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the same homesite. In North America the hoary marmot (Marmota caligata), a rodent

of similar size, lives in rock piles on the mountains and feeds on surrounding vege-

tation. The three species have converged in form and ecology.

There are many examples of convergence in birds. The yellow-throated longclaw

(Macronyx croceus), a member of the pipit family Motacillidae, lives in the dry open

grasslands of eastern Africa. It is brown, yellow below, with a black chest band. It

sits on bushes and sings constantly. In North America the western meadowlark (Sturnella

neglecta) is similar in appearance, behavior, and habitat but it belongs to the entirely

different new world family Icteridae. Penguins (Spheniscidae) of the southern hemi-

sphere are the ecological equivalents of the unrelated Alcidae (auks, murres, puffins,

guillemots) of the northern hemisphere.

Adaptive radiation is the name given to the divergence of a single lineage to

provide a variety of forms. Adaptive radiation is the evolution of ecological and

phenotypic diversity within a rapidly multiplying lineage. It is the differentiation of

a single ancestor into an array of species that inhabit a variety of environments and

that differ in the morphological, physiological, and behavioral traits used to exploit

22 Chapter 3

Fig. 3.2Examples of
convergent evolution
between placental and
marsupial mammals.

3.4.2Adaptive
radiation