Coevolution

1
Coevolution

• Coevolution Coadaptation
• Ehrlich Raven (1965) Butterflies Plants

Plants eaten by larvae ? under selection to
produce chemicals ? larvae under selection to
de-toxify ? plants under selection to more
toxify.
2
Requirements of Coevolution
1. Specificity i.e. evolution of trait in 1 spp
consequence of evolution of trait in
another spp 2. Reciprocity i.e. both traits
evolve (Janzen 1980)
3
Consequence Evolutionary Arms-Race
4
Bats vs Moths
5
Hearing Insects
6
Moth Hearing to Detect Bats?

• Peak sensitivity 20 60 kHz
• Sensitivity correlated with bat community
  diversity
• Auditory degeneration in day moths
• Tympanate ears of large moths have lower best
  frequencies more sensitive than ears of
  smaller moths(Waters 2003)

7
Moth Hearing Success
Arctiidae
Geometridae
gt 80 of moth spp (Pavey and Burwell
1998, Schoeman and Jacobs 2003)
Noctuidae
Notodontidae
Pyralidae
8
Moth Hearing Success

• Tympanate moths are 40 more successful at
  evading bats (Acharya Fenton 1994)? i.e.
  exert considerable selective pressure on bats to
  evolve adaptations to overcome these defenses

9
Have Bats Responded?
1. Use frequencies lt 20 kHz gt 60 kHz allotonic
frequencies
10
Allotonic Frequency Hypothesis
11
Moth
Peak Echolocation Frequency (kHz)
12
(No Transcript)
13
Have Bats Responded?
1. Use frequencies lt 20 kHz gt 60 kHz allotonic
frequencies 2. Use passive listening low
intensity / short duration echolocation
calls
14
(No Transcript)
15
Have Bats Responded?
1. Use frequencies lt 20 kHz gt 60 kHz allotonic
frequencies 2. Use passive listening low
intensity / short duration echolocation
calls ? However, low intensity calls may not be
an adaptation per se to avoid detection by
moths. This is likely the case with short
duration calls used to avoid pulse-echo
overlap in cluttered habitats.
16
Conclusions

• Moths certainly evolved ears to detect foraging
  bats
• Evolutionary responses of bats less certain
• ? perhaps example of diffuse or guild
  coevolution

17
Conclusions

• What is necessary to show coevolution
  conclusively ?