Ant communities more segregated in palm oil plantations than rainforest

By: Thomas Handley
March 21, 2013

Oil palm estate in Malaysia. Photo by: Rhett A. Butler.
Oil palm estate in Malaysia. Photo by: Rhett A. Butler.

Ants are an important ecological group in both degraded and natural habitats. They interact with many other species and mediate a range of ecological processes. These interactions are often interpreted in the context of ant mosaics, where dominant species form strict territories, keeping other ants out. This segregation between ant species is well-documented in monoculture plantations. Now new research published in Ecography has shown that these changes are driven by the replacement of rainforests with monocultures and not the arrival of non-native species.

Sampling oil palm plantations and primary lowland rain forest in the Danum Valley Conservation Area, Sabah, Malaysia, researchers found that high degrees of species segregation, i.e. ant mosaics, were present in oil palm plantation, and were absent, or at least much weaker, in primary rainforest.

"Oil palm plantation is much hotter and drier [than rainforest]. This means that there are fewer available nesting locations that are suitable cool and damp. One of the few remaining canopy nest sites in oil palm plantation are epiphytic bird's nest ferns, and we found high levels of species segregation for the ant communities in these ferns. This indicates that ants may be competing for these valuable resources to a greater extent than they would in primary forest, giving rise to ant mosaics," lead author Tom Fayle, with the University of South Bohemia, and a Member of the Forest Ecology and Conservation Group, Imperial College London told mongabay.com.

Unidentified ant in Malaysian Borneo. Photo by: Rhett A. Butler.
Unidentified ant in Malaysian Borneo. Photo by: Rhett A. Butler.
Fayle's research showed that the most common [ant] species in primary forest ferns was Diacamma, a generalist predator and scavenger, while, as predicted, the most common species in plantation ferns were from two myrmicine genera, both of which are known to survive of the sweet nectar secreted by these ferns.

In rainforest there are many more tree species than in palm oil; to be precise for every species in oil palm there are 587 species rain forest across 8 hectares. The enormous reduction in complexity of the canopy that occurs when a rainforest is converted into plantation means a single ant species can dominate a single oil palm canopy (since this is a rather small, and relatively isolated habitat patch); in rainforest, even within a single canopy, there is a vast number of different habitats for ants to inhabit. A single square meter of canopy could potentially consist of multiple species of trees across different canopy layers, so even if there is a single dominant species, other species may be able to co-exist with the dominant one. This high-level of connectivity in the rainforest canopy may also make it difficult to maintain a coherent territory, at least in contrast to the more simple structure of the plantation canopy.

The study also found that non-native species might act to disassemble ant communities in oil palm plantations, but whether or not these non-native species are detrimental to other ant species, and to other animals and plants remains to be seen, at least in oil palm plantations.

"Our data indicate that these non-native species do not, in fact, compete strongly with native species," Fayle told mongabay.com. "It may be that clearing forest merely makes the habitat more suitable for these species, while making it less suitable for native species".

Fayle also noted that non-native ant species can actually be useful. For example, the yellow crazy ant (Anoplolepis gracilipes) has been used to control herbivores in cocoa and coconut plantations.

The exciting world of invertebrates

Given the amazing complexity of ant communities as demonstrated by Fayle's study, it is easy to wonder why it is easier to rouse public interest in the cute and cuddly than in small creepy crawlies.

"I would certainly agree that it seems easier to excite people in general about vertebrates than invertebrates, and that it is important that scientists who work on invertebrates try to engage the public as much as possible," Fayle, whose work can be seen at www.tomfayle.com, told mongabay.com.

An ecosystem approach, showing how important some of these species are for humans, is perhaps one way of doing this. Alternatively it might be simply be a case of getting people interested in these animals for their own sake. Fayle refers to this as "the David Attenborough method", a good example of which is the 'School of Ants', a project encouraging US school children to make collections of ants."

Rainforest in Danum Valley. Photo by: Rhett A. Butler.
Rainforest in Danum Valley. Photo by: Rhett A. Butler.

CITATION: Tom M. Fayle, Edgar C. Turner and William A. Foster.Ant mosaics occur in SE Asian oil palm plantation but not rain forest and are influenced by the presence of nest-sites and non-native species. Ecography 36: 001–007, 2013. doi: 10.1111/j.1600-0587.2012.00192.x

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By: Thomas Handley (March 21, 2013).

Ant communities more segregated in palm oil plantations than rainforest .