lsm2251-06 populations ii
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LSM2251Ecology & the EnvironmentPopulations II
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Red JunglefowlGallus gallus
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PART II. POPULATION
DISTRIBUTION ANDABUNDANCE
(CONTD)
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Populations I
ContdII - Population distribution and abundance
[Molles 4/5th Edn - Chapter 9]
4. What is a population?
5. Environmental limits to species distribution
6. Distribution patterns7. Applications to conservation - rarity
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Popula t ion dis t r ibu t ion and abundance
6. Distribution patterns Regular, Random and clumped
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How are populations
distributed?Small scale and large scale
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6.1 Patterns on a small scale
Small-scale phenomenaSmall distances over which there is little environmental
change signicant to the population under study.
Distribution patterns inuenced by(i) interactions between individuals within a population
(attract, repel or ignore),
(ii) the structure of the physical environment(patchy nutrients, nesting, water source, etc)
(ii) or by a combination of both
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Think of the distribution of a bee species in a specic area,e.g. the Carpenter bee in Kent Ridge forested area, NUS
Distribution patternsSmall-scale patterns as a result of social interaction,
and the physical environment:Random, Regular and Clumped
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Distribution of tropical bee coloniesHubbell & Johnson (1977)
Fit prediction?
Physical environment was not limitingThere were more than enough potential nest sites
Aggressive beesWas the distribution regular or random?
Non-aggressive beesWas the distribution regular or random?
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Distribution of tropical bee coloniesHubbell & Johnson (1977)
Fit prediction!
Small-scalepatterns as a
result of socialinteraction
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6.2 Patterns on a large scaleLarge-scale phenomena
Areas over which there is substantial environmentalchange, inuencing the population under study,
e.g. across a continent.
Are there hot spots?(Conservation question)
Winter distribution of theAmerican crow, Corvus brachyrynchos
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Hotspot concept applied to all of biodiversity as a conservation strategy:
44% of vascular plants and 35% of four vertebrate groups are conned
to 25 hotspots comprising only 1.4% of the Earths land surface
Biodiversity hotspots for conservation priorities
Norman Myers, Russell A. Mittermeier, Cristina G. Mittermeier,Gustavo A. B. da Fonseca and Jennifer KentNature 403, 853-858(24 February 2000)
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Hots pot: Sundaland
http://www.conservation.org/explore/priority_areas/
hotspots/asia-pacic/Sundaland/Pages/default.aspx
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http://www.conservation.org/explore/priority_areas/hotspots/asia-pacific/Sundaland/Pages/default.aspxhttp://www.conservation.org/explore/priority_areas/hotspots/asia-pacific/Sundaland/Pages/default.aspxhttp://www.conservation.org/explore/priority_areas/hotspots/asia-pacific/Sundaland/Pages/default.aspxhttp://www.conservation.org/explore/priority_areas/hotspots/asia-pacific/Sundaland/Pages/default.aspxhttp://www.conservation.org/explore/priority_areas/hotspots/asia-pacific/Sundaland/Pages/default.aspx -
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Popula t ion size , adap t a t ion and dis t r ibu t ion
7. Applications to
conservationUnderstanding rarity
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Rabinowitzs seven forms of rarity
Combination of: geographic range:
extensive vs restricted habitat tolerance:
broad versus narrow population size:
small vs large
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Example of rarity: Tiger
Rarity: geographic range:
extensive habitat tolerance:
broad population size:
small
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Tiger distribution,
Malaysia (DWNP)
geographic range:extensive
habitat tolerance:broad population size:
small
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Example of rarity: Tasmanian Devil
Rarity: geographic range:
restricted habitat tolerance:
broad
population size:small
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Example of rarity: Mountain Gorilla
Rarity: geographic range:
restricted habitat tolerance:
narrow population size:
small
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Population distribution
data alone is insufcientCrisis affecting
Tasmanian devils willaffect species survival
status
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http://www.iucnredlist.org/
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Straw-headed bulbul(Pycnonotus zeylanicus)Widespread in Pulau Ubin
Global population estimate
10-20,000Population trend: decreasing
Distribution: Southeast AsiaStatus: Vulnerable.
The population is declining rapidlyacross its range due to high levels of
trapping for the cagebird trade,compounded by habitat loss within
their rather specic habitat type.
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Part III - Population dynamicsPart IV - Population Growth
Part V - Life History Classication
Populations II[Molles 4/5th Edn - Chapters 10-12]
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POPULATIONS PART III.POPULATION DYNAMICS
Populations are not static but dynamic.Factors affecting expansion, decline and
maintenance of populations
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Popula t ion D ynamics
8. Dispersal Dispersal into or out of populations.
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Dispersal
Dispersal into = increase ( immigration) ordispersal out of = decrease ( emigration)in a population
Adult, seed/larval populations may differ inmechanisms
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8.1 Dispersal of expanding populations- Eurasian collared dove
The expansion acrossEurope took place in
small jumps
Mating adults are mostly
sedentary
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8 1 Di l f di g l ti
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8.1 Dispersal of expanding populations- Eurasian collared dove
Comparison of rates
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8.2 Dispersal in response to
resource availability
Factors affecting
distribution Speed due to biology Prey supply
Kestrel & Owl density vs Voles
Voles populations uctuated
Predators moved around to ndprey populations
Synchronicity due to migration36
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9. Patterns of survival Estimating cohort survival
Popula t ion D ynamics
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Estimating life history Cohort life table: record birth to death - hard
work! Static life table: record death-ages of a large
number of individuals - estimation based onassumptions about age of dead individuals.Useful in species with seasonal growth spurts.
