Insights on the distribution of the endemic Hawaiian fern genus Adenophorus Gaudich. (Polypodiaceae) on the island of Oʻahu, Hawaiʻi.

Date
2021
Authors
Thomas, Miles Kealoha
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Ticktin, Tamara
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Botany
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Abstract
Epiphytes, plants that grow on other plants, are conspicuous members of manyecosystems around the globe but are most pronounced in humid forests. In tropical regions such as Hawaiʻi, upland wet forests sustain diverse communities of epiphytic vegetation, mainly consisting of bryophytes and ferns. Of the epiphytic ferns, the endemic genus Adenophorus Gaudich. (Polypodiaceae) is the most species-rich and represents a considerable amount of the biomass of Hawaiian epiphytic communities. However, little is known about the ecology and conservation status of this genus. This study assessed the distribution, abundance, and conservation status of Adenophorus species on the island of Oʻahu and identified some of the factors affecting it. I carried out surveys on transects along eight ridges of the Koʻolau mountains as well as in the Kaʻala Natural Area Reserve and sampled epiphytes on a total of 242 trees. Adenophorus abundance overall increased at higher elevations, although elevational patterns differed between species. Adenophorus oahuensis and A. haalilioanus distributions appear to be limited by elevation, the former at low elevations and the latter at higher elevations. Adenophorus abundance increased with bryophytes cover, and bryophytes appear to be important in the establishment of the gametophyte stage of these ferns. Adenophorus haalilioanus may exhibit host bias, but further studies are needed to confirm this. Several species of Adenophorus may be experiencing population declines (i.e., A. oahuensis, A. tripinnatifidus, and A. haalilioanus), a result of habitat degradation as well as shifts in precipitation likely due to climate change. Adenophorus abietinus shows great phenotypic variability and may warrant further investigation of two distinct varieties, one of which is mostly found at higher elevations near the Koʻolau summit ridge and may also be susceptible to perturbation by climatic changes in the near future if current trends of current climate change persist. These insights provide a strong foundation for the future conservation of these endemic ferns.
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Ecology, Adenophorus, Conservation, Ecology, Epiphytes, Ferns, Hawaiʻi
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66 pages
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