n African Entomology - Conservation of biodiversity in urban environments : invertebrates on structurally enhanced road islands
|Article Title||Conservation of biodiversity in urban environments : invertebrates on structurally enhanced road islands|
|© Publisher:||Entomological Society of South Africa (ESSA)|
|Author||C. Whitmore, T.E. Crouch and R.H. Slotow|
|Publication Date||Mar 2002|
|Pages||113 - 126|
|Keyword(s)||Invertebrate diversity, Island biogeography, Species richness and Urban conservation|
Urbanization has resulted is severe alteration and destruction of natural habitats. Durban, South Africa, is one of the fastest growing cities in the world and the demand for land is increasing. The Durban Metropolitan Open Space System (D'MOSS) was created for both ecological and social enhancement through an integrated approach to urban open space establishment and management. We assessed a subsection of the D'MOSS for its contribution to biodiversity enhancement. Invertebrates were selected as indicators of diversity. Pitfall trapping was conducted on a seasonal basis on traffic islands from two landscaping management regimes : extensive mown areas (i.e. limited structural diversity) and the inclusion of indigenous and exotic shrubs, herbs and trees (i.e. structurally enhanced). The influence of adjacent remnant natural areas as a source for these islands was also assessed. Species-area and species-distance predictions based on island biogeography theory were tested to determine whether they apply at this small scale. In this study, urban traffic islands accommodated 232 invertebrate morphospecies, i.e. 71% of the estimated species richness for a larger sampling effort. A total of 23 881 individuals were sampled, 81% of which were a single species of ant and a collembolan. Species abundance followed expected seasonality (high in summer and low in winter) irrespective of island treatment. While enhanced islands supported a higher richness during spring, as well as a greater number of unique species overall, our results were not conclusive in their support of either the movement of invertebrates along corridors of semi-natural vegetation, or the value of larger areas of urban open space. The lack of independence between distance and area in this study, the limited scale over which diversity was measured, and the influence of multiple sources of emigration are discussed.
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