The Brenton Blue butterfly, Orachrysops niobe (Trimen, 1862) [Lepidoptera, Lycaenidae]

We thank David Edge for allowing us to reprint this article, first published in 2007 in the magazine Vision of Endangered Wildlife Society of Africa. David Edge is a member of the Executive Committee of the BBT and the Lepidopterists' Society of Africa (LepSoc). Most of the photos below are from David Edge.

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Dave Edge: The Brenton Blue butterfly, Orachrysops niobe (Trimen, 1862) [Lepidoptera, Lycaenidae]

Introduction

The Brenton Blue butterfly, Orachrysops niobe (Trimen, 1862) is Currently Known To Be extant only at one locality in the southern Cape (the Brenton Blue Butterfly Reserve BBBR =), and is Globally Red Listed as "Critically Endangered". It Became year icon of the conservation movement in South Africa During The 1990s After a colony of the near-extinct butterfly WAS found at Brenton-on-Sea was Proclaimed site for property development. An intensive publicity campaign by the Lepidopterists' Society and the local Environmental activists Galvanised Several NGO's and private Individuals, led by the Endangered Wildlife Trust, to form the Brenton Blue Trust (BBT) in 1994, with the main AIM of Conserving the butterfly. Negotiations with the developer and pressure on government at all Levels Caused Eventually the then Minister of Environment Affairs Dr Pallo Jordan to invoke the Environment Act to Prevent destruction of the habitat, Followed by expropriation. The BBT finally primary objective icts Achieved in July 2005 When The BBBR WAS Proclaimed as a Special Nature Reserve falling from under the control of CapeNature, assisted by a Management Committee with Representatives from WESSA, the Lepidopterists' Society and Ratepayers Association Brenton, Knysna Municipality, and the Endangered Wildlife Trust, and Whose Aim ​​is to manage the BBBR in a sustainable fashion to Ensure the long-term survival of the butterfly.

Research program: "Ecological Factors Influencing the survival of the Brenton Blue butterfly"

A scientific research program, commenced in 2000, resulted in a PhD thesis by Dave Edge Being Accepted by North West University, Potchefstroom. This research investigated the life history and ecological interactions of O. niobe and recommended management techniques for the BBBR.

Life history of the Brenton Blue

The surviving larvae like 3rd down to the base of the host plant THEY burrow underground Where to feed on the woody rootstock, Attended by ants Camponotus baynei ARNOLD, 1922 (Figure 8). The final (4th) like larvae (Figure 7) continuous feeding on the rootstock Until They Are Ready To pupate underground. After hatching, the adult butterflies crawl to the surface. First brood adults emerge from late October - early December, with a second brood from late January to early March, and occasionally a Third-brood DURING April.

Larval - ant interactions (myrmecophily)

O. niobe is a polyommatine (blue) of the butterfly family Lycaenid, Many species of Whose Have a Variety of ant interactions (myrmecophily). The Specific Nature of the myrmecophilous Behaviour of O. niobe WAS Established by field observations and captive rearing. The larvae Have a tough skin and spines (for defense), tentacle organs (TOs - see Figures 5 and 7) to emit ant pheromones, and a nectar organ (desirable exuding a substance to appease the ants). C. baynei ants are thereby induced to tend and protect the larvae from predators and assist em with excavating around the rootstock of the plant host. Larval growth patterns of O. niobe Were Compared To Other polyommatines, and Demonstrated That It Was feeding ACCELERATES rootstock growth in the later instars. Contrary to what the OCCURS Closely related genus in the larvae of O. Lepidochrysops niobe do not enter the ant nests to feed on the ant brood. Evidence is presented ant That the relationship of O. niobe, predominantly with C. baynei, is nonetheless essential for Successful breeding.

The Communities at the ant BBBR, the Nature's Valley Fynbos Reserve (NVFR) and Uitzicht 216/40 (a site near Brenton calculated previously burnt with a Good Host plant population) Were Sampled by pitfall traps and bait, and when consoling differences were found. The host ant C. baynei, only OCCURS in the shares of the unburnt BBBR, and not at all at The Other Two sites. C. Because this may Be nests in dead wood baynei lying on the ground, Which is Destroyed DURING a fire. The Argentine ant, a Potential Threat to indigenous ant Communities, was not found At Any of These sites, since it Prefers habitats close to human disturbances.

Population dynamics

Egg and adult butterfly counts Were Used To study the population dynamics of O. niobe. The egg counting method WAS Highly labor-intensive and impractical to use Regularly. Two methods of counting adult visual Were devised, After Rejecting the mark / release / recapture method, Which Could adversely effect the butterfly population. Both methods yielded visual counting on counts, the actual calibration goal by brood adult butterfly populations Were Estimated (see Figure 9). The recent decline in the population at the BBBR Could Be a result of poor rains in the Growing période critical for the host plant (August - October).

A population dynamics model WAS Constructed using life history data, Incorporating Several factoring Impacting fecundity and Mortality. It Was Concluded That the principle mortalité factors (overcrowding on the host plant and larval cannibalism) Were dependent density, stabilising the population at a level dependent on the number of healthy host plants available, Provided That Sufficient host ant populations exist in the vicinity of These host plants.

Biology and population dynamics of the host plant Indigofera erecta

The morphology, reproductive biology and autoecology of the legume papilionoid I. Were Described erecta. Three of the Indigofera found at the BBBR, only I. erecta HAS smooth leaves Whereas The Other species are unpalatable to the bushy and larvae of O. niobe. Microhabitat variations at different sites, Where I. erecta OCCURS because in exchange icts vegetative morphology (eg larger, Tougher leaves) and may affect larval palatability.

