Figs (Ficus, Moraceae) in urban Hong Kong, south China

Hong Kong (22 degrees N) is on the northern margins of the Asian tropics and has a native fig flora of 24 species. A total of 3.4 km(2) of the urban area on Hong Kong Island was surveyed for spontaneous and planted fig plants of reproductive size. The 1124 individuals included 14 species in four subgenera: seven native species (F. fistulosa, F. hirta, F. hispida, F. microcarap, F. pumila, F. subpisocarpa, and F. variegata), four of which were sometimes planted, one probably native (F. virens), one naturalizing species (F. religiosa), and five exotic species that occurred only in cultivation, two of which (F. altissima, F. rumphii) are pollinated and produce viable seeds. The native species in the two most common subgenera form distinct ecological guilds: those in subgenus Sycomorus bear large, many seeded, green or yellow figs and are bat-dispersed pioneers on exposed soil; those in subgenus Urostigma bear small, few-seeded, dark-purple figs and are largely bird-dispersed and epilithic. The density of potentially fruiting fig plants in the study area (2.3/ha) was within the range reported for tropical forests and between them they were visited by the entire urban frugivore fauna. This study shows the importance of the urban fig flora to urban wildlife and also highlights the risk of cultivated Ficus species becoming invasive, despite their obligate species-specific pollinator mutualisms.