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The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth.

Publication ,  Journal Article
Ford, KR; Ness, JH; Bronstein, JL; Morris, WF
Published in: Oecologia
October 2015

The impact of mutualists on a partner's demography depends on how they affect the partner's multiple vital rates and how those vital rates, in turn, affect population growth. However, mutualism studies rarely measure effects on multiple vital rates or integrate them to assess the ultimate impact on population growth. We used vital rate data, population models and simulations of long-term population dynamics to quantify the demographic impact of a guild of ant species on the plant Ferocactus wislizeni. The ants feed at the plant's extrafloral nectaries and attack herbivores attempting to consume reproductive organs. Ant-guarded plants produced significantly more fruit, but ants had no significant effect on individual growth or survival. After integrating ant effects across these vital rates, we found that projected population growth was not significantly different between unguarded and ant-guarded plants because population growth was only weakly influenced by differences in fruit production (though strongly influenced by differences in individual growth and survival). However, simulations showed that ants could positively affect long-term plant population dynamics through services provided during rare but important events (herbivore outbreaks that reduce survival or years of high seedling recruitment associated with abundant precipitation). Thus, in this seemingly clear example of mutualism, the interaction may actually yield no clear benefit to plant population growth, or if it does, may only do so through the actions of the ants during rare events. These insights demonstrate the value of taking a demographic approach to studying the consequences of mutualism.

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Published In

Oecologia

DOI

EISSN

1432-1939

ISSN

0029-8549

Publication Date

October 2015

Volume

179

Issue

2

Start / End Page

435 / 446

Related Subject Headings

  • Symbiosis
  • Population Growth
  • Population Dynamics
  • Herbivory
  • Fruit
  • Ecology
  • Cactaceae
  • Behavior, Animal
  • Ants
  • Animals
 

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Ford, K. R., Ness, J. H., Bronstein, J. L., & Morris, W. F. (2015). The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth. Oecologia, 179(2), 435–446. https://doi.org/10.1007/s00442-015-3341-3
Ford, Kevin R., Joshua H. Ness, Judith L. Bronstein, and William F. Morris. “The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth.Oecologia 179, no. 2 (October 2015): 435–46. https://doi.org/10.1007/s00442-015-3341-3.
Ford KR, Ness JH, Bronstein JL, Morris WF. The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth. Oecologia. 2015 Oct;179(2):435–46.
Ford, Kevin R., et al. “The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth.Oecologia, vol. 179, no. 2, Oct. 2015, pp. 435–46. Epmc, doi:10.1007/s00442-015-3341-3.
Ford KR, Ness JH, Bronstein JL, Morris WF. The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth. Oecologia. 2015 Oct;179(2):435–446.
Journal cover image

Published In

Oecologia

DOI

EISSN

1432-1939

ISSN

0029-8549

Publication Date

October 2015

Volume

179

Issue

2

Start / End Page

435 / 446

Related Subject Headings

  • Symbiosis
  • Population Growth
  • Population Dynamics
  • Herbivory
  • Fruit
  • Ecology
  • Cactaceae
  • Behavior, Animal
  • Ants
  • Animals