Lec 15: Species distributions; indicator species

Ecology Lec 2

species distribution

a species is spread out or arranged in a particular area or ecosystem

• overlap within biomes (Larrea tridentata found in the Sonoran Desert and Chihuahuan desert biome)

dispersal

the movement of individuals or gametes away from (& potentially back to) their original location

• mobile

• wind

• water

often limits species distributions

dispersal limitation

• fear of movement or inability to move (for animals, e.g. trying to cross highways)

• need to modify conditions before new locations are suitable (e.g. after glacier retreat)

• long lifespans or slow reproduction.

environment

everything in an organism’s surroundings

biotic: living components of the environment

abiotic: non-living components

biotic limit

herbivory- eat plant species and reduces plants’ distribution

competition- hedgehog competiting for similar respurces

abiotic limit

temperature- (heat tolerance in the California mussel- high temperatures increase mortality 😕 )

drought -(multi-year drought) where the Juniper tree is drought tolerant and Piñon has drought intolerant (dies)

behavior

actions performed by organisms in response to stimuli, influencing their interactions with the environment and other individuals.

environmental gradient

can be physically continuous or patchy and range over various environmental conditions

• temperature gradient

• elevation gradient

• storm (hurricane) risk gradient

• predation risk gradient

indicator species

bioindicators: provide a holistic overview actual health of a system and consequences of pollution

Organisms sensitive to environmental changes, providing early warnings about ecosystem health and indicating pollution levels (AI)

ex) measuring species presence and diversity to asses stream health - stream assessments)

What are the three major factors that influence species distributions? Do they act
sequentially or at the same time?

1. Humans

2. Behavior (limits dispersal/ fear of predators)

3. Environment (abiotic and biotic)

• Occur Simultaneously

Key Limits

1. Can the species disperse to a location?

2. Is the abiotic environment suitable for the survival, growth, and reproduction of the species?

3. Is the biotic environment suitable for the survival, growth, and reproduction of the species?

Notes

• Biomes are ‘shorthand’ for combinations of climate and species with similar ranges

The coast redwood is a common tree species in Berkeley. Its range map is to the right. What factors do you think might limit the distribution of the species? Why does it not occur further north/south/east of where it does?

Abiotic limits on distribution, such as requiring a coastal climate (further east means lest access to coastal rain and fog) or a specific temperature range (further north than Oregon could be too cold, further south than Monterey could be too hot).