Fruit–feeding butterfly assemblages at Dlinza and Entumeni Nature Reserves, KwaZulu–Natal : a quantitative biodiversity study
Forrester, Wayne Steven
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Fruit-feeding butterfly assemblages at two indigenous forests in KwaZulu-Natal, the Dlinza and Entumeni forests were studied with baited traps during a year cycle June 2008-May 2009 and an additional March-May 2010 (autumn) survey. A total of 2801 butterflies were trapped, which consisted of 28 species, representing five subfamilies of the Nymphalidae, with the most abundant and species rich subfamily being Charaxinae. Higher than expected abundances and numbers of species trapped during the present study, though significantly lower than some tropical areas in Africa, demonstrate that this technique of quantifying assemblages with baited-traps are effective in forests of KwaZulu-Natal, South Africa and should be included in future butterfly assessments. During a mark-release-recapture survey, very few fruit-feeding butterflies were recaptured, with no observed dispersal events between the two forests. A high turnover of fruit-feeding butterfly populations reflects adequacy of habitat quality and size at both the forests for the conservation of this guild of butterfly fauna. Season had a marked effect on butterfly assemblages with optimal times of the year emerging as autumn and winter, when butterfly abundance and species richness were highest. Abundance and diversity (Shannon index) at the smaller Dlinza forest were marginally higher or at least very similar to that of the larger Entumeni forest. Higher species richness (d) was recorded at the larger Entumeni forest. A greater number of individuals and higher number of species were trapped at both forest edges in comparison to forest interior (clearings). Species richness (d) and diversity (Shannon index) at Dlinza forest were higher at the interior (forest clearings) compared to that of the Dlinza forest edge. In contrast higher species richness and diversity (Shannon index) were recorded at the Entumeni edge if compared to the Entumeni interior. Highest species richness (d) was consistently recorded at the Entumeni forest edge. Similarity between the species compositions of both forests was high. The Entumeni forest are imbedded in a larger zone of natural grassland in contrast to the Dlinza forest which is partly located in an urban setting with small or absent grassland buffer zones. Altitudinal differences between these forests had lesser influence on the fruit-feeding butterfly assemblages whilst the closer urban edge at the Dlinza forest appears to contribute to a negative impact on the species richness at the forest margin. Recommendations to the conservation management of the Dlinza and Entumeni forests, stemming from this study, include conserving small forest remnants as part of stepping stone corridors between the forests, eradication of alien invasive plant species, conserving grassland buffer zones in which the forests are embedded and caution to any future developments in this unique area. Awareness to preserve and understand the wealth of indigenous smaller fauna, which are dependent on these magnificent forests, is to be promoted.