Results for some of the student projects
Project: Morphological and behavioral correlates of melanism (Dahné du Toit, Ph.D. student)
As part of her Ph.D. study on melanistic cordylids, Dahné investigated the climatic conditions associated with the distribution of these species. A summary of the results is presented here.
Most melanistic (black) cordylid lizard species occur in small populations along the west coast of South Africa and in the western parts of the Cape Fold Mountains. However, there are two exceptions. In contrast to the coastal or montane distribution of most of these species, Peers’Girdled Lizard (Cordylus peersi) is found in Namaqualand, and in contrast to the limited
distribution ranges of most species, the Graceful Crag Lizard (Pseudocordylus capensis) has a
relatively wide distribution. A detailed analysis of the geographical distribution of melanistic cordylid species, and a search for climatic correlates to explain the observed patterns of distribution,
were conducted. A geographic
information system (GIS) was used
to determine altitude, minimum
temperature, maximum temperature,
potential evaporation, precipitation,
solar radiation, fog, and cloud cover
for each locality. Data were
analyzed by means of a Principal
Component Analysis (PCA).
Melanistic species with restricted
distribution ranges were
characterized by a specific set of
climatic variables, while the more
widespread species spanned a wide
range of climatic conditions. In
general, there was a good correlation between the distribution of coastal and montane populations and cool climatic conditions. Coastal species were mainly associated with a high incidence of fog and minimum temperatures, while montane species were associated with cloud cover and rainfall. A dark body would absorb radiant energy more efficiently than a light body, and melanism is thus often considered an advantage in a cool environment. However, this correlation does not hold true for all melanistic species, as Pseudocordylus capensis and Cordylus peersi were associated with
warmer climatic conditions. This suggests that these two species have a broader tolerance range for warm climatic conditions than other melanistic cordylids, or that these species occupy very specific habitats within their distribution range. A regional scale analysis of climatic variables will not reveal the climatic conditions associated with specific microhabitats. A fine-scale investigation of the microhabitats- and climates associated with these species was conducted in order to better understand the ecology of melanistic cordylids in warm climates. Results will be available soon.
Project: Armadillo lizards and termites (Cindy Shuttleworth, M.Sc. student)
Cindy recently completed her M.Sc. thesis and received her degree in December 2006. Several articles are being prepared for publication and will be posted as they become available. A summary of her work is presented here.
The role of the southern harvester termite, Microhodotermes viator, and several climatic
parameters in the distribution of the group-living lizard, Cordylus cataphractus, was investigated.
Microhodotermes viator is considered the most important prey item of C. cataphractus and
termitophagy as the causative agent in the evolution of group-living in this species. One would therefore expect a high degree of correspondence in the ranges of C. cataphractus and M. viator.
As climate will also play a role in the distribution of any
species, various climatic variables were investigated to
determine their influence on the distribution of C.
cataphractus. Species distributions were visualized
using the minimum polygon technique and the degree
of overlap was determined using standard geographic
information systems (GIS) techniques. A total of 52 C.
cataphractus localities were investigated for the
presence of termites. The climatic limits of the
geographical distribution of C. cataphractus were