Pollination mechanism and pollinator mediated selection in Cyclopogon elatus (Orchidaceae).

BENITEZ-VIEYRA, S.; MEDINA, M.; GLINOS, E.; COCUCCI A. A.

FUNCTIONAL ECOLOGY

Año: 2006 vol. 20 p. 948 - 957

0269-8463

1.Pollinator-mediated selection on traits associated with mechanical fit and attractionof pollinators were investigated through both sexual functions inCyclopogon elatus(Sw.) Schlechter (Orchidaceae).2.Only halictid bees, principallyAugochlora nausicaa, were observed as pollinators.The pollinarium becomes attached to the ventral surface of the bee’s mouthparts (labrum)when the proboscis, which closely matches the length of floral tube, is projected into theflower to reach nectar.3.We detected directional selection on nectary depth, with deeper nectaries favouredonly through male fitness, because this trait affects pollinaria removal but not deposition.Correlational selection was detected through male function between nectary depth andthe number of flowers in an individual’s floral display. These traits affect pollination ina multiplicative way: flower number is positively related to the number of bee visits, andnectary depth positively affects the effectiveness of pollinaria removal at each visit.4.We also detected stabilizing selection on display size. For smaller displays there wasa strongly positive association between number of flowers and overall reproductivesuccess, which can be attributed to a simple numerical effect. However, the expectedperformance of individual flowers is impaired in large displays by pollinator limitation,because bees visiting the display pollinate few flowers per visit and each bee carries, atmost, one pollinarium.