The Brenton Blue butterfly, Orachrysops niobe (Trimen) is currently only known to be extant at
one locality in the southern Cape (the Brenton Blue Butterfly Reserve = BBBR), and currently
globally Red Listed as "Critically Endangered". This research investigates the life history and
ecological interactions of o. niobe and recommends management techniques for the BBBR.
Adult nectar sources and female oviposition behaviour are described. The first two larval instars
feed on the leaflets of the host plant Indigofera erecta Thunb., and the 3rd and 4th instar larvae feed
on this plant's woody rootstock, attended by ants Camponotus baynei Arnold. Cannibalism takes
place in the early larval stages. Adults emerge from late October - early December, from late
January to early March, and occasionally there is a third brood in April. Morphological and
behavioural features of the larvae are described, and larval growth patterns are compared to other
polyommatines. The nature of the myrmecophilous behaviour is assessed and the phylogenetic
relationships between Orachrysops, Euchrysops, Lepidochrysops, and other polyommatine genera
are discussed.
Ant assemblages at the BBBR are described from pitfall trap sampling and field observations of
interactions between O. niobe larvae and ants. The ant assemblages at the BBBR, Nature's Valley
Fynbos Reserve (NVFR) and Uitzicht 216/ 40 are compared. The potential impact of the
Argentine ant at the BBBR is discussed.
Adult and egg counts are used to study the population dynamics of O. niobe, leading to an
estimate of the adult butterfly population and its fluctuations. A population dynamics model is
constructed, and several factors impacting fecundity and mortality are assessed. Population studies
on other polyommatines are compared and discussed.
The morphology, reproductive biology and autoecology of the papilionoid legume I. erecta are
described. An explanation is offered why the larvae of O. niobe are monophagous on this plant.
Microhabitat variations cause changes in its vegetative morphology and this further explains the
restricted range of O. niobe. The population dynamics of I. erecta is investigated and the effects of
biotic and abiotic factors (including fire) assessed.
Braun Blanquet methodology is used to sample and classify the vegetation communities at the
BBBR. Ordination techniques are used to confirm the classification and to diagnose for
environmental gradients. Hypotheses are generated about the ecological processes functioning at
the site, and the environmental niche occupied by I. erecta. Correlations between the occurrence
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of vegetation types and other plant species and I. erecta are sought and a strong association with
Pterocelastrus tricuspidatus is demonstrated.
Three study sites are described and the ecological history of the region is reconstructed.
Ecosystems are no longer fully functional because natural fire regimes and megaherbivores are
absent. It is suggested that O. niobe currently inhabits an interglacial refugium under stress from
the current global warming trend. The remaining suitable habitat is threatened by coastal property
development and environmental degradation. An increased population of o. niobe at the BBBR,
and establishment of new populations is essential to avoid extinction. Management techniques are
evaluated and a management strategy for the BBBR is proposed. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2006.
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/990 |
| Date | January 2005 |
| Creators | Edge, David Alan |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
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