Phylogenetic analysis of floral integration inSchizanthus(Solanaceae): does pollination truly integrate corolla traits?

Abstract

To assess whether floral integration patterns result from the action of pollinator selection on functionally related traits, we compared corolla integration patterns in eight Schizanthus species differing in pollination systems and in their degree of pollinator dependence across a molecular phylogeny. Integration patterns differed among species and these differences were not related to their phylogenetic relatedness. When the putative original function of some corolla traits was lost in pollinator‐dependent species, the integration among nonfunctional characters and the rest of the corolla traits was disrupted. This pattern was not presented in species adapted for late autonomous selfing, which exhibited higher corolla integration than their pollinator‐dependent relatives. These results suggest that corolla integration in pollinator‐dependent species was shaped by pollinator‐mediated selection. Decoupling of nonfunctional traits in these species may result from a relaxation of correlational selection or from selection acting against a default covariation provided by genetic and developmental connections.

Modularity and intra-floral integration in metameric organisms: plants are more than the sum of their parts

“…The second set of integrated traits detected in the flowers of Nicotiana was associated with the corolla limb (the flared portion of the corolla) and corolla tube aperture. This second set of flower features likely functions in pollinator attraction [39,66,67,72,75]. For Nicotiana, the two sets of traits are each putatively related to function and are…”

“…For example, among species of Schizanthus (Solanaceae), transitions from bee pollination to hawkmoth or hummingbird pollination are associated with changes in the function of the individual corolla lobes [66]. Only those lobes that are involved in providing a landing platform and determining pollen deposition are integrated.…”

The role of pollinator diversity in the evolution of corolla-shape integration in a pollination-generalist plant clade

“…According to this idea, the role of natural selection in favouring the functional coordination of the flower parts has long been acknowledged [3]. In particular, in animalpollinated plants, it is widely assumed that pollinators play a large role in the evolution of not only floral traits but also floral integration [4][5][6][7][8][9][10][11][12][13]. Pollinators, besides affecting the mean and variation of floral traits by exerting directional and stabilizing selection, can also impose correlational selection on certain combinations of floral traits [14,15].…”

“…Pollinators, besides affecting the mean and variation of floral traits by exerting directional and stabilizing selection, can also impose correlational selection on certain combinations of floral traits [14,15]. The morphological integration of flowers pollinated by animals is expected to be higher than the integration of wind-and self-pollinated flowers [5][6][7]10].…”

Floral trait variation and integration as a function of sexual deception inGorteria diffusa

“…Pollinator-mediated selection may therefore weaken existing developmental genetic integration by relaxed selection or opposing selection on correlated traits [13,14]. Additional mechanisms must also maintain accurate pollen transfer within self-compatible species, contributing to floral integration independent of pollinator-mediated selection [12 -14].…”