This study quantified the fine-scale habitat requirements of
The habitats were quantified in terms of plant species composition and structure with reference to their environmental characteristics.
A modified area-based phytosociological approach was used to collect floristic data along with environmental characteristics of habitats occurring on the Witwatersrand and Ventersdorp Geological Systems.
Species recorded were predominantly forbs and graminoids with a slightly higher number of plant species in the habitats of the Ventersdorp Geological System. Few dwarf shrubs and shrubs and very few trees were recorded. A higher number of plant species were recorded during the late growing season on both geological systems. The butterfly food plant
Monitoring of the
Butterflies are well known for their role in the pollination of flowering plants and they often perform unique functions in pollination (Mecenero et al.
The Heidelberg Opal Butterfly,
The life history of
Various vegetation studies have been conducted in the larger study area where
This study aimed to quantify the fine-scale floristic composition and vegetation structure of all 11 known habitats of
Suitable habitat for
The mean annual temperature in the study area is 15.6°C–16.4°C, with mean monthly maximum and minimum temperatures for January and July recorded as 30.8°C and -1.8°C respectively (in Krugersdorp) (Mucina & Rutherford
Three sample plots were placed in each of the 11 known habitats, parallel to each other and 10 m apart, thus totalling 33 sample plots with a combined surface area of 3300 m². A sample plot consisted of a belt transect of 100 m² (5 m × 20 m) and all sample plots were placed perpendicular to the slope in order to maximise species variation (Panagos
All the living plant species rooted within the sample plots were identified during the surveys, using field guides (Bromilow
Dominant plant species (species with a mean canopy cover > 1.5%) for the early and late growing seasons were quantified in terms of cover per habitat (Westfall et al.
The geological information of all habitat localities was obtained using a geological map (2628 East Rand, 1:250 000, Land Type Series
The presence or absence of the various life stages (egg, larvae, pupae and butterfly) of
The floristic data recorded for all sample plots were analysed using the PHYTOTAB-PC computer programme (Westfall et al.
Dominant plant species (mean canopy cover > 1.5% as quantified using the PHYTOTAB-PC) for the butterfly habitats, for both growing seasons, were quantified in terms of mean percentage canopy cover per habitat (Westfall et al.
Species recorded in the habitats were predominantly forbs and graminoids. Few dwarf shrubs and shrubs, and only two trees were recorded in the habitats. During the early and late growing seasons, a slightly higher number of plant species was recorded in the habitats in the Ventersdorp Geological System compared to the number recorded in the Witwatersrand Geological System (
Number of plant species per geological system and number of species per growth form in the Witwatersrand and Ventersdorp Geological Systems in the early and late growing seasons.
Measurements | Witwatersrand Geological System |
Ventersdorp Geological System |
||
---|---|---|---|---|
December 2011 | March 2012 | December 2011 | March 2012 | |
Total no. of sample plots in geological system | 24 | 24 | 9 | 9 |
Total no. of species in geological system | 141 | 151 | 148 | 155 |
Species richness (mean number of species per sample plot) | 35 | 41 | 53 | 62 |
Trees | 1 | 2 | 2 | 2 |
Shrubs | 7 | 5 | 8 | 12 |
Dwarf shrubs | 16 | 18 | 21 | 23 |
Forbs | 82 | 93 | 97 | 106 |
Graminoids |
41 |
39 |
27 |
21 |
Species richness per growth form per geological system (number of species; some species were recorded in more than one growth form, for example, as a dwarf shrub, shrub and tree)
The cover was mostly ascribed to forb and graminoid species for both the early and late growing seasons. Forb and graminoid cover were greater in the Ventersdorp than in the Witwatersrand Geological System in both seasons (
Mean percentage canopy cover per growth form, the food plant cover percentage and the density of
Measurements | Witwatersrand Geological System Mean percentage canopy cover |
Ventersdorp Geological System Mean percentage canopy cover |
||
---|---|---|---|---|
2011 | 2012 | 2011 | 2012 | |
Tree | 0.00 | 0.00 | 0.06 | 0.07 |
Shrub | 0.04 | 0.02 | 0.71 | 1.92 |
Dwarf shrub | 1.77 | 3.20 | 4.37 | 4.66 |
Forb | 5.50 | 5.18 | 7.41 | 13.16 |
Graminoid |
11.45 |
29.63 |
21.01 |
49.69 |
0.90 | 1.81 | 1.64 | 1.65 | |
Density (m²) of |
0.50 | 0.50 | 0.50 | 0.60 |
The graminoids
Dominant plant species (mean percentage canopy cover), mean height (mm) and number of habitats with flowers present in the Witwatersrand and Ventersdorp Geological Systems in the early growing season.
Growth forms | Species | Witwatersrand Geological System |
Ventersdorp Geological System |
||||
---|---|---|---|---|---|---|---|
Canopy cover (%) | Plant height (mm) | Flower presence | Canopy cover (%) | Plant height (mm) | Flower presence | ||
Graminoid | - | - | - | 8.92 | 123 | 3 | |
- | - | - | 2.35 | 323 | 2 | ||
6.66 | 189 | 8 | - | - | - | ||
- | - | - | 7.71 | 157 | 3 | ||
Forb | - | - | - | 1.64 | 279 | 3 | |
3.44 | 588 | - | - | - | - | ||
- | - | - | 1.88 | 189 | 3 | ||
Dwarf shrub | - | - | - | 1.97 | 905 | 2 |
Dominant plant species (mean percentage canopy cover), mean height (mm) and number of habitats with flowers present in the Witwatersrand and Ventersdorp Geological Systems in the late growing season.
