Species Diversity and Abundance in Insular Systems

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Research on the importance and mechanisms of ecological interactions, as exemplified in subtropical island ecosystems will be continued. An experiment with lizards, web spiders, both, or neither removed from large enclosures will determine the separate effects of lizards and spiders on ambient insects and foliage damage, as well as whether an increase in spiders compensates for lizard removal. How lizards reduce prey consumption by spiders will be determined by monitoring prey in traps, prey in webs and prey actually consumed; by observing diurnal versus nocturnal consumption; and by testing whether spiders use more productive sites in no-lizard enclosures. Food levels in natural webs will be raised to those of no-lizard enclosures to see the effect on spider fecundity. Lizards will be introduced onto no-lizard islets to measure effects on ambient insects and foliage damage, and by comparison with adjacent lizard islands, tests will be made of whether the experiment can eventually mimic the natural situation. About 250 spider and about 35 lizard populations will be monitored on over 100 islands to determine causes of extinction, long-term population stability and results of ongoing competition experiments. An overall premise is the use of islands as a model for understanding community and ecosystem processes.