Quarter-degree Grid Research Articles

The effects of habitat loss and fragmentation on the relative abundance and conservation of Ludwig’s Bustard Neotis ludwigii in South Africa

Ludwig’s Bustard Neotis ludwigii is near-endemic to the semi-arid shrublands of southwestern southern Africa and is listed as Endangered. The primary threat to this species is collisions with overhead powerlines; however, loss and fragmentation of its habitat may contribute to its population decline. The 1990 and 2020 land-use land-cover (LULC) maps prepared for South Africa were used to determine the LULC categories that best describe suitable habitat for Ludwig’s Bustard using beta regressions and data on exact localities, as recorded in the real-time BirdLasser logging app. Optimized Hot Spot Analysis was used to determine the priority areas for conserving Ludwig’s Bustard and its habitat. Beta regression models were compiled using the reporting rate for this bird and the total surface area of suitable habitat, and three other landscape metrics, calculated using the per pentad LULC categories considered suitable habitat for the bird. These analyses revealed that, between the first and second Southern African Bird Atlas Projects, the distribution range of Ludwig’s Bustard increased by 153 quarter-degree grid cells, whereas the reporting rate for the species declined by 5.6%, along with a small net decline in its quarterdegree-grid-cell-based area of occupancy, its pentad-based area of occupancy and habitat. The habitat of Ludwig’s Bustard is dominated by shrubland with limited grassland, in primarily the Nama Karoo and Succulent Karoo biomes, and the Grassy Karoo Biome in the eastern part of its distribution. In the relative abundance hot spot of Ludwig’s Bustard, there does not currently appear to be any significant loss or fragmentation (distance between patches) of its habitat. A landscape-based approach to conserving Ludwig’s Bustard can be achieved by expanding the current network of protected areas and conserving critical biodiversity areas and ecosystem support areas, especially in the bird’s relative abundance hot spots in the Nama Karoo and Succulent Karoo biomes.

Climate Trend Estimation of the Powell Basin Hydrophysical Characteristics

The trend assessment of the dynamic state of the Powell Basin waters in the Weddell Sea was made on the basis of the hydrological data of the 79th cruise of the R/V AkademikMstislavKeldysh (January 16–February 6, 2020) and the World Ocean Database-2018 data for January-February from 1975 to 2020. At each node of the quarter-degree grid, a linear trend was constructed for the calculated values of the maximum buoyancy frequency and the maximum amplitude of the vertical component of the internal wave velocity. It is shown that the southwestern and northwestern parts of the Powell Basin differ significantly in their hydrophysical characteristics. In the northwest of the basin, the linear trend of the maximum buoyancy frequency is negative, the trends of the depths of the maximum values of the Väisälä-Brent frequency and the amplitude of the vertical velocity component are positive. In the southwestern part of the basin, the opposite is true: the trend of the maximum buoyancy frequency is positive, the trends in the depths of the maximum values of the Väisälä-Brunt frequency and the amplitude of the vertical velocity component are negative.

Atlas of the butterflies and moths of Nigeria, LepiMap report, 2010–2021

Interest in citizen science, notably biodiversity mapping, has soared recently in Africa, owing to several converging factors. First, is the growing recognition that biodiversity is threatened, and second, there is a need for collective effort among the public to improve the state of biodiversity, driven by human activities. Amongst the important biodiversity components is Lepidoptera (butterflies and moths) which underpin crucial roles in the ecosystem. Although Lepidoptera has been a major field of study for the past decades, its ecology and distribution have only recently gained important attention among the public, particularly in West Africa. This paper reports on the number of butterflies and moths recorded for Nigeria on the LepiMap database. The database contains 1578 records from January 2010 up to August 2021, from 98 quarter-degree grid cells of the 1306 grid cells in Nigeria (7.5% of grid cells). There are 1219 recorded identified to species level (77%), with 359 awaiting identifications, mostly moths. The number of Lepidopterans recorded was 219 species belonging to 16 families. The most frequently recorded species were Catopsilia florella (28 grid cells, 64 records), Telchinia serena (27 grid cells, 61 records), and Danaus chrysippus alcippus (23 grid cells, 49 records). One of the most important successes of LepiMap during the last three years in Nigeria was the increase in the number of observers and coverage by 600%, which is crucial to gathering lepidopteran mapping data for conservation action. It is recommended that data collection be geared toward areas having no or low coverage, yet refreshing old records are also important for understanding changes in species composition across grid cells.

