Conservation genetics and status of Orania sylvicola palms in Singapore - native relicts or historical re-introductions?

Abstract

Orania sylvicola (Griff.) H.E.Moore is a large, single-stemmed palm species widely distributed across Malesia. It is the only species of Orania present in Peninsular Malaysia and Singapore. In Singapore, the species is rare and critically endangered, although a full understanding of its distribution is hampered by sparse historical collections. However, conflicting records on the known localities in the literature, along with a recent discovery of a substantial population of Orania sylvicola within the Tyersall Learning Forest in Singapore Botanic Gardens, have led to questions on the origin of the extant populations of O. sylvicola. There are known instances of past introductions of non-native plant species in Singapore, which raised suspicions that some of the individuals were historical reintroductions from overseas. Genetic analyses, a comprehensive survey of existing literature and herbarium collections, and a topographical study of existing Orania sylvicola populations were carried out to determine the origin of these individuals in Singapore. Our results suggested that all Orania sylvicola individuals in Singapore are of native origin, with two populations present. The distribution of the two populations overlaps in the Singapore Botanic Gardens, which may indicate that some of the plants have been transferred to the Botanic Gardens from another location in Singapore. Preliminary results also revealed that sampled populations within Peninsular Malaysia and between Peninsular Malaysia and Singapore are highly differentiated from each other with very little gene flow either by pollen or seed dispersal. Our study highlights how the integration of genetic information, historical collections and topographical analyses can contribute to assessing the origin and conservation potential of endangered plant species in Singapore and provide insights into suitable conservation actions for Orania sylvicola.