Overview
Cyathea drypteroides, commonly known as the elfin tree fern, is a fern endemic to the elfin (cloud) or dwarf forests of the central mountains of Puerto Rico. It is found in the peaks of Monte Guilarte, Guilarte Commonwealth Forest, Cerro Rosa, Toro Negro Commonwealth Forest, and Monte Jayuya. It was originally listed as an endangered species on 1987 under the Endangered Species Act. As part of a collaborative effort, the Service, the Puerto Rico Department of Natural and Environmental Resources, and Fairchild Tropical Botanic Garden, have worked together towards the recovery of the species by assessing current populations and collecting spores for propagation in an effort to enhance the species’ currently known populations and establish new ones.
Scientific Name
Identification Numbers
Characteristics
Life Cycle
Little is known about the phenology and recruitment of the elfin tree fern. The low number of individuals per population may suggest that the elfin tree fern has highly specialized ecological requirements to grow or to produce viable spores.
As assessed by Fairchild Tropical Botanic Garden germination tests, the elfin tree fern germination starts 6 days after they are fully developed (dark brown color) and by day 18 most of the spores germinated (72%). Within 5 months of germination, sporophytes had formed.
As a fern, Cyathea drypteroides has two different stages; sporophyte (the “fern” as we know it) and gametophyte. The sporophyte stage releases the spores. Spores released need to fall into suitable substrate, with enough water and light, to grow into a gametophyte. During the gametophyte stage, both sperm and eggs are produced. In presence of water, the sperm swims into the egg to fertilize it. Therefore, ferns are dependent of water for reproduction. Fertilized eggs grow into the sporophyte stage, or the fern as we know it. At this stage spore are produced and life cycle starts again.
Physical Characteristics
The elfin tree fern is a small or dwarf tree fern reaching 24 inches (in)(60 centimeters (cm)) in height and approximately 1 in (2 to 3 cm) in diameter. The fronds are bipinnate. A pinnate is a compound leaf having leaflets arranged on either side of the stem, typically in pairs opposite each other. The dwarf tree fern leaflets are further subdivided in a pinnate fashion, nearly hairless, tapered at both ends, and reach 36 in (90 cm) in length and 10 in (25 cm) in width. The sori - where spores are stored - are located dorsally and are enclosed in a cup-shape indusium, a thin round membranous covering.
Habitat
The elfin tree fern is only known from the elfin (cloud) or dwarf forest of the central mountains of Puerto Rico. This forest type is found on exposed peaks and ridges above 2,723.1 feet (ft) (830 meters (m)) in elevation. Topography is rough and highly dissected by intermittent streams, although the elfin forest is found on more rounded mountain tops. Soils are very steep, well to moderately drained, and clayey over a layer of highly weathered rock. The vegetation in these areas is evergreen montane forest where only a single strata is present, and the stocky, relatively small (8-10 m (26.3- 32.8 ft) trees present form a dense thicket.
A dense growth of trees and underbrush covering a large tract.
A landmass that projects conspicuously above its surroundings and is higher than a hill.
Geography
The elfin fern is geographically restricted to Puerto Rico, specifically to elfin or dwarf forest of the central mountains of Puerto Rico.
Timeline
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