Platysaurus Research Articles

A new species of spectacularly coloured flat lizard Platysaurus (Squamata: Cordylidae: Platysaurinae) from southern Africa.

We describe a new species of flat lizard (Platysaurus attenboroughi sp. nov.) from the Richtersveld of the Northern Cape Province of South Africa and the Fish River Canyon region of southern Namibia. This species was formerly confused with P. capensis from the Kamiesberg region of Namaqualand, South Africa. Genetic analysis based on one mtDNA and two nDNA loci found Platysaurus attenboroughi sp. nov. to be genetically divergent from P. capensis and these species can also be differentiated by a number of scalation characters, coloration and their allopatric distributions. To stabilize the taxonomy the type locality of Platysaurus capensis A. Smith 1844 is restricted to the Kamiesberg region, Namaqualand, Northern Cape Province, South Africa.

An index of spring diet in the common flat lizard, Platysaurus intermedius wilhelmi

Flat lizards of the genus Platysaurus are primarily insectivorous, but some species are omnivorous, eating significant amounts of plant material. The common flat lizard, P. intermedius, is thought to forage on arthropods, flowers, leaves and fruit. However, this assertion is based on a single study that documents the presence of various food items in a large series of museum specimens from several subspecies of P. intermedius. I examined faecal pellets from P. i. wilhelmi collected during October 2013 in order to survey the spring diet of this subspecies. I found that P. i. wilhelmi preyed mostly on ants, bees and wasps, and included only a minimal amount of vegetation in its diet, some of which was likely to have been incidentally ingested while feeding on arthropods. This study provides only the second examination of the feeding ecology of P. i. wilhelmi, and shows that during spring, flat lizards from one population in South Africa feed largely on insects from the order Hymenoptera.

Flat lizard female mimics use sexual deception in visual but not chemical signals.

Understanding what constrains signalling and maintains signal honesty is a central theme in animal communication. Clear cases of dishonest signalling, and the conditions under which they are used, represent an important avenue for improved understanding of animal communication systems. Female mimicry, when certain males take on the appearance of females, is most commonly a male alternative reproductive tactic that is condition-dependent. A number of adaptive explanations for female mimicry have been proposed including avoiding the costs of aggression, gaining an advantage in combat, sneaking copulations with females on the territories of other males, gaining physiological benefits and minimizing the risk of predation. Previous studies of female mimicry have focused on a single mode of communication, although most animals communicate using multiple signals. Male Augrabies flat lizards adopt alternative reproductive tactics in which some males (she-males) mimic the visual appearance of females. We experimentally tested in a wild population whether she-males are able to mimic females using both visual and chemical signals. We tested chemical recognition in the field by removing scent and relabelling females and she-males with either male or female scent. At a distance, typical males (he-males) could not distinguish she-males from females using visual signals, but during close encounters, he-males correctly determined the gender of she-males using chemical signals. She-males are therefore able to deceive he-males using visual but not chemical signals. To effectively deceive he-males, she-males avoid close contact with he-males during which chemical cues would reveal their deceit. This strategy is probably adaptive, because he-males are aggressive and territorial; by mimicking females, she-males are able to move about freely and gain access to females on the territories of resident males.

Does the Lizard Platysaurus Broadleyi Aggregate Because of Social Factors?

Abstract Aggregations are a common feature of many species although for most taxa, the mechanisms underlying these aggregations are poorly understood. The Augrabies Flat Lizard (Platysaurus broadleyi) is a sexually dimorphic lizard that experiences intense conflict as a result of sexual selection. In the wild, P. broadleyi share communal crevices and aggregate in the presence of large insect plumes. We experimentally tested whether lizards aggregate as a result of social factors. We also tested whether aggregative behavior differed between the sexes and depends on density. We found no evidence that Augrabies Flat Lizards preferentially group for social reasons in the absence of resources or thermoregulatory benefits. This was true for both sexes and at both densities (two-lizard and four-lizard trials). Although social factors did not promote grouping, males sheltered alone significantly more often than expected by chance, suggesting that males actively avoid one another. Therefore, social factors may wor...

Male flat lizards prefer females with novel scents

In lizards, pheromonal cues are important for mate recognition and are expected to diverge during the speciation process. We tested for divergence in pheromonal mate and species recognition between male flat lizards (Platysaurus broadleyi) belonging to the same population, a different population, and a sister species. Males were given a choice between two refuges, an odourless control and one of the following: a conspecific female from the same population (sympatric), a conspecific female from a distant population (allopatric), and a female from their sister species (heterospecific), P. capensis. Males chose refuges treated with the scent of a heterospecific over an odourless control refuge but showed no preference for refuges that were scented with female conspecific (allopatric or sympatric) cues over the control. These results were consistent in the breeding and non-breeding seasons. In a second experiment males were offered a choice of female scents between sympatric and allopatric conspecifics; an allopatric conspecific and a heterospecific; and a sympatric conspecific and a heterospecific. Males showed a trend of preferring heterospecific over conspecific refuges and allopatric over sympatric conspecific-scented refuges, but these results were not significant at alpha <0.05. Contrary to our original expectations, these experiments do not provide any evidence for a pheromonal pre-mating isolation mechanism within this species complex. However, our results suggest a preference for novel female scents by males, consistent with selection for genetic diversity.

