Regularity: Regularly occurring
Global Range: A Florida endemic known only from a few sites in the Florida Keys (Monroe County). This cactus was first discovered on Big Pine Key in 1919 (Small, 1930), and subsequently on Key Largo. It was considered well established at both of these sites. The species was not discovered on Little Torch Key until 1965; it was probably introduced there from stock that was originally removed from wild populations and cultivated in nurseries (Avery, 1963; Austin, 1980). The disappearance from Big Pine Key is probably a result of road construction and over-collected by nurserymen and amateur horticulturists (Avery, 1963). A second extant population was discovered in November, 2002, on Swan Key, with as many as 570 individuals. This population has an unknown trend. This population is unlikely to be the result of transplants. This new population is 145 km from Little Torch Key.
Opuntia (Consolea) corallicola is endemic to the Florida Keys. It was discovered on Big Pine Key in 1919, but this population was extirpated as a result of road building and poaching. The species is now known to occur naturally in only two areas, on Swan Key (within Biscayne National Park) and on Little Torch Key. Outplantings have been attempted in several locations in the upper and lower Keys, but success has been limited. Few plants remain in the population at The Nature Conservancy's Torchwood Hammock Preserve on Little Torch Key. During monitoring work conducted in 2005, a total of 655 plants were documented on Swan Key. In 2008 this population was estimated by Biscayne National Park staff to consist of at least 600 plants. (U.S. Fish & Wildlife Service 2009)
The Big Pine Key population apparently disappeared in the 1960s. The Little Torch Key population was discovered some time before 1965. The Swan Key population was not discovered until 2001 (Bradley and Woodmansee 2002; Gann et al. 2002). Small reported this species from Key Largo in the early 1930s, but Gann et al. (2002) were unable to locate specimens to verify these records. This species is sometimes used as a landscape plant in South Florida (Gann et al. 2002).
Habitat and Ecology
The populations are represented by male plants only, which produce a lot of flowers. Sometimes seeds are produced (hermaphroditic). Seed germination does not occur in situ but does sometimes occur ex situ. The seedlings, however, only grow to a certain size and do not survive.
This species is pollinated by ants and possibly by bees, hawkmoths, hummingbirds and bats (Possley et al. 2004). The ants feed on the pollen and in doing so, passively load the stigmatic lobes with self-pollen (Negrón-Ortiz 1998). The remnant individuals on Little Torch Key rarely set viable seeds, and ovaries tend to abscise before the development of fruit. Consolea corallicola may be self-incompatible, and the individuals on Little Torch Key appear to be clones from a single lineage (Negrón-Ortiz 1998). Most field-collected seeds are viable but there is no recruitment under natural conditions. However, vegetative reproduction is common (Negrón-Ortiz 1998). Dispersal is primarily by means of dropped pads (Possley et al. 2004).
Consolea corallicola flowers throughout the year, peaking December-April, especially February and March (Possley et al. 2004). There are rarely fruits, and attempts to grow plants from fruit have failed (Possley et al. 2004; J. Maschinski, pers. comm. 2011). Vegetative reproduction is the main mode of reproduction (Cariaga et al. 2005).
Genetic studies (Inter Simple Sequence Repeat, or ISSR) indicate that the two subpopulations have no genetic diversity, and only four of 64 ISSR loci showed differences between them (Cariaga et al. 2005). A single individual from an extirpated population on Big Pine Key and maintained ex situ at Fairchild Tropical Botanic Garden is genetically different lacking six alleles found in the two wild subpopulations (Cariaga et al. 2005).
Consolea corallicola is a hexaploid (Pinkava et al. 1985).
Comments: Small (1930) reported that in Florida the plants occur on bare rocks with only a slight covering of humus in hardwood hammocks near sea level. Substrate material in this area of the Keys is almost entirely Key Largo limestone with some sand. The single remaining Florida population occurs in a transitional zone between mangrove and hardwood hammock habitats (Williams, pers. comm., 1989), and the most common associate species include: Sporobolus virginicus (L.) Kunth., Conocarpus erectus L., Maytenus phyllanthoides Benth., Manilkara bahamensis (Baker) Lam. & Meeuse, Hippomane mancinella L., Opuntia stricta var. dillenii (Ker-Gawl.) L. Bens.
Opuntia (Consolea) corallicola grows close to salt water on bare rock with a minimum of humus soil cover in or along the edges of hammocks near sea level (U.S. Fish & Wildlife Service 2009).
Opuntia (Consolea) corallicola is found in low buttonwood (Conocarpus erectus) transition areas between rockland hammocks and mangrove swamps, and possibly other habitats, such as openings in rockland hammocks (Gann et al. 2001).
