Community Ecology I: Introduction

• The email address for Dr. Natasha McGowan is [email protected].
• Community Ecology I is part of semester 2.

Learning Outcomes

• Community ecology is defined and understood.
• Population interactions within a community are studied.
• Factors influencing community structure are examined.
• Methods for studying communities are explored.

Hierarchy of Life

• The biosphere is the broadest level in the hierarchy of life.
• Biomes are large geographic areas with similar climate and ecosystems.
• Ecosystems include communities and their physical environment.
• Communities are assemblages of different populations.
• Populations are groups of individuals of the same species.
• Organisms are individual living things.
• Molecules are the basic building blocks of matter.
• Organs and Organ Systems are groups of organs working together.
• Tissues are groups of similar cells performing a specific function.
• Cells are the basic unit of life.
• Organelles are structures within cells that perform specific functions.
• Decreasing size goes from Biosphere to Molecules

Community Ecology

• A community includes interacting populations in the same spatial area at the same time.
• Ecology studies the relationships between organisms and their environment.
• Distribution, abundance, and interactions among populations are key aspects.

Interesting Aspects of Community Ecology

• Species interactions affect the health and stability of ecosystems.
• Identification of species is used in diversity studies.
• Understanding how species are affected by others helps with conservation efforts.

Community Structure

• There was an early 20th-century debate about community structure.
• Gleason proposed the "individualistic" hypothesis.
• Clements proposed the “integrated” hypothesis.

Gleason’s Hypothesis

• Species occur in an area due to similar habitat requirements.

Clements’ Hypothesis

• Species are “locked” into communities via mandatory biotic interactions.
• Includes the concept of "Superorganisms."

Community Interactions

• Community interactions involve assemblages of populations with the potential to interact.
• Interactions between species are called interspecific interactions.
• Types of interspecific interactions include competition.
• Other types of interactions include predation/herbivory and parasitism.
• Mutualism and commensalism are also types of interspecific interactions.

Interspecific Interactions

• Competition is when both species are negatively impacted (-/-).
• Predation/Herbivory is when one species benefits and the other is harmed (+/-).
• Parasitism is when one species benefits and the other is harmed (+/-).
• Mutualism is when both species benefit (+/+).
• Commensalism is when one species benefits and the other is not affected (+/0).
• Antibiosis (Amensalism) is when one species is harmed and the other is not affected (-/0).

Defence Mechanisms

• Defence mechanisms include crypsis (camouflage).
• Defence mechanisms include aposematic coloration (warning coloration).

Mimicry

• Batesian mimicry is when palatable species mimic unpalatable ones. In addition, safe-to-eat species mimic noxious species.
• Müllerian mimicry is when mutually noxious species mimic each other.

Study Scale

• Global ecology examines ecological processes at a worldwide scale.
• Landscape ecology studies the interaction between ecosystems.
• Ecosystem ecology focuses on the community plus the abiotic factors.
• Community ecology studies interactions between populations.
• Population ecology studies the dynamics of a single population.
• Organismal ecology studies how an organism interacts with its environment.
• Emerging properties are a result of multispecies interactions.

Community vs. Ecosystem

• An ecosystem encompasses all organisms in a community plus abiotic factors.
• Ecosystems vary in size (scale).

Global Biomes

• Global biomes include tropical forests.
• Other types of global biomes include savanna and desert.
• They also include chaparral, temperate grassland, and temperate broadleaf forest.
• Northern coniferous forests (taiga) and tundra are also global biomes.
• High mountains and polar ice are additional global biomes.

Biome Features

• Deserts are located near 30° north and south of the equator, with low precipitation.
• Tundra has herbaceous vegetation and permafrost restricting plant growth.
• Grasslands have highly seasonal precipitation.
• Coniferous forests are dominated by pine, spruce, and fir trees.
• Broadleaf forests have vertical layers, including a canopy, understory, and shrub layer.

Habitats

• Marine habitats include lakes and wetlands.
• Marine habitats also include streams and estuaries.
• Intertidal zones and ocean pelagic zones are marine habitats.

Intertidal Zonation

• Intertidal zones are subject to cycles of emersion and submersion.

Studying Community Ecology - Output

• Count/list of species to measure Richness.
• Species diversity is analyzed using Diversity Indices like Shannon’s and Simpson’s.

Population Sizes

• Population sizes in communities are rarely constant.
• Population sizes are influenced by various factors.

Population Growth

• Without disease, predation, and with excess space and food growth is exponential.
• Initial population growth is slow, but quickly speeds up.

In Reality

• In reality space & resources become limited
• Disease & predation are often present
• Growth starts exponential
• Then evens out(logistics growth)
• Carrying capacity occurs

Density-Dependent Limiting Factors

• Density-dependent factors depend on population size in a given area.
• They are often affected by interactions within species.

Density-Independent Limiting Factors

• Density-independent factors affect all populations in the area similarly.
• These factors include weather.
• They also include natural disasters and anthropogenic effects.

Studying Community Ecology - Study Scale

• Study scale depends on the question.
• Selection of populations (species) or taxa is of interest.

Metacommunities

• Metacommunities

Metacommunity Structure

• Metacommunity Structure

Soil

• Predatory mites control collembolans.
• Oribatid mites are diverse and feed on fungi and organic matter.
• Prostigmatid mites are dominant in extreme systems and feed on fungi and algae.

Summary of Community Ecology

• Community ecology studies patterns of distribution, abundance, and interactions between different populations.
• It helps understand interspecific relationships and inform conservation efforts.
• Populations/species may interact positively, negatively, or not at all.
• Community ecology is affected by biome/ecosystem/habitat variables and stratification.