[Botany • 2017] Athyrium haleakalae • A New Rheophytic Fern Species (Athyriaceae) from East Maui, Hawaiian Islands: with Notes on Its Distribution, Ecology, and Conservation Status

Athyrium haleakalae K.R. Wood & W.L. Wagner   

DOI: 10.3897/phytokeys.76.1163 

Abstract

Athyrium haleakalae K.R. Wood & W.L. Wagner (Athyriaceae), a small lithophytic fern from East Maui, Hawaiian Islands, is described and illustrated. Notes on its distribution, ecology, and conservation status are also presented. The new species appears to be an obligate rheophyte, preferring sites of fast moving water along concave walls of streams and waterfalls. Athyrium haleakalae differs from the only other known Hawaiian Athyrium, A. microphyllum (Sm.) Alston, in having rhizomes 1–3 cm long and lanceolate blades 1- to 2-pinnate-pinnatifid, 3–8(–11) × 1–3(–4) cm, as compared to A. microphyllum having rhizomes (10–)15–30 cm long and ovate to ovate-triangular blades 3-pinnate-pinnatifid to 4-pinnate, 30–82 × 20–50 cm.

Keywords: Athyriaceae, Athyrium, new species, rheophyte, Hawaiian Islands, East Maui endemic, Critically Endangered

Figure 4. A Mature plants of Athyrium haleakalae, showing habitat preference along concave hollow of stream, Hana Forest Reserve, East Maui, HI (22 Aug 2013, Wood & Oppenheimer 15639) B Mature plant of Athyrium microphyllum, showing terrestrial habitat preference, erect rhizome, and large size, Mohihi, Kaua‘i, HI (18 Dec 2014, Wood & Flynn et al. 16175). Photos by K.R. Wood. 

Figure 3. Typical habitat of Athyrium haleakalae around stream plunge pools, Hana Forest Reserve, East Maui, HI. Photo by K.R. Wood, 21 Aug 2013. 

Athyrium haleakalae K.R. Wood & W.L. Wagner, sp. nov.

  Diagnosis: Athyrium haleakalae differs from the only previously known Hawaiian Athyrium, A. microphyllum, in having rhizomes 1–3 cm long and lanceolate blades 1- to 2-pinnate-pinnatifid, 3–8(–11) × 1–3(–4) cm, as compared to A. microphyllum with rhizomes (10–)15–30 cm long and ovate to ovate-triangular blades 3-pinnate-pinnatifid to 4-pinnate, 30–82 × 20–50 cm.

Etymology: The new species is named after Haleakalā, East Maui, a massive, dormant shield volcano (3,057 m tall) and the only known location of Athyrium haleakalae.

Kenneth R. Wood and Warren L. Wagner. 2017. Athyrium haleakalae (Athyriaceae), A New Rheophytic Fern Species from East Maui, Hawaiian Islands: with Notes on Its Distribution, Ecology, and Conservation Status.
PhytoKeys. 76; 115-124. DOI: 10.3897/phytokeys.76.1163