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Vachellia collinsii | |
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V. collinsii in Guanacaste, Costa Rica. | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Rosids |
Order: | Fabales |
Family: | Fabaceae |
Subfamily: | Caesalpinioideae |
Clade: | Mimosoid clade |
Genus: | Vachellia |
Species: | V. collinsii |
Binomial name | |
Vachellia collinsii | |
Synonyms | |
Acacia collinsiiSaff. |
Vachellia collinsii, previously Acacia collinsii, is a species of flowering plant native to Central America and parts of Africa. [2]
Vachellia collinsii is native to Central America and parts of Africa. In southern Central America, where there are seasonally dry ecosystems, this tree grows in secondary succession, preferring Savanna-like climates. Acacias like full sun and are rarely found in the trophic understory of many jungles. Acacias can thrive in climates with higher humidity, above 70% humidity. The Vachellia collinsii has a wide distribution across the world compared to other acacias, as well as a wide ecological distribution, considering it can grow from sea level to 1000 meters elevation. [2]
The Vachellia collinsii can grow upwards of 40 feet tall. The tree grows relatively straight with thorns generously distributed across the branches. The small, pinnate leaves grow opposite from each other similar to a Mimosa. Since this species has a diverse geological and ecological distribution, it has a wider range of morphological traits. Nonetheless, differences between other ant-acacias can be seen through elongated cylindrical inflorescences, somewhat small stipular spines, terete—cylindrical—spines that wrap around a cross section, 3-5 often dome-shaped petiolar glands, a lack of rachis glands, and leaflets with lateral veins. [2] On the petioles, are green bumps called extrafloral nectaries that create sugar for symbiotic ants. From top to bottom of these trees, there is less suppression of lateral growth, thus, allowing for more numerous and full branches near the base of the tree, creating a pyramid shape with a strong central trunk. While most tree species typically have auxin that grow downward, suppressing branch growth on the sides, this is not the case for Vachellia Collinsii, as it lacks a strong apical meristem. This results in branching throughout the entire length of the tree. They are extrafloral because the true, yellow flowers produce a different kind of nectar. The tips of leaflets may produce Beltian bodies, food bodies which are rich in protein and lipids. These are also created as part of their symbiotic relationship with ants. [3]
Vachellia collinsii exhibits a symbiotic relationship with several species of ants. Some noted species include Pseudomyrmex spinicola and Pseudomyrmex ferruginea. The ant-Vachellia system involving this species has been studied by ecologists like Daniel Janzen in Palo Verde National Park and Santa Rosa National Park, which are both located in Guanacaste Province, Costa Rica. The ants chew holes in the tips of the hollow stipular thorns, known as domatia, so that they can enter and create their colony inside. A single ant colony may span several V. collinsii trees. Medium sized herbivores are often deterred by the thorns alone, but the ants help protect the trees from other potentially threatening animals. Smaller animals such as caterpillars have no issue avoiding the thorns, and larger animals like elephants are less affected by these thorns. When a predator brushes and shakes the plant’s thorns in an attempt to feed, the ants will become disturbed, run outside, and release alarm pheromones to alert other ants. All ants that come in contact with the alarm pheromones become aggressive and attack the animal by biting and stinging. Beyond defending the trees from herbivores, ants occupying V. collinsii trees may even cut down surrounding vegetation and trim the encroaching branches of other plants. This provides V. collinsii with valuable space and unimpacted access to sunlight, allowing the trees to thrive. In exchange, V. collinsii not only provides the ants with hollow thorns in which to live, but also produces lipid- and protein-rich food bodies, known as Beltian bodies, on the tips of new leaflets. These bodies are consumed by the ants, providing critical nutrients for the colony. When starved of nutrients, V. collinsii produces more Beltian bodies to encourage the presence of ants. When the tree has enough extra nutrients, it will create less Beltian bodies. This behaviour suggests a feedback loop. Vachellia collinsii also provides the ants with sugar-rich nectar from extrafloral nectaries located at the leaf petiole. Since there are several species of ants that may occupy a V. collinsii, there has been observations of intraspecific interactions between these species of ants, especially between Pseudomyrmex spinicola and Crematogaster brevispinosa. C. brevispinosa may take over trees occupied by Pseudomyrmex spinicola or Pseudomyrmex nigrocinctus . C. brevispinosa will also occupy trees that are dying or heavily damaged, or trees that were previously inhabited. [4] Furthermore, a hypothesized benefit to hosting ant colonies is that the acacia may have receptors within the domatia for ant feces that triggers absorption pathways for additional nutrient uptake at the extremities of the plant's stem tissue. When ants defecate in the domatia, their feces contain nutrients from their food which could be good for the plant. This allows the plant to obtain additional nutrients and in a shorter period of time as the nutrients do not need to travel all the way up starting from the roots.[ citation needed ]
The symbiotic ants living on this tree become alarmed at tissue disruption of the plant’s leaves by herbivores like the scarab, Pelidnota punctulate. This beetle only feeds on ant-acacias and is protected by its heavy cuticle. Tissue disruption of the tree leaves releases trans-2-hexenal, a compound that ants detect as a kairomone. On exposure to test samples of this compound the ants become alarmed and displayed alarm behavior. [5] This compound is not found in the mandibular gland secretions of Costa Rican acacia ants, that are likely to be the source of the ant’s alarm pheromones. [6]
