Chapter #16 – Community Structure (pg. 334 – 348)

Chapter #16 – Community Structure (pg. 334 – 348) 16.1 – The Number of Species and Their Relative Abundance Define Diversity. 16.2 – Numerical Supremacy Defines Dominance. 16.3 – Keystone Species Have an Influence on Community Structure Disproportionate to Their Numbers. 16.4 – Food Webs Describe Species Interactions. 16.5 – Species Within a Community Can Be Classified into Functional Groups. 16.6 – Communities Have a Definitive Physical Structure. 16.7 – Zonation is Spatial Change in Community Structure. 16.8 – Defining Boundaries Between Communities Is Often Difficult. 16.9 – Two Contrasting Views of the Community.

Ecological “Lines of Dependency” Individual to Individual Territory, Home Range, Density Abundance, Distribution Species to Species Predator-Prey Compete (?) for access to essential resources Species to Abiotic (non-living) Components Soil, Topography, Weather Species A Species B Species C Species D

Chapter #16 – Community Structure (pg. 334 – 348) The group of species that occupy a given area, interaction either directly or indirectly is called a community.

Chapter #16 – Community Structure (pg. 334 – 348) 16.1 – The Number of Species and Their Relative Abundance Define Diversity. Perhaps the simplest and easiest measure of community structure is a count of the number of species that occur within the community: species richness. The percentage or rank abundance of the species in a community is called Relative Abundance.

Chapter #16 – Community Structure (pg. 334 – 348) 16.1 – The Number of Species and Their Relative Abundance Define Diversity.

Chapter #16 – Community Structure (pg. 334 – 348) 16.1 – The Number of Species and Their Relative Abundance Define Diversity. Simpson’s Index (D) measures the diversity and dominance of species in a community.

Chapter #16 – Community Structure (pg. 334 – 348) 16.2 – Numerical Supremacy Defines Dominance. When a single or few species predominate within a community, these organisms are referred to as dominants.

Chapter #16 – Community Structure (pg. 334 – 348) 16.3 – Keystone Species Have an Influence on Community Structure Disproportionate to Their Numbers. A species that has a disproportionate impact/effect on the community relative to its abundance is referred to as a keystone species.

Chapter #16 – Community Structure (pg. 334 – 348) 16.3 – Keystone Species Have an Influence on Community Structure Disproportionate to Their Numbers. Creel, S. 2005. Elk Alter Habitat Selection as an Antipredator Response to Wolves. Ecology 86(12):3387-3397.

A – Autotrophs, H – Herbivores, C – Carnivores, P - Predator Chapter #16 – Community Structure (pg. 334 – 348) 16.4 – Food Webs Describe Species Interactions. Each circle represents a species, each line represents a “link”, or connection to another species. A – Autotrophs, H – Herbivores, C – Carnivores, P - Predator

Chapter #16 – Community Structure (pg. 334 – 348) 16.5 – Species Within a Community Can Be Classified into Functional Groups. Guilds: another approach to grouping organisms that derive their food energy in a similar manner. As defined, guilds typically represent strong species interactions.

Chapter #16 – Community Structure (pg. 334 – 348) 16.6 – Communities Have a Definitive Physical Structure. Factors: in terrestrial communities, vegetation is the principle factor governing community structure. In aquatic communities, vegetation and the physical nature of the water (depth, temperature, flow rate, salinity, pH, light availability) are used to define the community.

Chapter #16 – Community Structure (pg. 334 – 348) 16.7 – Zonation Is Spatial Change in Community Structure. Zonation: the changes in the physical and biological structures of communities as one moves across the landscape. Zonation also involves changes associated with scale.

Chapter #16 – Community Structure (pg. 334 – 348) 16.7 – Zonation Is Spatial Change in Community Structure.

Chapter #16 – Community Structure (pg. 334 – 348) 16.7 – Zonation Is Spatial Change in Community Structure.

Chapter #16 – Community Structure (pg. 334 – 348) 16.8 – Defining Boundaries Between Communities Is Often Difficult.

Chapter #16 – Community Structure (pg. 334 – 348) 16.9 – Two Contrasting Views of the Community. The Organismic concept of communities Frederic Clements Species similar evolutionary and climatic histories. “Succession”

Chapter #16 – Community Structure (pg. 334 – 348) 16.9 – Two Contrasting Views of the Community. The Individualistic concept of communities H. A. Gleason Species similarities in their tolerances and requirements, not evolutionary history. “Gradual Change”

Chapter #16 – Community Structure (pg. 334 – 348) The Ecological Niche Defines the Place and Role of Each Species in Its Ecosystem Adaptations Reduce the Overlap of Ecological Niches Among Coexisting Species Helps Control Population Size and Distribution

Chapter #16 – Community Structure (pg. 334 – 348) Ecological Niche (fundamental and realized) The total requirements of a species for all resources and physical conditions determine where it can live and how abundant it can be at any one place within its range.

Chapter #16 – Community Structure (pg. 334 – 348) Ecological Niche Encompasses all aspects of a species’ way of life, including Physical home or habitat. Physical and chemical environmental factors necessary for survival. How the species acquires its energy and materials. All the other species with which it interacts.

Chapter #16 – Community Structure (pg. 334 – 348) Resource Partitioning – Coexistence Gause's Principle: no two species can coexist on the same limiting resource. Species avoid competition by partitioning resources and habitats among themselves.

Chapter #16 – Community Structure (pg. 334 – 348) Resource Partitioning Does not desiccate at high tide Competition Desiccates at low tide.

Chapter #16 – Community Structure (pg. 334 – 348) Reducing Niche Overlap When species with largely overlapping niches are allowed to compete, their niches may focus on a different part of the resource spectrum. Example: North American Warbler Species.

Species – Area Curve Chapter #16 – Community Structure (pg. 334 – 348) Species – Area Curve In general, the larger the area, the greater the number of species.