Community Ecology and Interspecific Dynamics

Comprehensive practice vocabulary flashcards covering community ecology, interspecific interactions, competition models, predation, parasitism, mutualism, community structure, and succession dynamics.

Commensalism

A two-species interaction ($+\,/\,0$) in which one species benefits by obtaining essential conditions or resources while the other species is neither helped nor harmed, such as an epiphytic orchid growing on a tree.

Amensalism

An asymmetric interspecific interaction ($-\,/\,0$) in which one species is negatively affected or inhibited while the second species experiences no effect.

Parasitoidism

An interspecific interaction ($+\,/\,-\text{arrow}$) where an organism spends a significant portion of its life history attached to or within a single host, ultimately killing the host as a routine outcome of its development.

Coevolution

A process of reciprocal evolutionary change between interacting species, where an evolutionary adaptation in one species acts as a selective pressure driving evolutionary change in the other.

Diffuse Coevolution

A coevolutionary process occurring across a whole network of species rather than between an isolated pair, where whole guilds of species undergo reciprocal evolutionary adjustments (e.g., generalist pollinators visiting multiple flower species).

Fundamental Niche

The complete range of physical and abiotic environmental conditions (the hypervolume) under which a species can survive and reproduce indefinitely in the absence of interspecific interactions like competition or predation.

Realized Niche

The portion of the fundamental niche that a species actually exploits and occupies as a result of constraints and interactions imposed by other species, such as competitors and predators.

Adaptive Radiation

An evolutionary divergence where a single ancestral species rapidly diversifies into a multitude of new species that occupy different ecological niches and exploit distinct habitat features.

Brood Parasitism

A reproductive strategy in which a female evades parental investment by laying eggs in the nests of host individuals of the same or different species, leaving the host to incubate and rear the young.

Preemption Competition

A mechanism of interspecific competition where passive occupation of physical space by individuals of one species precludes the establishment and colonization of another species (e.g., sessile barnacles on rocky shores).

Overgrowth Competition

A competitive interaction occurring when an organism physically grows above or over another, intercepting and limiting its access to shared resources such as light (e.g., tall plants casting shade over smaller understory plants).

Allelopathy

A form of chemical competition in plants where individuals produce and release toxic metabolic compounds into the environment that inhibit the germination, growth, or survival of other species.

Competition Coefficient ($\alpha$ and $\beta$)

Constants in the Lotka-Volterra competition model that quantify the per capita competitive effect of one species on another; $\alpha$ measures the per capita effect of species 2 on species 1, and $\beta$ measures the per capita effect of species 1 on species 2.

Zero-Growth Isocline

A line on a phase-plane diagram representing population densities of two competing species at which the net population growth rate of a given species equals zero ($dN/dt = 0$).

Competitive Exclusion Principle

The ecological principle stating that two species competing for the exact same limiting resources cannot coexist indefinitely under stable environmental conditions; the superior competitor will drive the other to local extinction.

Competitive Release

The expansion of a species' realized niche and geographic or resource distribution following the removal, absence, or extinction of a competing species.

Resource Partitioning

The differential utilization of shared limiting resources by coexisting species in space, time, or morphology, which minimizes interspecific competition.

Character Displacement

The evolutionary divergence of morphological, behavioral, or physiological traits in sympatric populations of two competing species, driven by natural selection to lessen competition.

Functional Response

The relationship between an individual predator's rate of food consumption and the prey population density, categorized into Type I (linear), Type II (decelerating to a plateau due to handling time), and Type III (sigmoidal due to search images or switching).

Numerical Response

The change in predator population density across time in response to changes in prey density, brought about by changes in reproduction, survival, or immigration/emigration.

Search Image

A learned mental perceptual filter acquired by a foraging predator that enables it to more readily detect, target, and capture a specific abundant prey type.

Handling Time

The time required by a predator to capture, subdue, consume, and digest a single unit of prey once it has been located.

Optimal Foraging Theory

A behavioral ecology framework stating that natural selection favors foraging strategies that maximize net energy intake per unit of feeding time, balancing search time and handling time against caloric reward.

Red Queen Hypothesis

The evolutionary principle proposing that organisms must continuously adapt, evolve, and proliferate simply to maintain reproductive fitness relative to the coevolving organisms around them.

Aposematism

Conspicuous warning coloration, patterns, or odors exhibited by unpalatable, toxic, or dangerous prey to warn off potential predators.

Batesian Mimicry

A defensive adaptation where a palatable or harmless prey species evolves physical resemblance to an unpalatable or venomous model species to deceive predators.

Müllerian Mimicry

A defensive phenomenon where two or more unpalatable, noxious, or dangerous species evolve shared warning color patterns, mutually reinforcing predator avoidance.

Constitutive Defenses

Fixed defensive structures, coloration patterns, or chemical compounds that are continuously present in an organism regardless of whether predators are present.

Induced Defenses

Defensive structures, behavioral modifications, or toxic chemical compounds synthesized or activated only in direct response to consumer presence or tissue damage.

Cleptoparasitism

A form of parasitism where the parasite feeds by stealing food, prey, or nesting provisions gathered by another individual or host.

