The diversity of Hoya (Apocynaceae: Asclepiadoideae) in some parts of Kedah and Perak, Peninsular Malaysia

This study provided data on the diversity of Hoya species reported to occur in some parts of the northern region of Peninsular Malaysia. Seven locations were chosen between two states, Kedah (Lata Celak, Sedim, and Bukit Hijau) and Perak (Mahang, Belukar Semang, Sungai Rui, and Pondok Tanjung). This extensive fieldwork was carried out from 2018 until the end of 2019 to provide a baseline checklist for this genus in this northern region. All living specimens found were recorded, and some species were cultivated for further identification and ex-situ conservation purposes. A total of 27 species and one variety were recorded, out of which 15 species were newly reported for the northern region of Peninsular Malaysia. The newly described species, Hoya peninsularis Rodda & Zakaria, was also reported in this study. One unknown species was found and labelled as Hoya sp. cf. scortechinii. Further identification process together with molecular analysis of this plant is still ongoing. The most diverse forests are Sungai Rui and Lata Celak, having the Shannon index of 2.741 and 2.622, respectively. Both forests possess the richest in Hoya species, but with low dominance index. The Sorenson similarity index is 6.74%, indicating a very low similarity of Hoya species between the studied sites. Due to the high diversity recorded, the number of Hoya species in the country is expected to increase if the genus is explored continuously. However, most of the study areas were exposed to extreme logging activities and had a high degree of human disturbances, indicating the need for intensive conservation efforts in this genus.