Myrmecophytes

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A myrmecophyte is a plant that has evolved specialized structures that provide nesting resources for ants. These nesting structures made by the plants are called domatia. The term Myrmecophyte is translated as "ant-plant," which is rather vague. This has likely contributed to some using the term myrmecophyte to mean different things. For example, some consider plants that produce food resources for ants, such as extrafloral nectaries, are also be myrmecophytes. The most liberal, generalized use of the term implies myrmecophytes are plants with almost any kind of persistent association with ants. This page includes information about plants that produce specialized nest structures and the ants associated with them. The page Ants and Plants and the navigation box at the bottom of this page provides a list of linked topics where you can learn about other types of ant-plant associations.

Introduction

Co-evolved species typically have specialized structures and life histories that are intimately tied to their mutualistic ant-partners. One example is the epiphyte Dischidia major. Highly modified leaves of the plant (‘pitchers’) provide lodging for numerous ant species, especially those in the genus Philidris. In return, the ants bring organic debris into their nest, which provides nutrients to the plants when it is placed with branching adventitious roots that grow within the inhabited pitchers.

Cluster of pitcher leaves of Dischidia major growing on a tree trunk. Note the normal leaves at bottom. From Songkla, Thailand (Photo by Christian Peeters).
Philidris ants build soil runways to connect the entrances of adjacent pitchers of Dischidia major (the central stem can no longer be seen). (Photo by Christian Peeters).
Inhabited pitcher cut away to reveal Philidris workers and brood, as well as roots and inner partitions. (Photo by Christian Peeters).
Philidris build inner partitions by using the internal roots as framework. Ants bring debris from outside as construction material. These roots allow the epiphyte to use ant faeces and food remains as a nitrogen source. (Photo by Christian Peeters).

Myrmecophytic Plants

Acacia

The taxonomy of this genus has changed dramatically in recent decades. Once treated as a large group of species with a widespread distribution across the areas regions of the world, it was found to be polypyhletic in contemporary phylogentic studies. It was proposed to maintain Acacia for only some of the species, with others falling under other generic names, e.g., Vachellia, Mariosousa and Turnera . This proved to be controversial, there has not been a consensus as to what is the best solution, and many species are referred to by different names as there is more than one classification system in use.

The acacias of the New World tropics (Vachellia) are pioneer species that form mutualisms with Pseudomyrmex ants. The interactions between these plants and ants ants were famously written about by Belt (1874) in A Naturalist in Nicaragua. These ant-plant interactions were also the subject of Janzen's classic studies (e.g. Janzen 1966) of mutualism that are often detailed in ecology textbooks. The plants provide food and shelter for the ants and the ants in turn attack herbivores and destroy any encroaching plants around the base of the tree.

Some Pseudomyrmex species are considered a parasite of the acacia-ant mutualism. Pseudomyrmex nigropilosus, for example, will use the hollow-thorn domatia for nesting and exploit the food produced by the plants, i.e, beltian bodies and nectar from extrafloral nectaries, but they are not effective at decreasing herbivores and do not remove encroaching vegetation.

Turnera velutina

(previously Acacia hindsii) A new world tropical and subtropical plant species. The majority of individual plants are inhabited by the aggressive Pseudomyrmex ferrugineus. The ants defend the plant from herbivores and enchroaching plants, with the plant in turn producing both hollow thorns for nesting and beltian bodies for food. Fonseca-Romero et al. (2019) found the opportunistic ant Pseudomyrmex gracilis, that can sometimes become established in this plant, effectively exploits the hollow thorns and beltian bodies without providing robust defensive functions like the very aggressive Pseudomyrmex ferrugineus. The lack of a strong defensive function alters the plant by its producing thicker leaves and reducing its production of food bodies.

Vachellia collinsii

(previously Acacia collinsii) A common new world acacia that is typically inhabitated by a single colony of the mutualistic species Pseudomyrmex spinicola, Pseudomyrmex nigrocinctus or Pseudomyrmex flavicornis

Cecropia

A neotropical genus of fast growing pioneer trees. Ants of the genus Azteca are most commonly found living in and patrolling these plants. Neoponera luteola nests exclusively inside the stems of Cecropia tessmannii trees in Peru, feeding on glycogen-rich Müllerian bodies produced by the plant to guarantee the protection of ants against herbivores.

Cecropia

Leonardoxa africana

A complex of subspecies, this is an African forest understory plant with some forms having extrafloral nectaries and/or domatia. Two ant species Petalomyrmex phylax and Cataulacus mckeyi are known to be associated with these plants.

Leonardoxa africana

Macaranga

A southeastern Asian genus of pioneer tree species.

Macaranga

Triplaris

A neotropical plant genus. One common name of these plants is "Ant tree". These dioecious species of trees are most often associated with Pseudomyrmex but other species also inhabit their hollow stems.

Triplaris

References

  • Belt, T. 1874. The Naturalist in Nicaragua. E. Bumpus, London.
  • Janzen D.H. 1974. Epiphytic myrmecophytes in Sarawak: mutualism through the feeding of plants by ants. Biotropica 6: 237 – 259.
  • Hölldobler B. and Wilson E.O. 1990. The Ants. Cambridge, Mass. Harvard University Press.
  • Kaufmann E. and Maschwitz U. 2006. Ant-gardens of tropical Asian rainforests. Naturwissenschaften 93: 216 – 227.
  • Peeters, C. & D. Wiwatwitaya 2014. Philidris ants living in Dischidia epiphytes from Thailand. Asian Myrmecology 6: 49-61.
  • Fonseca-Romero, M. A., J. Fornoni, E. del-Val, and K. Boege. 2019. Ontogenetic trajectories of direct and indirect defenses of myrmecophytic plants colonized either by mutualistic or opportunistic ant species. Oecologia. 190:857-865. doi:10.1007/s00442-019-04469-y
  • Weir JS and Kiew R. 1986. A reassessment of the relations in Malaysia between ants (Crematogaster) on trees (Leptospermum and Dacrydium) and epiphytes of the genus Dischidia (Asclepiadaceae) including ‘ant-plants’. Biological Journal of the Linnean Society 27: 113 – 132.