Intercomparison of global ERA reanalysis products for streamflow simulations at the high-resolution continental scale

Watershed-scale streamflow routing models play a key role in real-time flood forecasting, flood risk evaluation, and water resource management, but the accuracy of modeled streamflow depends on both the spatial resolution and the accuracy of the runoff data used as the model forcing. The production of new, higher-resolution runoff datasets therefore motivates an evaluation of the relative improvement in streamflow model performance. This study evaluates streamflow routing output for the Mississippi River Basin, with the simulations driven by three different runoff products from the European Centre for Medium-Range Weather Forecasts. The first runoff product is the ERA-Interim surface and subsurface runoff dataset (ERAI), which was projected to a grid with a resolution of ∼39 km at the equator. Second, this study considers the ERA5 reanalysis dataset (ERA5-25km) placed on a quarter degree grid (∼25 km resolution at the equator). The simulations which generated ERA5-25km included land–atmosphere coupling and land data assimilation. The third runoff product is the ERA5-Land dataset (ERA5L-9km), which was produced in an offline simulation at 9-km resolution without land–atmosphere coupling or land data assimilation, forced by the coarser ERA5 meteorological input. For each runoff input, streamflow was simulated by applying the Routing Application for Parallel computation of Discharge (RAPID) model to the vectorized NHDPlus stream network, which comprised 1.2 million reaches within the study area.Comparison of modeled and measured daily and monthly mean discharge from 60 USGS gages reveals several broad trends. Streamflow simulated using the ERAI runoff tends to generate an earlier peak monthly discharge, while peak discharge from the ERA5L-9km runoff systematically exceeds peak discharge from the ERA5-25km runoff. Basin-aggregated model performance varies by metric, with discharge simulated using the ERA5-25km runoff having the smallest median root-mean-square error even as the discharge modeled using ERA5L-9km runoff has the smallest median Kling-Gupta efficiency. Model performance also varies spatially, with all three simulations exhibiting the least accurate results in the western region of the Mississippi River Basin, and by drainage area, with more accurate results generally obtained for larger drainages. These results suggest that streamflow model accuracy will benefit from the use of either ERA5-25km or ERA5L-9km runoff in place of ERAI. However, the selection of ERA5-25km versus ERA5L-9km depends on regional considerationsas well as which components of model performance are most critical to the user.

Karoo BioGaps project – butterfly survey results and their interpretation

The Karoo BioGaps project (KBGP) data acquisition phase was executed between March 2016 and December 2018. Butterfly surveyors made 82 visits to 46 survey sites, selected statistically to represent the types of habitats found in the Karoo. 600 species records were made of 101 species and 262 DNA samples were collected. The data have been analysed to compare expected butterfly occurrence with the actual observations; identify new quarter degree grid square species records and new species records for the entire KBGP study region; assess the impact of the new data on the Red List status of selected butterfly taxa; identify the butterfly functional types found in the Karoo; determine the average species richness in the Karoo vegetation types and biomes; and assess the impact of rainfall and veld condition on species richness. Recommendations are made to improve the efficiency of data acquisition in future surveys in the Karoo.

Biogeographical patterns of grasses (Poaceae) indigenous to South Africa, Lesotho and Eswatini

The ecological and economical importance of African grasses in sustaining animal production prompted studies to quantify the wealth of grass genetic resources indigenous to southern Africa. Plant collection and occurrence data were extracted from two southern African datasets, BODATSA and PHYTOBAS, and analysed to establish biogeographical patterns in the grass flora indigenous to South Africa, Lesotho and Eswatini. A total of 1 648 quarter degree grid cells, representing 674 grass species, were used in an agglomerative hierarchical clustering to determine biogeographical units being referred to as grasschoria. Six distinct groups formed, mainly following existing biome vegetation units, termed the Grassland, Indian Ocean Coastal Belt, Fynbos, Savanna, Central Arid Region and Succulent Karoo grasschoria. The description focuses on associated phytochoria, floristic links, key species, climate and soil properties. The main gradient distinguishing grasschoria was a rainfall-temperature gradient. The collection, conservation and breeding of pasture grass species adapted to especially arid and semi-arid environments, could be managed more efficiently by using these results, but also calling on the need to describe and label infraspecific genetic variants, including ecotypes.

