Overview
Varronia rupicola is large shrub endemic to southwestern Puerto Rico, Vieques and Anegada islands in the British Virgin Islands, where it is restricted to the subtropical dry forest life zone. The species was federally listed as threatened on September 9, 2014, and it is considered critically endangered by the International Union for Conservation of Nature Red List, which is a critical indicator of the health of the world's biodiversity. This species is threatened by habitat degradation due to urban development, habitat invasion by non-native plant species like grasses, human induced fires, hurricanes, and severe drought events associated to climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change . Five V. rupicola discrete populations have been documented throughout its range, which include two populations in mainland Puerto Rico, one in Vieques Island and two in Anegada Island.
Scientific Name
Identification Numbers
Characteristics
Physical Characteristics
Varronia rupicola is a large shrub reaching up to 4.9 to 16.4 feet (5 meters) in height, and grows as a single stem shrub or with multiple branches from the base. The alternate leaves are ovate to elliptic or oblong-elliptic, measure 0.8 to 3.5 inches (2 to 9 centimeters) long and 0.4 to 1.8 inches (1 to 4.5 centimeters) wide, with an acute apex, rounded to obtuse at the base and is chartaceous, or papery. Leaves margins are whole or crenate, meaning scalloped or notched, toward the apex. The upper surface of the leaf is rigidly scabrous, meaning rough surface, and puberulous, meaning densely covered by hairs, underneath, with strigose, meaning having straight hairs, petioles ranging from 0.1 to 0.4 inches (0.2 to 1.0 centimeters) long. Flowers are white, growing in a solitary globular heads of up to 20 flowers, which are grouped into a globose terminal structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.
Learn more about structure , and up to 1.0 inches (2.5 centimeters) in diameter. The corolla is white and 0.3 inches (0.7 centimeters), with long with four to five lobes and the fruit is a one-seeded red drupe that measures about 0.2 inches (0.5 centimeters) long.
Life Cycle
Varronia rupicola has been reported flowering and fruiting in December through January, and in June through July. From February to April, all plants observed in wild populations were sterile, consistently with seasonal droughts. Fruit production in the populations at the Guánica Commonwealth Forest and the municipalities of Ponce and Peñuelas seem to be high, and there is evidence of recruitment associated to the majority of the clusters of individuals. Under greenhouse conditions, seed germination has been reported as not less than 67%.
Material of Varronia rupicola germinated under nursery conditions developed into reproductive individuals, which produced flowers and fruits in about one year following germination. The rapid reproductive development of the species and the finding of individuals along recently disturbed sites, like new dirt roads, as well as natural forest gaps or openings, suggest that V. rupicola is an early colonizer or pioneer species. This is consistent with other species of Varronia. However, seedlings and saplings may remain dormant for years in the wild until there are favorable conditions for their development. Adult individuals at the Guánica Commonwealth Forest have been monitored for more than 20 years, which indicates that the species may live for several decades if conditions are favorable.
Despite the showy red fruits of V. rupicola, currently its dispersion in Puerto Rico, including Vieques Island, seems to be almost limited to gravity as the majority of seedlings are fund under the parent plant or downslope, as observed by O. Monsegur and others in 2013 and later documented by M.A. Hamilton and others in 2015. In 2016, M.A. Hamilton noted that this may be an effect of habitat fragmentation and small populations size. This may result in a deterrence of dispersers, as possible vectors may focus on more reliable and abundant plant species. Ongoing research through the use of trap cameras aims to address information about species phenology, pollinators and seed dispersers, as well as potential predation by exotic animals. In 2013, O. Monsegur, and others observed in Puerto Rico that flowers of V. rupicola are visited by several insect species, including honeybees (Apis mellifera) and butterflies like Electrostrymon angelia.
Habitat
Varronia rupicola is known to occur in the subtropical dry forest life zone, overlying limestone substrate. This habitat receives a mean annual rainfall that ranges from 24 to 40 inches (600 to 1110 millimeters). The vegetation in this life zone is deciduous on most soils, with tree species dropping leaves during the dry season. The vegetation usually consists of a nearly continuous single-layered canopy, with little ground cover. The leaves of dry forest species are succulent or coriaceous and species with spines and thorns are common. Varronia rupicola occurs in forested hills with open to relatively dense shrublands/shrublands 6.5 to 9.8 feet (2 to 3 meters) in height; in low forest with canopy from 8 to 15 feet high (3 to 5 meters) and at the edge of a dense low coastal shrubland forest. In the island of Anegada, V. rupicola is found in open limestone pavement and sand dunes.
Arid land with usually sparse vegetation.
The land near a shore.
A natural chamber or series of chambers in the earth or in the side of a hill or cliff. An irregular limestone region with sinkholes, underground streams and caverns.
Geography
The distribution of V. rupicola extends along the southern coast of Puerto Rico, from the municipalities of Guánica to Peñuelas. Outside Puerto Rico’s mainland, V. rupicola also occurs in Vieques Island, where recent work confirmed the occurrence of the species in Puerto Ferro within the Vieques National Wildlife Refuge. In addition, the easternmost distribution of the species extends into the island of Anegada in the British Virgin Islands, where two populations have been identified - Anegada west and Anegada east.
Timeline
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