On 'various contrivances': pollination, phylogeny and flower form in the Solanaceae

Abstract

Members of the euasterid angiosperm family Solanaceae have been characterized as remarkably diverse in terms of flower morphology and pollinator type. In order to test the relative contribution of phylogeny to the pattern of distribution of floral characters related to pollination, flower form and pollinators have been mapped onto a molecular phylogeny of the family. Bilateral flower symmetry (zygomorphy) is prevalent in the basal grades of the family, and more derived clades have flowers that are largely radially symmetric, with some parallel evolution of floral bilateralism. Pollinator types ('syndromes') are extremely homoplastic in the family, but members of subfamily Solanoideae are exceptional in being largely bee pollinated. Pollinator relationships in those genera where they have been investigated more fully are not as specific as flower morphology and the classical pollinator syndrome models might suggest, and more detailed studies in some particularly variable genera, such as Iochroma and Nicotiana, are key to understanding the role of pollinators in floral evolution and adaptive radiation in the family. More studies of pollinators in the field are a priority.

Figure 1.

Flower forms in the Solanaceae: (a) insect flower of Withania somnifera L. (MPIZ, Cologne, Germany), (b) insect flower of Lycium barbarum L. (Knapp IM-10134, China), (c) bee flower of Physalis pubescens L. (MPIZ, Cologne, Germany), (d) buzz-pollinated bee flower of Lycianthes sp. (Monro et al. 5301, Panama, photo A. Monro), (e) butterfly flower of B. grandiflora D. Don (Knapp et al. 9161, Panama), (f) moth flower of N. sylvestris Speg. & S. Comes (MPIZ, Cologne, Germany), (g) bird flower of Plowmania nyctaginoides (Standl.) Hunz. & Subils (Christenhusz et al. 5355, Guatemala, photo M. Vorontsova), (h) bat flower of Merinthopodium neuranthum (Hemsl.) Donn. Sm. (Monro et al. 260, Costa Rica). All scale bars, 1 cm; photos S. Knapp except where indicated.

Figure 2.

Distribution of flower form (right-hand cladogram) and pollination syndromes (left-hand cladogram; see table 1 for definitions). In the right-hand cladogram, radial flower symmetry is indicated with white, bilateral flower symmetry with green. In the left-hand cladogram, pollination syndromes are indicated as follows: insect flower, white; bee flower, dark blue; butterfly flower, turquoise; moth flower, yellow; bird flower, red; bat flower, black. Boxes associated with each terminal indicate the different syndromes or forms with their respective colours.