Diving deeper into why the acacia collinsii produce traits of the “swollen thorn syndrome,” the mechanism and pathways are still unknown but there have been experiments and strong evidence related to a change in gene expression of miR156/miR157 and SPL transcription factors, in different environmental conditions. The production of food bodies that are high in proteins and lipids as well as extrafloral nectaries is very costly so the plant must have some indication of when to start producing those traits. Generally, an acacia will not produce these traits immediately after germinating so it is age dependent and the extrafloral nectaries will be produced first around 50–75 days of age, then swollen and elongated stipules, followed by full beltian bodies. Along with the production of these traits, are declines in miR156/miR157 genes. [7] The miR156-SPL pathway has been known in many plants to coordinate when the plant flowers as well as plant development combined with stress tolerance. In an Arabidopsis, the miR156 will keep the plant juvenile, then become suppressed when it is in the right conditions in order to further develop adult traits. [8] When put in low light conditions, there is higher miR156/miR157 as well as a delay in swollen thorn syndrome traits. The other way around is also true in that when put in well lit conditions such as the natural environment, there is a low expression of miR156/miR157 genes when the plant is producing extrafloral nectaries, swollen stipules, and beltian bodies. Although it is unknown how the expression of the traits are linked to the miR156/miR157 genes, hypotheses include temporal coordination or regulation where the miR156/157 turn on and off in a pattern in order to turn on those genes for the swollen thorn syndrome(which are still unknown). There is also evidence that these traits are part of their defense mechanism and that nectar secretion from the extrafloral nectaries depend on jasmonic acid but the mechanism is unknown as jasmonic acid could have a different function here than in a typical plant. The developmental timing of the “Swollen Thorn Syndrome” can also be influenced by natural selection as well. More research needs to be done on what developmental constraints and factors that may have influenced the later development of these traits. [7]
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.
Allomerus decemarticulatus is an Amazonian ant species found in the tropics of South America. This species is most notable for the workers’ complex and extreme predatory behavior, which involves a symbiosis with both a plant and fungal species. They live in leaf pockets of a host plant species, Hirtella physophora. These leaf pockets are areas inside of the plant between the leaves and the stem. Each colony, which consists of about 1,200 workers, inhabits a single tree; however, the ants are spread among the leaf pockets, with typically 40 workers per pocket. Their diet primarily consists of large insects that are captured on the plant, but they also eat some kinds of food bodies produced by the plant as well as its nectar. They are able to capture their prey, which is much larger than themselves, by constructing a platform that acts as a trap for the unsuspecting prey. The ants hide in the trap and attack when any insect lands on it. This technique is an example of ambush predation.
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.
Thomas Belt, an English geologist and naturalist, was born at Newcastle-on-Tyne in 1832, and educated in that city. He is remembered for his work on the geology of gold bearing minerals, glacial geology, and for his description of the mutualistic relationship between certain bullthorn Acacia species and their Pseudomyrmex ants.
Vachellia sphaerocephala, the bull's horn thorn or bee wattle, is a plant species in the family Fabaceae. The name comes from the shape of the thorns which do indeed resemble the horns of a bull. The tree has a strong, symbiotic relationship with a species of stinging ant, Pseudomyrmex ferruginea. This tree is endemic to Mexico.
Vachellia cornigera, commonly known as bullhorn acacia, 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 that occur in pairs at the base of leaves, and resemble the horns of a steer. In Yucatán it is called "subín", in Panamá the locals call them "cachito". The trees are commonly found in wet lowlands
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.
Vachellia tortilis, widely known as Acacia tortilis but now attributed to the genus Vachellia, is the umbrella thorn acacia, also known as umbrella thorn and Israeli babool, a medium to large canopied tree native to most of Africa, primarily to the savanna and Sahel of Africa, but also occurring in the Middle East.
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.
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.
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.
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.
A domatium is a tiny chamber that houses arthropods, produced by a plant.
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.
Bagheera kiplingi is a species of jumping spider found in Central America, including Mexico, Costa Rica, and Guatemala. It is the type species of the genus Bagheera, which includes three other species, including B. prosper. B. kiplingi is notable for its peculiar diet, which is mostly herbivorous. No other known species of omnivorous spider has such a markedly herbivorous diet.
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.
Pearl bodies are small, lustrous, pearl-like food bodies produced from the epidermis of leaves, petioles and shoots of certain plants. They are rich in lipids, proteins and carbohydrates, and are sought after by various arthropods and ants, that carry out vigorous protection of the plant against herbivores, thus functioning as a biotic defence. They are globose or club-shaped on short peduncles, easily detached from the plant, and are food sources in the same sense as Beltian bodies, Müllerian bodies, Beccarian bodies, coccid secretions and nectaries. They occur in at least 19 plant families (1982) with tropical and subtropical distribution.
Tritrophic interactions in plant defense against herbivory describe the ecological impacts of three trophic levels on each other: the plant, the herbivore, and its natural enemies. They may also be called multitrophic interactions when further trophic levels, such as soil microbes, endophytes, or hyperparasitoids are considered. Tritrophic interactions join pollination and seed dispersal as vital biological functions which plants perform via cooperation with animals.
Hydnophytum formicarum, commonly called a "Baboon's head" or "Ant plant", is an epiphyte native to Southeast Asia and is considered critically endangered in Singapore. It is a myrmecophyte as ants live in its tuber, also known as a caudex, and pollinate its flowers. It resides in open-canopied areas, rainforests, and terrestrial regions of high elevation.
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.