dN
N= Nr
dt
Stano Pekár“Populační ekologie živočichů“
a major sub-field of ecology which deals with
description and the dynamics of populations
within species, and the interactions of
populations with environmental factorsp p
expanding field (Price & Hunter 1995):
- populations 52 %, communities 9 %, ecosystemsp p , , y
10 %
main focus on
- Demography = description of populations that
gave rise to Life-history theory
- Population dynamics = describe the change inPopulation dynamics describe the change in
the numbers of individuals in a population
populations of member species may show a range of dynamic patterns
in time and space
central question: “WHAT DOES REGULATE POPULATIONS?“
Change in abundanceg
of Lynx and Lepus in
Canada
density independent factors food supply intraspecific competitiondensity independent factors, food supply, intraspecific competition,
interspecific competition, predators, parasites, diseases
1. Conservation biology
World Conservation Union (IUCN) uses several criterions (populationWorld Conservation Union (IUCN) uses several criterions (population
size, generation length, population decline, fragmentation, fluctuation) to
assess species status
by means of Population viability analysis (PVA) estimates the
extinction probability of a taxon based on known life history, habitat
i t th t d ifi d t tirequirements, threats and any specified management options
critical: 50% probability of extinction within 5 yearsp y y
endangered: 20% probability of extinction within
2020 years
vulnerable: 10% probability of extinction within
Saiga tatarica
100 years
2. Biological control
to assess ability of a natural enemy to control
a pest
in 1880 Icerya purchasi was causing
infestations so severe in California citrus groves
h b i h i
Rodolia cardinalis (Coccinellidae) eating
Icerya purchasi (Hemiptera)
that growers were burning their trees
in winter 1888-1889 Rodolia cardinalis and Cryptochaetum were
i t d d i t C lif i f A t li t k th i iti ti dintroduced into California from Australia, growers took the initiative and
applied the natural enemies themselves
by fall 1889 the pest was completely controlledby fall 1889 the pest was completely controlled
Rodolia cardinalis has been exported to many other parts of the world
the interest of growers and the public in this project was due to its
spectacular success: the pest itself was showy and its damage was obvious
and critical; the destruction of the pest and the recovery of the trees wasand critical; the destruction of the pest and the recovery of the trees was
evident within months
3. Epidemiology
to predict the diffusion of a disease and to plan a vaccination
phocine distemper virus was identified in 1988 and caused death of
18 000 common seals in Europe18 000 common seals in Europe
during 4 months the disease travelled from Denmark to the UK
the population of common seals in the UK declined by about half
400
b d
Grenfell et al. (1992)
250
300
350
eals
observed
predicted Observed and predicted
epidemic curves for virus in
common seals in the UK
150
200
no.ofdeadse
0
50
100
0
0 2 4 6 8 10 12 14 16 18 20
week
4. Harvesting
to predict maximum sustainable harvest in fisheries and forestry but
also used to regulate whale or elephant hunting
when population is growing most rapidly (K/2) then part of population
can be harvested without causing extinction
Beddington (1979)
Relationship between capture
and fishing effort
Panulirus cygnus
Population + environmentPopulation + environment
= population systemp p y
population conditions
resources enemiesresources enemies
molecules → organels → cells → tissues → organs → organ
systems → organisms → populations → communities →
ecosystem → landscape → biosphere
a group of organisms of the same species that occupies a
particular area at the same time and is characterised by an
average characteristic (e.g., mortality)
characteristics:
Individual → PopulationIndividual → Population
Stage structure
A t t
Developmental stage
A Age structure
Size structure
Sex ratio
Age
Size
Sex Sex ratio
Spatial distribution
Sex
Territorial behaviour
Event – an identifiable change in a population
P i f id ti l tProcess – a series of identical events
• rate of a process – number of events per unit time
PE t
Natality (birth rate)Birth [inds]
ProcessEvent
Mortality (mortality rate)
Growth (growth rate)
P l ti i ( t f i )
Death [inds]
Increment [gram]
I t [ b ] Population increase (rate of increase)
Consumption (consumption rate)
Increment [number]
Acquisition of food [gram]
inherent characteristics of the
evironment (pH, salinity,
temperature, moisture, wind
speed, etc.)
reproduction
nce
speed, etc.)
not modified by populations
t d b l ti growth
erforman
not consumed by population
⇒ no feedback mechanisms
⇒ do not regulate population
growth
survival
pe
g p p
size
limit population size
optimal
suboptimal
survival
unfavourable
conditionsconditions
any entity whose quantity is reduced (food, space, water,
minerals oxygen sun radiation etc )minerals, oxygen, sun radiation, etc.)
modified (reduced) by populations
d f d d b i di id l (i f i i )defended by individuals (interference competition)
regulate population size
non-renewable resources - space
Renewable resourcesRenewable resources
- regeneration centre outside the population system ⇒ no effect of
the consumer (e.g., oxygen, water)
- regeneration centre inside of the population system ⇒ influenced
by the consumer (e.g., prey)
competitors, predators, parasites, pathogens
negative effect on the population
top-down regulation of the population
Absolute
number of individuals per unit areap
number of individuals per unit of habitat (leaf, plant, host)
sieving, sweeping, extraction, etc.
Relative
number of individualsnumber of individuals
trapping, fishing, pooting
Capture-recapture method – for mobile individuals
Assumptions:
k d i di id l ff d d k ill b l- marked individuals are not affected and marks will not be lost
- marked animals become mixed in the population
- all individuals have same probability of capture- all individuals have same probability of capture
- capture time must be short
Closed populationClosed population
population do not change over sampling period - no death,
births, immigration, emigrationbirths, immigration, emigration
Petersen-Lincoln estimator:
N .. number of individuals in population
a .. total number of marked individuals
r total number of recaptured marked individualsr .. total number of recaptured marked individuals
n .. total number of individuals recaptured
an
N = 3
2
)( rnna
SD
−
=Variance:
r
3
r
Open population
h d d h bi h i i i i ichanges due to death, births, immigration, emigration
at least 3 sampling periods
Stochastic Jolly-Seber method
Ni .. estimate of population on day ii p p y
ai .. number of marked individuals on day i
ni .. total number of individuals captured on day i
f k d i di id l d d iri .. sum of marked individuals recaptured on day i
Zi .. sum of marked individuals that were captured only on later days
R sum of marked individuals that were later recapturedRi .. sum of marked individuals that were later recaptured
i .. day of capture
j .. day of marking
∑∑
−n i
Z
1
i
ii
i r
R
Za
M +=ii
i
nM
N = where
∑
−1i
∑∑+= =
=
ik j
kji rZ
1 1
∑
n
i
i
i
R
i
i
r
N w e e
∑=
=
1j
iji rr∑+=
=
ik
kii rR
1