Rhizophora stylosa (Rhizophoraceae) newly recorded from Thailand: lectotypification, leaf anatomy, and pollen morphology

Rhizophora stylosa (Rhizophoraceae), previously known from India (Andaman and Nicobar Islands), China to Indo-China, and the Pacific Island, is reported here as a new record from coastal areas with muddy-sandy, sandy or sandy-rocky substrates at Ko Lidi and Ko Bulon Le, within Mu Ko Phetra National Park, La-ngu District, and at Ao Talo Wao, Ko Tarutao, Tarutao National Park, Mueang Satun District, Satun Province, Peninsular Thailand.

A detailed morphological description, illustrations and a distribution map of the species are provided, along with notes on distribution, habitat and ecology, phenology, a preliminary conservation assessment, etymology and specimens examined. In addition, Rhizophora stylosa is lectotypified, the Thai vernacular name “ Kongkang phetra ” is herein proposed for this species, and an updated identification key to the species of Rhizophora in Thailand is presented.

The species is currently assessed as Least Concern [LC] under the IUCN conservation status. Furthermore, detailed descriptions of leaf anatomical features and pollen morphology are provided. The thick cuticles, sunken stomata, large hypodermal cells, and cork warts are adaptive anatomical features of leaves in Rhizophora that live in the mangrove environments.

The pollen grains of Rhizophora stylosa are tricolporate, prolate spheroidal or oblate spheroidal shapes, small-sized, and reticulate exine sculpturing.