Biology
provided by Arkive
Opuntia cacti are a key species in the ecology of the Galapagos Islands, the pads forming a major food source for tortoises and land iguanas, and the fruits being eaten by iguanas, doves and mockingbirds. The flowers, fruits and seeds are eaten by cactus finches, which may also obtain water by pecking at the fleshy pads (3) (9). In return, these species help to disperse the seeds of the cactus, and also act as important pollinators of the flowers, particularly on islands lacking insect pollinators such as bees (3) (9) (11). Flowering of Opuntia echios has been reported to occur between November and February, with each plant producing a few flowers every day throughout the flowering season. The seeds take several months to mature, and the long flowering season means that the fruits ripen over a period of time rather than simultaneously (11). The species may also be able to reproduce vegetatively (3), an entirely new individual growing from a detached portion of the plant. It is thought that the Opuntia species of the Galapagos Islands are very long-lived, potentially reaching ages of 150 years or more (8).
Biology
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The six species of Opuntia found in the Galapagos are one of the principal sources of food for animals occupying areas of lowland. Tortoises and land iguanas eat the pads; doves, mockingbirds and iguanas eat the fruit; and finches eat the flowers, fruits and seeds, and obtain water from the succulent pads (8). Indeed Darwin was one of the first to notice the predilection of cactus finches for the fruits and flowers of Opuntia galapageia in particular (5). The animals that feed upon the fruit of Opuntias provide an indispensable service in dispersing the seeds stored within the nutritious flesh (8).
Biology
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Interestingly, Opuntia helleri relies on birds to aid pollination, as the northern islands occupied by this cactus are not inhabited by any suitable insect pollinators (7). A number of bird species visit Opuntia helleri, including doves, cactus finches and mockingbirds. The soft-spines allow easy access to this species' flowers, and while feeding on the pollen, nectar and even petals, the birds receive a dusting of pollen which is transferred to, and fertilises, the other flowers visited (4) (7). This adaptation to bird pollination is only possible because the absence of large, herbivorous reptiles, such as giant tortoises, from the northern Galapagos Islands, allows Opuntia helleri to survive without the protection of hard, sharp spines (8) (9).
Despite producing flowers all year round, Opuntia helleri's main flowering season occurs between November and February (9). Interestingly, even if the flowers are not pollinated, fruits and seeds may still develop. This is due to a remarkable process called apomixis, in which the female, unfertilised gametes develop into an embryo without needing to fuse with male gametes (10). Whether pollination occurs or not, fruits take several months to mature. Eventually dropping off the pads, many of the fruits are consumed by mockingbirds and cactus finches, which later pass the seeds in their faeces, thereby helping Opuntia helleri to disperse its offspring (7).
Flowering only occurs in larger specimens of Opuntia helleri (8), but individuals of any size can reproduce simply by dropping their pads. In a process called vegetative reproduction, an entirely new plant may grow from the detached portion, giving rise to large thickets of cacti, all of which are genetically identical (7).
Biology
provided by Arkive
The six species of Opuntia found in the Galapagos are one of the principal sources of food for animals occupying areas of lowland. Tortoises and land iguanas eat the pads; doves, mockingbirds and iguanas eat the fruit; and finches eat the flowers, fruits and seeds, and obtain water from the succulent pads (8). Indeed Darwin was one of the first to notice the predilection of cactus finches for the fruits and flowers of Opuntia galapageia in particular (5). The animals that feed upon the fruit of Opuntias provide an indispensable service in dispersing the seeds stored within the nutritious flesh (8).
Conservation
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Opuntia echios receives some protection from international trade under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (4). However, the threats posed by introduced species and human activities need to be addressed if this cactus is to be adequately protected. The Charles Darwin Foundation is currently working in the Galapagos to research and survey all Opuntia populations, to help develop appropriate conservation actions for each species. These are likely to include the control of feral herbivores, as well as possible restoration projects (9)
Conservation
provided by Arkive
With so many of the Galapagos's native animals dependant on Opuntias, the conservation of this cactus genus is critically important in the preservation of the archipelago's renowned biodiversity (10). The Charles Darwin Foundation is undertaking detailed surveys of Opuntia populations to establish appropriate conservation actions for each species. This is likely to involve the eradication of feral herbivores which has already been carried out successfully on several of the islands (8).
Conservation
provided by Arkive
The Charles Darwin Foundation, a Galapagos conservation organisation, is working to restore damaged populations of Opuntia species. By conducting detailed surveys, they aim to determine the status and vulnerability of each species and develop specific conservation action plans to help preserve them (8).
