BIOL 4120: Principles of Ecology Lecture 11: Species Interaction

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BIOL 4120 Principles of Ecology Lecture 11
Species Interaction

• Dafeng Hui
• Office Harned Hall 320
• Phone [phone]
• Email dhui_at_tnstate.edu

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An example of species interaction Prickly pear
cactus population is controlled by its predator,
the cactus moth Prickly pear cactus was
introduced into Australia as ornamental plant,
and out of control. Cactus month was introduced
in 1920s Now prickly pear cactus maintain a low
level of equilibrium, mosaic isolated inlands.
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Species interactions
Consumer-resource interactions fundamental
ecological relationship between species, organize
biological communities into food chains include
predator-prey, herbivore-plant,
parasite-host. Competition two consumers share
the same resource, each reduces the availability
of resources of the other. Mutualism
interactions benefit both species
(pollinator-plant) Commensalism benefit one, but
do no harm on another (bird nests on a
tree) Amensalism elephant crushes a grasshopper
under foot.
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Topics (Chapter 14)

• 11.1 All organisms are involved in
  consumer-resource interactions
• 11.2 Dynamics of consumer-resource interactions
  reflect mutual evolutionary responses
• 11.3 Parasites maintain a delicate
  consumer-resource relationship with their hosts
• 11.4 Herbivory varies the the quality of plants
  as resources
• 11.5 Competition may be an indirect results of
  other types of interactions
• 11.6 Individuals of different species can
  collaborate in mutualistic interactions

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11. 1 All organisms are involved in
consumer-resource interactions
Consumer-resource interactions are the most
fundamental interactions, as all
non-photosynthetic organisms must eat, and all
organisms are at risk of being eaten. Consumer
organisms Predator, Parasite, Parasitoid,
Herbivore, Detritivore Resource organisms
plants, animals etc
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• Predation
• Consumption of all or part of one living
  organisms by another
• Serve as energy transfer Predators are agents of
  mortality and feed on organisms
• Carnivory
• Direct taking of animal prey for immediate
  consumption
• Hawk or an owl taking a mouse
• Decrease prey population, gain nutrition to
  support reproduction.
• Parasitism
• Predator lives in or on a host and consumes,
  consumers part of a living host, but does not
  usually kill the host
• Ticks on mammals
• Parasites that can cause disease symptoms
  pathogens
• Parasitoidism
• Predator lives in or on a host and eventually
  kills to provide a food source
• Parasitic wasps
• Herbivory
• Consumption of whole or parts of plant material
• Consumption of nuts and seeds (predator) or
  leaves of plants (parasite)
• Grazing (when apply to grasses and herbaceous
  vegetation) or browsing (wood vegetation)

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• Detritivores consume dead organic material
  such as leaf litter, feces, and carcasses
• No direct effects on the populations that produce
  resource (commensal interaction)

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11. 2 Dynamics of consumer-resource interactions
reflect mutual evolutionary responses
From evolution point of view, resource organisms
should develop many tactics to avoid being eaten
(for consumer-resource relationships). Consumers
(like predators) should develop better ways to
hunt prey. Plants produce thorns and defensive
chemicals that dissuade herbivore. Animals hide
or seek refuge in a safe microhabitats produce
foul-smelling or stinging chemical secretions
(scorpions) to dissuade predators armored body
covering (armadillos).
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Boomnardier beetle sprays a noxious liquid at the
temperature of boiling water toward a predator.
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Avoiding predators may result in reduced growth
rates Bullfrog experiments by Relyea and Werner,
1999
Grew tadpoles in aquaria with caged dragonfly
larvae or fish. Fish and dragonfly larvae are
predators here.
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11. 3 Parasites maintain a delicate
consumer-resource relationship with their hosts

• Parasitism a relationship of two organisms
  living together (symbiosis) and one derives its
  nourishment at the expense of the other
• Parasite and host
• Parasitism has
• Negative effect on hosts
• But do not usually kill hosts
• Parasite consists of a wide range of organisms,
  including
• Virus, bacteria, protists, fungi, plants, and
  invertebrates (include arthropods)
• 50 of the species on Earth (typically feed on
  only one or a few host species).

