Britton, Adam William; (2019) Assessing human impacts on Lake Tanganyika cichlid fish communities. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis assesses the human impacts on rocky shore cichlid fish communities from the biodiversity hotspot Lake Tanganyika, by comparing the diversity of its protected and unprotected areas. Chapters two and three use cichlid community composition data collected from a range of localities in the Tanzanian section of Lake Tanganyika, to investigate whether human impact is negatively affecting their species, functional, and phylogenetic diversity, and to assess whether protected areas are conserving these components of diversity. In terms of species diversity, alpha diversity was higher in protected areas than adjacent unprotected localities, and the pattern of beta and zeta diversity in protected areas indicate a more even community composition. Additionally, benthic feeding herbivores were the most affected trophic group. Functional diversity, which was defined as the shape variation of geometric morphometric landmarks reflecting key traits, was also higher in protected areas than adjacent unprotected localities, as was phylogenetic diversity. Furthermore, functional and phylogenetic diversity were both linked to species richness, possibly due to a lack of variation in species uniqueness. Chapter four investigates the possible reasons for changes in cichlid diversity in unprotected areas using stable isotope and stomach content analysis. Benthic feeding species from the most disturbed locality had significantly higher nitrogen stable isotopes and stomach sediment proportions than a less disturbed locality, which may contribute to the lower species diversity of this trophic group. In conclusion, protection from human disturbance prevents a reduction in the core components of cichlid fish diversity in Lake Tanganyika, and therefore the network of freshwater and terrestrial protected areas should be increased. Moreover, protection of species appears to be an effective conservation strategy for the core components of biodiversity, so species richness could be used as a surrogate for biodiversity assessments in other systems.

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