Patrick Lai & Joseph Yip, Hong Kong Herbarium
The Shing Mun Arboretum was established in the early 1970s, for ex-situ plant conservation and as an outdoor classroom to complement the Hong Kong Herbarium for studying living specimens of native plants in Hong Kong. The Arboretum has been recently enriched with a new climber collection, one species of which is the Illigera celebica (Illigera). When we visited the Arboretum in June this year, most of the leaves of the Illigera were found half-eaten. The plants looked miserable, with the appearance that most gardeners or horticulturists would not like to see.
On closer examination, there were numerous caterpillars feeding on the leaves and almost none of the leaves remained intact. The tiny creatures are not ordinary kind of “pest” but the larvae of the uncommon butterfly White Dragontail (Lamproptera curius). We also noticed a few adults nearby, flying restlessly like dragonflies. The co-existence of the butterflies and their food plant was, despite the “plant damage”, a good sign of biodiversity conservation.
There is only one species of Illigera in Hong Kong. S.T. Dunn named it as a new species Illigera platyandra in 1908 in the Journal of the Linnean Society, Botany -- based on a specimen originally collected in Wong Nai Chung and cultivated in the Hong Kong Botanical Garden. The scientific name was later on considered as a synonym of Illigera celebica which has a distribution range from Yunnan, Indochina to Malaysia.
Illigera has a local conservation interest not only because it is the larval food plant of the uncommon and elegant White Dragontail, but also because of its local rarity. It has only been recorded from a few localities in Fung Yuen, Sai Kung, She Shan Tsuen and Tai Mo Shan. The species is listed in the Forestry Regulations, a subsidiary legislation of Forests and Countryside Ordinance, Cap. 96. Collection, selling or possession of this species are prohibited.
Several trials of propagating Illigera have been carried out in the last few years but all attempts by cutting have not been promising. However, seeds collected from various locations have fairly good germination rates (ca. 30%) and the young seedlings have relatively high survival rates. A few batches of Illigera seedlings have been raised in the nursery and reintroduced to suitable locations in the natural or semi-natural environment (e.g. Tai Tong, Shing Mun Arboretum and Fanling). The populations are establishing quite well and the recent observation that White Dragontail larvae feeding on the Illigera population at the Shing Mun Arboretum is an encouraging initial sign of our conservation work for the Illigera and White Dragontail.