salit kark the biodiversity research group department of evolution, systematics and ecology
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Conservation Biology (Ecology) Lecture 8 December 2009. Salit Kark The Biodiversity Research Group Department of Evolution, Systematics and Ecology The Silberman Institute of Life Sciences The Hebrew University of Jerusalem. A dispersal buffer: an isoline of dispersal probability. - PowerPoint PPT PresentationTRANSCRIPT
Salit Kark
The Biodiversity Research Group
Department of Evolution, Systematics and Ecology
The Silberman Institute of Life Sciences
The Hebrew University of Jerusalem
Conservation Biology (Ecology)
Lecture 8
December 2009
Dr. Salit Kark. The Hebrew University of Jerusalem
A. Patchy B. Classical
C. Nonequilibrium D. Mainland-Island
A dispersal buffer: an isoline of dispersal probability
A subpopulation
Metapopulation Types
Separate metapopulations
Dr. Salit Kark. The Hebrew University of Jerusalem
Patchy
Classical Mainland-Island
Mainland-Mainland
Nonequilibrium Disjunct
Highlyconnected
Pat
ch is
olat
ion
Highlyisolated
All small All large
Patch SizeDr. Salit Kark. The Hebrew University of Jerusalem
The case study of the Florida Scrub Jay
Dr. Salit Kark. The Hebrew University of Jerusalem
Aphelocoma coerulescens
Biology of the Florida Scrub Jay
Florida’s only endemic bird species
Juveniles disperse after one year
Cooperative breeding
The bird was listed as threatened
species in 1987 by the U.S. Fish and
Wildlife Service (USFWS)
Dr. Salit Kark. The Hebrew University of Jerusalem
Distribution of Florida scrub jay groups in 1993. Note the discontinuous distribution and variability in patterns of aggregation
Dr. Salit Kark. The Hebrew University of Jerusalem
Statewide jay distribution with dispersal buffers. Shaded areas depict subpopulations within easy dispersal distance (3.5 km) of one another (191 separate subpopulations). Thick outer lines delineate demographically independent (42 metapopulations) separated from each other by at least 12 km
3.5 km
12 km
A subpopulation
A metapopulation
Dr. Salit Kark. The Hebrew University of Jerusalem
Dispersal Distance (km)
Fre
quen
cy
From natal to breeding territories 1970-1993
3.5 km
85%
97%
6.7 km
Accumulative
A subpopulation buffer is the distance where occupancy rates remain high
Dr. Salit Kark. The Hebrew University of Jerusalem
North Gulf Coast of Florida: each of the 6 metapopulations contains fewer than 10 pairs of jays, except for the centrally located system that contains a single, midland-sized subpopulation
Examples of Nonequilibrium metapopulations
3.5 km
12 km
Dr. Salit Kark. The Hebrew University of Jerusalem
Examples of a “classical” metapopulation from 3 counties in central Florida. Note the occurrence of jays in small islands of intermediate distance from one another.
Dr. Salit Kark. The Hebrew University of Jerusalem
Portion of the largest mainland-midland-island metpopulation in interior Florida.
The large central subpopulation (enclosed by the thin black line) contains nearly 800 pairs of jays. Small subpopulations to the south and east are within known dispersal distance of the large, central mainland. A small metapopulation to the west (in DeSoto County) contains a single subpopulation of 21 territories.
Dr. Salit Kark. The Hebrew University of Jerusalem
Statewide jay distribution with dispersal buffers. Shaded areas depict subpopulations within easy dispersal distance (3.5 km) of one another (191 separate subpopulations). Thick outer lines delineate demographically independent (42 metapopulations) separated from each other by at least 12 km
3.5 km
12 km
A subpopulation
A metapopulation
Dr. Salit Kark. The Hebrew University of Jerusalem
Subpopulation Size (# of birds)
Fre
quen
cy
Numbers above the bars indicate the number of subpopulations
Only Six subpopulations >
100 birds
Total 191 subpopulations
Dr. Salit Kark. The Hebrew University of Jerusalem
Metapopulation Size
Fre
quen
cy
Nonequilibrium metapopulations
Total 42 metapopulations
Dr. Salit Kark. The Hebrew University of Jerusalem
PVA Model
Biology of Individuals
Environmental Factors
Population Dynamics
(demography)
Population Survival or Extinction
PVA Model
Biology of Individuals
Environmental Factors
Population Dynamics
(demography)
Extinction
Environmental disturbance
--Growth--Population (n)--Distribution
Genetic effective P size
Demographic uncertainty
Extinction
(Deterministic)
Extinction resulting from some inexorable change or force from which there is no escape.
Such as the effect of:
Glaciations
Deforestation, divergence of river
Deterministic extinction:
PVA Model
Biology of Individuals
Environmental Factors
Population Dynamics
(demography)
Extinction
Major loss of habitat
Fragmentation
-- Population size
-- Distribution
Extinction
(Deterministic)
Demographic randomness
PVA is the study of how the main demographic factors interact to determine extinction probability of a population and to estimate MVP.
Population Viability Analysis (PVA)
MVP - Minimum Viable Population imply some thresholds for the number of individuals that will insure (at some acceptable level of risk) that a population will persist in a viable state for a given interval of time
Approaches to PVA
Count-based PVAUses census dataAssumes all individuals identical
Demographic PVAIncorporates information about vital ratesvital rates: probabilities of survival and reproduction Can include population structure
Spatially explicit PVAIncorporates migration and colonization
Approaches to PVACount Demographic Spatial
Biological realism
Data requirements
Bias
Precision
Precision—the closeness of agreement among test results obtained under prescribed conditions.
