Ecology and conservation of critically endangered forest amphibians in an eastern arc centre of hyper-endemism

Tonelli, Elena (2023) Ecology and conservation of critically endangered forest amphibians in an eastern arc centre of hyper-endemism. Masters by Research thesis (MPhil), Manchester Metropolitan University.

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Abstract

The Earth is undergoing the sixth great mass extinction event, with the class Amphibia containing the greatest proportion of species at risk of extinction. Yet, many species remain undescribed or Data-Deficient, which prevents protection of species and their habitats in conservation programmes. I analysed the importance of cryptic species by compiling a genetic-based inventory for the amphibians of the Uzungwa Scarp Nature Forest Reserve (USNFR; 327 km2) within the Eastern Afromontane Hotspot. This is the first study of the site’s full range of amphibian species and ecological predictors, and indeed one of only a handful of ecological studies of amphibians anywhere in Africa. To collect genetic samples while limiting the impact on species I tested the efficacy of skin swabbing and since my results validated the use of epithelium sampling on most species I relied on dorsal swabbing as much as possible during this study. Using barcode information from all my sampling I compiled distributional information for these species to investigate amphibian richness and endemism. Over 14 months of fieldwork at 21 sites across the Scarp I recorded a minimum of 42 amphibian species from 13 genera and nine families, including at least ten species new to science. Phylogenetic analyses based on the mitochondrial 16S mtDNA revealed a high rate of crypsis among Arthroleptis, suggesting that two currently recognized species within this genus be split into a total of ten candidate species. Species richness at sites ranged between six and 13 and was significantly influenced by standing water habitats. Investigated sites had amphibian communities that differed by around 10% or more, with a marked split between low and high-altitude sites. Nearly all communities consisted mainly of Eastern Arc endemics or near-endemics, with a large proportion of single-site endemic species. Altitude and habitat heterogeneity significantly affected community diversity across sites, while geographic distance, distance from the edge, proportion of rainy days and effort did not show any significant impact on species turnover. The striking amphibian diversity, together with the small ranges of narrow-endemic taxa indicate the USNFR as one of the most important conservation sites for Eastern Afromontane amphibians. My results also suggest that rapid amphibian assessments, as so far undertaken, and lack of genetic data may seriously underestimate species richness. Conservation efforts should attempt to protect the altitude range of the USNFR along with its extent and to preserve the forest edge to strengthen forest stability. The topographical features of this forest make it a very suitable candidate for future landscape genetic studies and to test the hypothesis that, even at such small scale, sky-island valleys exist and can lead to high levels of endemism.