Tuesday 25th September 2018 - Evolution of Behaviour Flashcards

1
Q

Fossil Records

Behaviour isn’t preserved in fossil records … but can leave us clues.

• Some things are left behind that give us clues about how animals might have behaved.

Question: what kinds of fossilised things can we get clues from?

A

• Physical remains.

– E.g., bones, teeth, etc.

• Evidence of animals’ presence/activity (trace fossils).

– E.g., tracks, burrows, bite marks, etc.

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2
Q

Fossil Records

Composition, form, and location of fossils can provide hints at behaviour. •

Dinosaurs

– Birds exhibit parental care.

– Where did it originate?

– This fossil suggests dinosaurs.

A
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3
Q

Fossil Records

Fossil records of morphology can give clues about certain behaviours.

• E.g., horses.

– Structure of teeth and feet in horses

. – Were browsers, now grazers.

Question: what else might give us clues about diet?

A

• Faeces/coprolites.

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4
Q

Fossil Records Interactions between species can sometimes be observed.

• E.g., food chain in aquatic species (Kriwet et al., 2007).

A
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5
Q

Fossil Records Predator-prey interactions can be inferred.

• E.g., probable predation (Wilson et al., 2010).

A
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6
Q

Fossil Records Predator-prey interactions can be inferred.

• E.g., probable predation (Wilson et al., 2010).

A
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7
Q

Fossil Records Information about feeding behaviour can be gleaned from coprolites.

  • E.g., fossilised T. rex faecal matter (Chin et al., 1998).
  • Evidence of bone crushing during feeding. • Incomplete digestion of bone fragments.
  • Prey appeared to be a sub-adult dinosaur.
A
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8
Q

Fossil Records Mating behaviour may be revealed via fossils.

• E.g., intrasexual selection (male-male competition) and weaponry.

A
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9
Q

Other clues remain:

Modes of locomotion

– E.g., footprints showing if feet were wide-/closely-set.

Predation

– Scratches, holes, etc.

Habitat selection

– Dens, burrows.

Vocalisations

– Bony structures.

A
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10
Q

Comparing Species Comparative method = comparing [closely-related] species, examining behaviour patterns to determine how they evolved.

  • Differences and similarities.
  • Assumes that behaviour traits are heritable.
  • And that behaviour traits evolved from simple → complex forms.
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11
Q

Fossilised footprints are excellent indicators of Animal behaviours such as locomotion.

https://www.youtube.com/watch?time_continue=58&v=jtbpusl0Vo0

A
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12
Q

Comparing Species

E.g., balloon flies (Kessel, 1955) – possible evolutionary stages.

A
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13
Q

Comparing Species

E.g., balloon flies

– questions remain.

It’s a logical arrangement, but there are limitations of this comparative method.

• Don’t know if balloon flies went through all stages during evolution.

• Is the order of stages correct?
– Traits don’t always evolve linearly, simple → complex.

– Some phenotypes are optimal for some environments (which are not static).

• Correlation ≠ causation.

– Could be additional variables.

• Knowledge of function can be useful.

– E.g., Kessel (1955) suggested nuptial feeding reduced chances of males being eaten during copulation.

– Thornhill (1976) suggested food provisioning = parental investment, females selecting on basis of quality.

A
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14
Q

Comparing Species Limitations of this comparative approach:

• Some animals remain relatively unchanged.

– E.g., horseshoe crabs.

• Not all animals are perfectly adapted to environment. Trait similarities can arise via shared ancestry, or independent evolution.

• Ancestral traits = ?

• Derived traits =?

A

• Ancestral traits = shared by a common ancestor.

• Derived traits = evolved more recently, not present in common ancestor.

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15
Q

Comparing Species Example:

Mobbing in blacked-headed gulls.

• Hypothesis: mobbing is an evolved response to predation risk to eggs in ground nests

– to distract predators

If correct, other gulls whose young are not at this risk should not display this behaviour

A
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16
Q

Comparing Species

Example: mobbing in blacked-headed gulls.

• Two potential explanations

A. Ground-nesting ancestor; kittiwakes are descended from more-recently evolved cliff-nester.

B. Original ancestors were cliff-nesting; this trait was lost and then regained. • More changes.

A
17
Q

Comparing Species Example:

Mobbing in blacked-headed gulls.

• Simpler scenarios are more likely parsimony.

(Parsimony: extreme unwillingness to spend money or use resources.)

  • Fewer predators can reach cliff nests, thus selection pressures for mobbing should be different anyway.
  • The case of cliff-nesting kittiwakes, who do not mob predators …

– Kittiwakes’ different behaviour is example of divergent evolution.

– Supports original hypothesis.

A
18
Q

Comparing Species Another comparative approach

– animals from different lineages, in same environments, may evolve similar traits due to shared selection pressures.

• Convergent evolution.

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19
Q

Comparing Species Phylogenetic comparison/analysis can help.

  • Phylogenetic trees are constructed, based on morphology / genetics.
  • Behaviour traits mapped onto these.
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20
Q

Example: burrowing behaviour in mice

Varied burrowing behaviour within one genus, Peromyscus.

  • First, constructed phylogenetic tree from genetic data.
  • Second, behavioural studies determined each species’ burrowing characteristics.
  • Last, mapped behaviour onto phylogeny.
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21
Q

Variation in burrow presence/complexity.

• Results indicate:

– Ancestral trait = no burrowing.

– Derived trait = large, complex burrows.

A
22
Q

Comparing Species

Example: swordtail fish, some males have ‘sword’ tail extensions.

Females prefer swords.

– Females in species with no natural swords – also prefer swords.

Phylogenetic analysis suggests females’ preference for swords evolved before swords.

A
23
Q

Comparing Species Example: swordtail fish

Some males have ‘sword’ tail extensions.

• But, perhaps this trait evolved/was lost more than once over time.

– Traits evolved via sexual selection may be particularly likely to change over evolutionary time.

• Therefore, the standard comparative approach could be limited here.

A