Figure 2.

Hybridization, polyploidy and flower phenotypes. (a) Interspecific hybridization can generate a large range of characters in hybrids, including intermediate characters and potentially characters that fall outside the range found in the parents (transgressive characters). Hybrids usually backcross to one or both of the parents, providing gene flow between species. Herbivores and/or pollinators may select for particular combinations of characters. (b) F1 and F2 hybrids between bee-pollinated Mimulus lewisii and predominantly hummingbird-pollinated M. cardinalis. In F2 the different flowers show a range of intermediate characters. Adapted, with permission, from [59] (Copyright (1999) National Academy of Sciences, U.S.A.). (c) Synthetic allopolyploids of Nicotiana attenuata and Nicotiana obtusifolia generate flowers and seeds with a larger range of characters than is found within the range encompassed by the parental phenotypes. Adapted, with permission, from [110].