and colonization, e.g. in an island context, the
sequence of interisland dispersal events.
pioneer species Early colonizing species within a
succession.
plate boundary The edge of one of the Earth’s
lithospheric plates: boundaries can be either
constructive (divergent), destructive (convergent),
or conservative.
Pleistocene The first epoch of the Quaternary
period, formally taken as beginning about 1.8 Ma
(although the climate cooling that marked the
period began perhaps as early as 2.5 Ma), which
ended about 11 500 years BP, with the transition to
the present Holoceneepoch.
Pliocene The final epoch of the Tertiary period,
spanning approximately 5.3 to 1.8 Ma.
pollination The transfer of pollen grains to a
receptive stigma, e.g. by wind or by pollinating ani-
mals.
polyphyletic group A taxonomic group compris-
ing several monophyletic groups.
population viability analyses (PVA) Population
analyses based on data for key demographic and
genetic parameters, which set out to assess the
probability that a population of a given size will
persist for a particular time period.
productivity rate The rate at which a community
of organisms manufactures new biomass.
propagule The minimal number of individuals of
a species capable of successfully colonizing a habit-
able island.
pseudoturnover In island ecological analyses,
species appearing to turn over (undergo extinction
and re-immigration) due to incomplete census
data, when they have actually been residents
throughout or, alternatively, never properly
colonized.
pyroclastic flow High-speed avalanche of hot ash
mobilized by expanding gases and travelling at
speeds in excess of 100 km/h.
Quaternary The most recent period of the geolog-
ical timescale, following the end of the Pliocene and
continuing to the present day; and comprising the
Pleistoceneand the Holoceneepochs.
radiation In evolutionary biology, a term for the
expansion of a group, implying that many new
species have been produced.
radiation zone The zone within an ocean, near
the effective dispersal limits of a higher taxon
(e.g. terrestrial mammals), where few lineages
colonize and where radiation in those lineages is
correspondingly greater as a consequence of the
‘empty niche space’ encountered.
red (data) book A catalogue listing species that
are rare or in danger of becoming extinct locally,
nationally or globally (e.g. the IUCN red data
books).
refugia Areas of survival of species during
adverse conditions, most notably during glaciation
episodes.
relictualism The possession by some islands of
palaeoendemic, i.e. relict taxa, which formerly had
a continental distribution, and which have gone
extinct from the source region since colonizing the
island, e.g. due to climatic or geological changes.
reproductive isolation Inability of individuals
from different populations to produce viable off-
spring.
rescue effect The prevention of extinction of a
small insular population by the occasional influx of
individuals from another (e.g. mainland) area.
Sahul Pleistocene continent constituted by
Australia, New Guinea, and Tasmania.
seamount A mountain beneath the sea (see also
guyot).
sexual selection Depends on the success of
certain individuals over others of the same sex, in
relation to the propagation of the species, and can
result in the evolution of character traits that carry
a fitness cost, and would otherwise not seem
advantageous.
shield volcanoes Wide volcanoes, of gradually
sloping sides, build up in layers by basaltic magma
flows erupting from lengthy fissures or vents.
sink population A term used in the metapopula-
tion literature for a population occupying an
unfavourable habitat, which maintains its presence
by supplementary immigration of offspring from
source populations.
SLOSS debate The debate as to which strategy is
the best for protected area systems: Single Large Or
Several Small reserves.
source population A population occupying a
favourable habitat and thus producing an excess of348 GLOSSARY