Global Biodiversity and Island Biogeography

Vocabulary practice flashcards covering global biodiversity trends, spatial heterogeneity, island biogeography theories, equilibrium models, and community ecology formulas.

Primary Productivity Hypothesis

The hypothesis proposing that differences in species richness are driven by primary productivity, where higher energy and resource availability support larger population sizes and a greater number of species.

Competition Theory of Biodiversity

The explanation for global species richness proposing that stable tropical latitudes favor $K$-selected species with narrow, specialized niches packed closely together, whereas variable temperate latitudes select for $r$-selected species with broad niches.

$d/w$ Ratio

The ratio of distance between two species in average resource use ($d$) to the standard deviation of resource use or niche breadth ($w$); full co-existence occurs when $d/w > 3$, while no co-existence is possible when $d/w < 1$.

Spatial Heterogeneity Theory

The hypothesis positing that complex physical environments create more microhabitats and ecological niches, where greater plant richness supports more herbivore species, subsequently supporting a higher richness of predator species.

Architectural Rating (Opuntia)

A quantitative index of structural complexity in prickly pear (Opuntia) cacti that shows a direct positive linear relationship with the number of associated insect species for a constant photosynthetic surface area.

Environmental Age Theory

The theory proposing that tropical regions are biologically richer because they have experienced longer evolutionary time without major catastrophic disruptions, whereas temperate regions underwent recent disturbances such as glaciations.

Cordilleran Ice Sheet

The massive ice sheet that covered the Yukon, British Columbia, Vancouver Island, and northern Washington during the Glacial Maxima approximately $15{,}000\text{ years ago}$.

Pollen Influx Diagram

A paleoecological graph derived from sediment cores (such as a 3-meter core from Yukon Territory) showing the accumulation rate of specific plant pollen types in units of $\text{grains/cm}^2/\text{year}$ across geological time.

Diversity-Stability Hypothesis

Charles Elton's hypothesis proposing that communities with higher species diversity exhibit greater resilience and stability, allowing them to return more effectively to their pre-disturbance state.

Rivet Hypothesis

Paul and Anne Ehrlich's hypothesis analogizing species to rivets in an airplane wing, where an ecosystem can tolerate the loss of some initial species, but exceeding a threshold causes catastrophic system failure.

Redundancy Hypothesis (Passenger Hypothesis)

Brian Walker's hypothesis stating that ecosystem stability relies heavily on a few critical 'pilot' species (keystone or dominant species), while the majority of species function as ecological 'passengers' whose loss does not impair overall system function.

Idiosyncratic Hypothesis

John Lawton's hypothesis stating that community stability changes unpredictably as species diversity varies, because the individual roles, interaction types, and strengths of different species are highly variable and context-dependent.

Keystone Species

A species that exerts disproportionate control over community structure and ecosystem stability relative to its actual numerical abundance or biomass (exemplified by sea otters controlling kelp forest communities).

Dominant Species

A species that possesses high numerical abundance or total biomass within a community, thereby exerting substantial influence over community structure and ecosystem processes.

Global Biomass Distribution

The breakdown of Earth's biomass by habitat: terrestrial environments account for approximately $86\%$ ($\approx 470\text{ Gt C}$, with plants comprising nearly $100\%$), deep subsurface environments represent $13\%$ ($\approx 70\text{ Gt C}$), and marine environments comprise just $1\%$ ($\approx 6\text{ Gt C}$).

Species-Area Relationship

The ecological principle that species richness ($S$) increases predictably as sampling area ($A$) expands, modeled as $S = cA^z$ or in linear log form as $\log(S) = \log(c) + z\log(A)$, where $z$ is the slope.

$z$-Value on Arbitrary Mainland Areas

The slope of the species-area curve measured within continuous mainland habitats, which typically ranges from $0.10$ to $0.16$ due to ongoing immigration and lack of isolation.

$z$-Value on Oceanic Islands

The slope of the species-area curve on true oceanic islands, which typically ranges from $0.18$ to $0.37$, reflecting geographic isolation and dispersal limitations.