Odonata of the Kruger National Park

The number of species of dragonflies and damselflies recorded in the Kruger National, South Africa, was 103 in April 2018. This figure was based on a database containing 2,817 records of Odonata, made since 1980, from the 52 quarter degree grid cells which intersect with the Kruger National Park. Records were available for 41 of the 52 grid cells. The most frequently recorded species were Red-veined Dropwing Trithemis arteriosa (167 records) and the Orange-veined Dropwing Trithemis kirbyi (144 records), both recorded in 33 grid cells, and Southern Banded Groundling Brachythemis leucosticta (175 records) and Broad Scarlet (141 records) both in 29 grid cells. Based on records up to April 2018, the median date of the most recent record for species was September 2017, so that half of the 103 species had been recorded during summer 2017/18. This report could be used to motivate the proclamation of the river and wetland systems of the Kruger National Park as a “Wetland of International Importance” in terms of the Ramsar Convention. Two-thirds of the Odonata of South Africa, and one-eighth of the Odonata of Africa, have been recorded in the Kruger National Park.

Quantifying the decline of the Martial EaglePolemaetus bellicosusin South Africa

SummaryHuman populations in Africa are growing at a faster rate than in any other region; this growth will exert increasing pressures on the continent’s wildlife resources and declines in wildlife are already being observed. Species occupying higher trophic levels may be amongst the most useful indicators of this pressure and raptorial birds have already proven to be particularly useful in highlighting problems with their environment. The Martial Eagle is an African endemic which is thought to be declining and was recently uplisted to globally Vulnerable, although data on population trends are almost entirely lacking. The Southern African Bird Atlas Project (SABAP) 1 and 2 are citizen science projects that represent a rare opportunity, within an African context, to quantify population changes over a 20-year period. We use data from these surveys to explore changes in reporting rates for this species in South Africa between SABAP 1 (1987–1992) and SABAP 2 (2007–2012) at the scale of quarter-degree grid cells. Previous research suggests that such comparisons accurately reflect changes in breeding numbers for this species. We found an overall decline in reporting rates of c.60%, with more cells showing loss or declines (75%) than those showing colonisation or increases (25%). No differences in reporting rate change were found between provinces, suggesting a relative uniform decline across the country. There were, however, differences between biomes with declines recorded in all biomes apart from Albany Thicket, Succulent Karoo and Fynbos (south-western biomes). Declines differed inside and outside protected areas, with larger declines outside (64%) than inside (42%) protected areas, although even within large protected areas significant declines were observed. These results support the uplisting of the species’ conservation status and suggest that even within protected areas the species is not immune to the drivers of decline.

Railway side mapping of alien plant distributions in Mpumalanga, South Africa

Background: Alien plant invasions are among the major threats to natural and semi-natural ecosystems in South Africa on approximately 18 million hectares of land. Much of the available data are not suitable for planning of local scale management because it is presented at a quarter degree grid square scale, which makes accurate location and estimates of invaded areas difficult.Objectives: The aim was to identify the dominant alien plant species and quantify their areal extent along a 479 km railway corridor in the Mpumalanga province.Method: The extent of the invaded area was obtained by manual digitising of alien plant distribution and density from Satellite Pour l’Observation de la Terre 5 imagery and by further applying an Iterative Self-Organising Data Analysis technique of the unsupervised classification method. Species’ occurrences were located and identified in the field using a Global Positioning System.Results: The most dominant invaders in terms of the number of individual polygons and the infested area were Eucalyptus spp., Acacia spp., Populus alba L., Pinus patula Schltdl Cham., Salix babylonica L. and Caesalpinia decapetala (Roth) Alston. These species have also been previously classified as major invaders, although the Conservation of Agricultural Resources Act regulations permit their planting provided spreading to adjacent areas is avoided except for C. decapetala, which must be cleared under all circumstances.Conclusion: Knowledge of the species’ occurrence and their extent will assist landowners and relevant authorities to control the spread of alien plants, which impact rail safety, agricultural production, water availability and biodiversity.

Diversity and biogeographical patterns of legumes (Leguminosae) indigenous to southern Africa.

