Biology 8th Edition by Kenneth Mason ,Jonathan Losos,Susan Singer,Peter Raven,George Johnson

Exercise 8

Refer to figure 22.6. In Europe, pied and collared fl ycatchers are dissimilar in sympatry, but very similar in allopatry, consistent with character divergence in coloration. In this case, there is no competition for ecological resources as in other cases of character divergence discussed. How might this example work
Figure 22.6 Reinforcement in European flycatchers. The pied flycatcher (Ficedula hypoleuca) and the collared flycatcher (F. albicollis) appear very similar when they occur alone. However, in places where the two species occur sympatrically (indicated by the yellow color on the map), they have evolved differences in color and pattern, which allow individuals to choose mates from their own species and thus avoid hybridizing.