Bias—a systematic error that contributes to the difference between the mean of a large number of test results and an accepted reference value;
U.S. Endangered Species Act (1973) codifies in law a national policy of avoiding the extinction of species
U.S. National Forest Management Act (1976)
“[f]ish and wildlife habitat shall be managed to maintain viable populations of existing native and desired nonnative vertebrate species in the planning area…In order to insure that viable populations will be maintained, habitat must be provided to support at least a minimum number of reproductive individuals and the habitat must be well distributed so that those individuals can interact with others in the planning area”
Why run population “viability”analysis?
Demographic Stochasticity - Random Demographic Variation
Arises because, at any time, individuals of a given age or developmental stage have probabilities of survival and reproduction, called vital rates.
Assuming that these apply independently to each individual, demographic stochasticity produces sampling variances of the vital rates inversely proportional to population size
In any real population, individuals don’t usually produce
the average number of offspring. They usually have
more than the average, fewer than the average, or have
no offspring
As long as the population size is large the average
provides a rather good description of the population
But, once the population size drops below a certain size
(say 50 individuals), individual variation in birth and
death rates begin to cause the population size to fluctuate
randomly up and down
If population size fluctuates downward, then the resulting smaller population will be even more susceptible to demographic fluctuations in the next generation, possibly resulting in extinction
Population Size
Sampling Variance
In contrast to demographic stochasticity, Environmental Stochasticity is represented by temporal changes in the vital rates that affect all individuals of a given age or stage similarly.
The sampling variances of the vital rates are then nearly independent of population size
vital rates: probabilities of survival and reproduction
Some Real World Examples:
One of the best documented cases where demographic stochasticity likely played a role, comes from a study of the persistence of 120 bighorn sheep populations followed for up to 70 years in the US southwest
Berger, J. 1990. Persistence of different-sized populations: an empirical assessment of rapid extinctions in bighorn sheep. Conservation Biology 4:91-98
All the populations with fewer than 50 individuals went extinct within 50 years
n of 50-100 is a threshold
0
20
40
60
80
100
120
10 20 30 40 50 TIME (YEARS)
% OF POPULATIONS PERSISTING
N=101+
51-100
31-501-15
16-30
Population size
Extinction rates of birds on Channel Islands as a function of population size over an 80-year period
0
30
60
1 10 100 1000 10,000**
***
*
10 breeding pairs – 39% went extinct10-100 pairs – 10% went extinct1000>pairs – none went extinct
*
Population Size (no. pairs)
% Extinction
Jones, L. and J. Diamond. 1976. Short-term base studies of turnover in breeding bird populations on the California Channel Islands. Condor 78:526-549.
* - extinction rate of all species
in a given population size
class
PVA requires lots of data, which takes time, work, and money, whereas managers want answers (predictions on extinction) now.
Few species will get thorough PVA.
When should PVA be used and what type of PVA (how complex)?
Predictions from PVA can only be as good as the data that go into the analysis. We can only have probabilities in the predictions from PVA.
Populations should not be managed to their “minimum viable population”size. One of the greatest strengths of PVA is the ability to play “what if”games with the model.
Some thoughts on PVASome thoughts on PVA
How do we decide what to conserve?
Setting conservation priorities
לפי מינים
Species based
Setting conservation priorities
קביעת סדרי עדיפויות לשימור
לפי אזורים
Area based
לפי מינים
קביעת סדרי עדיפויות לשימור
מעמד
סיכון
נדירותאנדמיות
פוטנציאל אבולוציוני
שירותים
קצב הכחדהפגיעות בית הגידול
אטרקטיביות
(ניצול ע"י האדם)
תפקיד במערכת
אסטרטגיות: דגל, מטריה, אינדיקאטור,
מפתח
Species based
Setting conservation priorities
Status
risk
rarityendemism
evolutionary potential
services
Decline rateHabitat
vulnerabilityAttractiveness
(human exploitation)
Role in ecosystem
Strategies: flagship, umbrella, indicator, keystone
Strategies: focal species
flagship, umbrella, indicator, keystone
Focusing on important species may provide short cuts to more successful conservation
Flagship sp: charismatic, public appeal and awareness
Umbrella sp: species providing “shelter” for many others, large and diverse area required
Indicator sp: environmental change, other groups
Keystone sp: predominating ecological role in community and ecosystem functioning
Conservation statusIUCN = The World Conservation Union is the world’s largest
and probably most important conservation network.
The Union brings together 82 States, 111 government agencies, more than 800 non-governmental organizations (NGOs), and some 10,000 scientists and experts from 181 countries in a unique worldwide partnership.
The Union’s mission is to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable.
Conservation statusIUCN Species Survival Commission (SSU)
– Provide conservation status in IUCN red list of threatened species
– Updated yearly
http://www.redlist.org/info/categories_criteria2001.html
to provide a system that can be applied consistently by different people;
to improve objectivity by providing users with clear guidance on how to evaluate different factors which affect the risk of extinction;
to provide a system which will facilitate comparisons across widely different taxa;
to give people using threatened species lists a better understanding of how individual species were classified.
The IUCN Red List Categories & Criteria have several specific aims:
The criteria can be applied to any taxonomic unit at or below the species level
Category in IUCN redlist EXTINCT (EX) no reasonable doubt that the last individual has died
when exhaustive surveys have failed to record an individual EXTINCT IN THE WILD (EW) known only to survive in captivity CRITICALLY ENDANGERED (CR) facing an extremely high
risk of extinction in the wild ENDANGERED (EN) VULNERABLE (VU) NEAR THREATENED (NT) does not qualify for CE or E, but is
close to qualifying in the near future LEAST CONCERN (LC) Widespread and abundant taxa are
included in this category