The 1883 discovery, research into generic life histories and taxonomic investigations into the
aphytophagous butterfly Thestor brachycerus brachycerus (the Knysna Skolly) from Knysna,
South Africa are described. Its slide towards extinction through loss and degradation of habitat in
the late 20th century left only one known colony by 2009 leading to it being assessed as Critically
Endangered in the 2013 South African Red List and Atlas. During searches for more populations
in 2011, a second T. b. brachycerus colony was found which differed markedly with respect to
aspect, altitude and vegetation. Study areas were defined around the original colony on the
Pezula Golf Estate (Pezula) and the newly discovered coastal colony east of Coney Glen (Coastal
site). An assessment is made of the ecological differences and similarities between the two sites.
The extent and size of the two known populations was measured; the Extent of Occupancy was
found to be 7.5 km2 and the Area of Occupancy as 1.05 x 10-3 km2. During observations over 5
seasons in December and January 2009 – 2014 the average number of butterflies observed at
the original Pezula colony varied from 1 – 8 males and 0 – 3 females per survey, compared with
1 – 6 males and 1 – 3 females observed over 3 seasons from 2011 to 2014 at the Coastal colony.
The mating, territoriality, oviposition and predation avoidance behaviour of the adult T. b.
brachycerus butterflies was studied by direct observation. Males were found to exhibit territorial
behaviour, spending long periods of time perched in one spot, particularly in areas where the
vegetation was open or low. Oviposition was rapid and no preference was shown by females for
any particular plant. Between the two colonies, oviposition was observed on a total of 16 different
plants.
The vegetation composition at the two study sites was analysed using Braun–Blanquet
methodology. Only one plant, Tarchonanthus littoralis, was found to be common to both. There
appeared to be no correlation between floristic composition and the occurrence of T. b.
brachycerus. All the Thestor species so far studied by other workers have been found to be
myrmecophilous, having an association with the pugnacious ant Anoplolepis custodiens. Ant
communities were sampled by employing pitfall traps and direct sampling by hand. At both the
Pezula and Coastal sites A. custodiens was the most ubiquitous ant species.
The insights gained have enabled implementation of a habitat management plan. Experimental
management methods are recommended at the Pezula site which include small scale burning
and selective cutting of vegetation. Search for more colonies is ongoing, using the improved
ecological knowledge of the butterfly. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/14218 |
| Date | January 2015 |
| Creators | Bazin, Elizabeth Ann |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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