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Plant Reproduction and Optimal Foraging: Experimental Nectar Manipulations in Delphinium Nelsonii

Michael Zimmerman
Oikos
Vol. 41, No. 1 (Aug., 1983), pp. 57-63
Published by: Wiley on behalf of Nordic Society Oikos
DOI: 10.2307/3544346
Stable URL: http://www.jstor.org/stable/3544346
Page Count: 7
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Plant Reproduction and Optimal Foraging: Experimental Nectar Manipulations in Delphinium Nelsonii
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Abstract

Delphinium nelsonii Greene (Ranunculaceae) individuals which were watered produced significantly more nectar per flower than did control individuals. The watered plants also set significantly more seeds per flower than did the controls. Hand pollinations suggest that the seed set difference was due to the increased nectar volume rather than to watering directly. Bumblebee pollinators' responses to the increased standing crop of reward were consistent with predictions from optimal foraging theory and explain the increase in seed set. Pollinators both visited more flowers per inflorescence and spent more time in flowers on nectar-rich plants relative to controls. These results imply that D. nelsonii individuals could increase the female component (i.e. seed set) of plant fitness by increasing their nectar production rate. The results do not, however, allow an accurate assessment of the male component (i.e., pollen donation) of fitness. /// Растеня Delphinium nelsonii Greeni (Ranunculaceae), которые поливали, да-вали гораздо больше нектара в расчете на цветок, чем контрольные. Поливае-мые растения продуцировали также гораздо больше семян в расчете на цветок, чем контрольные. Ручное опыление показало, что различия в количестве семян определяются скорее объемсм нектара, чем непосредственно поливом. Реакции шмелей-опылителей на увеличение продуюции нектара согласуются с теоретичес-кими предположениями оптимизации фуражировки и объясняют увеличение продук-ции семян. Опылители посещали больше цветков в соцветии и проводили больше времени на цветах на растениях, более богатых нектаром в сравнении с кон-трольными. Эти результаты показали, что растения D. nelsonii могут расши-рать женский компонент (те. количество семян) приспособленности за счет увеличения скорости продукции нектара. Результаты, однако, не поэволяют точно оценить значение мужского компоненга (т.е. отдачу пыльцы) в степени приспособленности.

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