The principal aim of this study was to establish biogeographical patterns in the legume flora of southern Africa so as to facilitate the selection of species with agricultural potential. Plant collection data from the National Herbarium, South Africa, were analysed to establish the diversity and areas covered by legumes (Leguminosae/Fabaceae) indigenous to South Africa, Lesotho and Swaziland. A total of 27,322 records from 1,619 quarter degree grid cells, representing 1,580 species, 122 genera and 24 tribes were included in the analyses. Agglomerative hierarchical clustering was applied to the presence or absence of legume species in quarter degree grid cells, the resultant natural biogeographical regions (choria) being referred to as leguminochoria. The description of the 16 uniquely formed leguminochoria focuses on defining the associated bioregions and biomes, as well as on the key climate and soil properties. Legume species with a high occurrence in a leguminochorion are listed as key species. The dominant growth form of key species, species richness and range within each leguminochorion is discussed. Floristic links between the leguminochoria are established, by examining and comparing key species common to clusters, using a vegetation classification program. Soil pH and mean annual minimum temperature were found to be the main drivers for distinguishing among legume assemblages. This is the first time that distribution data for legumes has been used to identify biogeographical areas covered by leguminochoria on the subcontinent. One potential application of the results of this study is to assist in the selection of legumes for pasture breeding and soil conservation programs, especially in arid and semi-arid environments.

<i>Schoenefeldia transiens</i> (Poaceae): Rare new record from the Limpopo Province, South Africa

Background: Schoenefeldia is a genus of C4 grasses, consisting of two species in Africa, Madagascar and India. It is the only representative of the genus found in southern Africa, where it was previously only known from a few collections in the southern part of the Kruger National Park (Mpumalanga Province, South Africa), dating from the early 1980s.Objectives: The objective of this study was to document a newly recorded population of Schoenefeldia transiens in an area that is exploited for coal mining.Method: A specimen of S. transiens was collected between Musina and Pontdrift, about 30 km east of Mapungubwe National Park, in the Limpopo Province of South Africa. The specimen was identified at the National Herbarium (Pretoria).Results: This is not only a new distribution record for the quarter degree grid (QDS: 2229BA), but is also the first record of this grass in the Limpopo Province. The population of S. transiens has already been fragmented and partially destroyed because of mining activities and is under serious threat of total destruction.Conclusion: It is proposed that the population of S. transiens must be considered to be of conservation significance, and the population should be made a high priority in the overall environmental management programme of the mining company that owns the land.

Scale-area curves: a tool for understanding the ecology and distribution of invasive tree species

Scale-area curves are increasingly used in ecology to predict population trajectories, based on the assumption that observed patterns are indicative of population dynamics. However, for introduced species, scale-area curves might be strongly influenced by introduction history. We examined the spatial structure of an invasive tree species (Acacia elata; Fabaceae) introduced to South Africa as an ornamental plant and compared our findings with previous work done on a species introduced for dune stabilization (A. longifolia). A fractal sampling method was used to map the occupancy of A. elata at twelve spatial scales for ten quarter-degree grid cells throughout South Africa. Based on the fractal dimension (D ij ) calculated at different spatial scales we found that populations were more contiguous at plot (2.5–25 m) and regional scales (2.5–25 km) than at local and landscape scales (0.025–2.5 km). We argue that the lack of contiguous A. elata populations over 250 m to 2.5 km is not indicative of a low risk, but the result of the spatial structure of available land in suburban environments. When working with introduced species, scale-area curves representing fragmented populations at the edge of invasions should not be considered to indicate a lack of invasive spread/threat. Rather they can be used to identify “missing links” in the invasive introduction-naturalization-invasion continuum, but only if the life-history traits, introduction history, and area suitable for invasion are well understood and are used in interpreting the results. We suggest that their greatest value will lie in their use as a method for long-term monitoring of introduced species.

