Evolution, 4th Edition

EvoluTion And dEvEloPmEnT 395

the rate of growth and development in plants and ectothermic animals. The tad-

poles of populations of green frogs (Rana clamitans) at cold, high elevations develop

more rapidly than do those from warmer lowlands, when both are reared at low

temperatures (FIGURE 15.29) [6]. The high-elevation populations have evolved

a genetic change (faster growth) that compensates for the plastic environmental

effect (slower growth). How often phenotypic plasticity leads to the evolution of

new adaptations is not yet known.

FIGURE 15.29 Populations of green frogs (Rana clamitans) at different elevations

have evolved different norms of reaction that compensate for differences in environ-

mental temperature. (A) The tadpoles’ rate of growth in size, in relation to the tempera-

ture at which they were reared in the laboratory. Blue circles are individuals from a

montane population, red circles are from a lowland population. Both populations have

maximal growth at about the same temperature. At lower temperatures, the montane

population has higher growth rate than the lowland population, compensating for

the direct effect of temperature on developmental rate. The difference between the

populations is reversed if tadpoles are reared at higher temperatures. (B) In the same

experiment, similar results were obtained for another measure of development rate.

Differentiation rate describes the rapidity with which the tadpoles reach metamorpho-

sis to the frog stage. (After [6].)

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

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Evolution4e_15.29.ai Date 02-08-2017

13 18 23 28 33

0.002

0.004

0.006

0.01

0.001

(A)

(B)

Montane

Lowland

Temperature (°C)

Growth rate

13 18 23 28 33

0.002

0.001

0.004

0.006

0.01

0.06

0.1

0.4

Montane

Lowland

Temperature (°C)

Differentiation rate

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