Community Ecology

Chapter 54

Community

Interspecific interactions Interactions with different species Competition Predation Herbivory Symbiosis

Interspecific Competition

Two species compete for resources Competitive exclusion: One species utilizes resources

more efficiently Eliminates the other

Paramecium

Niche

Species use of resources in its environment

Abiotic & biotic Fundamental niche: Area that a species is capable of

utilizing Realized niche: Actual resources the species utilizes

Resource Partitioning

Species use similar niches Subdivide available resources Warbles (small bird)-spruce trees Lizards in Dominican republic Character displacement: Sympatric species diverge more

than allopatric species

Barnacles

Resource partitioning

Predation

Consuming of one organism by another

Predators

Animal defenses

Hide or run Chemicals (bees, wasps, scorpions,

spiders) Snakes, lizards, frogs Coloration Aposematic: warning Cryptic: blending

Aposematic

Cryptic

Animal defenses

Mimicry Batesian: Harmless animals mimic harmful

animals Mullerian: Several harmful animals look the

same (safety in numbers)

Batesian mimicry

Mullerian mimicry

(a) Mechanicaldefense

(b) Chemicaldefense

(c) Aposematic coloration:warning coloration (d) Cryptic

coloration:camouflage

(e) Batesian mimicry:A harmless speciesmimics a harmfulone.

(f) Müllerian mimicry:Two unpalatablespecies mimiceach other.

▶ Porcupine ▶ Skunk

◀ Poisondart frog

▶ Canyontree frog

◀ Nonvenomoushawkmoth larva ◀ Cuckoo bee

◀ Yellowjacket

▲ Venomous greenparrot snake

Mimic octpus(a) Mimicking a

sea snake

(b) Mimicking a flounder

(c) Mimicking a stingray

Herbivory

Organism eats part of a plant Thorns, spines, prickles Chemicals Mustard oils, milkweed, nicotine

herbivore

Symbiosis

2 or more organisms interact in a permanent relationship

Lichen Mycorrhizae Types of symbiosis Commensalism Mutualism Parasitism

Commensalism

Interaction benefits one organism But neither harms nor helps the

other Fish & sea anemones Egrets & cattle

Commensalism

Commensalism

commensalism

Mutualism

Interactions benefit both species Flowers and bees, birds or bats Ants and acacias (plant)

Mutualism

mutualism

Mutualism

Parasitism

One organism benefits at the cost of its host organism

Parasite is usually smaller than host Ectoparasites (external) Ticks. lice Endoparasites (internal) Tapeworms

Parasitism

Community structure

How these interspecific interactions work all together

1. Predation reduces competition 2. Parasitism vs competition 3. Indirect effects (rodents and ants) 4. Keystone species Species that has a strong effect on the

composition of a community

Keystone species

Succession

Communities change from simple to complex over time

Secondary succession: New community arises where an

old community was disturbed Primary succession: New community arises on bare

lifeless substrate (glacier receding)

Primary succession

Secondary succession