LSM2251-06 Populations II

8/3/2019 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


restricted habitat tolerance:

broad

population size:small

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Example of rarity: Mountain Gorilla


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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http://www.iucnredlist.org/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 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


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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


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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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M d i Si


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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


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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


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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

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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Documents

LSM2251-06 Populations II