Stano Pekár“Populační ekologie živočichů“
 dN
= Nr
dt
 a major sub-field of ecology which deals with
description and the dynamics of populations
within species, and the interactions of
populations with environmental factors
 expanding field (Price & Hunter 1995):
- populations 52 %, communities 9 %, ecosystems
10 %
 main focus on
- Demography = description of populations that
gave rise to Life-history theory
- Population 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 abundance
of Lynx and Lepus in
Canada
density independent factors, food supply, intraspecific competition,
interspecific competition, predators, parasites, diseases
1. Conservation biology
 World 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
requirements, threats and any specified management options
Saiga tatarica
critical: 50% probability of extinction within 5 years
endangered: 20% probability of extinction within
20 years
vulnerable: 10% probability of extinction within
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
that growers were burning their trees
 in winter 1888-1889 Rodolia cardinalis and Cryptochaetum were
introduced into California from Australia, growers took the initiative and
applied the natural enemies themselves
 by 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 was
evident within months
Rodolia cardinalis (Coccinellidae) eating
Icerya purchasi (Hemiptera)
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 Europe
 during 4 months the disease travelled from Denmark to the UK
 the population of common seals in the UK declined by about half
0
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14 16 18 20
week
no.ofdeadseals
observed
predicted Observed and predicted
epidemic curves for virus in
common seals in the UK
Grenfell et al. (1992)
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 + environment
= population system
population conditions
resources 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  Population
Stage structure
Age structure
Size structure
Sex ratio
Spatial distribution
Developmental stage
Age
Size
Sex
Territorial behaviour
Event – an identifiable change in a population
Process – a series of identical events
• rate of a process – number of events per unit time
Natality (birth rate)
Mortality (mortality rate)
Growth (growth rate)
Population increase (rate of increase)
Consumption (consumption rate)
Birth [inds]
Death [inds]
Increment [gram]
Increment [number]
Acquisition of food [gram]
ProcessEvent
 inherent characteristics of the
evironment (pH, salinity,
temperature, moisture, wind
speed, etc.)
 not modified by populations
 not consumed by population
 no feedback mechanisms
 do not regulate population
size
 limit population size
optimal
suboptimal
unfavourable
reproduction
growth
survival
performance
conditions
 any entity whose quantity is reduced (food, space, water,
minerals, oxygen, sun radiation, etc.)
 modified (reduced) by populations
 defended by individuals (interference competition)
 regulate population size
 non-renewable resources - space
Renewable 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 area
 number of individuals per unit of habitat (leaf, plant, host)
 sieving, sweeping, extraction, etc.
Relative
 number of individuals
 trapping, fishing, pooting
Capture-recapture method – for mobile individuals
 Assumptions:
- 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
- capture time must be short
Closed population
 population do not change over sampling period - no death,
births, immigration, emigration
Petersen-Lincoln estimator:
N .. number of individuals in population
a .. total number of marked individuals
r .. total number of recaptured marked individuals
n .. total number of individuals recaptured
For small populations Chapman (1951)
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Open population
 changes due to death, births, immigration, emigration
 at least 3 sampling periods
Stochastic Jolly-Seber method
Ni .. estimate of population on day i
ai .. number of marked individuals on day i
ni .. total number of individuals captured on day i
ri .. sum of marked and recaptured individuals on day i
Zi .. sum of marked individuals that were recaptured 2 and more
days after marking
Ri .. sum of recaptured individuals marked later than 1st day
i .. day of capture
j .. day of marking
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