Vachellia cornigera

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Vachellia cornigera
A-cornigera.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Subfamily: Caesalpinioideae
Clade: Mimosoid clade
Genus: Vachellia
Species:
V. cornigera
Binomial name
Vachellia cornigera
(L.) Seigler & Ebinger
Acacia-cornigera-range-map.png
Range of Vachellia cornigera
Synonyms
  • Acacia campecheana Schenck
  • Acacia cornigera (L.) Willd.
  • Acacia cornigera var. americana DC.
  • Acacia cubensis Schenck
  • Acacia furcella Saff.
  • Acacia hernandezii Saff.
  • Acacia interjecta Schenck
  • Acacia rossiana Schenck
  • Acacia spadicigera Schldl. & Cham.
  • Acacia turgida Saff.
  • Mimosa cornigera L.
  • Tauroceras cornigerum (L.)Britton & Rose
  • Tauroceras spadicigerum (Schldl. & Cham.)Britton & Rose [1]

Vachellia cornigera, commonly known as bullhorn acacia (family Fabaceae), is a swollen-thorn tree and Myrmecophyte native to Mexico and Central America. The common name of "bullhorn" refers to the enlarged, hollowed-out, swollen thorns (technically called stipular spines ) that occur in pairs at the base of leaves, and resemble the horns of a steer. In Yucatán (one region where the bullhorn acacia thrives) it is called "subín", in Panamá the locals call them "cachito" (little horn). The trees are commonly found in wet lowlands [2]

Contents

Morphology

Bullhorn acacias are often found as 10 meter (33 ft.) trees. Their bark is gray to brown in color and has small furrows. The new growth of the branches is a reddish brown color and is covered in a pubescence, or a covering of small hairs. The leaves are alternate with a pair of stipular spines where the leaf connects to the branch. The spines can vary widely in color from brown, red, and yellow. [3] The spines are home to ants that protect the plant from herbivory. Beltian bodies can be found at the tips of the leaves. They are full of fats and sugars that feed the ants. [2] The tree also produces carbohydrate-rich nectar from glands on its leaf stalk. This type of relationship is called myrmecophily.

Symbiotic relationship

Acacia ants Pseudomyrmex ferruginea Ryan Somma.jpg
Acacia ants

Bullhorn acacia is best known for its symbiotic relationship with Pseudomyrmex ferruginea, an ant that lives in its hollowed-out thorns. Unlike other acacias, bullhorn acacias are deficient in the bitter alkaloids usually located in the leaves that defend against ravaging insects and animals. Bullhorn acacia ants fulfill that role.

The ants act as a defense mechanism for the tree, protecting it against harmful insects, animals or humans that may come into contact with it. The ants live in the thorns. In return, the tree supplies the ants with Beltian bodies, or protein-lipid nodules, and nectar. These Beltian bodies have no known function other than to provide food for the ants. The aggressive ants release an alarm pheromone and rush out of their thorn "barracks" in great numbers.

According to Daniel Janzen, livestock can apparently smell the pheromone and avoid these acacias day and night. [4] Getting stung in the mouth and tongue is an effective deterrent to browsing on the tender foliage. In addition to protecting V. conigera from leaf-cutting ants and other unwanted herbivores, the ants also clear away invasive seedlings around the base of the tree that might overgrow it and block out vital sunlight.

Physiology

The physiology of bullhorn acacia (vachellia cornigera) and P. ferrugineus ant's chemical signalling uses the typical herbivore response signaling pathways expressed in plants.  However, the bullhorn acacia extends the function of this signaling to recruit ants to help protect against herbivores.  This results in the acacia having an obligate relationship with the P. ferrugineus ants. In this relationship, the plants provide ants with shelter, in the form of swollen stipular spines, food (in the form of protein-lipid-rich beltian bodies) and sugar-secreting extrafloral nectaries. The beltian bodies, small detachable tips on the pinnules of the bullhorn acacia, have evolved into multicellular structures to provide food for protective ant colonies. The P. ferrugineus ants cut small holes in the thorns of the acacia where they lay eggs and care for larvae. These thorns are waterproof and hold in moisture which protects the ants.

