Consequences of a severe drought associated with an El Nino-Southern Oscillation on a light-attracted leaf-beetle (Coleoptera, Chrysomelidae) assemblage in Borneo.

摘要

This study was conducted in a lowland dipterocarp forest in Lambir Hills National Park, Sarawak, Malaysia, to determine the relative significance of a 1998-ENSO related drought compared with normal conditions before the drought in influencing species richness and species composition of chrysomelid assemblages across a 5-year period (1994-99). A total of 17 336 individuals belonging to 304 species were captured. The number of species in a monthly catch varied from 19 to 89 throughout the study period. The mean number of species during the first collection period immediately following the drought was 27.7 (April-June 1998), while that of all other periods was 59. The proportion of species loss ranged between 0.20 and 0.57 during pre- and post-drought periods, with the mean being 0.40, while the only species-loss proportion across the drought was 0.78. Results indicate that the number of species of light-attracted chrysomelid at the study site remarkably decreased after the drought associated with the 1997-98 ENSO, and that the degree of species loss across the drought period was extremely high, compared with usual levels of species loss during the non-drought periods.