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This chapter explores the various interspecific interactions in community ecology, including competition, predation, herbivory, and symbiosis. It discusses concepts such as niche, resource partitioning, animal defenses, mimicry, herbivory, and different types of symbiotic relationships. The chapter also covers community structure, succession, and the role of keystone species.
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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
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
Predation • Consuming of one organism by another
Animal defenses • Hide or run • Chemicals (bees, wasps, scorpions, spiders) • Snakes, lizards, frogs • Coloration • Aposematic: warning • Cryptic: blending
Animal defenses • Mimicry • Batesian: • Harmless animals mimic harmful animals • Mullerian: • Several harmful animals look the same (safety in numbers)
(a) Mechanicaldefense (b) Chemicaldefense ▶Porcupine ▶Skunk (c) Aposematic coloration: warning coloration (d) Crypticcoloration:camouflage ◀Poisondart frog ▶Canyontree frog (e) Batesian mimicry:A harmless speciesmimics a harmfulone. (f) Müllerian mimicry:Two unpalatablespecies mimiceach other. ▲Venomous greenparrot snake ◀Yellowjacket ◀Nonvenomoushawkmoth larva ◀Cuckoo bee
(a) Mimicking asea snake Mimic octpus (b) Mimicking a flounder (c) Mimicking a stingray
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
Mutualism • Interactions benefit both species • Flowers and bees, birds or bats • Ants and acacias (plant)
Parasitism • One organism benefits at the cost of its host organism • Parasite is usually smaller than host • Ectoparasites (external) • Ticks. lice • Endoparasites (internal) • Tapeworms
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
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)