Conservation
provided by Arkive
With so many of the Galapagos's native animals dependant on Opuntias, the conservation of this cactus genus is critically important in the preservation of the archipelago's renowned biodiversity (10). The Charles Darwin Foundation is undertaking detailed surveys of Opuntia populations to establish appropriate conservation actions for each species. This is likely to involve the eradication of feral herbivores which has already been carried out successfully on several of the islands (8).
Description
provided by Arkive
During his explorations of the Galapagos Islands, Darwin recorded Opuntia galapageia in a simple sketch of a tree-like cactus with a compact crown of pads (4) (5). While most Opuntia galapageia do indeed have well-developed trunks and rounded crowns (6) (7), some are more low-growing and shrubby in appearance (2). The flat, fleshy green pads are usually egg-shaped and dotted with evenly spaced clusters of 5 to 35 yellow to brown spines that are an obvious deterrent to predators (2) (6) (8). The trunk, when present, is initially covered with spines, but with age, develops dark reddish 'bark' (2) (6). Yellow flowers arise amongst the spine clusters and eventually develop into the spiny, spherical to oblong fruit, for which the genus gets the name 'prickly pear' (6).
Description
provided by Arkive
Forming large, sprawling thickets, Opuntia helleri is one of the characteristic cactus species of the northern Galapagos Islands (3) (4). The stem is divided into broad, fleshy pads up to 37 centimetres long and 22 centimetres wide, covered with evenly-spaced clusters of 7 to 28 yellowish-white or brown spines (4). In contrast with the strong, hard spines of many cactus species, the spines of Opuntia helleri are soft and flexible (4) (5). The pads produce striking yellow flowers, up to eight centimetres wide, from which large, green, fleshy fruits develop. Commonly known as “prickly pears”, these fruits are generally ovoid, covered in clusters of small spines and usually contain multiple seeds. Although generally a low-growing species, older specimens of Opuntia helleri will sometimes grow into a taller shrub or tree-like form up to two metres in height, developing a woody trunk with a coating of reddish-brown bark (4).
Description
provided by Arkive
During his explorations of the Galapagos Islands, Darwin recorded Opuntia galapageia in a simple sketch of a tree-like cactus with a compact crown of pads (4) (5). While most Opuntia galapageia do indeed have well-developed trunks and rounded crowns (6) (7), some are more low-growing and shrubby in appearance (2). The flat, fleshy green pads are usually egg-shaped and dotted with evenly spaced clusters of 5 to 35 yellow to brown spines that are an obvious deterrent to predators (2) (6) (8). The trunk, when present, is initially covered with spines, but with age, develops dark reddish 'bark' (2) (6). Yellow flowers arise amongst the spine clusters and eventually develop into the spiny, spherical to oblong fruit, for which the genus gets the name 'prickly pear' (6).
Description
provided by Arkive
The five varieties of Opuntia echios are quite variable in form, a phenomenon thought to result from adaptation to differing conditions on different islands (2) (3) (5) (6). The smallest, such as O. e. zacana, are shrubby and low-growing, never reaching more than a metre or two in height (2) (5) (7), while others, such as O. e. gigantea, grow into tall trees and are among the largest Opuntia species in the Galapagos (2) (3) (8). Opuntia echios usually has a well-developed trunk, which is spiny when young and later develops reddish, flaky bark (2) (3) (5). The more shrubby forms generally have softer spines, and tend to grow on islands where there are fewer browsing herbivores and lower competition with other plant species (3) (6) (9).
Opuntia echios produces flat, fleshy pads, up to 45 centimetres long and 32 centimetres wide, covered in evenly spaced groups of 2 to 20 or more yellowish to brown spines. The spines, up to 12 centimetres in length, tend to be erect, stiff and sharp on young plants, and more bristly, almost hairlike, on mature individuals (2) (5). The pads of Opuntia echios produce large yellow flowers, up to ten centimetres across, which develop into the greenish “prickly pear” fruits which give the Opuntia cacti their common name. These roundish to oblong fruits may be over seven centimetres in length, and are covered in spines and short, barbed hairs, known as glochids (2) (3) (5) (9).
Habitat
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Opuntia galapageia generally grows in the arid zone near sea level but is sometimes found in more forested areas at higher altitude (6) (7).
Habitat
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Opuntia galapageia generally grows in the arid zone near sea level but is sometimes found in more forested areas at higher altitude (6) (7).
