

inbreeding depression

close relative mating that leads to lower fitness

three factors that drive population decline

1. environmental stochasticity

2. demographic stochasticity

3. genetic stochasticity

stochasticity

variation that can’t be predicted

extinction vortex

1. due to environmental variability, a population dips to low numbers for a generation

2. this results in a small increase in inbreeding and ID

3. favorable environmental conditions return but, due to ID the population growth rate will not be as fast as before

4. if the population dips to low numbers again, it will tend to stay there for longer due to poorer per-capita performance resulting in more genetic loss

what is the most basic need for all species?

Species-Area Relationship (SAR)

Equation for SAR

S = c x A^z

S = # of species

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

A = area

z = rate at which new species accumulate (slope)

why are some species more sensitive to fragmentation than others?

• size

• mobility

• how skittish they are

• their boldness and shyness

what species tend to react better to fragmentation

smaller species

oceanic islands

• never attached to the mainland

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

• species with great dispersal abilities

• islands are species-poor: few mammals and few top predators

land bridge islands

• once attached to mainland, become separated slowly

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

• have species that could never have made it to the island on their own

habitat islands

• created by habitat destruction

• exist in a matrix of inhospitable habitat

faunal relaxation

it takes a while for species to be lost once a land bridge or habitat fragments forms

extinction debt

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

richness

total number of species

trophic cascade

indirect positive effect of one species on another that is at least one tropic level removed

example of trophic cascade

predators eating herbivores which minimizes the animals eating the plants—the plant’s predator

SLOSS

a single large reserve or several small reserves

advantages of several small

• they are better protected from external factors (ex: wildfires and diseases)

single large

• more species to protect

• may better protect species with large home ranges

• less edge effect

• more connectivity

• larger population less prone to extinction/decline

edge effect

an increase or decline in abundance or occurrence of a species near the edge