05AntiPred06x - Natural selection fitness What to do to...

Natural selection & fitness
What to do to pass on genes?
1. survival (viability)
2. sexual
3. fertility

Surviving 1:
Escaping
true
predators
(or parasites)
From the mind in
PAT 323

1. Avoiding encounter
- 1
st
& simplest
A. Appear (or be) rare
i. unlikely places (selection to differ) or
active when predators not
ii. hide
(=crypsis; see below)
iii. polymorphism

Polymorphism in detail
- individual strategy
(usu.)
only via offspring
production
-
(usu.)
discrete morphs
- multiple, sympatric; even among sibs
- usu. limited number of genes
H1. prevents predators from wiping out sp.
H2. each morph adapted to different part of a
super-niche (e.g.,
Littorina
snails, moth larvae
and food plant)
H3. frequency-dependent
(apostatic)
predation
your faves?`

Frequency-dependent predation
0
25
50
75
100
0 25 50 75 100
Proportion available
Proportion taken
(hypothetical data)

- rarest morph has ↑est survival
- predators specialise on 1 morph ( search
images ) & don’t recognise rest as food
B. One-up-animal-ship
- detect predators 1st; vigilance
- eyes, sniffing, ears (incl. sonar)
- cooperating & warning displays (e.g.,
vervets)

2. Avoid detection
A. freeze
- predators sense motion (e.g., shorebirds,
ptarmigan)
B. crypsis
- most studied
- morph & behav; immobility
- smell, electrical, …

i. disruptive coloration
- breaks outline, body
extends to background
- hard to see contour, shape
(e.g., snakes, bittern, zebra)

ii. countershading (fish incl. photophores,
seabirds, mammals)
- but mammals not preyed on from below;
H2? H3?
- reduce effects of uv ?
- thermal benefits?

iii. transparency
- aquatic (jellyfish, eel
larvae)
iv. background matching
- rapid colour change
(cuttlefish, flatfish
in
Newport
, chameleons)

- slow (poplar hawkmoth vs. larval food,