Higo chumbo is a columnar cactus that is currently found at three small offshore islands of western Puerto Rico - Mona, Monito and Desecheo. In addition, several individuals are known to occur at Caja de Muertos, an offshore island south of Puerto Rico. Currently, disease and predation from goats, feral hogs and otherare considered major threats. Additionally, lesions in higo chumbo that are caused by hemipteran, meaning true bugs in like Leptoglossus sp., have been observed on the Mona Island population. This insect causes damages to the cactus by laying eggs and feeding on their branches and main stems. This activity will eventually lead to bacterial and fungal infections that, within a few months, usually kills the plant. Another potential threat to higo chumbo is the Harrisia cacti mealybug (Hypogeoccoccus pungens). Although this pest has not been recorded on Mona, Monito or Desecheo islands, it has been documented in Puerto Rico and impacts different species of the Cactaceae family. This mealybug infests the apical meristems of the stems, producing abnormal stem growth of the plants and negatively impacts the production of flowers and fruits. This activity eventually causes the plants to stop growing and die. Competition with invasive plant species is another threat to higo chumbo. Some of these invasive species, including guinea grass (Megathyrus maximus), may alter the microclimate conditions and nutrient cycling of the habitat that higo chumbo depends upon. This especially impacts natural recruitment and seedling survival.
We work with other federal and state agencies, as well as academic and non-profit organizations throughout the species range, in order to conserve and recover the higo chumbo. The islands of Mona, Monito and Desecheo are public land that are managed for conservation by the Puerto Rico Department of Natural and Environmental Resources. Additionally, a cooperative agreement between the U.S. Fish and Wildlife Service and the the Puerto Rico Department of Natural and Environmental Resources has been in place since 1984, which establishes and implements a vigorous endangered species program within the Commonwealth of Puerto Rico and seeks to recover this listed species. Moreover, the Puerto Rico Department of Natural and Environmental Resources has been conducting a wildlife restoration program which is supported by the Wildlife and Sport Fish Restoration Program of the U.S. Fish and Wildlife Service on Mona for more than two decades. One of the objectives of this program is to control feral goats and hogs for the protection of the higo chumbo and other federally-listed species from predation by these non-native species. Another partner is the University of Puerto Rico at Río Piedras, that has provided essential information for the recovery of the species by evaluating the role of different biotic and abiotic factors in the population dynamics of the natural higo chumbo population on Mona Island. In addition experts with the university have conducted research on the species reproductive biology, exploring pollinators and seed viability. Island Conservation, between 2008 and 2009, entered into an agreement with the U.S. Fish and Wildlife Service to control invasive species in Desecheo Island. The project resulted in the eradication of goats, macaque monkeys and rodents. After eradication, a monitoring plan has been established in order to assess the recovery the island’s ecosystem over time.
Higo chumbo is described as night-flowering with large, white, hermaphroditic flowers. Some botanist state that higo chumbo can start producing flowers after 8 to 10 years. Flowers open for only one night and after pollination flowers wilt within about one hour. Observations have found that it is very likely that the species has a wind-aided self-pollination mechanism since visits to flowers by animals are uncommon. A 2011, assessment of higo chumbo phenology found that this species reproduce throughout the year and its reproductive output is positively correlated with plant size. It has been also found that bud production in higo chumbo is positively associated with temporal changes in monthly mean and minimum temperatures, while flower production was positively associated with total monthly rainfall.
On an average , seeds begin germinating 54 days after sowing if suitable conditions are present. Germination, survival and growth of higo chumbo seedlings is greater in shaded areas than open areas due to less exposure to rough climate conditions, such as direct sunlight. A research found that seedling growth rate is higher under native shrubs rather than exotic grasses.
Higo chumbo's nocturnal flowers have a partially self-compatible breeding system that requires an external mechanism for the movement of pollen to set fruit. Flowers are nectariferous, meaning that they produce nectar, but visits by animals are highly infrequent and pollination is mainly wind-facilitated with most of the fruit production resulting from self-pollination. The higo chumbo may require eight to 10 years for development as a reproductive adult. Fruit production under natural conditions is high, with 88% fruit-set. Fruits are usually dispersed by birds and mature in approximately 56 days. Flowering and budding occurs many times during the year, and is influenced by different environmental factors like temporal variation in temperatures and rainfall.
This species occurs on three small offshore islands - Mona, Monito and Desecheo - on the Mona Passage in western Puerto Rico. In addition, some individuals are known to occur at Caja de Muertos, an offshore island south of Puerto Rico and near the type locality, meaning where it was first reported. These islands fall under the subtropical dry forest life zone, where mean annual rainfall ranges from 600 to 1000 millimeters. Mona and Monito islands are composed almost entirely of carbonate rocks, stratified limestone, as well as domolite, reef rock and boulder rubble. Desecheo Island is composed of early tertiary volcanic sandstones, with volcanic breccia and mudstone, as well as calcareous sandstones and mudstones. The relief and flat-topped topography of Monito Island is similar to that of Mona, while Desecheo is much hillier.
Recent data on the establishment and growth of early life history stages of higo chumbo indicate that seedlings and juveniles are susceptible to changes in local microclimatic conditions, like direct sunlight and soil temperature. Moreover, it has been observed that perennial native shrubs, like lechecillo (Croton discolor) and Reynosa uncinata, act as nurse plants that provide suitable and stable microclimatic conditions which significantly improve survival, establishment and growth of higo chumbo seedlings.
The habitat on which the higo chumbo depends is protected by the Commonwealth of Puerto Rico and the U.S. Fish and Wildlife Service. Mona and Monito islands were declared as natural reserves by the Commonwealth of Puerto Rico, and managed for conservation by the Puerto Rico Department of Natural and Environmental Resources since 1973. Also, Puerto Rico Department of Natural and Environmental Resources has been managing Caja de Muertos since 1980. Desecheo Island was established asin 1976, and has been managed by the U.S. Fish and Wildlife Service since then. The protection and management of these areas as natural reserves and refuges, respectively, is ensured by local and federal statutes.
Higo chumbo is a slender, upright, columnar cactus, which may grow more than 2 meters in height and usually is extensively branched. The stem has 8 to 11 longitudinal ribs separated by shallow grooves. The stem and branch have 2 to 7 centimeter long spines in groups about 1 to 2 centimeters apart. Reproductive plants produce large, 17 to 22 centimeter long, greenish-white hermaphroditic funnel-shape flowers, which opens at night. Mature fruits are yellow, spineless berries with numerous small black seeds enclosed in a white pulp.
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