FIGURE 16.3 Sympatric speciation. Flowering plants such as wheat commonly form new species through the process of polyploidy, an increase in the number of sets of chromosomes beyond the normal two sets. (a) The ancestral einkorn wheat (Triticum boeoticum) has two sets of chromosomes and produces small seeds. (b) Durum wheat (Triticum durum), which is used to make pasta, was bred to have four sets of chromosomes and produces medium-sized seeds. (c) Common wheat (Triticum aestivum), which is used mostly for bread, was bred to have six sets of chromosomes and produces the largest seeds.

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