Age distribution: identify cohort sizes (i.e.assume no immigration, emigration, differencesin age classes due to death etc; may be a weak estimate)
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Life table
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How would youdescribe this
graph?
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2.2 Patterns of survival
Survival types: High survival amongst the young (die old) Constant rate of survival
High mortality amongst the young (die young)
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Constant rateof decline
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How would you describe this graph?
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High rate of survival inwhich age groups?
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Survivorship Types
Convex Constant Concave
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10. Age distributions History, rates, trends, predictions
Popula t ion D ynamics
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10.1 What can agestructure of a speciespopulation predict ?
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Does this populationhave long-term
viability?
What does the agestructure predict?
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What does this age structure show?
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What does this age structure show?
2. Observation -what is absent?
1. Observation - whatdominates?
3. Conclusion - what doesthis age structure suggest?
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Mandai mangrove, Singapore
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Mandai mangrove, Singapore
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M d i Si
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Mandai mangrove, Singapore
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Mandai mudats andhorseshoe crabs
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10.2 What can agestructure of a species
population reveal ?
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Grant & Grant (1989) - Galpagos Islands
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Grant & Grant (1989) - Galpagos Islands
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POPULATIONS PART
IV. POPULATIONGROWTH
Geometric and Exponential growth Exponential growth
Logistic curve
Limits
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Popula t ion Gr o w t h
12. Geometric and exponential growth
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12.1Geometric growth
Rate of increase = N 1/N 0 N2 = N1 x Rate of increase N3 = N2 x Rate of increase
= N1 x Rate of increase 2
Grow inpulses
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12.1Geometric growth
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12.2 Exponential growthassociated with colonisation
Continuous growth in anunlimited environment
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13. Logistic population
growth Resource limitation
Popula t ion Gr o w t h
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13. Logistic population
growth
i.e. Exponentialgrowth is limited!
As resources are depleted, population growth rate slows and eventually stops
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13.1 Logistic curve
Exponentialgrowth islimited!
Sigmoid or S-shaped curve of
resource-limited growth
Same curve forparamecium,
barnacle larvaesettlement,
buffalopopulationexamples
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What limits populations Barnacles - space on rocks for attachment African buffalo - disease, grass availability Yeast - availability of sugar in immediate
environment
Remember the Extinction game? Intraspecic competition [next lecture]
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13.2 Logistic
e uationdNdt =
r max N(1- NK
)
Describes the rateof increase of a
resource-limitedpopulation
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13.2 Logistic
e uationdNdt = r max N(1-
NK )
change inpopulation
number
changein time carryingcapacity
populationnumber
intrinsic
growthrate
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What happens to the
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ppcurve when N
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ppcurve when N ~~ K ?
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Human Growth Rate
Popula t ion Gr o w t h ?
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14. Limitations on
growth
Popula t ion Gr o w t h
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How does climate affectpopulations?
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Coupling of Red kangaroo(Macropus rufus )population levels to El Nio.
Drought/scarcity of foodconditions:
High mortality rate of
embryos/young. Reproductive rate drops or
cessation of breeding.
El Nio: global biological impacts- terrestrial ecosystems
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Malayan Sun Bear in Borneo
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The 1997/8 El Nino event resulted in a severeand prolonged haze which led to the local
extinction of g wasps. In the absence of pollinators g, trees aborted
their fruits in 1999 [Rhett Harrison, 2000].
Orang utans resorted to other food sourceslike young shoots and plant sap. Famine in Sabah and Kalimantan for frugivores.
Sun bears starve
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Sun bears and bearded pigs starved. Orang utans resorted to other food sources
like young shoots and plant sap. Wong Siew Te: all six radio-collared sun bears
were emaciated and two died.
This is suspected to be a reason for the verylow density of large animals in Borneanrainforests."
Sun bears starve
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Bearded pigs and Sun bears in Kalimantan
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and Sabah starved to death in 1999.
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POPULATIONS PART V.LIFE HISTORY
CLASSIFICATION
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15 Life History
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15. Life History
classication r and K selection: (MacArthur & Wilson,1967; Pianka, 1970; 1972)
r -selected : selection favouring a higherpopulation growth rate - colonists; type 3survivorship; small, fast (also many marineinvertebrates)
K-selected : organism living closer tocarrying capacity - competition; type 1 or 2survivorship; large, slow
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