Dynamic occupancy models for analyzing species' range dynamics across large geographic scales

Large-scale biodiversity data are needed to predict species' responses to global change and to address basic questions in macroecology. While such data are increasingly becoming available, their analysis is challenging because of the typically large heterogeneity in spatial sampling intensity and the need to account for observation processes. Two further challenges are accounting for spatial effects that are not explained by covariates, and drawing inference on dynamics at these large spatial scales. We developed dynamic occupancy models to analyze large-scale atlas data. In addition to occupancy, these models estimate local colonization and persistence probabilities. We accounted for spatial autocorrelation using conditional autoregressive models and autologistic models. We fitted the models to detection/nondetection data collected on a quarter-degree grid across southern Africa during two atlas projects, using the hadeda ibis (Bostrychia hagedash) as an example. The model accurately reproduced the range expansion between the first (SABAP1: 1987–1992) and second (SABAP2: 2007–2012) Southern African Bird Atlas Project into the drier parts of interior South Africa. Grid cells occupied during SABAP1 generally remained occupied, but colonization of unoccupied grid cells was strongly dependent on the number of occupied grid cells in the neighborhood. The detection probability strongly varied across space due to variation in effort, observer identity, seasonality, and unexplained spatial effects. We present a flexible hierarchical approach for analyzing grid-based atlas data using dynamical occupancy models. Our model is similar to a species' distribution model obtained using generalized additive models but has a number of advantages. Our model accounts for the heterogeneous sampling process, spatial correlation, and perhaps most importantly, allows us to examine dynamic aspects of species ranges.

Using the extended quarter degree grid cell system to unify mapping and sharing of biodiversity data

AbstractInformation on the distribution of animal populations is essential for conservation planning and management. Unfortunately, shared coordinate‐level data may have the potential to compromise sensitive species and generalized data are often shared instead to facilitate knowledge discovery and communication regarding species distributions. Sharing of generalized data is, unfortunately, often ad hoc and lacks scalable conventions that permit consistent sharing at larger scales and varying resolutions. One common convention in African applications is the Quarter Degree Grid Cells (QDGC) system. However, the current standard does not support unique references across the Equator and Prime Meridian. We present a method for extending QDGC nomenclature to support unique references at a continental scale for Africa. The extended QDGC provides an instrument for sharing generalized biodiversity data where laws, regulations or other formal considerations prevent or prohibit distribution of coordinate‐level information. We recommend how the extended QDGC may be used as a standard, scalable solution for exchange of biodiversity information through development of tools for the conversion and presentation of multi‐scale data at a variety of resolutions. In doing so, the extended QDGC represents an important alternative to existing approaches for generalized mapping and can help planners and researchers address conservation issues more efficiently.

Distribution and host plant range of Nysius natalensis Evans (Hemiptera: Orsillidae) in the sunflower production area of South Africa

Feeding by Nysius natalensis (Hemiptera: Orsillidae) adults on sunflower heads reduces grain yield, oil content and seed germination. Since the insect is known to feed on several host plants, a study was conducted on its host plant range to assess the role that weeds played in the pest status of this insect throughout the sunflower production area of South Africa. Roadside surveys of hosts, conducted in every quarter-degree grid of the sunflower production area, showed that N. natalensis was ubiquitous. The insect survived, developed and reproduced across a wide range of temperature and rainfall conditions. Feeding of nymphs and adults, as well as the presence of eggs was observed on 26 plant species belonging to eight families. The polyphagous habits of N. natalensis, together with a favourable temperature range for development in its distribution area, are important factors in determining population density of the pest. Late-planted sunflowers were prone to N. natalensis damage because seed-fill coincided with high numbers of the insect that increased during spring and summer. These individuals migrated onto sunflower with senescence of host weeds prior to winter. Recommendations are made on weed manage

The distribution and biology of Bittacus tjederi Londt, 1970 (Mecoptera: Bittacidae)

