| Abstrakt: |
Presents the results of tests of two hypotheses to explain changes in species richness of gall-forming insects. The first hypothesis proposes that gall-forming insect species richness increases as more potential host-plant species are available. The second hypothesis implies that soil fertility affects plant colonization by gall-forming insects. Seven sites, representing strong differences in vegetation and soil were chosen at the Lacandona tropical rain forest region, Chiapas, Mexico. Overall, we found 1522 individual plants belonging to 340 different plant species. From this, we found gall-forming insects on 737 (43.9%) plants and on 74 (22%) of total plant species. We found a significant negative correlation between gall-forming insect species richness and species richness of plants, which does not support the hypothesis that plant species richness is an important factor in generating the radiation of gall-forming insects. Using phosphorus as an indicator of soil fertility, we found the lowest number of plants with gall-forming insects and the smallest gall-forming insect load per individual plant in the more fertile soil (alluvial). In contrast, the highest number of plants with galls and the highest gall-forming insect load per plant were found at a savanna-like vegetation site, where the poorest soil was recorded. These results did not support the soil fertility hypothesis in terms of species richness, but did with respect to abundance of plants with galls. |
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