n African Entomology - Testing a bioindicator assemblage : gall-inhabiting moths and urbanization

Volume 9, Issue 1
  • ISSN : 1021-3589



Natural habitat is under increasing pressure from urbanization. Urban and suburban areas are therefore growing in significance as elements of the matrix within which conservation must be undertaken. The ability of such areas to maintain biodiversity may be assessed using biological indicators. However, the robustness of such bioindicators must be established by independent tests of initially identified patterns and relationships, by repeating studies at different times and localities. Here, the utility of a Lepidoptera assemblage inhabiting fungus-induced galls, as a bioindicator of habitat quality in urban areas, is reassessed. Marked differences were found in gall resources, as well as Lepidoptera larval abundances and species rank abundances between studies. These were attributed to weather and phenological differences between years. Although assemblage structure and species composition is highly dependent on gall resource quality and quantity and the latter differed significantly between studies, habitat-associated differences in the lepidopteran assemblage were consistent between studies. Species richness, larval density and larval abundance were generally lower at sites closest to the city centre than at those further away. Larval abundance and density was significantly lower at roadside sites than at rural and suburban garden sites. This study has thus shown that this lepidopteran assemblage is a robust bioindicator, and also re-emphasized the importance of green areas for conserving diversity in cities and urban environments.

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