Habitat
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Opuntia helleri is scattered throughout the arid lowlands, increasing in abundance towards the coast (4) (6).
Habitat
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Opuntia echios is commonly found in the arid zone, often growing in thin soil, sand or even bare lava, but also occurs at higher elevations in tropical dry forest (2) (7) (8) (10).
Range
provided by Arkive
Endemic to the Galapagos, the three subspecies all occur on different islands. Opuntia galapageia galapageia is found on Bartolomé, Santiago and Pinta Islands (7), O. g. macrocarpa is found on Pinzón Island, and O. g. profusa is foundon Rábida Island (6).
Range
provided by Arkive
Endemic to the Galapagos, the three subspecies all occur on different islands. Opuntia galapageia galapageia is found on Bartolomé, Santiago and Pinta Islands (7), O. g. macrocarpa is found on Pinzón Island, and O. g. profusa is foundon Rábida Island (6).
Range
provided by Arkive
Endemic to the Galapagos Islands, the five varieties of Opuntia echios occur on different islands. O. e. echios is found on Daphne Major, Santa Cruz, Baltra and Las Plazas Islands, O. e. barringtonensis is found on Santa Fé Island, and O. e. gigantea is found on Santa Cruz Island, in the vicinity of Academy Bay. O. e. inermis is known only from Volcán Sierra Negra, on Isabela Island, and O. e. zacana is found on Seymour Island, where it is the only Opuntia species on the island (2) (5) (7).
Range
provided by Arkive
Endemic to the Galapagos, Opuntia helleri is restricted to the northern islands of Darwin, Genovesa, Marchena and Wolf (4).
Status
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Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (2).
Status
provided by Arkive
Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3). Subspecies Opuntia galapageia galapageia is classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3) and O. g. macrocarpa and O. g. profusa are classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).
Status
provided by Arkive
Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (4). Varieties Opuntia echios gigantea, O. e. inermis and O. e. echios are classified as Endangered (EN) and O. e. zacana and O. e. barringtonensis are classified as Vulnerable (VU) on the IUCN Red List (1).
Status
provided by Arkive
Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3). Subspecies Opuntia galapageia galapageia is classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3) and O. g. macrocarpa and O. g. profusa are classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).
Threats
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The main threats affecting the Opuntia species found in the Galapagos are competition with invasive plants for space, light and nutrients; overgrazing by invasive herbivores such as goats and pigs; and expanding urban development and agriculture. Overgrazing is probably the most significant of these threats, since the consumption of dropped pads prevents vegetative reproduction, and means that only the larger plants capable of flowering are able to reproduce (8).
Threats
provided by Arkive
In common with other Opuntia cacti on the Galapagos Islands, Opuntia echios is threatened by introduced plants, with which it competes for space, light and nutrients, and also introduced animals such as goats, donkeys, pigs and cattle. These non-native species often trample smaller Opuntia plants or eat into the trunks of older, less spiny individuals. If the cacti are knocked down and eaten, no vegetative reproduction can occur, and only the remaining larger plants are able to flower (9). The Galapagos Islands as a whole are also under increasing pressure from uncontrolled tourism, human population growth, farming and urbanisation (12) (13). The restricted ranges of many of the Opuntia echios varieties may make them particularly vulnerable to any threats.
Threats
provided by Arkive
In common with much of the native flora of the Galapagos, Opuntia populations have been negatively affected by agriculture, urbanisation, and the introduction of non-native animals and plants (8). Owing in particular to damage caused by feral animals such as goats and donkeys, Opuntia galapageia is now scarce in parts of its range where it was once abundant (4) (8) (9).
Threats
provided by Arkive
In common with much of the native flora of the Galapagos, Opuntia populations have been negatively affected by agriculture, urbanisation, and the introduction of non-native animals and plants (8). Owing in particular to damage caused by feral animals such as goats and donkeys, Opuntia galapageia is now scarce in parts of its range where it was once abundant (4) (8) (9).
Endemic range
provided by EOL authors
Opuntia galapageia is endemic to the Galapagos Islands of Ecuador in western South America; in fact, the three subspecies of this taxon are all endemic to the Galapagos Islands. This species is the furthest west occurring of all the cactaceae family species in South America.
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- C.Michael Hogan
- bibliographic citation
- C.Michael Hogan. 2011. Cactus. Topic ed. Arthur Dawson. Ed.-in-chief Cutler J.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC
- author
- C. Michael Hogan (cmichaelhogan)
Opuntia echios
provided by wikipedia EN
Opuntia galapageia is a species of cactus. It is endemic to the Galápagos Islands, part of Ecuador. Forms occurring on different islands have been treated as separate species and subtaxa of these species. Opuntia echios, Opuntia helleri, Opuntia insularis, Opuntia megasperma, Opuntia myriacantha and Opuntia saxicola are now sunk within O. galapageia.