I. erecta only south facing slopes OCCURS is close to the sea and subject to coastal mists. I. erecta performs best in partial shade, Under a high canopy trees with gold in an open space adjacent to shading shrubs. It reproduces by resprouting from woody rootstock icts gold by growing from seed. The mature plants (2 years old) Produce copious flowers pollinated by That Are a guild of small bees. The legume seeds Develop in pods, and are Dispersed by explosive dehiscence, casting the seeds up to 2 meters from the parent. There is negligible secondary seed dispersal. Consequently populations persist in TOO locations for long periods. Experiments Showed That germination is induced by moisture and light - heat HAD little effect.

Recruitment of I. erecta is Most Favoured When open space Becomes available and competition is Reduced. Fire disturbance is The Most Radical Producing thesis requirements and prolific post-fire recruitment OCCURS in patches Where the plant has-been as dormant seed or underground rootstocks. Within a year or so post-fire MOST of These new plants have expired Vigorous bracken fern Competitors Such as (Pteridium aquilinium) asteraceous and plants (eg Cullumia decurrens) usurp the space. Less radical and repeated Disturbances, Such as the activities of browsing megaherbivores, are more effective in sustaining I. erecta populations. The cutting and maintaining of a network of paths at the BBBR simulates browsing and laundry charges this year HAS Caused I. erecta and therefore O. niobe population (see Figure 9).

Vegetation Communities at the BBBR

The vegetation at the BBBR is a mosaic of (predominantly) dune thicket and moist dune fynbos, Which of c. 20% WAS burnt in October 2000. Braun Blanquet WAS Methodology Used To sample and classify the types of vegetation at the BBBR, ordination and technical Were Used To confirm the diagnosis to classification and for environmental gradients (None were detected). I. erecta OCCURS mostly in Just Two thicket vegetation types - with Pterocelastrus tricuspidata (Hampton) and Ficinia ramosissima (a sedge) as the dominant species. A census of all and all the Candlewoods I. erecta plants at the BBBR Revealed That 83% of the I. erecta plants Were Growing Within The crown cover of a Candlewood. By contrast I. Virtually missing from erecta WAS fynbos vegetation type and Dominated burnt from parking areas.

Ecological history and current status

The Three study locations are Described and the ecological history of the area WAS reconstructed. Sea level exchange During The Late Pleistocene Were instrumental in Generating the current landforms. Ecosystem fonctionnement Has Changed since the advent of man, Because natural fire regimes and free roaming megaherbivores no longer play a dominant role.

The ranks of O. niobe has-beens and Reduced Dramatically Altered FOLLOWING the inundation of the continental shelf by rising sea Levels since the end of the last ice age. Moreover O. niobe's Requirement for a cool, moist climate Makes it vulnerable to the current global warming trend. The residual Suitable habitat has-been further Top Reduced by coastal property development and General Environmental degradation (alien infestation and loss of ecosystem function). Year population of O. laundry charges niobe at the BBBR, and the establishment of new populations at Suitable locations are judged essential to avert To Be extinction.

Management Policies at the BBBR

The main technical management discovered and Used During The research at the BBBR is the cutting and Maintenance of paths to simulate herbivore activities. Along the paths thesis host plant I. erecta grows, a delicate plant That Can Be Easily damaged by trampling. The public is therefore only access Allowed Into the BBBR with the permission of CapeNature. Disturbance of the gold reserve in Any Way the collection of the butterflies aussi Strictly prohibée and is Closely Monitored, With The Neighbours of the year playing BBBR active role.

Alien plants in the reserve Such as Acacia cyclops (Rooikrans) and Acacia melanoxylon (Blackwood) are Actively controlled. Kikuyu grass (Pennisetum clandestinum), growing on road in yards and gardens Bordering the reserve, and is Being Eradicated mittal with indigenous non-invasive grass species, with the co-operation of the owners of properties Bordering on the reserve.

An audit of the ecological BBBR HAS Recently Been Done.

Re-introduction of the Brenton Blue to Nature's Valley

Establishment of new populations of O. niobe réception is high priority. Since the butterfly Originally Occurred at Nature's Valley, a re-introduction is Being Attempted by CapeNature, LepSoc and the Nature's Valley Trust (NVT). The Reasons That the butterfly died out in the early 1970's are not Entirely clear, goal THEY Probably included destruction of Some of ict habitat for housing Developments, and transformation (overgrowth) of the Remaining habitat-through Lack of fires and the reduction of grazing and animal browsing activities. Fortunately share of the Brenton Blue's original habitat is at Nature's Valley Fynbos Reserve Conserved in a (NVFR). FOLLOWING restoration of the fynbos at the reserve (through a Planned fire in April 2003 Organised by CapeNature) to a more healthy condition, the host plant of the butterfly (I. erecta) enjoyed a renaissance for a Few Years goal now is unfortunately in decline .

An ant DURING 2005 survey found That the ant C. baynei, Had not yet Become Established After re-burning of the reserve. Nonetheless, a re-introduction WAS Attempted-through release of caterpillars in early 2006, but no adults emerged succeeding twelve months During The. Continuing efforts are, and establishment of a viable population of C. baynei at the Fynbos Reserve is Being Given priority this year. Botanical experts are Investigating how the population of I. erecta Could Be expanded and made ​​more sustainable. The prospects of successfully re-Introducing the Brenton Blue are still 'reasonable. However the program is as threatened by the Bitou Municipality's plan to sell the Fynbos Reserve to a developer to build a hotel. These Plans are Being Strongly Opposed by Both the NVT and the BBT.

(Photos: David Edge)

Other species of the genus Orachrysops VARI, 1986

Brenton-on-Sea

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