BI113 Lecture 34

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BI-113 Lecture 34

• Organismal Ecology

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Defense Against Predation

• Plants with two primary forms of predatory
  defense
• Morphological defenses
• Thorns, spines, etc
• Make some plants unpalatable, or at least painful
  to eat
• These types of defenses are size restrictive
• They only work on larger predators.
• Secondary compounds
• Chemicals used as defense
• Various secondary compounds (alkaloids,
  phenolics, and sterols) that serve to make
  predators sick or with disagreeable tastes
• A constant arms race of co-evolved plants and
  animals

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Animal Defenses Against Predators

• Active
• Run away
• Fight
• Passive
• Hiding
• Cryptic coloration (camouflage) or morphology
• Blend in - match background or shape of
  surroundings
• Butterflies that look like leaves
• Caterpillars that look like twigs
• Leaf hoppers shaped like thorns
• Some bugs that look like bird shit

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Cryptic coloration
Crypsis in katydids
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Anti-predator tactics

• Deceptive markings
• Usually designed to startle potential predators
• False eye spots
• This type of defense only works so long
• Predators become habituated to it ? prey cannot
  reach high density

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Aposematic coloration

• Coloration with a message, and the message is
  Beware!!
• Often associated with distasteful flavor, sting
  or toxins
• Dendrobates sp. (with combinations of
  red/orange/yellow and black)
• Micrurus sp. and Micruroides sp. (coral snakes,
  with red, yellow, black rings)
• Bees (with yellow and black)
• Many harmless species have taken advantage of the
  protection that these color combinations afford
  and copied them

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Aposematic coloration
Frogs of the genus Dendrobates - the arrow poison
frogs
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Mimicry

• Müllerian mimic system
• Incorporates the common color schemes utilized by
  phylogenetically related taxa (some researchers
  believe that these taxa are evolutionarily
  constrained to these color schemes)

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Aposematic coloration
Toxic nudibranchs from Australia
Various bees and wasps with yellow and black
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Mimicry

• Batesian mimicry
• Incorporates a harmful model and a harmless mimic
  that benefits from copying the model
• Monarch/Viceroy butterfly
• Bumblebee, wasp, yellow jacket - flies with
  similar body shape and same colors
• Coral snakes and milk snakes (Lampropeltis
  triangulum)

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Batesian mimicry
Apparent mimicry between pairs of snakes living
throughout Mexico and Central America. In each
case, the snake on the left is a venomous member
of the genus Micrurus (coral snakes), while the
snake on the right is a relatively harmless
member of the genus Pliocerus.
Scaphiodontophis sp.
Micrurus sp.
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Batesian mimicry
Viceroy
Monarch
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Anti-predator tactics

• Thanatosis
• death-feigning behaviours
• Heterodon sp. - hognose snakes
• Didelphis virginianus - Opossum
• Play dead
• Many predators wont eat dead stuff

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Thanatosis
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Deflection of Attack

• Birds with broken-wing behavior
• Lead predator away from nest with eggs/chicks
• Killdeer
• Snakes with tail-waving behavior
• False head directs predator away from
  vulnerable body parts

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Anti-predator tactics

• Autotomy
• Loss of body parts of save vital organs and
  principle portion of organism

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Parental care and Investment

• Selfish gene
• All of these practices are designed to benefit
  the reproductive fitness (genetic contribution to
  future generations) of those individuals engaging
  in the tactic
• Altruism
• The practice of helping others, generally (in the
  animal world) those that are genetically related
• There is a greater tendency to help closer
  relations - kin selection

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Altruism

• Nest helpers
• Mother-daughter pairs that cooperate in rearing
  young
• Extended matrilineal family groups
• Florida scrub jays
• Acorn woodpeckers
• Daughters help with the raising of younger sibs
  in the nest
• Daughters ultimately benefit by inheriting
  nesting/foraging sites (which represent a limited
  resource)

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Nest helpers
Florida scrub jay
Acorn woodpecker
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Altruism

• Sentry
• In some species, a watchful sentry sounds an
  alarm when a potential predator is spotted
• There is a cost (increased likelihood of being
  predated) to calling
• Callers tend to be related to those individuals
  in the vicinity
• Seen in ground squirrels

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Sentries sound alarms
Prairie dogs with communal social structure
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Infanticide

• Killing of young, generally those that do not
  belong to the father
• Lions
• New male will kill cubs when he takes over a
  pride, then reinseminate females to ensure
  paternity of young
• Prairie dogs
• Females will raid nearby burrows and kill the
  young of unrelated females
• This is especially true if resources (like food)
  are likely to be limited (during bad years for
  plant growth - drought)

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Interspecific interactions

• Predator/prey
• Symbiotic relationships
• Host/parasite
• One organism (parasite) benefits, while the host
  is weakened or suffers a loss of fitness
• May even lead to the death of a host
• Commensalism
• One organism benefits, while the other receives
  no harm or benefit
• Mutualism
• Both organisms benefit
• Competition

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Competition between species

• Can lead to a change in a species niche
• (Ecological) Niche
• The role an organism plays in a particular
  habitat, and its interactions with other
  organisms
• Fundamental niche
• All conditions under which a species can survive
  and reproduce in the absence of any competitors
• Realized niche
• The situation that actually exists in nature

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Competition leads to . . .

• Based on competitive exclusion principle
• Niche partitioning
• Decreases direct competition between species
• Character displacement
• The tendency for characters to be more divergent
  when populations are in the same community
  compared to when they are isolated
• Ultimately, these may lead to species
  distinctiveness

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Competition
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Other examples of competition
Niche partitioning among warbler species