Description
The subspecies, variety or forma "Opuntia g. echios" has the most formidable spines; up to ten inches (25 centimeters) in length.[7]
Taxonomy
Opuntia galapageia was first described by John Stevens Henslow in 1837. It was first recorded by Charles Darwin on Santiago (James) Island.[8] Darwin was ashore there for nine days in 1835.[9] Subsequently, at least five other species of Opuntia were described from the Galápagos: Opuntia helleri, Opuntia insularis, Opuntia megasperma, Opuntia myriacantha and Opuntia saxicola. All were treated by David Hunt in 2006 as included within O. galapageia, a placement accepted by the IUCN Red List as of 2017, although they had been assessed as separate species in 2000.[1] Plants of the World Online also accepts the placement within O. galapageia, and includes Opuntia echios, in most cases placing the species in an infraspecific taxon (see the list below).
Infraspecific taxa
A large number of varieties and other infraspecific taxa have been named. As of June 2021, Plants of the World Online accepts the following:[6]
Two other infraspecific taxa that have been named are not recognized by Plants of the World Online as distinct from the species:[6]
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Opuntia galapageia var. brossettii Backeb.
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Opuntia galapageia subvar. orientalis (J.T.Howell) Backeb.
Distribution
Opuntia galapageia is endemic to the Galápagos Islands. Forms occurring on different islands have been described as subtaxa of the species (see the list above).[6] Island distributions given by Plants of the World Online include:
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Fernandina
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O. galapageia var. insularis
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Isabela
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O. galapageia subvar. inermis
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O. galapageia var. insularis
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O. galapageia var. profusa
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O. galapageia var. saxicola
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Seymour
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O. galapageia var. zacana
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Pinzon
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O. galapageia var. macrocarpa
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Santa Cruz
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O. galapageia var. gigantea
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Santa Fe
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O. galapageia subvar. barringtonensis
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Santiago
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O. galapageia var. profusa
References
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^ a b Tye, A.; Kling, M. (2017). "Opuntia galapageia". IUCN Red List of Threatened Species. 2017: e.T21053131A121621159. doi:10.2305/IUCN.UK.2017-3.RLTS.T21053131A121621159.en. Retrieved 14 November 2021.
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^ a b c "Opuntia galapageia var. myriacantha (F.A.C.Weber) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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^ a b "Opuntia helleri K.Schum.". The International Plant Names Index. Retrieved 2021-06-04.
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^ a b "Opuntia galapageia var. insularis (A.Stewart) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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^ a b "Opuntia galapageia var. saxicola (J.T.Howell) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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^ a b c d "Opuntia galapageia Hensl.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-03.
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^ Dawson, E. Yale (September–October 1965). "Further Studies of Opuntia in the Galapagos Archepelago". Journal of the Cactus and Succulent Society. 37 (5): 146.
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^ "Opuntia galapageia ;Hensl&period". The International Plant Names Index. Retrieved 2021-06-04.
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^ Keynes, Richard (2000), Charles Darwin's zoology notes & specimen lists from H.M.S. Beagle., Cambridge University Press, pp. 360–367, retrieved 2009-01-27
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^ "Opuntia galapageia subvar. barringtonensis (E.Y.Dawson) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-03.
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^ "Opuntia galapageia var. gigantea (J.T.Howell) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-03.
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^ "Opuntia galapageia var. helleri (K.Schum. ex B.L.Rob.) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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^ "Opuntia galapageia subvar. inermis (E.Y.Dawson) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-03.
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^ "Opuntia galapageia var. macrocarpa E.Y.Dawson". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-03.
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^ "Opuntia galapageia var. profusa E.F.Anderson & Walk.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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^ "Opuntia galapageia var. zacana (J.T.Howell) Backeb.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2021-06-04.
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Opuntia echios: Brief Summary
provided by wikipedia EN
Opuntia galapageia is a species of cactus. It is endemic to the Galápagos Islands, part of Ecuador. Forms occurring on different islands have been treated as separate species and subtaxa of these species. Opuntia echios, Opuntia helleri, Opuntia insularis, Opuntia megasperma, Opuntia myriacantha and Opuntia saxicola are now sunk within O. galapageia.
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