Microparasites

Small, microscopic parasites (such as viruses, bacteria, and protozoans) characterized by short generation times, rapid reproduction inside the host, and direct transmission.

Macroparasites

Large multicellular parasites (such as helminths, lice, fleas, and ticks) with comparatively long generation times that typically do not complete their entire lifecycle within a single host.

Hemiparasitic Plants

Photosynthetic parasitic plants that contain chlorophyll and produce their own carbohydrates, but extract water, mineral nutrients, or additional resources from their host's xylem.

Holoparasitic Plants

Non-photosynthetic parasitic plants completely devoid of chlorophyll that rely entirely on the host's xylem and phloem for carbon, water, and nutrients.

Obligate Mutualism

A co-dependent mutualistic relationship essential for the survival, growth, or reproduction of one or both partner species, such that neither can survive indefinitely without the other.

Facultative Mutualism

A non-essential mutualistic interaction that provides fitness advantages to both partner species, although both are capable of surviving and reproducing independently.

Defensive Mutualism

A mutualistic interaction where one partner receives food or shelter in exchange for defending the second partner against herbivores, predators, or competitors (e.g., Pseudomyrmex ants and Vachellia acacia trees).

Mycorrhizae

Mutualistic associations between soil fungi and plant roots, in which the fungus enhances the plant's uptake of soil nutrients and water while obtaining photosynthesized carbon compounds in return.

Species Richness

The total count of distinct species inhabiting a sampled community or defined geographic area.

Species Evenness

The equitability with which individuals in a community are apportioned among the various co-occurring species; maximum evenness occurs when all species have equal abundance.

Simpson's Diversity Index

A mathematical index ($D$) that calculates the probability that two individuals randomly picked from a community will belong to the same species.

Shannon Index

A widely used species diversity index (also known as the Shannon-Wiener index) that quantifies community diversity while accounting for both species richness and species evenness.

Dominant Species

One or a few species that numerically, physically, or functionally predominate within an ecological community by constituting the majority of biomass, numbers, or space.

Food Web Connectance

The proportion of all mathematically possible feeding links in a community food web that are actually realized, defined as $C = \frac{L}{S(S - 1)/2}$ or $C = \frac{L}{S^2}$, where $L$ is the number of links and $S$ is species richness.

Linkage Density

The average number of feeding links per species within a food web, calculated as $LD = \frac{L}{S}$.

Connectedness Web

A food web representation that delineates the presence of observed binary feeding links (who eats whom) among organisms without measuring trophic magnitude.

Energy Flow Web

A food web representation where the connections between trophic compartments are quantified and weighted according to the actual flux or volume of energy transfer between them.

Functional Web

A food web depiction that isolates and emphasizes the dynamically significant interaction strengths and the direct/indirect influences of species populations on each other's growth rates.

Zonation

Spatial patterns of distinct physical and biological communities arranged along an environmental gradient (e.g., changes in elevation, soil moisture, or tidal inundation).

Organismic Concept of Communities

Frederic Clements's theoretical framework viewing an ecological community as an integrated superorganism with discrete boundaries and obligate biotic interactions that bind species together.

Individualistic Concept of Communities

Henry Gleason's theoretical perspective viewing a community as an open, continuous assemblage of individual species whose distributions coincide simply because of shared environmental tolerances.

Keystone Species

A species that exerts an exceptionally large and disproportionate regulating effect on community structure and biodiversity relative to its numerical abundance or biomass.

Apparent Competition

An indirect negative interaction between two non-competing prey species mediated by a shared predator; an increase in the density of one prey item leads to an increase in predator abundance, elevating predation rates on the second prey species.

Trophic Cascade

An indirect interaction initiated by top predators that suppresses the abundance or alters the behavior of their prey (herbivores), thereby releasing the next lower trophic level (primary producers) from consumption.

Top-Down Control

The regulation of community structure and trophic biomass driven by consumer predation pressure from higher trophic levels descending to lower levels.

Bottom-Up Control

The regulation of community trophic structure where the biomass, abundance, and productivity of higher trophic levels are limited by primary productivity and nutrient availability at the basal level.

Succession

The non-seasonal, directional, and continuous pattern of colonization, colonization extinction, and species turnover in a community following disturbance or the creation of new substrate.

Sere

The entire chronological sequence of transitional communities (seral stages) that replace one another during ecological succession from pioneer stages to a climax state.

Primary Succession

Ecological succession that begins on newly exposed sites that have never supported an ecological community and lack pre-existing organic soil or seed banks (e.g., cooled lava, sand dunes, or retreated glacial till).

Secondary Succession

Ecological succession that occurs on a site where a previous community has been cleared or disturbed, but where viable organic soil, organic nutrients, and propagules remain intact.

Autogenic Environmental Change

Environmental shifts directly brought about by the biological activities and presence of organisms inhabiting the site (e.g., accumulation of organic leaf litter, light attenuation by tree canopies).

Allogenic Environmental Change

Environmental shifts generated purely by physical, abiotic geophysical forces independent of the resident organisms (e.g., changes in climate, sedimentation, weathering).

Intermediate Disturbance Hypothesis

The ecological theory proposing that species diversity is maximized at intermediate frequencies and intensities of disturbance, because competitive exclusion is prevented while pioneer and late-successional species coexist.