Seed dispersal in Hong Kong, China: past, present and possible futures

In the present article, published and unpublished information regarding seed dispersal in the degraded landscape of Hong Kong, China, is reviewed. Information was available for 1681 native plant species, of which 1165 were assigned to probable seed dispersal modes. Endozoochory accounted for one-third (34.4%) of all species evaluated, half (54.4%) of those from forests, and more than two-thirds (69.2%) of all trees and tall shrubs. Wind dispersal (25.9%) and dispersal by an unknown agent (30.7%) accounted for most of the rest, with the unknown species mostly small-seeded herbs. Although the frugivore fauna of the Hong Kong region has been truncated since the late Pleistocene, there are few clear examples of failed mutualisms. The most striking is the absence of scatter-hoarding rodents from Hong Kong, despite the presence of forest trees that appear to require them for effective dispersal. There are also some large Lauraceae fruits that appear to be targeted at larger-gaped birds than currently present. Most endozoochorous species are dispersed by 3 small passerine birds (Pycnonotus jocosus, P. sinensis, and Zosterops japonicus), with larger birds, fruit bats (Cynopterus sphinx, Rousettus leschenaulti), rhesus macaques (Macaca mulatta), civets (Paguma larvata, Viverricula indica), and muntjacs (Muntiacus muntjac) accounting for the remainder. The low plant diversity in frugivore droppings, seed traps, and secondary vegetation suggests plant succession may be dispersal limited, although this has not been investigated experimentally. Planting underdispersed species is the simplest solution but, in the longer term, the (re)introduction of a scatter-hoarding rodent should be considered as well as that of other locally and regionally extinct frugivores.