Glossary

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R

r selection
Selection of life-history traits which promote an ability to multiply rapidly in numbers - the traits being, broadly, small size, precocious reproduction, semelparity, a large reproductive allocation and the production of many but small offspring.
Radiative evolution
An evolutionary process that involves the branching of an evolutionary lineage and so leads to greater systematic diversity.
Ramet
An offshoot or module formed by vegetative growth in some plants and modular invertebrates that is actually or potentially independent physiologically, e.g. the runners of the strawberry, the tubers of the potato, the polyps on a colonial hydroid.
Random distribution
Lacking pattern or order. The result of (or indistinguishable from the consequence of) chance events.
Rank - abundance diagram
A graphical plot of differential abundances of species in a community.
Ranked preference
A preference exhibited by a consumer between food items all of which can be classified on the same simple scale (usually energy value).
Rarity
see Prevalence (of abundance) and Intensity of abundance.
Realized niche
That portion of its potential (fundamental) niche occupied by a species when competitors or predators are present.
Reciprocal predation
An interaction between two species (or individuals) in which each preys upon the other, so that the interaction is, in essence, competitive.
Recombination
The formation in offspring of combinations of genes not present in either parent. This results from the assortment of chromosomes and their genes during the production of gametes and the subsequent union of different sorts of gametes at fertilization.
Recruitment
Additions to a population, either through birth or immigration, or, in the case of net recruitment, the differences between such additions and the losses resulting from death or emigration.
Regression analysis
Analysis of the mathematical relationship between two variables.
Regular distribution
The arrangement of individuals with respect to each other which has some pattern or order that ensures that they are more widely separated from each other than would be expected by chance.
Regulation
see Population regulation.
Relative humidity
Very roughly, the dampness of the air; more correctly, the percentage saturation of the air with water vapor; better still, the mass of water vapor per unit volume of air as a percentage of the same measure for saturated air at the same temperature.
Relict population
An often very locally distributed residue from a large population that has declined.
Remoteness
In island biogeography, the distance an island is from a mainland source of colonizing organisms.
Reproduction
The production of new individuals, usually by sexual means, through the production of a zygote from which the new individual grows; though organisms that fall apart as they grow are often misleadingly said to undergo asexual reproduction.
Reproductive allocation
Strictly, the proportion of an organism's available resource input that is allocated to reproduction over a defined period of time; often in practice, the proportion of an organism's mass or volume that is reproductive tissue.
Reproductive cost
The decrease in survivorship and/or rate of growth, and hence the decrease in the potential for future reproduction, suffered by an individual as a result of increasing its current allocation to reproduction.
Reproductive isolation
The isolation from each other, in space or time, of two parts of a population of which the individuals would be capable of interbreeding were this not prevented by their isolation. Such isolation is believed to be normal precondition for the evolution of new species to occur, especially in animals.
Reproductive output
The production of offspring by an individual or population.
Reproductive rate
The number of offspring produced by an organism per unit time or over a defined period of time.
Reproductive value
The expected relative contribution of an individual to the population of its descendants, by reproduction, now and in the future.
Residual reproductive value (RRV)
The expected relative contribution of an individual to its population, by reproduction, for all stages of its life cycle subsequent to the present.
Resilience
The speed with which a community returns to its former state after it has been disturbed.
Resistance
The ability of a community to avoid displacement from its present state by a disturbance.
Resource
That which may be consumed by an organism and, as a result, becomes unavailable to another, e.g. food, water, nesting sites, etc.
Resource depletion zone
The region around a consumer in which the availability of a resource is reduced, e.g. the zone around the absorbing surface of a root from which nutrients and water are absorbed.
Resource partitioning
The differential use by organisms of resources such as food and space.
Respiration
Any or all of the processes used by organisms to generate metabolically usable energy.
Restoration ecology
The science concerned with the deliberate colonization and revegetation of derelict land, especially after major damage from activities such as mining and waste disposal and after land has been released from agricultural use.
Resurgence in pests
A rapid increase in pest number, after the immediate impact of a control measure has passed, resulting from adverse effects on the natural enemies of the pest.
Rhizosphere
The surface and immediate neighborhood of a root which provides a specialized environment for microorganisms. The term is also used to define the microflora that lives in this region.
Ring-barking
The removal of bark and the immediately underlying living tissues from a ring around the stem or trunk of a tree or shrub. This severs the route of transport of leaf products down to the roots.
Ruderal
A plant of waste places, usually associated with human disturbance. The word distinguishes this group of plants from 'weeds' which are plants that are a nuisance to human activities - the ruderal is not necessarily a nuisance.
Ruminant
Herbivorous mammals such as cows that chew the cud and have complex stomachs containing microorganisms that break down the cellulose in plant material.

 
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