Evolution, 4th Edition

InTERACTIonS Among SPECIES 329

frequency-dependent selection, since common phenotypes will be better recog-

nized and avoided, and deviants from the common pattern will be less likely to

survive.

Plants and herbivores

Almost all plants synthesize a variety of secondary compounds (so called because

they play little or no role in primary metabolism). Thousands of such compounds

have been described, including many that humans have found useful as drugs

(e.g., salicylic acid, the active ingredient of aspirin), stimulants (caffeine), condi-

ments (capsaicin, the “hot” element in chili peppers), and in other ways (can-

nabinol, in marijuana). Families of plants are often characterized by particular

groups of similar compounds, such as cardiac glycosides in milkweeds (Apocy-

naceae) and glucosinolates in mustards (Brassicaceae). Many of these compounds

are known to be toxic or repellent to animals, and there is plentiful evidence that

insects and other herbivores impose selection for chemical and other defenses.

Futuyma Kirkpatrick Evolution, 4e

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Evolution4e_13.10.ai Date 11-29-2016

Au: Retain male (bottom left) or not?

Amauris

niavius

Papilio

dardanus

swallowtail

Amauris

echeria

Danaus

chrisippus

Acraea

poggei

Acraea

jodutta

Models:

Female

mimics:

Male:

FIGURE 13.10 Mimetic polymorphism in the

African swallowtail butterfly Papilio dardanus.

Males have only one color form (at bottom),

but populations contain several color forms

of females (mimics, in the middle row), each

of which closely resembles a distantly related

distasteful species (models, in the top row).

Predators that have attacked a distasteful

model learn to avoid butterflies with that color

pattern. As the abundance of any specific

color morph of P. dardanus increases, its fit-

ness tends to decline, because predators are

increasingly likely to associate the pattern with

a tasty meal rather than a foul taste. (From [75].)

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_13.11.ai Date 02-06-2017

Common

model:

Mimics:

Mismatched Matched

H. sapho

Matched

Mismatched

Matched

Mismatched

H. eleuchia

Matched Mismatched

0.01

1 3 5 9 117

Days after release

1 3 5 9 117

Days after release

0.05

0.5

0.1

1.0

Proportion resighted 0.01

0.05

0.5

0.1

1.0

Proportion resighted

FIGURE 13.11 Müllerian mimicry protects Heliconius

butterflies. Two color morphs of Heliconius cydno

mimic two different species of models (H. sapho and H.

eleuchia). The models vary in abundance between locali-

ties, and the mimic that matches the common model

survives best. Left: In one locality, the model species H.

eleuchia is most common. Both morphs of the mimic

species were marked and released, and their survival was

monitored in the following days. The mimic that matched

the common model survived best. Right: In another

locality, the model species H. sapho is more common.

The same procedure used in the first experiment showed

that again the mimic that matched the locally abundant

model survived best. This second experiment confirms

that a mimic’s survival rate was determined by whether

it matched the model that was most frequent, not by an

intrinsic advantage of one mimic color pattern over the

other. (From [38].)

13_EVOL4E_CH13.indd 329 3/22/17 1:26 PM