The communication between the bullhorn acacia and the ants is mediated by volatiles which arise from damaged vegetation. The major volatile released from crushed leaves was identified via gas chromatography to be trans-2-hexenal.  In an experiment by William F. Wood and Brenda J. Wood, solutions of trans-2-hexenal and dichloromethane were placed on bull horn acacia to see if the ants would respond.  The results of this were that a statistically significant number of ants displayed more aggravated behavior and swarmed the area with trans-2-hexenal than dichloromethane, proving trans-2-hexenal was the main volatile used by the bullhorn acacia to signal its distress to the ants. [5] Thus, the initial signal of the damage response pathway is the physical damage of the leaf. This leads to a flux in Ca2+ levels in the leaf cells, generating a variation potential. The result of the variation potential is the damaged leaves releasing the volatile trans-2-hexena, which the ants sense and respond to by swarming the damaged area to drive off herbivores.

However, the volatile release in response to damage has a secondary function.  A study by Hernández-Zepeda et al. revealed that the release of volatiles corresponded with the activation of the jasmonic acid pathway in plants: a common pathway in plants that activates in response to damage.  Furthermore, the application of jasmonic acid to leaves resulted in an increase in extrafloral nectar production by CWIN (an invertase regulator of nectar secretion found in the cell wall). Thus, it can be understood that when damaged, the Bullhorn acacia creates a signal to the ants to defend it while also increasing the production of the ants' food source. [6]

The extrafloral nectaries, which are nectar secreting plant glands, are located on the acacia's petioles and are the location of the food source for the ants. The secreted nectar plays an important role as plant indirect defense through the attraction of defending ants. As long as the plants are inhabited by mutualistic ants, the extrafloral nectar will get secreted with a sharp diurnal peak (between 8-10am). The nectary is the site of nectar synthesis, and the components that get synthesized include sugar, amino acids, and nectarines. The metabolic machinery for the extrafloral nectar production is synthesized and active during secretion then degraded after. Invertase is an enzyme that was found by Orona-Tamayo et al. to play an important role in nectar secretion, as it collects in the nectaries right before secretion, then declines quickly after the secretion. [7]

The nectar secretion from nectaries and food bodies on leaves and shelter (hollow stipular spines at the base of a leaf) is known as swollen plant syndrome. This syndrome is vital to the acacia plant's survival because it facilitates the animal-plant mutualism with the P. ferrugineus ants. However, this syndrome does not develop until several weeks after germination.

It has been reported that swollen thorn syndrome (production of specialized traits in the form of hollow stipular spines, beltian bodies, and extrafloral nectaries) was absent in the early development of the bullhorn acacia. Leichty and Poethig linked the expression of swollen thorn syndrome to a change in the expression of genes in the miR156/miR157 and their corresponding increase in their target SPL transcription factors. Specifically, they found that gradual decline in miRNA156/157 was correlated with gradual increase in length of extrafloral nectaries and an increase in the number of beltian bodies. Furthermore, stipule swelling occurred at the nodes with the lowest levels of these miRNAs. Their results highlight that these traits are controlled by the miR156/miRNA157-SPL pathway, suggesting that this syndrome is an age-dependent (temporally regulated) consequence of genetic regulation and not of passive constraints on development. [8]

In a study by Heil et al. in 2014, [9] the research team found that acacia hosts manipulate their ant inhabitants (pseudomyrmex) by inhibiting their sucrose invertase. This enzyme breaks down sucrose in the ants. The invertase in the ants is inhibited by an extra floral nectar (EFN) protein chitinase that is in the nectar provided for the ants by the acacia. By binding to the sucrose invertase enzymes in the ants, the chitinase prevents the ants from breaking down sucrose containing sugars. The acacia tree EFN does not contain sucrose so the ants can digest the EFN provided by the acacia but no other sucrose containing nectars. Unknown to the ants, this very source (the EFN) contains the inhibiting chitinase. This manipulation of the ants physiology by acacia ensures the continuation of defense behavior of the ants.

The symbiotic relationship between the bullhorn acacia and P. ferrugineus ants is of a mutualistic nature for both species. This relationship has many physiological factors in both the acacia and ants. The behaviors that arise from these factors are currently known to include: Acacia defense by ants and nectar secretion by acacia resulting in partner manipulation of the ants by the acacia.

Uses

Decorative uses

The thorns of V. cornigera, are often strung into unusual necklaces and belts. In El Salvador the horn-shaped thorns provide the legs for small ballerina seed dolls which are worn as decorative pins.

Traditional medicine

The thorns of V. cornigera are also used in traditional Maya acupuncture. [10]

Related Research Articles

<i>Acacia sensu lato</i> Genus of legumes

Acacia s.l., known commonly as mimosa, acacia, thorntree or wattle, is a polyphyletic genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae. It was described by the Swedish botanist Carl Linnaeus in 1773 based on the African species Acacia nilotica. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. All species are pod-bearing, with sap and leaves often bearing large amounts of tannins and condensed tannins that historically found use as pharmaceuticals and preservatives.