In her study of the reproductive biology of Opuntia (Consolea) corallicola, Negron-Ortiz (1998) observed just one species of flower visitor, an ant (Crematogaster nr. ashmeadi), which she speculated might have been attracted by a faint rotten meat-like odor produced by the opened flowers. The ants were observed feeding on pollen and, in the course of doing so, passively delivering pollen (from the same flower) to the stigmas. Bees and hummingbirds are potential pollinators of this cactus, but these animals have not actually been observed visiting its flowers (Negron-Ortiz 1998).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 1 - 5
Comments: There are two populations of this species. There are several unconfirmed reports of additional individual plants on private property. In addition, pads of this cactus have been planted on North Key Largo in an attempt to establish another populaton (USFWS, 2004).
The Litte Torch Key population consists of eight individual plants none of which seem to have produced viable fruit (Williams, pers. comm., 1989). The flowers tend to drop off shortly after peak bloom is reached and these blooms occasionally take root beneath the parent plant (Avery, 1963; Williams, pers. comm., 1989). This type of vegetative reproduction is also mentioned by Small (1930) who suggests that the lack of proper ovary development is a result of not having been pollinated. In this same report, however, Small does mention that fruits have been observed and he describes the seeds from them. It is possible that the pollinators of the plant were present when the plant was better represented in the wild, but when the plants were extirpated the pollinators may have been effectively eliminated from the area. Species specific pollinators are not common in the Cactaceae, but they do occur (Grant and Hurd, 1979). It is also possible that the presence of a diversity of pollinators in past years was affecting more frequent pollination than now occurs. Research in this area is critical if anything more than clones are to be preserved. The population now extant on Little Torch Key, in all probability, originated from wild stock of the Keys population and thus is of the same gene pool.
In her study of the reproductive biology of Opuntia (Consolea) corallicola, Negron-Ortiz (1998) found that flower production occurred throughout the year, but peaked during the dry months of December through April. Flowers opened when they reached 0.9 to 1.0 cm in length, 14 to 20 days after flower buds emerged. Flowers produced a copious sticky nectar and nectar availability appeared to coincide with rainy periods.
Life History and Behavior
Negron-Ortiz and Strittmatter (2004) found that the Opuntia (Consolea) corallicola plants on Little Torch Key were functionally male. These plants produced two distinct flower morphs: primary flowers that were superficially bisexual (i.e., with both male and female parts) and secondary flowers that generally had only male, pollen-producing structures. In the primary flowers, however, although the ovules would complete development, most would subsequently abort prior to the maturation of the flower. Thus, most of the primary flowers, also, were functionally male. A few primary flowers, however, retained viable ovules, making some individuals weakly hermaphroditic. Later studies (unpublished) on the more recently discovered Swan Key population have shown that plants in this population are also functionally male (Vivian Negron-Ortiz, in litt., February 2010).
Negron-Ortiz (1998) found that Opuntia (Consolea) corallicola rarely sets viable seeds. Extensive hand pollination studies led her to conclude that the dozen plants at her study site (at the time, the only known wild individuals in the world) were unable to set fruit sexually. The few seeds produced were apparently produced by agamospermy (i.e. without fertilization). Although pollen tubes grew and reached the ovary, they failed to penetrate the ovules (Negron-Ortiz 1998). Most of those ovules were aborted before the flowers opened (V. Negron-Ortiz and L. Strittmatter, unpublished data, cited in Strittmatter et al. 2002).
Seeds have been observed germinating while still in the fruit after the fruit has fallen to the ground. This may be an adaptation that allows seedlings to avoid desiccation during the dry months, just before the onset of the rainy season (Negron-Ortiz 1998).
Evolution and Systematics
Systematics and Taxonomy
Although the name Opuntia spinosissima has often been used for this species in the literature, Austin et al. (1998) studied this group of Caribbean cacti and concluded that O. spinosissima and O. corallicola are clearly distinct species, endemic to Jamaica and the Florida Keys, respectively. Most researchers now recognize "Consolea corallicola" or "Opuntia corallicola" as the correct name for the Florida semaphore cactus (Austin et al. 1998; Gann et al. 2002). Consolea corallicola is the name under which this species was first described by John Kunkel Small in 1930. Areces (1996) and others recognize Consolea as a distinct genus, but some researchers treat this as a subgenus within Opuntia (Austin et al. 1998).
Physiology and Cell Biology
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G1 - Critically Imperiled
Reasons: One natural, one apparently introduced, and one recently planted population of this Florida-endemic cactus are known from the Florida Keys. Opuntia corallicola is found on bare rocks with only a slight covering of humus in hardwood hammocks near sea level. Substrate material in this area is almost entirely Key Largo limestone with some sand. The remaining populations occur near sea level in a transitional zone between mangrove and hardwood hammock habitats. Both sites are on protected land (private, federal), however, one population is composed entirely of male plants, in this obligate outcrossing species. Threats include: non-native species (especially a cactus-eating moth), large hurricanes, and small population size. Sea level rise is also a longer-term threat to these plants and their habitat.
Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.
Comments: Reintroduction attempts for this species have failed, citing factors including faulty site choice (too shady, too light). The species currently occurs in a narrow ecotone near sea level between salt tolerant communities (salt marsh/mangrove) and hammock (fire-intolerant) communities. This ecotone is now rare because of development.
Status: Proposed Endangered
Lead Region: Southeast Region (Region 4)
For most current information and documents related to the conservation status and management of Consolea corallicola, see its USFWS Species Profile
Opuntia (Consolea) corallicola is among the most endangered plant species in North America. As of late 2009, it was a candidate for listing under the U.S. Endangered Species Act, with a USFWS-assigned listing priority number of 2 (USFWS 2009).
According to Stiling et al. (2000) the population was declining in 2000.
The population size for this species is approximately 500 individuals (480 on Swan Key as of 2011 and 13 on Little Torch Key as of 2007). The subpopulation at Little Torch Key is declining; the subpopulation at Swan Key is stable.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Since there are only two populations an evaluation of the health of a population is conditional. In one population, there are only nine plants left (although at its maximum only 16 plants have been seen on site, not all at the same time) and these plants reproduce soley by vegetative progeny. Dispersal beyond this site is not expected as the majority of progeny fall within 100 m of the parent plant. Given that, this population has not been significantly reduced over the past 12 years, in large part because of extensive management and monitoring (on a weekly basis, The Nature Conservancy) of the individual plants. Therefore it is most likely stable to slight decline. The population on Little Torch Key is considered to be in a state of decline. Williams (pers. comm., 1989) noted that over the past one year one of "the most beautiful and largest has been butchered by a collector." Plants in the newly discovered (Swan Key) population are generally a smaller size (shorter, fewer pads), less flowering and an equal or greater number of presumed vegetative progeny (could be 100s per individual plant). This new, much larger population was discovered in November, 2002; no trends can be predicted yet.
Global Long Term Trend: Decline of 50-70%
Comments: This species is unlikely to ever have been very common, but there is evidence (herbaria) that it was once more common than it currently is (extinct populations on Big Pine Key, Key Largo), with one natural, one apparently non-natural, and one recently planted population remaining. Both mature extant populations of this species occur at or near mean sea level. The non-native moth, Cactoblastis cactorum is known to feed on the plant (and is the direct cause of one plants' death), and sexual reproduction has not been observed. Hurricanes also threaten the species, although Hurricane Georges passed directly over the Little Torch population with no significant damage. Human-caused reduction is now a remote threat due to management methods and remoteness of locations. Intrinsic vulnerability is the most likey dominant long-term threat.
Cactoblastis cactorum and root rot have not yet affected the Swan Key subpopulation.
Land development extirpated all other known subpopulations, and collectors threatened the subpopulation on Little Torch Key until it was protected by the Nature Conservancy in 1988 (Stiling et al. 2000). Pollution is also listed as a threat (Possley et al. 2004). An unknown pathogen or fungus was believed to attack juveniles (Possley et al. 2004), and stem browning has killed mature individuals (Stiling et al. 2000). Trampling has killed some plants; Key Deer were probably responsible (Possley et al. 2004).
Experts from Fairchild Tropical Botanic Garden USA, consider the species' low genetic diversity to be a major threat.
Degree of Threat: Very high - high
Comments: Opuntia corallicola is an extremely rare species, and therefore vulnerable to stochastic losses, especially at its smaller population. However, its ability to root from vegetative parts gives it some flexibility for recovery, especially after hurricanes (USFWS, 2004). The greatest immediate threat is the non-native invasive moth species Cactoblastis cactorum. The moth is being studied by USDA scientists as the range in the US expands and begins to affect other Opunita spp. The species occupies a relatively rare habitat over a narrow range at low elevation (1-2 ft msl), which also makes it vulnerable to hurricanes and sea-level rise. In addition, the population at one site is functionally male and does not reproduce sexually. Ongoing pressures from collecting and from development, which threatened the species in the latter half of the 20th century, are now nearly eliminated.
