Biology Now, 2e

232 ■ CHAPTER 13 Adaptation and Species

EVOLUTION

I

n 1971, the United States was at war in Viet-

nam, a gallon of gas cost 40 cents, a computer

engineer sent the first e-mail—and an Israeli

biologist named Eviatar Nevo captured 10 lizards

on Pod Kopište, a small, rocky island off the coast

of Croatia. Each lizard was about the length of a

pinky finger and as heavy as a nickel. There was

nothing remarkable about them.

Nevo and his team released the captured

lizards, a common Mediterranean species called

Podarcis sicula, on a nearby island just 3 miles

away, within sight of the original island but

separated by a deep ocean gulf (Figure 13.1).

Pod Mrcˇaru is a smaller, plant-covered island

that was already inhabited by two other lizard

species. Nevo was curious to find out what would

happen when the three species began to compete

for resources on Pod Mrcˇaru. But Nevo never

got the chance to return to the island. Shortly

after he and his team departed, unrest broke

out across Croatia, and war held the region in a

stranglehold throughout the 1980s and ’90s.

Scientists did not return to Pod Mrcˇaru until

2004. While visiting the University of Antwerp
      in Belgium, biologist Duncan Irschick from
      the University of Massachusetts, Amherst, and
      his Belgian colleagues decided to investigate
      the mysterious island. One of the researchers,
      familiar with an obscure paper that Nevo had
      published in 1972, thought it would be interest-
      ing to see what, if anything, had happened to
      the lizards. Further, Irschick would be able to
      complete some research on lizard behavior that
      he had planned to do in Europe anyway. “We
      didn’t know what we’d find,” recalls Irschick.
      “We decided, ‘Let’s just go check.’” This time, the
      lizards on the island were quite remarkable.

Leaping Lizards

Back in the 1970s, Nevo’s ten Podarcis sicula

lizards had been well adapted to the rocky,

sparsely vegetated environment of Pod Kopište.

They had specific adaptive traits, inherited

characteristics that enabled them to survive and

reproduce successfully on the island. Adaptive

traits can be structural features, biochemical

traits, or behaviors. In this case, the lizards were

fast, with long legs that may have helped them

catch the insects that made up most of their diet

on the island. They were also territorial, fighting

with other lizards over space and mating part-

ners. These adaptive traits, among others, enabled

the lizards to survive and reproduce better than

competitors lacking those traits on Pod Kopište.

When transplanted to Pod Mrcˇaru, however,

the lizards faced a new environment. Pod

Kopište is large and rocky with few plants, and

the lizards ate primarily insects; Pod Mrcˇaru is

smaller yet has an abundant supply of plants,

including leaves and stems of local shrubs and

grasses (Figure 13.2). Either the lizards would

adapt to their new surroundings, or they would

die. The term adaptation is commonly applied

to adaptive traits or the process of evolution

through natural selection that brings about

adaptive traits, as discussed in Chapter 12.

Therefore, an adaptation can be a trait that is

advantageous to an individual or a population

or, in broader terms, it can be the evolutionary

Figure 13.1

View of Pod Kopište from Pod Mrcˇaru

The island Pod Kopište (top), the original home of the Podarcis sicula lizards

(bottom), is only 3 miles from their new home on the island Pod Mrcˇaru.