Growth form | Species | Witwatersrand Geological System |
Ventersdorp Geological System |
||||
---|---|---|---|---|---|---|---|
Canopy cover (%) | Plant height (mm) | Flower presence | Canopy cover (%) | Plant height (mm) | Flower presence | ||
Graminoid | - | - | - | 17.60 | 582 | 3 | |
3.20 | 972 | 7 | - | - | - | ||
13.90 | 434 | 8 | - | - | - | ||
3.10 | 572 | 8 | - | - | - | ||
- | - | - | 17.30 | 433 | 3 | ||
- | - | - | 6.70 | 1 050 | 3 | ||
Forb | 1.80 | 400 | 8 | 1.70 | 331 | 2 | |
1.90 | 602 | - | - | - | - | ||
- | - | - | 3.90 | 175 | - | ||
- | - | - | 3.00 | 258 | - | ||
Dwarf shrub | 2.40 | 147 | - | ||||
- | - | - | 2.00 | 567 | - | ||
Shrub | - | - | - | 1.90 | 1400 | - |
In both growing seasons, the mean height for the dominant graminoids was similar in the two geological systems and the dominant forbs in the Witwatersrand Geological System had a greater height (
Various dominant graminoids had flowers present during the early and late growing seasons in the habitats of both geological systems (
The Witwatersrand and Ventersdorp Geological Systems differed in soil type, soil texture and clay percentage, rock size, land types, slope and terrain units (
Environmental characteristics of the habitats of the in the Witwatersrand and Ventersdorp Geological Systems.
Environmental characteristic | Witwatersrand Geological System | Ventersdorp Geological System |
---|---|---|
Altitude (m) | 1601–1791 | 1653–1784 |
Land type | Ib42 | Ib43 |
Soil type | Mispah | Glenrosa |
Soil depth (mm) | 30–280 | 70–320 |
Clay (%) | < 10 | 35–40 |
Soil texture | Sandy | Clayloam |
Rock cover (%) | 46–60 | 31–45 |
Rock size | Boulders (> 1000 mm) | Large rocks (> 250 mm–1000 mm) |
Terrain units | Scarp and mid-slope | Mid-slope |
Aspect | South facing | South facing |
Slope | Moderate to steep | Moderate |
Slope (°) | 8–28 | 12–20 |
Typical
Species richness in the habitats of the Witwatersrand and the Ventersdorp Geological Systems in the early and late growing seasons (
The
The topography and soil characteristics of the habitats and the shade from rocks may influence individual heights of
The habitats of
Graminoids, forbs and dwarf shrubs dominated the vegetation structure of all habitats. The current ratios between these different growth forms need to be maintained and managed to ensure habitat suitability for
The following management actions in known habitats and adjacent areas should be considered to ensure the conservation of
Monitoring of the
The existence of other suitable sites as butterfly habitats should be investigated, using the habitat details described here.
Monitoring of the vegetation structure, species composition and growth forms to determine the vegetation condition and trends in habitat persistence, possible habitat degradation or habitat improvement after planed fires (McGeoch et al.
The floristic characteristics, namely species richness, percentage canopy cover, dominant species, key species and density of the host plant, measured during this study should be used as baseline data for future vegetation condition comparisons. Monitoring surveys could be carried out every 3–4 years. The response of the vegetation to the burning programme should be monitored and the burning programme adapted when and where necessary. It is suggested that the vegetation structure in the habitats of the Witwatersrand Geological System be managed and monitored to allow the percentage canopy cover of dwarf shrubs, graminoids and forbs to fluctuate between the upper and lower recorded percentages of 1%–12% (dwarf shrubs), 23%–57% (graminoids) and 1%–20% (forbs), respectively. Similarly, for the habitats of the Ventersdorp Geological System, the mean percentage canopy cover should be managed for dwarf shrubs, graminoids and forbs, to fluctuate between 2% and 6% (dwarf shrubs), 30%–75% (graminoids) and 8%–16% (forbs), respectively (these cover percentages vary from the lowest to highest values recorded for the habitats).
The regular burning of habitats is required to maintain suitable vegetation composition and structure in these habitats for
The occurrence of alien invader plants (especially trees) could indirectly affect the microclimate at the butterfly habitats or disturb the movement of individual butterflies between colonies (Henning & Roos
The most important aspect of butterfly conservation is the quality and persistence of a species’ habitat and its ability to maintain gene flow between populations (Henning et al.
The authors would like to thank Tshwane University of Technology for financial assistance and the Gauteng Department of Agriculture and Rural Development for other resources and staff time during this study. The authors also thank Obeid Katumba, Natalie Horn, Sipho Ngoza, Obakeng Babuseng and Matimba Baloyi for their assistance and hard work during field surveys. Thanks to the SANDF, Heidelberg Kloof and the private land owners of Malanskraal for allowing field staff access to their properties during this study.
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
R.D. conducted all field surveys for Magister Technologiae, captured data and prepared the draft. W.J.M. and M.D.P. (both promotor and co-promotor on MTech, respectively) were involved from initial project proposal and planning through to the final thesis.