Species Interactions and Coexistence

Flashcards covering classical theories of coexistence, phylogenetic community structure, ecological network descriptors, mutualism, parasitism, and temporal dynamics of communities according to the lecture notes.

Interacting

The reciprocal action or influence between two or more people or things, and the relationship of exchange with someone.

Niche Processes (Hutchinson, 1959)

A coexistence theory based on local environmental filters and competitive exclusion, asserting that two ecologically similar species cannot coexist without competing.

Neutral Processes (Hubbell, 2001)

A theory suggesting ecological communities are open and not at equilibrium, regulated by random speciation, extinction, dispersal limits, and ecological drift rather than competition.

Historical Processes (Ricklef, 1987)

A theory emphasizing that initial conditions and the order of arrival (priority) of species determine later stages of colonization, acting as a compromise between regional and local processes.

Fast Processes

Density-dependent interactions occurring at small spatial and temporal scales, including physiological tolerance, abiotic factors (pH, temperature), and biotic factors (mutualism, disease).

Slow Processes

Biogeographic processes of speciation and extinction that operate over large spatial and temporal scales.

Phylogenetic clustering

A pattern where organisms in a community share common traits (such as chemical defenses) due to a shared phylogenetic origin.

Phylogenetic overdispersion

A pattern indicating characters shared between different groups of organisms without a common phylogenetic origin (convergence) or coexistence of non-closely related species.

Island Biogeography Theory (MacArthur & Wilson, 1967)

A theory stating that as a community approaches carrying capacity, niche occupation and species replacement increasingly rely on the existing pool rather than external propagules.

Nodes

The individual species within an ecological network.

Qualitative Link

A link in an ecological network representing a specific biological mechanism or process.

Quantitative Link

A link representing the net quantitative effect of a process, such as the transfer of biomass, energy, or nutrients.

Interaction Sign Networks

Networks where links represent the effect of one entity on another, categorized as positive-positive (mutualism) or negative-negative (competition).

Principle of Competitive Exclusion (Gause's Law)

The law stating that two species competing for the same limited resources and occupying the same niche cannot coexist; the more efficient species will eventually drive the other to extinction.

Transitive Network

A linear dominance hierarchy where Species A dominates B and C, and B dominates C, resulting in lower potential diversity.

Intransitive Network (Rock-Paper-Scissors)

A non-linear competitive structure where Species A dominates B, B dominates C, and C dominates A, allowing for higher coexistence.

Chaotic Dynamics

Fluctuations in species abundance that allow the coexistence of multiple competitors for the same resources in a complex environment.

Bipartite Networks (Two Layers)

A network structure typical of mutualism, such as plants and their pollinators, where links connect two distinct groups of organisms.

Connectance

A food web descriptor representing the number of realized links divided by the number of possible links.

Coevolution (Strict)

A long-term historical relationship between two organisms that causes specific morphological transformations in at least one of them, such as Darwin's moth and the comet orchid.

Diffuse Coevolution

A coevolutionary aspect where a relationship, such as tolerance to plant chemistry, does not necessarily lead to morphological changes.

Kleptoplasty (Furto di plasti)

The theft and retention of functional chloroplasts from algae by sea slugs (Sacoglossa), providing supplemental energy.

Host-jump (Host-shift)

A mechanism of speciation where an organism changes its host or bathymetric niche, leading to genetic differentiation.

Associational Defense

An ecological strategy where one organism selectively associates with another for protection, such as amphipods living on toxic algae to avoid fish predation.

Extended Phenotype

A concept where an organism's genes have effects outside of its own body, such as a parasite modifying the phenotype of its host for its own advantage.

Enemy Hypothesis

Predicts that galls with similar morphology exclude similar sets of parasitoids and thus possess similar parasitoid communities.

Regressive Evolution

Al adaptive process where a species loses complex organs or structures, often to synchronize physiologically with a host.

Dino loop

A marine cycle where dinoflagellates and dinospores serve as food, regulating the pool of parasitoids.

Viral loop

A cycle where viruses condition pico and nano phytoplankton but are not consumed due to their small size.

Hysteresis

A phenomenon in which forward and backward shifts between stable states occur under different critical conditions.

Deterministic Assembly

A situation where different habitat patches converge toward the same species composition regardless of colonization history, guided by environmental conditions.

Historically Contingent Assembly

A situation where habitat patches diverge into different species sets based on the specific history and order of immigration.

Succession

The gradual process through which an ecosystem develops from a bare or disturbed environment.

Climax

The final, stable stage of ecological development in perfect equilibrium with the local climate.

Priority Effect

The 'first come, first served' principle where the arrival order of species determines the final community composition.

Critical Tipping Points

The points of no return where a small change can push an ecosystem into a completely different stable state.

Allee Effects

Biological phenomena, often in free-spawning organisms like $Diadema\,antillarum$, where fertilization success fails when population density is too low.

Krill Surplus Hypothesis

The theory that the over-exploitation of whales led to a surplus of krill, which subsequently boosted the populations of smaller krill predators like fur seals.