Bittacus tjederi Londt, 1970, together with B. capensis (Thunberg, 1784), B. smithersi Londt, 1972, and B. milleri Londt, 1978, constitute a distinctive species-group of hangingflies which is distributed between Grahamstown and Citrusdal in the southern parts of South Africa (Londt 1978). The recent capture of some B. tjederi specimens prompts this short report. Londt described B. tjederi from a relatively long series collected by a South African Museum expedition (Londt 1970), and later added a second record (Londt 1972). Londt (1978), in describing B. milleri, briefly discussed the interesting distribution of this species-group. A list of all known specimens of B. tjederi follows – exact label data being provided (lines of information separated by the symbol ‘/ ’). The exact coordinates of previously published localities are not known, and quarterdegree grid references are all that can safely be provided (in square brackets after the relevant place names). Published records. SOUTH AFRICA: 218 (including holotype), 169 (including allotype), ‘Goedehoop/Heidelberg [3420BB] Distr., /C.P.’, ‘Mus., Exped., /Oct. 1951’. Primary types and most of the paratypes are housed in the Iziko South African Museum, Cape Town. Two pairs of paratypes, originally stated as being in my personal collection, now form part of the Natal Museum’s collection in Pietermaritzburg (NMSA); 18, 29, ‘South Africa/Swellendam [3420AB]/14.11.1964/F. Honiball’ (18, 19 in Stellenbosch University collection, 19 in NMSA). New record: 48, 59, ‘South Africa: W Cape/Pat Busch Nature Reserve/33°46’17”S: 19°59’55”E/ 18-20.x.2005 JGH Londt / 317m Renosterbos / and rocky road verges’ (NMSA – pinned except for 18 preserved in ethanol for molecular analysis). A map of the distribution of species within the B. capensis group was published by Londt (1978). Bittacus smithersi is known only from the vicinity of Grahamstown, B. capensis has a wider distribution between Port Elizabeth and Knysna, B. tjederi is now known to occur between Heidelberg and Robertson, and finally B. milleri is found between Citrusdal and Clanwilliam. The species are accordingly allopatric, their combined distributions extending as a narrow band across the southern tip of South Africa, between c. latitude 32–34°S and c. longitude 19–27°E. Far more data are needed before it will be possible to establish the exact limits of each species so that the factors responsible for maintaining their separation can be understood. As far as B. tjederi is concerned, the new locality is of special interest as it is situated on the southern slopes of the Langeberg mountain range. While the exact coordinates of the collection sites involved in the ‘Goedehoop’ and ‘Swellendam’ material are not known, both centres (i.e. Heidelberg and Swellendam) also lie south of the Langeberg and within 15 km of the mountains. It is tempting to suggest that all three collecting localities probably lie in the southern foothills of the Langeberg which are relatively cooler and better vegetated than surrounding areas. This extensive mountain range effectively separates the Cape Floristic Region to the south from the Succulent Karoo Region to the north. It is possible that B. tjederi is confined to a relatively narrow area along the northern boundary of the Cape Floristic Region, well known internationally for its rich floral diversity (Van Wyk & Smith 2001). The Cape Floristic Region receives winter rainfall, while the more arid Succulent Karoo receives low summer rainfall. Bittacus tjederi, like the other species in the B. capensis group, has been collected mainly during October and November. This relatively short period of adult activity coincides with the end of the local rainy season and the beginning of warmer summer weather. Without exception, all the Pat Busch Nature Reserve specimens of B. tjederi were found hanging from the twigs of a group of bushes, identified as Ortholobium candicans (Eckl. & Zeyh.) C.H. Stirt, found growing along the verges of a sandy farm road (Fig. 1). These plants reach a height of about 2 m and have small c. 15 mm long, narrow, trifoliolate leaves borne on rather straight branches (Fig. 2). The c. 10 mm wide creamy white flowers were much in evidence at the time of the collec-

Hierarchical processes define spatial pattern of avian assemblages restricted and endemic to the arid Karoo, South Africa

