Biology and conservation of the threatened Karkloof blue butterfly Orachrysops ariadne (Butler) (Lepidoptera: Lycaenidae)

Abstract

The Karkloof blue butt erfly, Orachrysops ariadne (Butler), is endemic to the Mistbelt grassland of KwaZulu-Natal province, South Africa, and is currently Red-listed as 'Vulnerable' . O. ariadne is univoltine and on the wing in March and April, when it utilizes eight species of nectar plants. This study confirmed that the larval hostplant is Indigofera woodii H. Bol. var. laxa H. Bol., an erect variety. It was also confirmed that this butterfly is ant-dependent, with the young larva being taken into the nest of Camponotus natalensis (F. Smith) where development continues, including pupation. This study compares the ecological conditions at the four known locations so as to make informed decision s regarding its conservation. A large proportion of the grassland in KwaZulu-Natal has been aforested and cultivated, and at least 92% of the Mistbelt has been transformed, with only about 1% in good condition remaining. Predictions on the habitat and habit at requirements of this species are necessary for developing a conservation strategy and action plan. Here , we propose O. ariadne as an indicator species for Mistbelt grass land. Saving enough of the remaining Mistbelt grassland is crucial, not just for the survival of the Karkloof blue, O. ariadne, but also for the Mistbelt grassland community as a whole. The population structure and movement of Orachrysops ariadne and O. subravus were studied by mark-release-recapture methods in 1999. There were 290 O. ariadne marked over 48 days between March and April, 124 (42 .8%) were recaptured at least once. Of 631 O. subravus marked over two months between September and November, 311 (49 .3%) were recaptured at least once. Both species exhibited protandry, male appearance about one to two weeks earlier. The sex ratio of O. ariadne is heavily male biased 5.6 :1 (246 males and 44 females), and the sex ratio of O. subravus is 1.6:1 (387 males and 244 females). The Jolly-Seber model was used to estimate daily population numbers (N ᵢ), survival rates (Ø ᵢ), recruitment rates (B ᵢ), proportion of marked animals in the total population (α ᵢ ), and the number of marked animals at risk (M ᵢ) . Average residence times of male adults were generally similar in both species in the range of 5.36-5.44 days, and were slightly longer for male than for female O. subravus (by 4.09 days). 0. ariadne is a strong and rapid back and forth flier, covering mean recapture distances of 157 m, almost twice that of 0. subravus, principally in search of scarce nectar sources. The extreme rarity of 0. ariadne is not so much to do with behaviour, survivorship or longevity, but rather the butterfly is limited in distribution by suitable habitat for both larva and adult. The aim of management is to optimize the habitat so that it best meets the present and future needs of the butterfly. The effects of the current fire regime on the butterfly, host plant and ant host were evaluated here. It is recommended that burning only take place after the larvae have hatch ed and gone underground with the ant host. Using GPS and GIS, core, quality habitat characteristics were defined. In cooperation with the landowner at one site, alien invasive plants are being removed to increase the area of quality habitat. Availability of host plants is limiting for success of the butterfly in the field. Guidelines are provided for propagation and introduction of the host plant, so as to provide the butterfly with more oviposition sites.