Community ecology

BY SURABHI TANWARMasters Student in the Environmental SciencesInstitute of Science, Mumbai

COMMUNITY ECOLOGY

What is a Community?

It is an assemblage of species living close enough together for potential interaction.

Communities differ in their species richness, thenumber of speciesthey contain, andthe relativeabundance ofdifferent species.

FOUR main kinds of species interactions; all play a role in the formation of community structure...

Competition (-,-)

Predation, parasitism (+,-)

Mutualism (+,+)

Commensalism (+,0)

Competition.◦Interspecies competition: can occur

when resources are limited.

Competition.

◦ Interspecies competition for resources can occur when resources are in short supply.

There is potential for competition between any two species that need the same limited resource.

◦ The competitive exclusion principle: two species with similar needs for same limiting resources cannot coexist in the same place.

G. F. Gause (1934) tested competitive exclusion principle

Ecological Niches

The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche

Ecologically similar species can coexist in a community if there are one or more significant differences in their niches

As a result of competition, a species’ fundamental niche may differ from its realized niche

Fundamental Niche vs Realized Niche

Fundamental Niche: the niche that a species potentiallycould occupy, in the absence of competitors.

Realized Niche: the niche to which a species is restrictedin the presence of competitors.

Classic experiments confirm this.

Fig. 53.2

Resource Partitioning

Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community

Character displacement

Body evolves as a result of resource partitioning.

Predation.

◦A predator eats prey.◦Herbivory, in which animals eat plants. ◦In parasitism, predators live on/in a host and

depend on the host for nutrition.

Offset oscillations in the population sizes of the predator and prey

Coevolution of predator and prey

◦Plant defenses against herbivores include chemical compounds that are toxic.

◦Animal defenses against predators. Behavioral defenses include fleeing, hiding, self-

defense, noises, and mobbing. Camouflage includes cryptic coloration,

deceptive markings.

Fig. 53.5Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Mechanical defenses include spines. Chemical defenses include odors and toxins Aposematic coloration is indicated by warning colors,

and is sometimes associated with other defenses (toxins).

Devil scorpionfish

backside

In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model

monarch viceroy

Cuckoo bee

Yellow jacket

In parasitism, one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process

Parasitism exerts substantial influence on populations and the structure of communities

Mutualism is where two species benefit from their interaction.

Coral polyp & zooxanthellae

Commensalism is where one speciesbenefits from the interaction, but other is not affected.

REFRENCES

http://www.bio.miami.edu/ecosummer/lectures/lec_coevolution.html

https://en.wikipedia.org/wiki/Ecological_niche

http://faculty.virginia.edu/bio202/lectures/LectureK7.pdf

http://ani_mardiastuti.staff.ipb.ac.id/files/2011/11/Biopop09_Resource-Partition.pdf