Abstract Aim To identify and quantify biotic and abiotic factors associated with the regional gradients in the distribution and abundance of bird communities restricted and endemic to the Succulent and Nama Karoo biomes of South Africa.Location The arid Nama and Succulent Karoo biomes in South Africa.Methods The quarter degree grid cell (QDGC) was used to extract environmental data, while the bird data previously atlased, was linked to the same geo‐referenced system, using a geographical information system (GIS). Bird species were grouped into different life‐history assemblages. A quantitative, systematic analysis of the different bird communities spanning the Karoo was undertaken to examine contributions of broad‐ and local‐scale physical environmental and biotic factors to regional variations in the species composition, using multivariate statistical and spatial analytical tools. These included two indirect gradient methods; principal components analysis (PCA) and detrended correspondence analysis (DCA), and two direct gradient methods; canonical correspondence analysis (CCA) and redundancy analysis (RDA).Results Principal components analysis results showed that the selected environmental variables accounted for about 85% of the variation in the region. The first two principal gradients defined regional temperature seasonality and variability especially in winter and summer. The third principal gradient mainly defined summer rainfall areas in association with the coefficient of variation of rain and regional primary production, while the fourth gradient defined winter rainfall areas, growth days and elements of landscape structure. CCA/RDA analysis produced shortened hierarchically ranked explanatory variables for each bird assemblage. Stepwise gradient analysis results showed summer rain, rainfall concentration, topographic heterogeneity and annual evapotranspiration, as the most important climate variables explaining species occurrence. Landscape, in terms of percentage transformation, morphology, coefficient of variation of primary productivity and distance between suitable habitat patches, were also important, but to a lesser degree. Total variation explained (TVE) by the supplied variables was between 23 and 37% of variation. Less than 20% of TVE was the intrinsic spatial component of environmental influence, indicating that any unmeasured factors were independent of spatial structuring. For all the eight bird assemblages, climate contributed most to TVE (24–57%). Landscape characteristics (human‐induced transformation, vegetation in terms of size if grassy clumps and the average distances between them) contributed theleast to TVE for all the different assemblages (0–6%), especially the granivorous assemblage where it was not significant at all (0%). Seasonal extremes and variability were more important in explaining species gradients than were annual climatic conditions, with the exception of annual potential evapotranspiration.Main conclusions This study was able to synthesize species environment relations at the broad scale and demonstrated the association of arid zone endemic species occurrence with climate extremes and seasonality. Given the predicted climate change scenarios for South Africa, this regional gradient study provides a quantitative ecological basis for finer scale modelling and analysis, developing regional strategies for conserving biodiversity as well as predicting and planning for the effects of global climate change. However, most importantly, it clearly showed that bird species restricted and endemic to the arid Karoo biome may be more sensitive to climate rather than vegetation structure as previously thought.

REPTILE SYSTEMATIC STUDIES IN SOUTHERN AFRICA: A BRIEF HISTORY AND OVERVIEW

SUMMARY Southern Africa has the richest reptile diversity in Africa, with a fauna that currently exceeds 490 species. Present rates of discovery, which for lizards are still comparable to those in the early phases of exploration, indicate that the fauna may approach, if not exceed, 600 species. Lizards form the dominant component (60.9%) of the reptile fauna. The 578 recognised taxa (species and subspecies) were described by 101 authors, of which 12 authors were responsible for 12 or more taxa and together named 68.9% of the total taxa. The five most productive authors were, in order: A. Smith, W. Peters, D. Broadley, J. Hewitt, and V. FitzSimons. The contributions of these authors, the growth in herpetological studies in the last 25 years, and the importance of regional surveys in the development of biogeographic models, are summarised. Over 50 species of reptile have very restricted distributions (less than 3 quarter-degree grid squares) and may be of conservation concern. Despite national rhetoric evincing concern for the biodiversity crisis, there has been a recent decline in herpetological posts and manpower.

AMPHIBIAN DIVERSITY AND SPECIES TURNOVER IN SOUTHERN AFRICA: INVESTIGATION BY MEANS OF A BLOEMFONTEIN-DURBAN TRANSECT

ABSTRACT A transect from Bloemfontein to Durban, partitioned into quarter-degree intervals, is analysed to examine the performance of a quarter-degree grid in biogeographical pattern analysis, and to evaluate the quantity of available data. Only 5 out of 21 intervals show an estimated 100% intensity (or success) of collecting, which makes the determination of species boundaries uncertain, and shows the distribution and quantity of data to be unsuitable for mechanical analysis. The data are nevertheless sufficient to show that the total species/subspecies diversity at the western end of the transect is only 42% that of the eastern end. A pattern is shown of overlapping diversity gradients from the coastal lowland (21 forms) and from the interior plateau (6 forms). A complex of 21 other forms is localized within the transect zone, and 5 forms appear to cover the length of the zone. The turnover from one end of the zone to the other is substantial (27% similarity). The zone has a smaller interior plateau Com...

Intensity of plant collecting in southern Africa

The intensity of plant collecting in southern Africa is mapped using records from the Pretoria National Herbarium Computerized Information System (PRECIS), For the entire area, over 85% of the quarter degree grid squares have fewer than 100 specimens recorded. Collecting intensities are compared for different countries, biomes and climatic zones. Future field work from the National Herbarium will be concentrated in areas most seriously under-collected.