Predation

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Predation
Great White Shark and Fur Seal
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Plant defenses are developed at a cost to fitness
when

• 1. Organisms evolve more defenses if they are
  exposed to much damage and fewer defenses if cost
  of defense is high
• 2. More defenses are allocated within an
  organism to valuable tissues that are at risk
• 3. Defense mechanisms are reduced when enemies
  are absent and increased when plants are attacked
  - mostly true for chemicals not structures
• 4. Defense mechanisms are costly and cannot be
  maintained if plants are severely stressed by
  environmental factors

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Pine beetle infestation British Columbia
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Pine Beetle and Pitch Tube
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Serengeti Grazing System
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Serengeti Grazing System
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Serengeti Grazing System
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Grazing facilitation

• Grazing facilitation occurs when the feeding
  activity of one herbivore species improves the
  food supply for a second species

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Opuntia stricta prickly pear
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Prickly pear infestation in Australia
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Area infested with prickly pear before biocontrol
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Same area after biocontrol
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Biocontrol Agent Cactoblastis cactorum
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Symbiosis
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Symbiosis

• Symbioses - species living in close association
• Parasitism ,- parasite benefits, host harmed
• Commensalism ,0 or 0,0 can have positive effect
  for one species or for neither
• Mutualism , both species benefit

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Gopher Tortoise Commensal Host
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Gopher Tortoise Distribution
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Epiphytes
Birds Nest Fern
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Nalini Nadkarni studying epiphytes
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Epiphytes
Figure 1 Hypothetical tree illustrating how
vascular epiphytes in humid forests tend to
partition substrates illustrating sensitivity to
micro climate, particularly humidity, and
associated development of the organic rooting
media required by some populations.
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Parasitism and Disease
Lyme Disease Cycle in the UK
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Parasitism

• Parasitism - intimate association between two
  species in which the parasite obtains its
  nutrients from a host - parasite usually causes
  some degree of harm to its host - either reduced
  growth or reproduction
• Pathogen disease causing agent
• Disease abnormal condition of host due to
  infection by a pathogen that impairs
  physiological functioning

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Parasites on Plants
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Insects are green, Fungi are brown, Worms are
blue, Protozoa are yellow
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Parasitism occurs on a continuum from

• ectoparasites - live outside hosts body and
  experience same conditions as host - ticks,
  mites, fleas, aphids
• endoparasites - live inside host's body cavity -
  buffered from outside conditions - tapeworms,
  flukes
• intracellular parasites - live inside individual
  cells of the host - viruses, bacteria, protozoa -
  often called microparasites

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Or another way to divide parasites

• microparasites - viruses, bacteria, protozoa -
  small, often live intracellularly, main point is
  that they reproduce in host and will have very
  large numbers in host
• macroparasites - tiny to very large - nematodes,
  tapeworms, flukes - larger individuals that grow
  in host but multiply by producing infective
  stages that are shed by host to environment where
  they infect new hosts

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Parasite Transmission

• Direct transmission from one host to another of
  the same species via air, water, coughing, blood,
  feces, etc.
• Indirect transmission from one host to another
  of the same species via another species called a
  vector
• Vector species which transmits parasite or
  pathogen from one host to another

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Microparasites Macroparasites
Direct transmission HIV virus, Amoebic dysentery, Mildews on plants Lice, fleas, ticks, aphids, hookworm, pinworm, mistletoe
Indirect transmission Plasmodium (mosquito), Plant viruses (aphids), Trypanosoma (tsetse fly) Tapeworms, Schistosomes (snails), Rust fungi
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Powdery Mildew on Grape Leaf
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Powdery Mildew Life Cycle
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Head Lice and Life Cycle
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Mistletoe
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Mistletoe Life Cycle
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Malaria disease cycle
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Schistosomiasis - Life cycle of the schistosome
worm
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Worldwide incidence of schistosomiasis
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Worldwide incidence of schistosomiasis
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Rust Fungus Canker
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Rust Fungus Life Cycle
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Two ways to study parasite numbers

• Prevalence percent of host population that is
  infected best for microparasites
• Intensity number of parasite individuals per
  host usually best for macroparasites

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Frequency of infection

• Parasites usually occur in aggregated
  distributions due to 4 possible factors
• 1) random colonization events followed by asexual
  reproduction in hosts that do get parasitized
• 2) environmental "hot spots" where parasite eggs
  and infective stages survive well
• 3) dispersal constraints - geographic or
  behavioral barriers limit dispersal of parasites
  to just a few hosts
• 4) variation in susceptibility of individual
  hosts - due to nutrition, genetics

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European rabbits as pests in Australia - 1938
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Introduced pests in Australia red fox, rabbit,
cat, pig, goat
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