Aleuritopteris hainanensis (Pteridaceae), a New Species From Hainan, China

Aleuritopteris hainanensis, a new fern of Pteridaceae from Hainan Province, China, is described and illustrated. Morphologically, A. hainanensis closely resembles A. squamosa, with both species bearing densely scaly fronds. However, the fertile fronds of A. squamosa (10.7-25.9 cm) are significantly longer than the sterile fronds (4.1-10.7 cm), whereas in A. hainanensis, the sterile (9.4-13 cm) and fertile fronds (10.1-14.1 cm) are nearly equal in length. In addition, the stipe and abaxial lamina scales of A. hainanensis are broadly lanceolate with nearly entire margins, while those of A. squamosa are lanceolate with margins erose-serrulate. Plastomes analysis futher reveals that the genetic distance between A. hainanensis and A. squamosa is significantly greater than the typical intraspecific variation, supporting the recognition of A. hainanensis as a distinct species. According to IUCN criteria, we propose that A. hainanensis should be categorized as a Vulnerable (VU) species.