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Effect of Floral Morphology and Temperature on Pollen Receipt and Removal in Ipomoea Trichocarpa
Author(s) -
Murcia Carolina
Publication year - 1990
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1937378
Subject(s) - pollen , biology , anthesis , pollination , botany , pollinator , nectar , pollen source , horticulture , cultivar
In Gainesville, Florida, the coastal morning glory Ipomoea trichocarpa varies considerably in flower size, shape, and stigma—anther separation. I studied some of the causes and reproductive consequences of this variation by exploring its effect on pollen receipt and removal. Variation in flower size was caused by variation within genets and, more drastically, by temperature fluctuations. While several insect taxa visited I. trichocarpa flowers, I concentrated on one hawk moth species (Enyo lugubris) and the bumble bee Bombus pennsylvanicus. Hawk moths visited the flowers from the time of anthesis until sunrise, when bumble bees arrived. Stepwise regression analyses indicated that flower morphology affected pollen deposition during single hawk moth visits, single bumble bee visits, or unlimited hawk moth and bumble bee visits. The morphological variables with strongest effects differed in each case, and could be related to the foraging technique of each pollinator. Floral morphology affected pollen removal from flowers more than it influenced pollen receipt. The morphological variables that best explained variation in the amount of pollen removed from the anthers during a single bumble bee visit differed from those influencing pollen receipt. In the field, hawk moths could potentially fully pollinate I. trichocarpa before pollen from later rising bumble bees could send tubes to ovules. However, tube growth rate increased with rising morning temperatures. Thus, ovules could potentially have been fertilized by a mixture of pollen deposited by hawk moths and by bumble bees. Furthermore, low morning temperatures excluded hawk moths entirely from I. trichocarpa pollination, by delaying anthesis. On cool mornings, flowers opened in time to receive bumble bee visits only. The effect of temperature on flower size and pollinator type, coupled with the physical interaction between flower and pollinator morphologies, determined the amount of pollen removed from and received by I. trichocarpa.