Tarebia granifera is a prosobranch freshwater gastropod from south-east Asia which has
invaded other sub-tropical parts of the world. This snail has recently also invaded the
iSimangaliso Wetland Park, often reaching population densities of over 20000 ind.mˉ2 and
dominating benthic invertebrate communities. A multiple method approach was used to address
several aspects of the biology and ecology of this non-native invasive species (NIS). The
tolerance of T. granifera to salinity and temperature was investigated through the experimental
manipulation of these factors. T. granifera survived exposure to temperatures between 0 ºC and
47.5 ºC. More remarkably, this snail was able to survive a salinity of 30 for 65 - 75 days.
Population density and size structure were monitored in estuaries and coastal lakes. T. granifera
successfully invaded estuaries despite frequent exposure to high salinity and desiccation. The
persistence of T. granifera was largely ensured due to the wider environmental tolerance of
adults (20 - 30 mm shell height) which carried an average of 158 ± 12.8 SD brooded juveniles.
Multiple introductions were not essential for the success of this parthenogenetic NIS. Using gut
fluorescence and carbon budget techniques it was estimated that T. granifera consumes 0.5 -
35% of the total available microphytobenthic biomass per day, or 1.2 - 68% of the daily primary
benthic production. The carbon component estimated from the gut fluorescence technique
contributed 8.7 - 40.9% of the total gut organic carbon content. A stable isotope mixing model
was used together with gut content analysis to estimate the diet of T. granifera and dominant
native gastropod species, potentially competing for resources. Results were used in the
formulation of an index of isotopic dietary overlap (IDO, %). This approach yielded detailed
information both on general changes in ecosystem functioning and specific species interactions.
Before/After-Control/Impact (BACI) logic was used in a multivariate approach to separate
human perturbations from natural spatio-temporal variability displayed by communities, and to
further separate perturbations due to NIS. Human intensification of drought negatively affected
biodiversity and T. granifera may exacerbate this problem by displacing native species from
critical refugia and contributing towards biotic homogenization. The present findings constitute
a contribution to the scientific knowledge on biological invasions and a useful tool towards
adaptive management in the iSimangaliso Park. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9743 |
| Date | January 2012 |
| Creators | Miranda, Nelson Augusto Feranandes. |
| Contributors | Perissinotto, Renzo., Appleton, Christopher C. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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