$z$-Value on Habitat Islands

The slope of the species-area relationship in isolated continental patches (e.g., lakes, mountaintops, caves), which can reach high values up to $0.72$ (such as for terrestrial invertebrates in West Virginia caves).

Equilibrium Model of Island Biogeography

Robert MacArthur and E. O. Wilson's dynamic model proposing that species richness on an island represents a balance between the immigration rate of new species and the extinction rate of resident species.

Equilibrium Species Richness ($S_0$)

The stable number of species on an island attained at the intersection point where the immigration rate equals the extinction rate.

Species Turnover

The ongoing process in island equilibrium where the identity of individual species changes continuously over time via new colonizations and extinctions while total species richness remains relatively constant.

Distance Effect (Island Biogeography)

The biogeographic pattern wherein islands located closer to a mainland source pool exhibit higher immigration rates and support higher equilibrium species richness than distant islands of equivalent size.

Area Effect (Island Biogeography)

The pattern wherein larger islands support larger populations and more varied habitats, leading to lower extinction rates and higher equilibrium species richness than smaller islands at equal distance.

Ecological Disharmony

The non-representative taxonomic composition of island biotas compared to mainland sources, characterized by an overrepresentation of good dispersers and an absence or scarcity of large predators.

Inbreeding Depression (Islands)

A decline in biological fitness and genetic diversity (e.g., loss of heterozygosity) in small island populations resulting from matings between close relatives, driving elevated extinction rates.

Tripartite Model of Island Biogeography

An extended island biogeography model that integrates three dynamic processes across geological timescales: immigration, extinction, and in situ speciation.

Endemism

The condition of an organism being strictly native and geographically restricted to a specific defined location, which commonly arises on large, isolated islands through long-term evolutionary speciation.

Mangrove Island Defaunation Experiment

Daniel Simberloff and E. O. Wilson's field experiment in the Florida Keys where red mangrove islands were enclosed in plastic scaffolding and defaunated to directly verify colonization rates and species equilibrium.

Krakatau Recolonization

The chronological re-establishment of plant life following the 1883 volcanic sterilization of Krakatau, characterized by an early surge in wind-dispersed species followed gradually by bird- and water-dispersed plants.

Connectance ($C$)

A food web metric representing the ratio of actual feeding links ($L$) to the maximum total number of possible links ($N$), expressed as $C = \frac{L}{N}$.

Total Number of Possible Links ($N$)

In food web connectance analysis for a community containing $n$ species, the total number of pairwise combinations calculated as $N = \frac{n(n - 1)}{2}$.

Lotka–Volterra Competition Equations

The paired differential equations modeling interspecific competition: $\frac{dN_1}{dt} = r_1N_1\frac{K_1 - N_1 - \alpha N_2}{K_1}$ and $\frac{dN_2}{dt} = r_2N_2\frac{K_2 - N_2 - \beta N_1}{K_2}$.

Competition Coefficient ($\alpha$)

The per capita inhibitory effect of individuals of species 2 on the population growth rate of species 1, where the total competitive impact of species 2 is given by $\alpha N_2$.

Latitudinal Niche Breadth

The ecological concept that niche breadths ($w$) are broad among temperate $r$-selected organisms experiencing seasonal variance, but narrow among tropical $K$-selected organisms experiencing consistent resource availability.

Minimum Viable Population (MVP)

The smallest isolated population size capable of surviving and persisting over a defined period despite demographic, environmental, and genetic stochasticity.

Minimum Viable Area (MVA)

The minimum territory or area of suitable ecological habitat necessary to sustain a minimum viable population of a species.

SLOSS Debate

A reserve design debate in conservation ecology evaluating whether biodiversity is better preserved by a 'Single Large Or Several Small' protected areas.

Facilitation (Ecological Succession)

A mechanism of ecological succession where pioneer or early seral species alter abiotic environmental conditions in ways that facilitate the establishment of later seral species.

Inhibition (Ecological Succession)

A mechanism in ecological succession where established species prevent or suppress the colonization and growth of other species, thereby prolonging a seral stage until disturbance occurs.