Biological Interactions

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Biological Interactions

• Predation
• Competition
• Symbiosis
• Combined physical and biological controls
• Niche concept

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Predation

• One organism consumes another
• Herbivory- animal consumes plant
• Carnivory animal consumes animal (and plant
  consumes animal!)
• Why discuss predation in biogeography?

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Predation Affects the Range of Predators

• Stenophagous selective predators
• Koala bears (Phascolartus cinereus) bluegum
  eucalyptus
• Chinese giant panda bear (Ailuropoda melanoleuca)
  bamboo
• Europhagous many prey sources
• large herbivores, carnivores

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Northern Range Limits of Monarch Butterflies and
Milkweed
80 of all N. Amer. butterflies are stenophagous!
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Conservation and StenophagyBay Checkerspot
Butterfly (Euphydryas editha bayensis)

• Federally threatened
• Host Plantago erecta

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Why feed on only one prey species?

• Optimal foraging strategy adapted to prey with
  high nutritional value
• May avoid competition
• Efficiency

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Can Predation Affect the Range of Prey?

• Accidental introduction of lampreys to Great
  Lakes (1920)
• Lake trout, other large fish

Sea Lamprey
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Why Dont Predators Typically Control the Range
of Prey?
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Linked Predator-Prey RelationshipsLotka-Volterra
Model

• Linked oscillations in pred/prey
• For prey
• dN/dt rN aPN
• dN/dt rate of change in prey population (N)
  over time (t)
• r rate of growth in the prey population
• P rate of growth in the predator population
• a hunting efficiency of pred. (attack rate)

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Lotka-Volterra Models

• http//www.kimvdlinde.com/professional/biology/pop
  dyn/index.html

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Lotka-Volterra Models

• Prey curve leads the predator curve
• When prey pop. low, predator pop. declines
• Selective predators unlikely to cause extinction
• Ex. Canada lynx (Lynx canadensis) and snowshoe
  hare (Lepus americanus)

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Do predators limit prey species ranges?

• Predator exclusion studies
• Pacific Coast algae increase diversity
• May result in extinction of prey
• Keystone Species concept

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Competition

• Interspecific interaction between species in
  which growth or fertility is decreased or
  mortality increased for both species
• Intraspecific - between individuals of same
  species
• How important is interspecific competition in
  determining range limits?

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Competition

• Resource exploitation two (or more) species
  compete for limited resource but do not
  physically or chemically interact
• Interference competition physical or chemical
  interactions occur
• Allelopathy

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Tree of Heaven (Ailanthus altissima)
Ailanthus leaves toxic to 35 species of
gymnosperms and 10 species of angiosperms (Mergen
1959)
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Kangaroo Rat RangesSharp Boundaries
What are the possible explanations?
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Interspecific Competition and Geographical Range

• Ranges that do not overlap
• Competition or competition avoidance?
• Climatic factors?
• Chance occurrences?

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Great Basin Chipmunks
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Great Basin Chipmunks

• All 3 species NOT present on every range
• Elevation, forest type, open or closed canopy
• Where Euatamias umbrinus or E. quadrivittatus are
  present, E. dorsalis is excluded from high
  elevation

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Gradient DistributionCompeting
Population Density
A
B
C
D
Mean Annual Temperature
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Gradient DistributionNon-Competing
Population Density
A
B
C
D
Mean Annual Temperature
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Symbiosis Mutualism, Commensalism, Parasitism

• Symbiosis Close association between two species
• Mutualism mutual benefit
• Commensalism one benefits, other neutral
• Parasitism parasite dependent on host, benefits
  at the expense of host

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Mutualism mutual benefit

• Pollination
• Obligate pollinators control range
• Lichen
• Photosynthetic algae (or cyanobacteria) and
  fungus

Tegeticula spp. and yucca
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Commensalism Clownfish and anemone

• Pink Anemonefish (Amphiprion perideraion)
• Anemone (Heteractis magnifica)

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Parasitic Relationships

• Parasites restricted to one host species
• Coral root, snow plant
• Microparasites viruses, bacteria etc.
• Host may control distribution of parasite
• West Nile Virus
• Hawaiis honeycreepers (Drepeninida) and avian
  malaria (Culex pipens fatigans)

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West Nile Virus

• Single strand RNA virus
• Maintained thru transmission cycle of birds
  mosquitoes
• Mammals are incidental hosts

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2006 West Nile Cases
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Hawaiis Honeycreepers

• Evolved in isolation
• Occur no where else
• Dramatic extinctions 1900-present
• Species above 600m persisted

Avian malaria carried by exotic mosquito
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Niche

• All of the physical and biological environmental
  conditions a species needs to thrive
• Habitat spatial environment where a species is
  found

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The Niche Reconsidered

• Fundamental niche in the absence of competition
• Realized niche in presence of competition
• Assumes competitive exclusion principle
  complete competitors cannot coexist

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Realized and Fundamental Niche
Realized Fundamental
Species C
Species B
Soil Moisture
Species A
Truncation to realized niche
Air Temperature
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Biological Interactions

• Predation
• Competition
• Symbiosis
• Combined physical and biological controls
• Multi-dimensional niche concept