Glossary
Adaptive evolution : genetic changes in a population that confer
directional changes in a fitness-related trait. The direction of trait
evolution is determined by the new phenotypic optimum, whilst the
magnitude of change results from the strength of selection (genetic
variation and heritability).
Baldwin effect : a novel state of a trait that emerges/changes
via plastic mechanisms that is subsequently reinforced by genetic
mechanisms that stabilize the trait across generations.
Bogert effect : the effect of plasticity in masking genetic
variation from selection. Common examples include thermoregulatory
behaviours in ectotherms.
Breeder’s equation : can be used to quantify the expected
difference in mean trait value as the product of the heritability of the
trait (\(h^{2}\)) and the selection differential the trait is exposed to
(\(S\)): \(Z=\ h^{2}S\).
Critical rate of change : The maximum rate of environmental
change the population can handle. Exceeding this limit inevitably
results in a population decline towards extinction.
Environmental changes : a shift in abiotic (e.g., temperature
and precipitation) and/or biotic factors (e.g., predation risk and
community structure) that shifts the phenotypic optimum of a trait.
Environmental novelty : the degree to which biotic and abiotic
factors differ between present and past. This can be quantified by the
distance the phenotypic optimum has moved relative to the optimum in a
normal environment.
Lag load : the gap between the moving phenotypic optimum and the
mean trait value in the population.
Life history strategies : the suite of vital rate functions
(e.g., survival, growth, reproduction) and associated phenotypes (e.g.,
morphology, behaviour, offspring investment) that work together to
optimize the fitness of individuals and viability of populations over
time.
Moving optimum theory : a body of work showing that, at any
point in time, there is a phenotypic optimum that maximizes the fitness
of individuals. This optimum can change over time due to biotic and
abiotic factors. In turn, populations track the moving optimum, at a
certain lag, via plasticity and/or adaptive evolution.
Phenotypic lag : a gap between the moving phenotypic optimum and
the population mean trait.
Phenotypic optimum : the phenotype that maximizes fitness at a
point in time.
Phenotypic plasticity : environmentally induced changes
in an individual’s phenotype without changes in its genetic makeup.
Plasticity-first hypothesis : genetically based variation in
plasticity among individuals in a population responds to selection in a
novel environment. This initial variation in plasticity allows for the
population to persist when it would not have been able to do so if it
were plastic and then to respond to selection.
Rate of mean change : the direction and magnitude of differences
in average environmental values (e.g., temperature and precipitation)
over time.
Temporal autocorrelation : the correlation of terms in series
separated by a time interval. Degree of autocorrelation is often
described by the “colour of noise” where negative autocorrelation
yields blue noise, zero autocorrelation yields white noise and positive
autocorrelation yiels red noise.
Temporal refugia : a period of time where the
degree/number/duration of perturbations in the environment that
negatively affect fitness are reduced, allowing for intermittent rescues
in population size and structure.
Trait heritability : the proportion of trait variance that is a
consequence of additive genetic variance.
Transient dynamics : short-term fluctuations in population
size/structure that arise due to both (1) perturbations in the
strucuture and/or size of the population and (2) probabilistic events
(e.g., survival and reproduction) as the population approaches an
equilibrium.
Variability : the variance of an environmental variable (e.g.,
temperature and precipitation) value over time.
Vital rates : a component of fitness (e.g., survival, growth,
reproduction, stasis) that varies across the structured life-cycle of an
organism (i.e., age, stage, size).