1 Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 1 BIOS 3010: Ecology Lecture 7: Processes: Predation • 1. Lecture summary: – Horizontal & vertical interactions. – Vertical interactions: – Predation: • Classifications • Defense Henri Rousseau, The sleeping gypsy” 1897, MMA, New York Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 2 2. The basic nature of interactions within and between trophic levels: • Horizontal interactions within a trophic level: – competition > amensalism > commensalism > mutualism • Vertical interactions between trophic levels: – Predation / parasitism / herbivory > mutualism Malcolm (1992) Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 3 Interaction Species 1 Species 2 a) Horizontal competition - - amensalism - 0 commensalism 0 + mutualism + + b) Vertical predation parasitism herbivory - - - + + + mutualism + + 3. Summary of ecological interactions: • NB neutralism is really an irrelevant 0/0 interaction; and it is also important to realize that herbivores are usually the prey or hosts for predators and parasites
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 1
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 3
Interaction Species 1 Species 2a) Horizontal
competition - -amensalism - 0
commensalism 0 +mutualism + +
b) Verticalpredationparasitismherbivory
---
+++
mutualism + +
3. Summary of ecological interactions:
• NB neutralism is really an irrelevant 0/0 interaction; and it is also important to realize that herbivores are usually the prey or hosts for predators and parasites
2
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 4
4. Vertical trophic interactions can be divided into two basic kinds:
• (1) Consumers that do not kill their food – these are the parasites which include
pathogens and herbivores - neither of which completely consume their food hosts.
• (2) Consumers that do kill their food – these are the predators which include typical
animal predators as well as insectivorous plants and seed-eating animals like birds, small mammals and insects.
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 5
5. Predation:
• Predation is a +/- or “exploitative” interaction between consumers and the things they consume. – Consumers affect the distribution and abundance of
what they consume and vice versa.
• Predation is consumption of one organism (the prey) by another organism (the predator), in which the prey is alive when the predator first attacks it. – This excludes detritivory as feeding on dead organic
matter
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 6
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 7
7. Predation
• Functional classification: • True predators:
– kill and consume prey immediately; kill many prey. – like lions and seed-eating beetles.
• Grazers: – attack many "prey"; rarely lethal; only partially consume. – like sheep and mosquitoes.
• Parasites: – attack few or single "prey"; rarely lethal; only partially consume. – micro & macroparasites - measles, tapeworms, gall wasps & aphids.
• Parasitoids: – attack single "prey", always lethal, complete consumption.
• This is why Begon et al. (2006) consider herbivory as a subset of predation - mostly as plant grazers, but also as plant parasites.
• Because there are important differences between predators and herbivores, herbivory will be considered in more detail in lecture 11!
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 8
8. The effect of predation on prey populations:
• Predators should be harmful to prey populations because they attack and kill individual prey, but this may not be true for 2 reasons: – 1) killed individuals may not be a random sample of the
population and may be those with lowest fitness (old, young or sick individuals) see Fig. 9.9.
– 2) there may be compensatory changes in growth, survival or reproduction of surviving prey. • e.g. recruitment curves in Fig. 5.10b indicate that predation of high
density individuals should lead to increased growth and reproduction - but at low density the effect could be reversed (this influences resource harvesting)
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 9
9. Prey as food resources for Predators:
• Increased food consumption leads to increased rates of growth, development & birth, and decreased rates of mortality - above a metabolic maintenance threshold and below a satiation threshold – Fig. 8.10 (3rd ed.) (a) Linyphiid spider (b) Daphnia water flea.
4
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 10
10. Prey defense:
• Predator satiation: – Predator satiation suggests that some prey
may target this as a defense against being consumed - and so they evolve mechanisms to synchronize their peak periods of population abundance:
• Like periodical cicadas (Magicicada) in which there are twelve, 17-year and three, 13-year broods currently in existence in eastern North America:
– see cover, Table 1 and Fig. 1 from Heliövaara et al. 1994,Trends in Ecology & Evolution 9(12): 476
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 11
11. Prey defense:
• Masting: • Fruit/seed masting in trees (Fig. 8.11), and inverse
density dependence in Fig. 8.12 to show that predators may not track prey food resources when they fluctuate (Fig. 9.12) unless they have short generation times.
• Nutritional quality: • Prey may reduce their nutritional quality by dilution or
other means such as toxins or digestibility-reducing chemicals.
• see protein availability for wildebeest in Fig. 9.13 - which argues for predator foraging behaviors; to be considered next time ...…
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 12
Figure 9.9: Age classes of Thomson’s gazelles lost to predators in the Serengeti
5
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 13
Figure 5.10b: Clover growth rate against leaf area index at different light intensities
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 14
Trends in Ecology & Evolution (1994) Vol. 9(12)
Periodical cicadas in the genus Magicicada form a complex of 6 species each with 13-year and 17-year life cycles. Broods X & XIX are separated by mtDNA genotypes in Fig. 3 below
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 15
Table 1: (Heliövaara et al. 1994, TREE 9(12):476
6
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 16
Figure 1: Heliövaara et al. 1994, TREE 9(12):478
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 17
Figure 8.11 (3rd ed.): Periodical masting in Scots pine and Norway spruce
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 18
Figure 8.12 (3rd ed.): Inverse density depen-dence in weevil attacks on witch hazel fruits
7
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 19
Figure 9.12: Inverse plant and mirid bug numbers in the Negev desert
Asphodelus fruits
nymphs
adults
Dr. S. Malcolm BIOS 3010: Ecology Lecture 7: slide 20
Figure 9.13: Wildebeeste food quality and bone marrow fat in the Serengeti