Ecology Notes: Communities, Interactions, and Niches

A set of vocabulary flashcards covering key concepts from the notes on diversity metrics, descriptions, species interactions, niches, partitioning, and a classic competition experiment.

Species richness

A simple count of the number of species in a community; widely used but not always a great indicator of diversity.

Shannon index

A diversity index that captures both richness and evenness of species abundances; more informative than richness alone.

Location-based description

Describing a community by its location, e.g., alpine plant community or rocky intertidal community.

Function-based description

Describing a community by what members do, e.g., pollinator community or predator community.

Dominant-member framing

Description based on the most common or dominant members to simplify communication.

Taxonomic-based description

Focus on a particular group, e.g., insect community or bird community.

Structural role-based description

Emphasis on the role or position in the community structure (e.g., understory vs tree community).

Bounds of description

The scope depends on the research question and practical needs; multiple perspectives may be used.

Predation / exploitation

Two-species interaction where the predator benefits and the prey is harmed; often called exploitation.

Predator

An organism that benefits by feeding on another (the prey), often killing it.

Prey

The organism that is killed or consumed by a predator.

Competition

Negative interaction where both species are harmed; reduces shared resources and can lead to resource partitioning.

Mutualism

A positive interaction where both species benefit.

Commensalism

A positive interaction for one species with little or no effect on the other.

Parasitism

Parasite benefits by feeding on a host, usually without killing it quickly; can be inside or outside the host.

Parasite

An organism that lives on or in a host and gains resources at the host’s expense, typically without immediate lethality to the host.

Ectoparasite

Parasites that live on the outside of the host (e.g., ticks).

Herbivory

A special case of predation where the prey is a plant or algae; e.g., deer eating plants.

Abiotic tolerances

Non-living environmental limits that constrain where a species can live (e.g., desiccation tolerance).

Niche

The set of resources and environmental conditions under which a species can persist; its ecological role or address.

Fundamental niche

The full theoretical range of environmental conditions under which a species can exist.

Realized niche

The actual conditions under which a species occurs in nature, given biotic interactions.

Realized niche ⊆ Fundamental niche

Relationship where the realized niche is a subset of the fundamental niche.

N-dimensional hypervolume

A conceptual, multi-axis space describing a species’ niche beyond three dimensions.

Niche partitioning

Coexisting species divide resources (space, time, or resource type) to coexist.

Canopy specialists vs canopy-shy

A conceptual example of niche partitioning where species differ in preferred habitat microhabitats.

Temporal partitioning

Partitioning resources by time (e.g., elephants active at night; humans daytime).

Spatial partitioning

Partitioning resources by space (e.g., elephants avoiding human activity areas).

Barbacles experiment

Classic test of whether competition shapes barnacle distributions by removing one species and observing shifts.

Balanus balanoides

Lower intertidal barnacle species used in the Barbacles experiment.

Tantulus

Upper intertidal barnacle species used in the Barbacles experiment.

Desiccation tolerance

The ability to withstand drying; a key abiotic factor shaping distribution.

Intertidal vertical distribution

The arrangement of species along the vertical gradient of the intertidal zone.

Abiotic constraint

Non-living factors (e.g., drying conditions) that limit a species’ distribution.

Coexistence

The ability of multiple species to persist in the same community, often via niche differentiation.