Saturday 11 October 2014

Interpreting the relationship between Ants and Termites from a single piece of Mexican Amber.

Ants and Termites are eusocial Insects that have dominated many tropical ecosystems since at least the Early Cretaceous. Relationships between the two groups (which are not closely related) are complex, with some species able to tolerate one-another and even share nests, while others are deeply hostile, typically with Ants feeding on Termites or Termites fighting to keep all Ants away from their territories. However, while these relationships have been extensively studied in modern representatives of the group, understanding how these Insects may have interacted in the remote past is much more difficult.

In a paper published in the journal PLoS One on 20 August 2014, David Coty of the Muséum National d’Histoire Naturelle in Paris, Cédric Aria of the Department of Natural History-Palaeobiology at the Royal Ontario Museum and the Department of Ecology & Evolutionary Biology at the University of Toronto, and RomainGarrouste, Patricia Wils, Frédéric Legendre and André Nel, also of the of the Muséum National d’Histoire Naturelle in Paris, describe a single piece of amber from the Salt River Amber Mine in Chiapas State, Mexico, which includes several different Ants and Termites, and discuss the implications of this for relationships between the groups.

General configuration of the Mexican amber. (A) Overview of the amber piece, under optical microscope. Scale bar is 3 mm. (B) Three dimensional replica of the same; colours define taxonomic groups, viz. purple for Azteca Ants, blue for Nasutitermes Termites, red for Neivamyrmex Ant, green for small Psocodea. Labels: Az1, Azteca Ant nearest to predation scene; Az2 and Az3, two other Azteca Ants, both trapped in a flow distinct to that of the others inclusions and whose physical density matches that of the Nasutitermes soldier; Na1, Nasutitermes worker trapped between the Neivamyrmex mandibles; Na2, isolated Nasutitermes termite closest to predation scene; Na3, Nasutitermes worker with damaged gaster; Na4, Nasutitermes soldier; Ne, Neivamyrmex Ant; Ps, Psocodea; Scale bar is 3 mm. Aria et al. (2014).

The Amber contains four Termites assigned to a single (unknown) species of the genus Nasutitermes, three workers and a soldier, as well as three Ants of the genus Azteca and one Neivamyrmex Army Ant.

Neivamyrmex, like all Army Ants, are voracious predators, attacking invertebrate and invertebrate prey alike, typically with a sudden attack by a large number of Army Ants overwhelming the prey. Other Ants and Termites are favoured prey for such Insects, and nests will always be attacked when encountered. The Neivamyrmex Ant in the amber has a small worker Termite in its jaws, which suggests that it was engaged in such an attack when it became stuck in, and overwhelmed by, the plant resin which later became preserved as amber. Potentially the Termite could have been seized reflexively by the trapped, dying Ant, or the Ant could have become trapper while trying to scavenge a Termite previously caught in the resin, but one of the other worker Termites shows signs of damage typical of an Army Ant attack suggesting that the two species were fighting before becoming overwhelmed. The presence of a soldier Termite also supports this hypothesis, as in modern members of the genus Nasutitermes, members of this caste remain inside the nest for most of the time, only emerging when the nest is threatened or attacked, and never moving far from the nest.

Details of the Termites. (A) General side view of the NeivamyrmexAnt holding a Nasutitermes Termite (Na1) between its mandibles, under optical microscope, scale bar is 1 mm. (B) Detail of damaged gaster of Nasutitermes worker (Na3) closely contiguous to a Nasutitermes soldier (Na4), scale bar is 1 mm. (C) Side view of closely contiguous Nasutitermes soldier (Na4) and worker (Na3), black arrow: digestive tube of Nasutitermes worker scale bar is 1 mm.Aria et al. (2014).

The situation with the AztecaAnts is more complex. Some modern members of this genus are able to co-occupy the nests of some species of Nasutitermes, on either a seasonal or permanent basis. This is not an entirely benign relationship, as the Ants do consume some of the Termites, but the benefits to the Termites appear to outweigh the costs of removing the Ants; the Termites consume dead Ants, which are a rich source of nitrogen, although they do not actively predate the Ants, and the two species appear to cooperate when defending the nest against mutual threats, such as Army Ants. Aria et al. suggest that the presence of Azteca Ants alongside Nasutitermes Termites that were apparently engaged in defending their nest against an Army Ant attack strongly suggests that such a relationship was occurring in this instance, and that the Ants and Termites were engaged in a defence of a mutual nest against the invading Army Ants.

The precise age of amber from the Salt River Mine has yet to be determined, however it is thought to be at least Middle Miocene in age, suggesting that the mutualistic relationship between Azteca Ants and Nasutitermes Termites is at least that old.

See also…

Leafcutter Ants harvest vegetation from the tropical rainforests of South and Central America, which they then carry back to their nests and use as feed in fungal farms. Each species of Ant has its own unique...

Thief Ants of the genus Solenopsis are one of the most numerous and widespread Ant groups, particularly in the tropics. However they are not greatly studied or understood, despite the fact that some species are...

Ants are among the most widespread and abundant of Insect groups, with over 13 000 described species. They play a major role in the shaping of modern ecosystems and landscapes, and many other species of animals, plants and even fungi have commensal...

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