Aside from the many risks that are typically associated with having very few and very small populations, the greatest risk to the continued persistence of Opuntia (Consolea) corallicola is the pyralid moth Cactoblastis cactorum. This South American moth is among the most famous biological control agents thanks to its spectacular success controlling New World Opuntia cacti that had been introduced to Australia in the late 18th and early 19th centuries. These cacti turned out to be aggressively invasive, taking over vast areas of formerly productive ranch land. Cactoblastis cactorum larvae (caterpillars) feed on Opuntia in their native range in Argentina, Paraguay, Uruguay, and southern Brazil (Stiling et al. 2004). When these moths were introduced to Australia with the hope that they would consume Opuntia in Australia as well, they thrived on the abundant Opuntia and rapidly brought it under control. This success led to later introductions to control alien Opuntia species in South Africa, Mauritius, and Hawaii (Stiling et al. 2004).
In the late 1950s and early 1960s, Cactoblastis cactorum was introduced to several Caribbean islands, far north of the moth's native range in southern South America, to control populations of native Opuntia cacti (Stiling et al. 2004 and references therein). Cactoblastis cactorum reached the United States (first noted on Big Pine Key, Florida) by 1989, possibly through the commercial cactus trade (Pemberton 1995), where it now poses a serious threat to Opuntia (Consolea) corallicola (Johnson and Stiling 1996) and, particularly if it reaches the southwestern U.S., many other native cacti.
Restoration Potential: No work in population biology or phenology has been done on this taxa (not in Florida or Jamaica), and thus no conclusions about its potential reestablishment can be drawn.
Management Requirements: Outright physical protection of the element is the first and most important step in protecting the species from complete extirpation in Florida. This natural community in general, does not need active management other than protection.
Management of the tract should begin with construction of a substantial fence to keep humans out of the population.
Monitoring Programs: Because there is but a single population [in the United States], the species must be carefully monitored on a regular basis. A monitoring plan has been developed for the population to measure plant height, main trunk height, number of branches, numbers of pods, flowering, seedlings and branch spread. The plants have been photographed and drawn.
Management Research Programs: Propagation efforts are being pursued by the Center for Plant Conservation at Fairchild Tropical Garden with material from Florida.
Relevance to Humans and Ecosystems
Stewardship Overview: One (particular) population of Opuntia corallicola should be physically protected from human encroachment immediately. Individuals with field experience in pollination systems should be consulted and a research project should be designed and initiated immediately.
Consolea corallicola is a species of cactus known by the common names Florida semaphore cactus and semaphore pricklypear. It is endemic to Florida in the United States, where it is limited to the Florida Keys.
This cactus is a species of tree which grows up to two meters tall. The stem segments are up to 30 centimeters long and are "copiously armed" with pink spines which can exceed 12 centimeters in length. The largest spines occur on the trunk. The flowers, which have a scent reminiscent of rotting meat, have fleshy outer tepals and red-colored inner tepals that reach 2.5 centimeters in length. Flowering occurs year-round, with a peak season in December through April. The fleshy fruit is yellow in color and up to 6 centimeters long. This cactus is colonial, forming colonies of "trunked" plants and several "pups". This species' common name refers to its resemblance to railway semaphore signals.
This "is an extremely rare species" that is "near extinction". It "may very well be the most endangered plant in the United States". It has been extirpated from several of the Keys, including Big Pine Key, the island where it was first discovered in 1919. Today there are two populations, one on Little Torch Key and one on Swan Key. There is also a patch of plants growing where several fragments were planted on North Key Largo. Because the plant is colonial, with what appear to be several plants actually being parts of one genetic individual, populations are very small, sometimes containing fewer than five true individuals. One population is composed of only male plants and cannot reproduce sexually. There are a total of under 20 distinct individuals living today.
The habitat for this species is bare rock with thin pockets of humus located in hardwood hammocks or the ecotone between hammock and mangrove habitat. The substrate is Key Largo limestone with a covering of sand. The habitat is near sea level. Associated species include Sporobolus virginicus, Conocarpus erectus, Maytenus phyllanthoides, Manilkara bahamensis, Hippomane mancinella, and Opuntia stricta var. dillenii.
The worst immediate threat to the species today is Cactoblastis cactorum, an invasive, non-native species of moth which eats cacti. It is also threatened by hurricane activity and sea-level rise, which can affect it because it lives near sea level. It has trouble reproducing because one population is all male and can only reproduce vegetatively. It is also suffering from a rot disease. Other threats include poaching and habitat destruction and degradation.
Consolea corallicola is endemic to the Florida Keys and near extinction. It is already extirpated from several keys and is known from fewer than twenty plants in the wild. Hurricanes, deer, and cactoblastis moths impact the health of the population.
Consolea corallicola is in the Center for Plant Conservation’s National Collection of Endangered Plants.
Names and Taxonomy
Comments: Formerly included in Opuntia spinosissima by Kartesz (1994 Checklist); now recognized as distinct, with O. spinosissima excluded from the range (Kartesz 1999). The U.S. Fish and Wildlife Service uses the name Consolea corallicola for this species in the June 2002 Candidate Notice of Review.
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