Log-normal distributionFrequency distribution of species abundances in which the
x-axis is expressed as a logarithmic scale; x-axis is (log) number of individuals
represented in the sample, y-axis is number of species.MacroparasitesParasiteswhich in general do not multiply within their definitive hosts
but instead produce transmission stages (eggs and larvae) that pass into the exter-
nal environment or to vectors(i.e. the parasitic helminthsand arthropods). The
immune response elicited by these metazoans generally depends on the number
of parasites present in a given host, and tends to be of a relatively transient nature.
Maximum sustained yield (MSY)The greatest sustainable rate at which individuals
may be harvested from a population without causing a decline to extinction; that
is, the harvest at which recruitment equals harvesting.
MesicReferring to habitats with plentiful rainfall and well-drained soils. (Cf. xeric.)
MetapopulationA set of local populations linked together through dispersal.
MicroparasitesParasitesthat undergo direct multiplication within their definitive hosts
(e.g. viruses, rickettsia, bacteria, fungi, and protozoa). Microparasites are charac-
terized by small size, short generation times, and a tendency to induce immunity
to reinfection in those hosts that survive the primary infection. Duration of infec-
tion is usually short in relation to the expected life span of the host (there are,
however, important exceptions, e.g. the slow viruses).
Mineral nutrientsElements such as nitrogen, phosphorus, sulfur, potassium, calcium,
and others that are necessary for the growth and development of plants.
Minimum viable population (MVP)The smallest population that can persist for some
arbitrarily long time, usually 1000 years.
Mortality (mx)Ratio of the number of deaths to individuals at risk, often described
as a function of age (x). (Cf. death rate.)
Multiple statesCommunities can exist in different combinations of species abun-
dances under the same environmental conditions. These multiple states within an
ecosystem are detected when a perturbation radically alters the abundance of many
species in the community, which then do not return to their original abundance
when the perturbation is removed.
MutationAny change in the genotype of an organism occurring at the gene, chro-
mosome, or genome level; usually applied to changes in genes to new allelic forms.
MutualismA relationship between two species that benefits both.Natal dispersalDispersal of young animals from their place of birth.
Natural selectionChange in the frequency of genetic traits in a population through
differential survival and reproduction of individuals bearing those traits.
Net productionProduction after respiration losses are subtracted.
Net reproductive rate (Re)The expected number of offspring produced by a female
during her lifetime.
NicheThe set of resources and environmental conditions that allow a single species
to persist in a particular region, often conceived as a multidimensional space. Also
called fundamental niche. (Cf. realized niche.)
Niche breadthThe variety of resources utilized and range of conditions tolerated by
an individual, population, or species. (Cf. niche width.)
Niche complementarityA situation in which species that overlap extensively in their
use of one resource differ substantially in their use of another resource.396 GLOSSARY
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