PLANT-MEDIATED INTERACTIONS BETWEEN ABOVE- AND BELOW-GROUND COMMUNITIES

http://onlinelibrary.wiley.com/doi/10.1111/jec.2010.99.issue-1/issuetoc

Special Issue
Journal of Ecology

Ant-Plant Mutualism

 

 

Summary

1.  Mutualistic interactions are characterized by conditional outcomes that depend on both the biotic and the abiotic context. However, limited information is available on the factors that affect the strength of ant–plant interactions among sympatric congeneric species.

2.  We compared the benefits gained from attracting ants via extrafloral nectaries – i.e. lowered herbivory and increased seed set – of three co-occurring varieties in the Chamaecrista desvauxii complex (Leguminosae) in a cerrado area in Uberlândia, Brazil. Using whole-individual exclusion experiments, we tested the hypotheses (i) that the relative strength of those benefits is higher in the variety with the largest extrafloral nectaries and (ii) that those benefits are conditional on the presence of predispersal seed predators.

3. Extrafloral nectaries are larger, produce more nectar and attract more ants in var. brevipes than in the other two varieties included in the study. Var. modesta has intermediate-sized nectaries, while a third, undescribed variety has small nectaries, and both attract relatively few ants.

4. For var. brevipes, extrafloral nectary (EFN) removal significantly increased folivory and attack on fruits by sucking insects, decreasing the relative number of flowers, fruits and seeds produced per individual. For the other two varieties, in contrast, ant effects were reduced, and ants did not significantly improve reproductive success. In addition, effects of EFN removal were less pronounced or absent when seed predators were excluded from fruits of var. brevipes.

5. Synthesis. We showed experimentally that benefits from interactions of three co-occurring varieties of Chamaecrista desvauxii with ants are context-dependent both within and among taxa. Variation in the strength of mutualisms among sympatric taxa may potentially reinforce ecological reproductive isolation and contribute to diversification in this group.

Journal of Ecology

Volume 100, Issue 1, pages 242–252, January 2012

Acacia plant controls ants with chemical

This is an old topic, but it is really amazing!

In Africa and in the tropics, armies of tiny creatures make the twisting stems of acacia plants their homes.
Aggressive, stinging ants feed on the sugary nectar the plant provides and live in nests protected by its thick bark.
This is the world of "ant guards".
The acacias might appear overrun by them, but the plants have the ants wrapped around their little stems.
These same plants that provide shelter and produce nourishing nectar to feed the insects also make chemicals that send them into a defensive frenzy, forcing them into retreat.

http://news.bbc.co.uk/2/hi/8383577.stm