CREW has developed spore cultivation methods in vitro on a 1/2 Murashige and Skooge 1.5% medium. Compared to other fern species, T. scerlophylla was very slow to grow sporophytes but growth was better on soil than agar. However, nearly 18 months passed before a sporophyte even emerged ((Possley and Maschinski 2007).
Cultivation of this species in the nursery is relatively easy once the plants have acclimated to soil and ambient air and due to its sclerophyllous nature, it appears to not be as vulnerable to drying out as many other rare, native ferns. At Fairchild, we have met success at growing this plant by adding a 1:2 mix of perlite to our standard nursery mixture (contains peat and soil conditioner) with irrigation every 1-2 days and use of slow-release fertilizer granules.
Augmenting wild populations at FUH and HRD may be an option for outplanting. If we only consider additional potential introduction sites within the historic range of T. sclerophylla, we would be limited to only a handful of Miami-Dade County preserves located within the 17 kilometers between occupied sites FUH and HRD. Sites containing the appropriate habitat (mature hammock, low light, high humidity, limestone outcroppings) within this narrow geographic area include HBH, MSH, SPH, SPG, and possibly CASH, CASR, and BCF.
Fairchilds ex situ collections are approaching 1/3 the side of the numbers in the wild, with 49 plants as of May 2015. We hope to conduct an outplanting into suitable habitat and further safeguard the status of this species in Florida.
At the least, continued annual monitoring of both Miami-Dade populations for health and sporulation, continued collection of spores from wild and ex situ for long term cryogenic storage at the NCGRP, as well as the augmentation of current populations, or reintroducing new ones to a suitable Miami-Dade habitat are all recommended steps to ensure the survival of this species.
At HRD and FUH, current management by Miami-Dade County Natural Areas Management (NAM) appears to be sufficient to maintain the population at current levels. However, this status of this species would be strengthened in South Florida by augmenting current populations and/or introducing new ones within its historic range.
Invasion by non native plants is a serious threat to T.sclerophylla and includes the following species within Miami-Dade County: Epipremnum pinnatum, Syngonium podophyllum, Schefflera actinophylla, Ardisia elliptica, and others.
T. sclerophylla may hybridize with a co-occurring native fern Thelypteris reptans, however, it is unclear whether this represents a threat to this species. A hybrid between these 2 taxa has been described from Cuba (Sanchez et al. 2006) and Possley believes she has observed it in Florida as well. Material was sent to Alan Smith at US Berkeley for examination in 2014.
Vegetation management crews may have an accidental impact due to activities such as off target herbicide damage, piling of vegetation debris, or the removal of non-native overstory species that can cause sudden increase in light and decrease in humidity. The off-site drainage or lowering of the regional water table may also play a negative role as well.
Although succession in mature hammocks where T. sclerophylla is found is not usually a problem, succession due to gap openings (from storms or weed removal) may pose a serious threat.
Hurricanes decrease hammock canopy cover, likely leading to increased light levels and decreased moisture levels, which would negatively impact this species. Major hurricanes could cause mortality.
Very rare in Florida. Locally frequent elsewhere in range, but range is limited to Greater Antilles and Florida.
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