<span class="mw-page-title-main">Lima bean</span> Species of plant

A lima bean, also commonly known as the butter bean, sieva bean, double bean or Madagascar bean is a legume grown for its edible seeds or beans.

<span class="mw-page-title-main">Myrmecophyte</span> Plants that live in association with ants

Myrmecophytes are plants that live in a mutualistic association with a colony of ants. There are over 100 different genera of myrmecophytes. These plants possess structural adaptations that provide ants with food and/or shelter. These specialized structures include domatia, food bodies, and extrafloral nectaries. In exchange for food and shelter, ants aid the myrmecophyte in pollination, seed dispersal, gathering of essential nutrients, and/or defense. Specifically, domatia adapted to ants may be called myrmecodomatia.

<span class="mw-page-title-main">Nectar</span> Sugar-rich liquid produced by many flowering plants, that attracts pollinators and insects

Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide herbivore protection. Common nectar-consuming pollinators include mosquitoes, hoverflies, wasps, bees, butterflies and moths, hummingbirds, honeyeaters and bats. Nectar plays a crucial role in the foraging economics and evolution of nectar-eating species; for example, nectar foraging behavior is largely responsible for the divergent evolution of the African honey bee, A. m. scutellata and the western honey bee.

<i>Vachellia collinsii</i> Species of legume

Vachellia collinsii, previously Acacia collinsii, is a species of flowering plant native to Central America and parts of Africa.

<span class="mw-page-title-main">Myrmecophily</span> Positive interspecies associations between ants and other organisms

Myrmecophily is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its more general use, the term may also refer to commensal or even parasitic interactions.

<i>Vachellia constricta</i> Species of legume

Vachellia constricta, also known commonly as the whitethorn acacia, is a shrub native to Mexico and the Southwestern United States.

<i>Pseudomyrmex spinicola</i> Species of ant

Pseudomyrmex spinicola is a species of red myrmecophyte-inhabiting neotropical ants which are found only in Nicaragua and Costa Rica. They live in the thorns of tropical trees like Acacia collinsii or Acacia allenii, feeding on nectaries along with the protein and lipid-rich beltian bodies. These bodies are named for Thomas Belt, a naturalist who first described the interactions between acacias and ants in his 1874 book Naturalist in Nicaragua. Belt's book in fact described ants of this species, then unknown.

<i>Vachellia horrida</i> Species of legume

Vachellia horrida is a low spreading shrub or sometimes tree native to both the wet and dry scrublands of tropical to subtropical East Africa. Common names for it are Cape gum, Karroo Thorn and dev-babul. It is also found elsewhere in Africa, Asia, India and South America. It frequently has stipular spines 9.5 cm long. V. horrida is an important browse plant in the tropics, particularly during the dry season.

<i>Vachellia seyal</i> Species of plant

Vachellia seyal, the red acacia, known also as the shittah tree, is a thorny, 6– to 10-m-high tree with a pale greenish or reddish bark. At the base of the 3–10 cm (1.2–3.9 in) feathery leaves, two straight, light grey thorns grow to 7–20 cm (2.8–7.9 in) long. The blossoms are displayed in round, bright yellow clusters about 1.5 cm (0.59 in) diameter.

<i>Vachellia tortuosa</i> Species of legume

Vachellia tortuosa, the twisted acacia , poponax or huisachillo, is a woody, leguminous thorn tree of the Caribbean, Florida, southern Texas, northeastern and central Mexico, and northern South America. It is found in tropical and desert habitats, such as the Rio Grande Valley, Central Mexican Plateau, and Colombian Tatacoa Desert.

<i>Vachellia drepanolobium</i> Species of legume

Vachellia drepanolobium, more commonly known as Acacia drepanolobium or whistling thorn, is a swollen-thorn acacia native to East Africa. The whistling thorn grows up to 6 meters tall. It produces a pair of straight spines at each node, some of which have large bulbous bases. These swollen spines are naturally hollow and occupied by any one of several symbiotic ant species. The common name of the plant is derived from the observation that when wind blows over bulbous spines in which ants have made entry and exit holes, they produce a whistling noise.

<span class="mw-page-title-main">Beltian body</span>

A Beltian body is a detachable tip found on the pinnules of some species of Acacia and closely related genera. Beltian bodies, named after Thomas Belt, are rich in lipids, sugars and proteins and often red in colour. They are believed to have evolved in a symbiotic relationship with ants. The ants live inside special plant structures (domatia) or near the plant and keep away herbivores.

