Abstract
BackgroundMany species inhabiting Kihansi gorge ecosystem in Southern Udzungwa Mountains, Tanzania are threatened with extinction due to habitat loss caused by constructed hydropower plant that diverted over 90% the water off the Kihansi River. Understanding ecological correlates and structure of an animal community in perturbed ecosystems is an important way to enhancing species conservation particularly in this system, where several species are already threatened with extinction. This study assessed influences of local habitat characteristics on the butterfly abundance, species richness and diversity and examined how the butterfly community structures across three structurally heterogeneous habitats in the Kihansi gorge forest. Butterfly abundance data were collected using baited traps and measured environmental variables in the field, where trapping occurred. To understand the diversity and butterfly richness, these parameters were computed under Primer software. Non-metric multidimensional scaling and analysis of community similarity were used to analyse the butterfly community structure. Furthermore, the generalized linear models (GLM) were used to assess how the measured variables explained observed species diversity, abundance, and richness.ResultsIn total, 72 species of butterfly in five families were recorded. Butterfly species diversity and richness did not vary across the habitat types or elevation gradient but showed strong correlation with some habitat characteristics. In addition, there was evidence of butterfly communities structuring into distinct groups that showed greater separation associated with the habitat characteristics they utilise. Furthermore, across the study area, butterfly species diversity increased significantly in high canopy and in trees with smaller DBH and at lower ground cover. Similarly, abundance significantly increased in the woodland and wooded grassland habitats, where there was high canopy and where tree density was high. Furthermore, butterfly species richness was strongly positively associated with high canopy cover and mostly increased in sites closer to water source.ConclusionFirst, this study shows strong positive correlation between the habitat characteristics and butterfly species and community structure, suggesting strongly that maintaining habitat quality should be a priority in conserving the butterfly communities in Kihansi. Second, conservation of environmental disturbance indicator butterfly taxa which are also endemic and rare is worthy of concern under the ongoing human-induced threats in the area. It is appropriate time that the Tanzania government should declare the Kihansi gorge forest among existing protected areas to secure effective conservation of biological diversity in this threatened ecosystem. Third, the ants–butterfly symbionts and their links to the potential lichen depletion are still unclear, and thus future research should explore the trophic cascades of depleting habitat quality on the endemic and rare butterfly species in the Kihansi gorge.
Highlights
Human development process is one among factors that are widely known to affect biodiversity in many regions
The ants–butterfly symbionts and their links to the potential lichen depletion are still unclear, and future research should explore the trophic cascades of depleting habitat quality on the endemic and rare butterfly species in the Kihansi gorge
The current study was conducted to fill this gap and to provide information on how butterfly abundance and diversity is influenced by local habitat characteristics, habitat types and how the two vary spatially along an altitudinal gradient
Summary
Human development process is one among factors that are widely known to affect biodiversity in many regions Construction activities such as opening up of new roads, erection of power transmission lines, energy development and river excavation and impoundment conducted for development have been documented to affect land cover and several species (Gasparatos et al 2017; Jones et al 2015; Preston and Kim 2016). Disturbance in natural areas resulting from construction activities directly removes important species requirements, such as food, cover and nesting sites. This can greatly reduce ability of the species to reproduce due to diminished suitable conditions for growth and reproduction (Decker 1994; Kocher and Williams 2000). The generalized linear models (GLM) were used to assess how the measured variables explained observed species diversity, abundance, and richness
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