Overview
Status: Threatened (reclassified on 11/4/2022)
Ottoschulzia rhodoxylon, commonly known as "palo de rosa" due to its pink colored wood, reaches up to approximately 49 feet in height. Its trunk can reach 16 inches in diameter. The leaves are alternate, elliptical or ovate, coriaceous and glossy with a slightly white margin. The flowers of this genus are small and composed of five sepals united at the base, and a corolla with a short tube in the shape of a cup and five lobes. The fruit is about 0.98 inches long and 0.86 inches wide, smooth and with a thin cover that turns dark purple when ripe.
Threats
Although limited species distribution is no longer considered an imminent threat, the species still faces threats related to habitat destruction and modification in privately-owned lands (particularly along the northern coast of Puerto Rico), and other natural or manmade factors such as hurricanes, 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 , and habitat encroachment by invasive plant species. Furthermore, there are biological and ecological limiting factors for the species, such as populations consisting of isolated trees and the requirement of cross-pollination (transfer of pollen from the flowers of one individual to neighboring trees) to maintain viable populations. This is exacerbated by slow growth of the species seedlings, and the species’ sporadic flowering and fruit production, which results in a low recruitment rate. Nonetheless, the slow growth of this tree and its reproductive biology suggest that palo de rosa is a late successional species, whose saplings stage might be prolonged under closed canopy conditions until a natural disturbance induces favorable conditions for their development to adulthood.
Conservation measures
The Service, in collaboration with several partners, is implementing recovery actions for palo de rosa. Among these conservation efforts are the propagation of the species in nurseries, the protection of the species in private lands, and the incorporation of protective measures for the species in public forests.
Nevertheless, to recover palo de rosa from a landscape perspective, we will need to increase our collaboration and partnership efforts with private landowners through outreach, and work with Puerto Rico Department of Natural and Environmental Resources in developing conservation strategies and recommendations when evaluating urban and infrastructure development projects that could affect these subpopulations. Such conservation measures should include the maintenance and enhancement of effective forested buffer areas and corridors to provide connectivity between subpopulations and to secure the microhabitat conditions necessary to sustain a viable population (e.g., maintaining recruitment).
Scientific Name
Identification Numbers
Characteristics
Life Cycle
The flowering and fruiting of this species are infrequent and, therefore, not clearly understood. Available data suggests that palo de rosa relies on scattered flowering events, the events are not synchronized among subpopulations, and depend on seasonal rain events. Due to current population locations on the tops of limestone hills, it has been suggested that the seeds were once dispersed by an animal. However, no dispersers have been identified. Clustering of seeds around the mature plants suggest seeds are not being dispersed by any mechanisms other than gravity.
Habitat
The habitat of the palo de rosa along the south coast of Puerto Rico includes moist drainages and rivers on serpentine soils within the Susúa Commonwealth Forest (SCF). In addition, the palo de rosa subpopulations found within the dry limestone forests along the southern coast of Puerto Rico occur at the bottom of forested ravines (areas that provide enough moisture for seedling recruitment). The species also occurs in the northern limestone belt in the karst region of Puerto Rico. Despite deforestation for agriculture in the 1930s, a west-to-east band of continuous forested landscape extends from Aguadilla to San Juan, and additional limestone outcrops extend to the northeast corner of Puerto Rico in the municipalities of Loíza and Fajardo providing habitat for palo de rosa. The southern and northern limestone belts differ in climate, with wet and moist life zones characterizing the environmental conditions along the north coast of Puerto Rico. The karst area is characterized by a steep topography and a dense concentration of haystack hills or mogotes, with valleys and sinkholes between the hills. The steep topography and low agricultural value provide refugia and serve as a seed source for natural regeneration on adjacent forested lands following the abandonment of agricultural lands.
A dense growth of trees and underbrush covering a large tract.
The land near a shore.
A natural body of running water.
Geography
When listed in 1990 only 10 individuals were known from a few localities in Puerto Rico. However, currently about 1,144 individuals are known from 66 subpopulations on the island. In general, "palo de rosa" trees are limited to rocky, alkaline soils and serpentine derivatives along the southwestern coast of Puerto Rico, from the municipality of Cabo Rojo to the municipality of Guayanilla; and along the northern coast of Puerto Rico, from the municipality of Aguadilla to the municipality of Fajardo. In Hispaniola, there is little information of the population’s current status and location(s).
Timeline
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