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Communities, ecosystems, and landscapes: Species Interactions.

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Presentation on theme: "Communities, ecosystems, and landscapes: Species Interactions."— Presentation transcript:

1 Communities, ecosystems, and landscapes: Species Interactions

2 Farming/Settlement Pine Spruce-Fir YBirchHeath Bald Old-growth Hemlock-hardwoods Oak

3 The Goldilocks problem Not too hot, not too cold, but just rightNot too hot, not too cold, but just right Species have ranges of tolerance and optima for given environmental parametersSpecies have ranges of tolerance and optima for given environmental parameters Species tend to have different set pointsSpecies tend to have different set points A particular change in the environment or conservation strategy will be good for some species and bad for othersA particular change in the environment or conservation strategy will be good for some species and bad for others

4 Pure Effects of Diversity: Niche division, Niche overlap ComplementarityComplementarity RedundancyRedundancy

5 Hemlock Beech Tuliptree

6 Then now is the chance for flowers That can’t stand mowers and plowers. It must be now, though, in season Before the not mowing brings trees on, …The trees are all I’m afraid of, That flowers can’t bloom in the shade of… The Last Mowing, 1928

7 Intermediate Disturbance Hypothesis Succession to trees that flowers can’t bloom in the shade of Can’t stand mowers and plowers Most flowers

8 Intermediate Disturbance Hypothesis Succession to trees that flowers can’t bloom in the shade of Can’t stand mowers and plowers Most flowers

9 Species response to a given disturbance IncreasersIncreasers DecreasersDecreasers InvadersInvaders RetreatersRetreaters IntegratorsIntegrators The challenge to management!

10 -0+ -CompetitionAmensalismPredationherbivoryparasitismallelopathy 0AmensalismNeutralismCommensalism +PredationherbivoryparasitismallelopathyCommensalismMutualism Types of interactions

11 Figure 8.6

12 Ficus carica – Edible Fig

13 So, naturalists observe, a flea hath smaller fleas that on him prey, and these have smaller fleas to bite ‘em, and so proceed, ad infinitum. --Jonathan Swift

14 Trophic Structure: Cascading effects “Just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer.” Aldo Leopold, Think like a mountain The enemy of my enemy is my friend… predators as the friend of plants

15 Hairston, Smith and Slobodkin (1960) ‘HSS model’ Why is the world green? 1. Decomposers are limited by their food (otherwise fossil fuels would build up (otherwise fossil fuels would build up quickly) quickly) 2. Plants are limited by their resources (as they are not all eaten up by the (as they are not all eaten up by the herbivores) herbivores)

16 Herbivores are not limited by their 3. Herbivores are not limited by their food (because they are only seen to food (because they are only seen to eat all their food plants when, rarely, eat all their food plants when, rarely, they are ‘protected’ by ‘human’ or they are ‘protected’ by ‘human’ or ‘natural events’). Therefore, herbivores ‘natural events’). Therefore, herbivores are limited by predators. are limited by predators. 4. Carnivores are limited by their food (since predators are controlling prey, (since predators are controlling prey, they must be limited by prey). they must be limited by prey).

17 HSSFretwell-Oksanen (1981) carnivores (3 o ) herbivores (2 o ) primary producers (1 o ) PRODUCTIVITY low medium high 1 o 1 o 1 o 2 o 3o3o Hairston NG, Smith FE, Slobodkin LD (1960) Community structure poplation control and competition. American Naturalist 94: Oksanen L, Fretwell SD, Arruda J, Niemela P (1981) Exploitation ecosystems in gradients of primary productivity. AmNat 118:

18 HSSFretwell-Oksanen (1981) carnivores (3 o ) herbivores (2 o ) primary producers (1 o ) PRODUCTIVITY low medium high 1 o 1 o 1 o 2 o 3o3o Hairston NG, Smith FE, Slobodkin LD (1960) Community structure poplation control and competition. American Naturalist 94: Oksanen L, Fretwell SD, Arruda J, Niemela P (1981) Exploitation ecosystems in gradients of primary productivity. AmNat 118:

19 Chemical defense in plants is big business Popular drugs & spices: Nicotine, caffeine, capsasins Spices more abundant in tropical cultures Addictive drugs morphine, coca, marijuana Medicinal drugs Taxus bark; aspirin; penicillin Changes in metabolism of predators

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21 Are the estimates accurate? Did the deer population irrupt? Was it reduction in predators or hunting (top down control)? Was it reduction in livestock use in the late 1800s, thus reduced competition for food (bottom up control)? When the deer population crashed: Was it overgrazing? Was K reduced?

22 Binckley et al Was Leopold right about the Kaibob deer herd? Ecosystems 9: The deer herd did irrupt from late 1910s through 1920s, though numbers impreciseThe deer herd did irrupt from late 1910s through 1920s, though numbers imprecise The early phase of this, at least, was coincident with increased livestock, so reduction in livestock competition not a viable explanationThe early phase of this, at least, was coincident with increased livestock, so reduction in livestock competition not a viable explanation Livestock reductions in fine fuels probably underlie reduction in surface fires leading to increase in aspen, the preferred deer food, which supported an increase in deer; but later changes in deer and aspen are unrelated to fire (fire absent)Livestock reductions in fine fuels probably underlie reduction in surface fires leading to increase in aspen, the preferred deer food, which supported an increase in deer; but later changes in deer and aspen are unrelated to fire (fire absent) When deer populations were high, food sources were drastically reduced, a change correlated with deer but not climateWhen deer populations were high, food sources were drastically reduced, a change correlated with deer but not climate No evidence of reduction in deer K, recovery rapid as deer population fellNo evidence of reduction in deer K, recovery rapid as deer population fell The two major irruptions of deer followed periods of reduced predation and/or reduced huntingThe two major irruptions of deer followed periods of reduced predation and/or reduced hunting Deer population under top down control when small, bottom up control when largeDeer population under top down control when small, bottom up control when large

23 Lake Guri: Terborgh & collaborators 2001, 2006

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25 Small islandsSmall islands –<15 ha IncreasedIncreased –Iguanas –Howler Monkeys –Leaf-cutter ants –Diet broadened DecreasedDecreased –Pumas, jaguars, anacondas, eagles… –Saplings

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