<i>Vachellia</i> Genus of legumes

Vachellia is a genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or acacias. It belongs to the subfamily Mimosoideae. Its species were considered members of genus Acacia until 2009. Vachellia can be distinguished from other acacias by its capitate inflorescences and spinescent stipules. Before discovery of the New World, Europeans in the Mediterranean region were familiar with several species of Vachellia, which they knew as sources of medicine, and had names for them that they inherited from the Greeks and Romans.

<span class="mw-page-title-main">Thorns, spines, and prickles</span> Hard, rigid extensions or modifications of leaves, roots, stems or buds with sharp, stiff ends

In plant morphology, thorns, spines, and prickles, and in general spinose structures, are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.

<i>Pseudomyrmex ferruginea</i> Species of ant

The acacia ant is a species of ant of the genus Pseudomyrmex. These arboreal, wasp-like ants have an orange-brown body around 3 mm in length and very large eyes. The acacia ant is best known and named for living in symbiosis with the bullhorn acacia throughout Central America.

<span class="mw-page-title-main">Pearl body</span>

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<span class="mw-page-title-main">Tritrophic interactions in plant defense</span> Ecological interactions

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Tetraponera penzigi, is a species of ant of the subfamily Pseudomyrmecinae, which can be found in East Africa. It forms an obligate symbiosis with the whistling thorn acacia, a dominant tree in some upland areas of East Africa.

<i>Passiflora glandulosa</i> Plant species

Passiflora glandulosa, more commonly known as wild passion fruit, is a short deciduous climbing plant with stems that can grow up to 20 m (66 ft) long. The genus Passiflora is known for its colorful flowers, which is also prominent in the glandulosa species. Named by Antonio José Cavanilles in 1790, Passiflora glandulosa is native to many regions of the northeast coast of South America, having a neotropic distribution. In specific, Passiflora glandulosa is heavily populated in Guyana, Suriname, Brazil and French Guiana.

References

  1. Acacia cornigera (ILDIS LegumeWeb)
  2. 1 2 Morse, Clinton. "Vachellia cornigera {Fabaceae} Bull-thorn Acacia". florawww.eeb.uconn.edu. Retrieved 2020-04-24.
  3. "Factsheet - cornigera". www.anbg.gov.au. Retrieved 2020-04-24.
  4. Daniel Janzen, Costa Rican Natural History, 1983
  5. Martins, Dino J. (2010-11-10). "Not all ants are equal: obligate acacia ants provide different levels of protection against mega-herbivores". African Journal of Ecology. 48 (4): 1115–1122. doi:10.1111/j.1365-2028.2010.01226.x. ISSN   0141-6707.
  6. Hernández-Zepeda, Omar F.; Razo-Belman, Rosario; Heil, Martin (2018). "Reduced Responsiveness to Volatile Signals Creates a Modular Reward Provisioning in an Obligate Food-for-Protection Mutualism". Frontiers in Plant Science. 9: 1076. doi: 10.3389/fpls.2018.01076 . ISSN   1664-462X. PMC   6066664 . PMID   30087690.
  7. Orona-Tamayo, Domancar; Wielsch, Natalie; Escalante-Pérez, María; Svatos, Ales; Molina-Torres, Jorge; Muck, Alexander; Ramirez-Chávez, Enrique; Ádame-Alvarez, Rosa-María; Heil, Martin (2013). "Short-term proteomic dynamics reveal metabolic factory for active extrafloral nectar secretion by Acacia cornigera ant-plants". The Plant Journal. 73 (4): 546–554. doi: 10.1111/tpj.12052 . ISSN   1365-313X. PMID   23075038.
  8. Leichty, A. R., & Poethig, R. S. (2019). Development and evolution of age-dependent defenses in ant-acacias. Proceedings of the National Academy of Sciences, 116(31), 15596–15601. https://doi.org/10.1073/pnas.1900644116
  9. Heil, Martin; Barajas-Barron, Alejandro; Orona-Tamayo, Domancar; Wielsch, Natalie; Svatos, Ales (2014). "Partner manipulation stabilises a horizontally transmitted mutualism". Ecology Letters. 17 (2): 185–192. doi:10.1111/ele.12215. ISSN   1461-0248. PMID   24188323.
  10. Saqui, Aurora Garcia (2016). Ix Hmen U Tzaco Ah Maya: Maya Herbal Medicine. Caye Caulker, Belize: Produccicones de la Hamaca. p. 42. ISBN   978-9768142863.