Community Ecology Chapter 54

Community An assemblage of populations of various species living close enough for potential interactions

54.1 Community interactions are classified by whether they help, harm, or have no effect on the species involved

Types of Interactions Interspecific Interactions Interactions with other species Intraspecific Interactions Interactions within one species

Ecological Niche Every species survives and reproduces utilizing a range of chemical and biological conditions Resource partitioning allows species to live in the same habitat by fulfilling different ecological niches

Competitive Exclusion Principle Direct interspecific competition will always lead to the extinction of one species One species will have a slight competitive edge in surviving and reproducing

Interspecific Species Interactions

Predation (+/-)

Predation Defense Strategies Cryptic coloration – camouflage Aposematic coloration – warning coloration Batesian mimicry – a harmless species mimics a harmful one Mullerian mimicry – two harmful species mimic each other

(a) Cryptic coloration(b) Aposematic coloration Canyon tree frog Poison dart frog (c) Batesian mimicry: A harmless species mimics a harmful one.(d) Müllerian mimicry: Two unpalatable species mimic each other. Hawkmoth Larva (harmless) Cuckoo bee Yellow jacket Green parrot snake (harmful)

Herbivory (+/-)

Parasitism (+/-)

Commensalism Commensalism (+/0)

Mutualism Mutualism (+/+)

Facilitation (+/+ or 0/+) One species influences the survival and reproduction of another species Ex: plant species that make soil hospitable for other species to thrive

54.2 Diversity and trophic structure characterize biological communities

Species Diversity Species richness: Total amount of species in a community Relative abundance: Total amount of one species in a community Diversity is key to a healthy, stable ecosystem

Simpson’s Index of Biodiversity Mathematical method of measuring diversity Accounts for abundance and richness of species in an ecosystem

Trophic Structure Trophic structure: feeding relationships Represented by food webs, chains How energy flows through ecosystem! Decomposers cycle matter in ecosystem! Energy availability limits length of food chains 10% rule Biomass: amount of mass of individuals in a population

Keystone Species Organism with a pivotal role in an ecosystem Not necessarily, usually the dominant (most abundant) species! The removal of a keystone species results in the collapse of the ecosystem Ex: sea otter (Enhydra lutris)

53.3 Disturbance influences species diversity and composition

Disturbance & Succession Disturbance – event that changes the dynamics of a community Succession – recovery of that community after a disturbance

Primary vs. Secondary Succession Primary – begins with rock Ex: glacier, volcano Secondary – begins with soil Ex: forest fire, flood Climax community – recovered, long term stability

Human vs. Natural Disturbance Humans – clearing land for own uses Ex: logging, agriculture Generally, no recovery to climax community

54.4 Biogeographic factors affect community diversity

Abiotic shapes biotic

54.5 Pathogens alter community structure locally and globally

Abiotic shapes biotic Pathogen: disease causing microorganism Zoonotic pathogen: pathogen of animal origin that are transferred to humans