Terrestrial Ecology

1
Terrestrial Ecology

• Introduction to ecology
• Competitive interactions_1
• Competitive interactions_2
• Predator-prey interactions
• Plant-herbivore interactions_1
• Plant-herbivore interactions_2
• More complicated ecological interactions

2
Main questions

• How do plants defend themselves from herbivores?
• Which plants use what defences?
• How do herbivores counteract plant defences?
• What are the consequences of these interactions
  on feeding patterns in herbivores?

3
Distribution of plant defenses
4
1st How can we classify herbivores?
By feeding niche
5
Examples of herbivores by feeding niche
6
Examples of herbivores by feeding niche
7
Grazers vs. Browsers
8
Counteracting plant defences?

• Behavioural
• Avoid, eat something else (defence successful)
• Eat less, mix diet (defence partly successful)
• Physiological
• ? effect once eatene.g. metabolise excrete
  toxin(defence partly or NOT successful)
• Physical
• Tough tongue/lips
• Tooth jaw morphology

9
How do grazers deal with grass?
structural
chemical
Grasses Forbs Trees/shrubs
10
How do grazers deal with grass?
Example eastern grey kangaroos Macropus
giganteus

• Physical

• Jaw
• curved tooth row

Sanson GD (1989) Morphological adaptations of
teeth to diets and feeding in the Macropodoidea.
In 'Kangaroos, Wallabies and Rat-kangaroos'. (Eds
G Grigg, P Jarman and I Hume) pp. 151-168.
(Surrey Beatty Sons Sydney)
11
How do grazers deal with grass?
Example eastern grey kangaroos Macropus
giganteus

• Physical

Sanson GD (1989) Morphological adaptations of
teeth to diets and feeding in the Macropodoidea.
In 'Kangaroos, Wallabies and Rat-kangaroos'. (Eds
G Grigg, P Jarman and I Hume) pp. 151-168.
(Surrey Beatty Sons Sydney)
12
How do grazers deal with grass?
Elephants also have molar progression
13
How do grazers deal with grass?
Example grazing zebra wildebeest

• Behavioural

• Select suitable plant parts for guts and teeth

Krebs 2001, Fig 14.10
14
How do browsers deal with browse?
structural
chemical
Grasses Forbs Trees/shrubs
15
How do browsers deal with browse?
Example koalas Phascolarctos cinereus

• Physiological

• e.g. eucalypt terpene p-cymene
• metabolise p-cymene enzymes oxidise it
• ? more polar
• ? excretion in urine

Boyle R., McLean S., Foley W. J., Moore B. D.,
Davies N. W. Brandon S. (2000) Fate of the
dietary terpene, p-cymene, in the male koala. J.
Chem. Ecol., 26, 1095-1111.
16
How do browsers deal with browse?

• Behavioural

Modified from McArthur C., Hagerman A. E.
Robbins C. T. (1991) Physiological strategies of
mammalian herbivores against plant defenses. In
Plant Defenses Against Mammalian Herbivores (eds
R. T. Palo C. T. Robbins) pp. 103-114. CRC
Press, Boca Raton, Florida.
17
Main questions

• How do plants defend themselves from herbivores?
• Which plants use what defences?
• How do herbivores counteract plant defences?
• What are the consequences of these interactions
  on feeding patterns in herbivores?

18
Feeding patterns of grazers?

• Diet quality
• low
• medium
• high

Bell R. H. V. (1971) A grazing ecosystem in the
Serengeti. Sci. Amer., 225, 86-93.
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Feeding patterns of grazers?
Bell R. H. V. (1971) A grazing ecosystem in the
Serengeti. Sci. Amer., 225, 86-93.
20
Feeding patterns of grazers?

• Zebra remove bulky low quality parts, for ?
• Wildebeest remove medium quality parts, for
  ?
• Thomsons gazelle select rarer nutritious bits
• Grazing facilitation?

Bell R. H. V. (1971) A grazing ecosystem in the
Serengeti. Sci. Amer., 225, 86-93.
21
Feeding patterns of grazers?
Hypothesis Grazing facilitation
Prediction ? zebra ? ? wildebeest ? ? Thomsons
gazelle (?)

• Not as predicted ?
• No grazing facilitation?
• ?
• 3 independent plant-herbivore interactions?

22
Feeding patterns of generalist browsers?
Hypothesis MUST mix diet (to deal with PSMs)
Prediction 1 Intake on Diet1 PSM1 OR Diet2
PSM2 ? Diet3 Diet1 Diet2

• Feeding trial
• 6 brushtail possums (Trichosurus vulpecula)
• 3 diets
• Diet 1 cineole (terpene)
• Diet 2 gallic acid (phenolic)
• Diet 3 Diet 1 and Diet 2 (side by side)
• Measure intake
• Film feeding behaviour

Wiggins N. L., McArthur C., McLean S. Boyle R.
(2003) Effects of two plant secondary
metabolites, cineole and gallic acid, on nightly
feeding patterns of the common brushtail possum.
Journal of Chemical Ecology, 29, 1423-1441.
23
Feeding patterns of generalist browsers?
Prediction 1 Intake on Diet1 PSM1 OR Diet2
PSM2 ? Diet3 Diet1 Diet2
Wiggins N. L., McArthur C., McLean S. Boyle R.
(2003) Effects of two plant secondary
metabolites, cineole and gallic acid, on nightly
feeding patterns of the common brushtail possum.
Journal of Chemical Ecology, 29, 1423-1441.
24
Feeding patterns of generalist browsers?

• Prediction 2 Feeding patterns differ?
• How much they ate per feeding bout

Wiggins N. L., McArthur C., McLean S. Boyle R.
(2003) Effects of two plant secondary
metabolites, cineole and gallic acid, on nightly
feeding patterns of the common brushtail possum.
Journal of Chemical Ecology, 29, 1423-1441.
25
Feeding patterns of generalist browsers?

• Prediction 2 Feeding patterns differ?
• How quickly they ate

Wiggins N. L., McArthur C., McLean S. Boyle R.
(2003) Effects of two plant secondary
metabolites, cineole and gallic acid, on nightly
feeding patterns of the common brushtail possum.
Journal of Chemical Ecology, 29, 1423-1441.
26
Feeding patterns of generalist browsers?
Hypothesis MUST mix diet (to deal with PSMs)
Prediction 3 foraging efficiency related to
scale of plant species diversity
Better for generalist?
Better for specialist?
McArthur C(unpubl.)
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Main points

• Plant-herbivore interactions
• Variety of plant types
• Variety of defences
• Variety of herbivore feeding niches
• Counteracting plant defences
• Behavioural
• Physiological
• Physical
• Feeding patterns affected by
• interaction with plant defences
• competition
• predation

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Summary

• Interactions affecting distribution abundance
  of animals include
• Competition
• Predator-prey
• Plant-herbivore
• Research questions across interactions
• Some similar
• Some different
• Depends on
• Our current state of understanding
• Time subject has been studied?
• Complexity of problem?