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Investigating the coexistence of fiddler crabs in the Wakatobi Marine National Park, Indonesia

Student thesis: Doctoral Thesis

The coexistence of ten species of fiddler crab was studied at Ambeua, on the island of Kaledupa, Indonesia. This remarkable level of biodiversity has been used to investigate the species-specific differences that support coexistence. Through studying their morphology, behaviour and the structure of their habitat it can be seen that they occupy distinct but overlapping niches. Each species is described and studied in detail, with notes and imaging based on morphology, phylogenetics, ecology and behaviour. Phylogenetic analysis was conducted using the cytochrome oxidase subunit I and sequences provided strong evidence to support classification.

Five transects were delimited in the area of coexistence as well as four outside of this area. Shore height profiles, shading and substrate type were quantified for all transects. Mouthpart morphology was analysed to determine whether associated substrate type correlated with mouthpart morphology. Tubuca coarctata, Tubuca demani, Tubuca dussumieri, Paraleptuca crassipes, and Austruca triangularis were all active in shaded areas and on fine muddy substrates. Austruca cryptica and Austruca mjoebergi were active in unshaded/open areas on sandy substrates, whilst Gelasimus jocelynae, Gelasimus tetragonon and Austruca perplexa were found in both shaded and unshaded areas on sandy substrates.

Morphological analysis showed that Tubuca coarctata, Tubuca demani, Tubuca dussumieri, Paraleptuca crassipes, Austruca triangularis, Gelasimus jocelynae and Gelasimus tetragonon all had mouthparts associated with finer sediments whilst Austruca cryptica, Austruca perplexa and Austruca mjoebergi had mouthparts associated with coarser sediments. Detailed analysis of distribution, individual home ranges and nearest neighbours revealed numerous interspecific overlaps and interactions. The close proximity of the local village increases habitat heterogeneity, with crabs recorded living underneath the stilted houses. These anthropogenic factors are directly altering the ecosystem, increasing niche availability and allowing crabs to dwell in places otherwise uninhabitable.
Original languageEnglish
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Award date2017

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