Patterns of contemporary phenotypic selection and flower integration in the hummingbird-pollinated Nicotiana glauca between populations with different flower-pollinator combinations

NATTERO J.; SERSIC A.N.; COCUCCI A. A.

OIKOS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 119 p. 852 - 863

0030-1299

We studied six populations of the hummingbird-pollinated Nicotiana glauca to determine if the marked diff  erences in the degree of fl  oral-pollinator mismatch between populations promote divergences in the pattern of pollinator-mediated phe-notypic selection on single traits and on the evolution of complexes of many interacting fl  oral traits. We found evidence that fl  ower phenotype is being shaped by pollinator-mediated phenotypic selection, since corolla length was consistently under contemporary directional or stabilizing selection. Weak directional selection for longer corol-las was found in two populations with low fl  ower–pollinator mismatch; much stronger directional selection was detected for shorter corollas in two populations with high fl  ower–pollinator mismatch; fi  nally, the remaining two populations with intermediate fl  ower–pollinator mismatch showed stabilizing selection for corolla length. N. glauca populations diff  ered in every fl  ower character measured but variations in pollinator-mediated selection among populations were only observed for corolla length. Multiple covariation among traits was favoured, as suggested by the predominately functional patterns of integration and selection of complexes of many interacting fl  oral traits. h  is was consistent with the patterns of correlational selection exhibited by four of the six populations, where corolla length was under signifi  cant selection in combination with corolla width, style length or stamen length. Overall fl  oral integration was relatively high in all popula-tions but phenotypic integration patterns were not clearly accounted by the degree of fl  ower–pollinator mismatch or type of phenotypic selection, suggesting that trait covariation at the entire fl  ower level is not explained by the current scenario of pollinator-mediated selection.