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Hosts provide diverse habitats for parasites

• Hosts are the habitats for parasites
• Depends on the places
• Ectoparasites live on the skin within the
  protective cover of feathers and hair
• Endoparasites live within the host
• Examples
• Fleas, ticks, are ectoparasites
• Liver flukes, lung flukes, flatworms, are
  endoparasites

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Parasite life cycles
Many parasites have complex life cycles Life
cycle of the malaria parasite Plasmodium Two
hosts mosquito and Human (or other mammal, bird
or reptile) Malaria 300-500m cases/yr, 1 Millon
died.
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Parasite virulence and host resistance

• Virulence a measure of the capacity of a
  parasite to invade host tissues and proliferate
  in them
• Balance between parasite and host populations is
  influenced by the virulence of the parasite and
  the immune response and other defenses of the
  host.
• Virulence can be reduced by actions of the hosts
  immune system, including inflammation responses
  and production of antibodies.
• Inflammation response (produce certain chemical,
  increase flood flow)
• Immune response. White cells produce anti-body
  bind to foreign proteins, helping counter infects.

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11. 4 Herbivory varies with quality of plants as
resources

• Nutrient quality and digestibility of plants is
  critical to herbivores.
• Herbivores usually select plants according to
  nutrient content, preferring young leaves (low
  cellulose), fruits and seeds.
• Defenses of herbivory
• Inherently low nutrient value of most plant
  tissue
• Toxic compound
• Structure defenses spines, hairs, tough seed
  coats, sticky gums and resins
• Digestibility secondary compounds such as
  tannin.

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• Secondary compounds
• Three major classes based on chemical
  construction
• Nitrogen compound (derived from amino acid), such
  as lignin, alkaloids
• Terpeniods include essential oils, latex, and
  resins.
• Phenolics simple phenols have anti-multimicrobial
  properties (carbolic acid).

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• Two type of defenses
• Constitutive defenses
• Fixed features of the organisms
• Some type of defense chemicals are maintained at
  high levels in plant tissues at all times
• Induced defenses
• Defenses are brought about or induced by the
  presence or action of predators, herbivores
• Chemical defense
• Behavior defense

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Structure and chemical defenses protect the stems
and leaves (catus and milkweed plants)
(constitutive defenses)
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Induced defenses Plant defenses can be induced
by herbivory Mean number of the mite were
lower on cotton plants that have previously
exposed to a closed related mite species. Cost
to produce.
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11.5 Competition may be an indirect result of
other types of interactions

• Direction interaction direct relationships
  between two species (e.g., predator and prey)
• Consumer () ? resource (-)
• Indirection interaction
• Ex1. predator () ? herbivore (-) ? plant
  ()
• Multiple trophic levels in a food web, trophic
  cascade
• Ex.2 Consumer 1 () ? resource (-) ? consumer
  2()
• seems like
• consumer 1 (-) ?? consumer 2(-)
• Exploitation competition or indirect competition
  

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A competition-facilitation continuum Facilitatio
n nurse plants Individuals of one species
facilitate the germination and growth of a second
species An example ironwood in desert provides
protected sites for the establishment of cacti
(later competition for nutrient, water and light)
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11.6 Individuals of different species can
collaborate in mutualistic interactions

• Mutualism interaction benefits both species
  involved
• honeybee and plants
• (plants provide honeybee with nectar, bees carry
  pollen between plants)
• Can be symbiosis lichens (algae and fungi)
• or non-symbiosis seed dispersal (birds and
  plants)
• Could involve more species
• Humans extract honeycombs (for honey)
• Birds eat the wax left behind
• Bacteria in the guts to digest the wax
• Three categories
• Trophic, defensive and dispersal mutualisms
• Trophic mutualisms feeding relationship,
  bacteria in rumens of cows

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Defensive mutualism Food and shelter, defend
partners against their consumers Cleaning fish
or shrimp
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A wonderful story of Acacias plants and ants in
Central America, see textbook (298).
Some mutualists need their partners to survive
and grow. Ants cant survive without plants and
plants cant survive without ants. Adaptation
improved the efficiency of their association
Ants work day and night to protect plants.
Acacias retain leaves all year. (both unusually)
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Dispersive mutualismBirds and mistletoe
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The End