Chap. 9 from populations to communities

Chap. 9 from populations to communities

鄭先祐 (Ayo)國立臺南大學 環境與生態學院生物科技學系 生態學 (2008)

Essentials of Ecology 3rd. Ed.

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From populations to communitiesFrom populations to communities

• 9.1 introduction

• 9.2 multiple determinants of the dynamics of populations

• 9.3 dispersal, patches and metapopulation dynamics

• 9.4 temporal patterns in community composition ( 群落組成 )

• 9.5 food webs ( 食物網 )

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9.1 introduction9.1 introduction

• Fig. 9.1 community matrix illustrating how each species may interact with several others in competitive interactions, or between grazers, or between predators and predator-prey interactions.

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9.2 multiple determinants of the dynamics of populations

9.2 multiple determinants of the dynamics of populations

• Fig. 9.2 correlation between population growth rate and food availability

• (a) red kangaroo• (b) Barn owl

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• Fig. 9.2 correlation between population growth rate and food availability

• (c) wildebeest • (d) feral pig

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9.2 fluctuation or stability?9.2 fluctuation or stability?

• Fig. 9.3 (a) the population dynamics of Androsace septentrionalis during an 8-year study.

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• Fig. 9.3 (b) irregular irruptions in the abundance of house mice in an agricultural habitat in Victoria, Australia,

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9.2.2 determination and regulation of abundance

9.2.2 determination and regulation of abundance

• Abundance is determined, or regulated?– Regulated, density-dependent factors– Determined, density-independent factors

Fig. 9.4 (a) population regulation with

(i) density-independent birth and density-dependent death

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• Fig. 9.4 (b) population regulation with density-dependent birth, b and density-independent death, d.

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• Fig. 9.5 idealized diagrams of population dynamics: (a) dynamics dominated by phases of population growth after disasters

• (b) by limitations on environmental carrying capacity, where the carrying capacity is high.

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• (c) same as (b) but where the capacity is low

• (d) dynamics within a habitable site dominated by population decay after more or less sudden episodes of colonization or recruitment.

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9.2.3 key factor analysis9.2.3 key factor analysis

• K- value, killing power value

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9.2.3 key factor analysis9.2.3 key factor analysis

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• Fig. 9.6 (a) density-dependent emigration by Colorado beetle summer adults

• (b) density-dependent starvation of larvae.

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• Fig. 9.7 key factor analysis of the sand-dune annual plant.

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9.3 dispersal, patches and metapopulation dynamics9.3 dispersal, patches and metapopulation dynamics

• The theory of island biogeography, MacArthur and Wilson (1967)

• Metapopulation dynamics, Levins (1969)1. The dynamics of individuals within patches

2. The dynamics of the occupied patches themselves within the overall metapopulation

– The whole idea of metapopulation was largely neglected during the 20 years after Levin’s initial work.

– The 1990s, however, saw a great flowering of interest.

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• Fig. 9.9 the metapopulation dynamics of the American pika in Bodie, California (a) the relative positions and approximate sizes.

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• Fig. 9.10 two metapopulations of the silver-studded blue butterfly in North Wales.

• (a) in a limestone habitat, where there was large number of persistent ( 長久的 ) local populations among smaller, much more ephemeral ( 短暫的 ) local populations

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• (b) in a heath land habitat, where the proportion of smaller and ephemeral population was much greater.

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9.4 temporal patterns in community composition (群落組成 )

9.4 temporal patterns in community composition (群落組成 )

• 9.4.1 founder-and dominance-controlled

• 9.4.2 Community succession

• 9.4 Topical ECOncerns: conservation sometimes requires manipulation of a succession– A giant New Zealand insect, the weta Deinacrida

mahoenuiensis (Orthoptera)( 直翅目 ).

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9.4.1 Founder-controlled and dominance-controlled communities

9.4.1 Founder-controlled and dominance-controlled communities

• Founder controlled: when all species are good colonists and essentially equal competitors– Communities of tropical reef fish (Table 9.4)

• Dominance controlled, when some species are strongly superior competitively– Fig. 9.12 (hypothetical succession)

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Founder-controlled communitiesFounder-controlled communities

24Fig. 9.12 Hypothetical succession in a gap.Fig. 9.12 Hypothetical succession in a gap.

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9.4.2 community succession9.4.2 community succession

• Primary succession• Secondary succession

Fig. 9.13 seedling emergence from added seeds of species typical of different successional stages on dunes of four ages.

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Fig. 9.14 variation in the relative importance of six species during an old-field succession on the Loess Plateau in China.

Fig. 9.14 variation in the relative importance of six species during an old-field succession on the Loess Plateau in China.

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Add.

Table 9-1

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Fig. 8-3. Comparison of the energetics of ecosystem development in (A) forests.

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Fig. 8-3. Comparison of the energetics of ecosystem development in (B) microcosms.

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9.5 food webs9.5 food webs

• 9.5.1 indirect and direct effects– Fig. 9.17, a simple model– Trophic cascade (indirect effect)

• 9.5.2 population and community stability and food web structure– Keystones species

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• Fig. 9.17 三者間關係。• 若有三者，則可共存。• 倘若缺少 superpredator ，

prey 會 extinction.

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• Fig. 9.18 when birds are excluded from the intertidal community, barnacles increase in abundance at the expense of mussels ( 貽貝 ), and three limpet ( 帽貝 ) species show marked changes in density.

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• Top-down control?

• Bottom-up control?

• Why is the world greens?– Because top-down control predominates:

green plant biomass accumulates because predators keep herbivores in check.

– Or the world is prickly ( 多刺的 ) and tastes bad (Pimm, 1991)

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• Fig. 9.20 top-down control, but only with low productivity.

• (a) snail biomass

• (b) plant biomass

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• Fig. 9.20 top-down control, but only with low productivity.

• (a) snail biomass

• (b) plant biomass

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9.5.2 stability and food web structure9.5.2 stability and food web structure

• Keystone species, the removal of some strong interactors leads to significant changes spreading throughout the food web, we refer to these as keystone species.

• The characteristics of food web– Numbers of species they contain– The connectance of the web– The average interaction strength between

pairs of species

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Add Fig. 9-2 typical food web for a terrestrial ecosystem.

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• Fig. 9.22 • The relationships

between connectance and species richness.

• (a) a compilation from the literature of 40 food webs from terrestrial, freshwater and marine environments.

• (b) a compilation of 95 insect-dominated webs from various habitats.

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• Fig. 9.22 • The relationships

between connectance and species richness.

• (c) seasonal versions of a food web for a large pond in northern England, varying in species richness from 12 to 32.

• (d) food webs from swamps and streams in Costa Rica and Venezuela.

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Review questionsReview questions

1. What is meant by a ‘metapopulation’ and how does it differ from a simple ‘population’?

2. What are meant by bottom-up and top-down control? How is the importance of each likely to vary with the number of trophic levels in a community?

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