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In which scenario does mark-recapture fail?

High mortality between marking and recapture violates the closure and equal-survival assumptions of the simple Lincoln–Petersen estimator. If marked individuals die disproportionately or many die before mixing, the number of marked recaptures R falls. Because N is estimated as MC/R, an artificially small R inflates the population estimate. Even equal mortality among marked and unmarked animals can undermine the interpretation if population size changes substantially during the interval. A closed population, uniform mixing, and equal marking or capture probabilities support rather than defeat t

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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If dispersion pattern is random, variance:mean ratio is:

Independent random placement of organisms is commonly modeled by a Poisson distribution. A defining property of the Poisson distribution is equality of its mean and variance, so the variance-to-mean ratio is expected to be 1. Values substantially below 1 indicate underdispersion or uniform spacing, because counts vary less than chance predicts. Values above 1 indicate overdispersion or clumping, because some units contain aggregations while others are nearly empty. An observed ratio will rarely equal exactly 1 in a finite sample; statistical tests evaluate whether the departure is greater than

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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High variance in population densities suggests:

A high variance among equal-area counts relative to their mean indicates that individuals are concentrated unevenly across space. Clumped populations produce many quadrats with few or no individuals and a smaller number with very high counts, inflating variance above the Poisson random expectation. The variance-to-mean ratio therefore exceeds 1 under aggregation. Uniform dispersion gives unusually similar counts and a ratio below 1, while random dispersion gives a ratio near 1. “High variance” should ideally be interpreted relative to the mean rather than in isolation, because variance natural

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Which parameter is NOT needed for mark-recapture estimation?

The Lincoln–Petersen estimate requires three counts: M, the number initially marked and released; C, the total number captured on the second occasion; and R, the marked individuals found within that second capture. The number unmarked in the second sample is C − R, so it is not mathematically independent but can help determine C when only marked and unmarked counts are recorded. Population sex ratio is unnecessary for the basic estimator because the marked proportion, not sex composition, drives N ≈ MC/R. Sex ratio becomes relevant only if capture probabilities differ by sex, sampling targets

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Deme is defined as:

A deme is a local interbreeding population: individuals share a geographic area and constitute a reproductive community with appreciable random mating relative to individuals outside the group. In population genetics, the idealized deme is often treated as panmictic, meaning mating is random with respect to genotype within that local unit. This permits allele-frequency models such as Hardy–Weinberg expectations to be applied, while migration connects different demes. Real demes may deviate from perfect random mating because of inbreeding, assortative mating, social structure, or spatial subdiv

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Recolonization of a previously extinct patch is an example of:

The rescue effect and recolonization are related but distinct. Rescue occurs when immigrants enter a patch that is still occupied and prevent its local population from going extinct. Recolonization occurs after extinction, when dispersers establish a new population in an empty patch. Therefore, the wording “recolonization of a previously extinct patch” describes colonization following local extinction, not rescue in its strict ecological meaning. Movement of colonists is migration or dispersal, making that listed alternative closer to the mechanism, although “recolonization” itself would be th

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Which sampling method assumes closed population?

The simplest two-sample Lincoln–Petersen mark–recapture model assumes demographic and geographic closure between sampling occasions. No births, deaths, immigration, or emigration should change the population or alter the proportion of marked individuals. Under closure, the marked fraction after thorough mixing remains interpretable, allowing M/N ≈ R/C and N ≈ MC/R. Quadrat and transect methods sample spatial units and do not inherently require a closed population in the same formal sense, although movement during counting can still create error. Satellite methods track individuals and may expl

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Which factor contributes most to clumped distribution?

Social warning systems can favor group formation because individuals gain information about approaching predators from nearby conspecifics. Alarm calls, collective vigilance, and dilution of individual risk make aggregation beneficial, producing clumped dispersion. A group may detect threats sooner than a solitary organism, while each member can spend less time scanning and more time feeding. Such behavioral attraction yields patches of high abundance separated by unoccupied space and often a variance-to-mean ratio above 1. Allelopathy creates local inhibition and is more likely to generate un

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Dispersion pattern determined by neutral interactions is:

Random dispersion arises when individuals are positioned independently at the scale of observation, with neither strong attraction nor strong repulsion among neighbors. This can occur when resources are relatively homogeneous, propagules disperse without directional bias, and interactions among individuals are weak or neutral. Quadrat counts then approximate a Poisson distribution, whose variance equals its mean. Uniform dispersion instead reflects negative interactions such as territoriality, competition, or allelopathy, while clumped dispersion reflects attraction, limited dispersal, social

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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Which estimate method uses nested grids for sampling immobile species?

Quadrat sampling estimates abundance or density by placing frames or grid cells of known area and counting organisms within them. It is especially appropriate for immobile or slow-moving species such as plants, corals, barnacles, and many soil organisms because individuals remain associated with a sampling unit during observation. Nested quadrats place progressively larger frames around the same point or subdivide a larger grid, allowing investigators to examine species–area relationships, choose an efficient quadrat size, or measure pattern at multiple scales. A line transect records organism

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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The term 'metapopulation' was coined by:

Richard Levins introduced the term and formal concept of a metapopulation in the late 1960s while developing models of populations occupying temporary habitat patches. His classic formulation tracked the fraction of suitable patches occupied, balancing colonization of empty patches against extinction of occupied ones. This abstraction showed how a species could persist regionally even when individual local populations repeatedly vanished. Robert MacArthur and E. O. Wilson developed island biogeography, a closely related theory balancing immigration and extinction in island species richness, bu

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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The 'rescue effect' refers to:

The rescue effect occurs when immigrants enter a small, declining local population and reduce its probability of extinction. New arrivals add individuals directly, can increase reproduction by supplying mates, and may restore genetic variation or reduce inbreeding. The patch remains occupied throughout; immigration “rescues” it before abundance reaches zero. This differs from recolonization, which establishes a population in a patch after local extinction has already occurred. In metapopulation models, both processes depend on connectivity, but they affect occupancy in different ways: rescue l

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9

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