Biology Now, 2e

Fast Lizards, Slow Corals ■ 243

E. lucunter

E. vanbrunti

E. viridis

E. lucunter

E. vanbrunti

E. viridis

Egg

Sperm from neither Echinometra viridis

nor Echinometra vanbrunti is able to

fertilize an egg from Echinometra

lucunter. (Egg and sperm size in relation

to each other are not to scale.)

Both E. lucunter and

E. viridis are found on the

Atlantic side of Panama.

E. vanbrunti is found

along the Pacific coast.

Figure 13.14

Gametic isolation among sea urchin species

The sea urchin species found along both coasts of Panama illustrate gametic isolation as a reproductive

barrier. At one point long ago, the Panama landmass was not continuous and did not separate the two

oceans. These three species likely evolved through both allopatric and sympatric speciation from a

recent common ancestor after the oceans were separated.

Q1: Which species is/are sympatric with Echinometra lucunter?

Q2: Which species is/are allopatric with E. lucunter?

Q3: If two individuals have incompatible gametes, what will be the result of a mating event

between them?

the next section of this book, we explore the

dramatic transitions in life-forms that have

walked, crawled, and swum around our planet,

from small dinosaurs with wings to the most

successful, most cunning species ever to traverse

the planet: humans.