RESUMO
ABSTRACT Ficus inflorescences host a species-rich chalcid wasp community, including pollinating fig wasps (Agaonidae: Tetrapusinae, Kradibiinae, and Agaoninae) and several species of non-pollinating fig wasps (NPFW), that show several life-history strategies, including gall-inducers, kleptoparasites (i. e. inquilines), and parasitoids. We analyzed the structure and degree of specialization of the fig wasp community associated with Ficus inflorescences in urbanized areas, agroecosystems, and on the edge of forest fragments in the state of Goiás (Brazil). We sampled 34 wasp species in four native Ficus tree species, from which four wasp species occurred in more than one host. Neotropical fig pollinators (Pegoscapus and Tetrapus) were the most abundant species, and they were host-specific, although two pollinator species were associated with Ficus obtusifolia. The Jaccard similarity index was higher in samples of fig wasps collected in the same host, indicating that the community composition was specific to each host species. Community structure indices indicate a specialized structure with low connectance, high bidimensional Shannon H2' and low partner diversity. The communities present a modular web structure in which modules were represented by each host and its associated insect species. These results indicate that the fig wasp communities analyzed are highly specialized, despite a few not strictly host-specific species.
RESUMO
The role of carabid beetles in reducing populations of phytophagous insects has been an elusive subject. A field experiment was established on a commercial wheat crop (cv. Otto) with an area of 4.5 ha in Valdivia, Chile, during the spring and summer of 1996-1997. The field had been under a prairie system for two years, before wheat sowing (fertilization and a pesticide had been applied during crop development). Samples were taken at approximately monthly intervals. Carabid beetles were sampled with a grid of pitfall traps and other insects were sampled with a vacuum insect net and soil cores. The genera of the carabids found are of neotropical origin. Exclusion by polythene barriers, together with removal of carabid beetles using traps, was an effective technique for controlling carabid populations in a commercial wheat crop. A reduction in the number of carabid beetles was associated with an increase in the number of springtails and arachnids, and a decrease of agromyzid adults. Phytophagous insects, such as homopterans and lepidopterous larvae, were not affected by carabid exclusion and removal. The action of carabid beetles on the arthropod fauna can be extremely complex, due to its predatory activity at multitrophic levels.