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

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

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

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

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