Pollination in a degraded tropical landscape: a Hong Kong case study

Although the pollination biology of many individual plant species has been investigated in the Oriental region, there have been very few community-level studies. The two most comprehensive of these were in the primary mixed dipterocarp forest of Lambir Hills National Park, Sarawak (4°20′N: Momose et al. 1998, Sakai et al. 1999) and in the warm temperate evergreen broad-leaved forest and cool temperate mixed forest on Yakushima Island (30°N: Yumoto 1987, 1988). Hong Kong (22°17′N) lies midway between these sites, at the northern margin of the tropics, where winter temperatures fall below 10 °C at sea-level for a few days every year and there are occasional frosts above 400 m (Dudgeon & Corlett 1994). Latitudinal effects, however, are compounded in comparisons with other well-studied East Asian sites, by centuries of massive human impact, leaving a degraded landscape of steep, eroded hillsides, covered in fire-maintained grassland, secondary shrublands and, locally, secondary forests (Zhuang & Corlett 1997). This history has left a relatively impoverished fauna but a surprisingly diverse flora, including 400 native tree species (Corlett & Turner 1997). In these circumstances, failures of pollination and dispersal mutualisms might be expected to accelerate the loss of plant species from the landscape (Bond 1994, Kearns & Inouye 1997). Previous studies have shown that most woody vegetation in Hong Kong is dominated by species whose seeds can be dispersed by the commonest avian frugivores, the light-vented and red-whiskered bulbuls (Pycnonotus sinensis (Gmelin) and P. jocosus (Linn.)) and the Japanese white-eye (Zosterops japonicus Swinhoe) (Corlett 1996, 1998), but there is no equivalent information available on pollination biology.