Male flat lizards prefer females with novel scents

In lizards, pheromonal cues are important for mate recognition and are expected to diverge during the speciation process. We tested for divergence in pheromonal mate and species recognition between male flat lizards (Platysaurus broadleyi) belonging to the same population, a different population, and a sister species. Males were given a choice between two refuges, an odourless control and one of the following: a conspecific female from the same population (sympatric), a conspecific female from a distant population (allopatric), and a female from their sister species (heterospecific), P. capensis. Males chose refuges treated with the scent of a heterospecific over an odourless control refuge but showed no preference for refuges that were scented with female conspecific (allopatric or sympatric) cues over the control. These results were consistent in the breeding and non-breeding seasons. In a second experiment males were offered a choice of female scents between sympatric and allopatric conspecifics; an allopatric conspecific and a heterospecific; and a sympatric conspecific and a heterospecific. Males showed a trend of preferring heterospecific over conspecific refuges and allopatric over sympatric conspecific-scented refuges, but these results were not significant at alpha <0.05. Contrary to our original expectations, these experiments do not provide any evidence for a pheromonal pre-mating isolation mechanism within this species complex. However, our results suggest a preference for novel female scents by males, consistent with selection for genetic diversity.

Ultraviolet signals ultra-aggression in a lizard

Understanding the role of multiple colour signals during sexual signalling is a central theme in animal communication. We quantified the role of multiple colour signals (including ultraviolet, UV), measures of body size and testosterone levels in settling disputes between male rivals in an elaborately ornamented, African lizard, played out in a large ‘tournament’ in the wild. The hue and brightness (total reflectance) of the UV throat in Augrabies flat lizards, Platysaurus broadleyi, as well as body size, were consistent and strong predictors of ‘fighting ability’. Males with high fighting ability were larger and displayed a UV throat with low total reflectance. In contrast, males with low fighting ability were smaller and had violet throats with broader spectral reflectance curves (higher total reflectance). As fighting ability is associated with alternative reproductive tactics in this system (territorial versus floater), we also examined the role of colour signals in predicting male reproductive tactic. Territorial males had UV throats with higher chroma but had poorer body condition than floater males, probably because of the energetic costs of maintaining a territory. Although testosterone was not a significant predictor of fighting ability or reproductive tactic, it was correlated with the hue of the UV throat, suggesting that testosterone may impose some constraint on signal expression. Lastly, we show that within the context of the natural signalling environment, UV-reflective throats constitute a conspicuous, effective signal that male Augrabies flat lizards use to advertise their status honestly to rivals.

Male mate preference for large size overrides species recognition in allopatric flat lizards ( Platysaurus broadleyi )

Species recognition and mate preference both influence mate choice but can be in conflict with each other. In such cases the relative importance of the two functions depends on the costs of mating with heterospecifics and the frequency of such interactions. We tested whether male flat lizards (Platysaurus broadleyi) are able to discriminate between conspecific females and females of its allopatric sister species P. capensis. Given a simultaneous choice between equally sized females of both species, males courted conspecific females in 85% of trials. We then tested whether mate preference for large female body size can override species recognition. When offered a choice between a larger heterospecific female and a smaller conspecific, males showed no preference for conspecifics and courted larger heterospecific females in 58% of trials. Comparison of the two sets of trials showed a significant effect of female body size on male mate preference, supporting the hypothesis that mate quality can override species recognition.

Tasty figs and tasteless flies: plant chemical discrimination but no prey chemical discrimination in the cordylid lizard Platysaurus broadleyi

Lizards use visual and/or chemical cues to locate and identify food. The ability to discriminate prey chemical cues is affected by phylogeny, diet, and foraging mode. Augrabies flat lizards (Platysaurus broadleyi) are omnivorous members of the lizard clade Scleroglossa. Within Scleroglossa, all previously tested omnivores are capable of both prey and plant chemical discrimination. At Augrabies Falls National Park, P. broadleyi feed on both insects (black flies) and plant material (figs), and as scleroglossans, are predicted to discriminate both plant and prey chemicals. However, Platysaurus broadleyi use visual, not chemical cues, to detect and capture black flies, which occur in large concentrations in the study area. We tested free-ranging individuals for the ability to discriminate insect and plant chemicals from controls. There was a significant stimulus effect such that lizards tongue-flicked fig-labelled tiles significantly more than the remaining stimuli, spent more time at the fig-labelled tile, and attempted to eat fig-labelled tiles more often than tiles labelled with control or insect stimuli. Platysaurus broadleyi is exceptional in being the first lizard shown to possess plant chemical discrimination but to lack prey chemical discrimination. We suggest that an absence of prey chemical discrimination may be a consequence of foraging behaviour and environmental effects. Because insect prey are highly clumped, abundant, and aerial, profitable ambushing using visual cues may have relaxed any selective pressure favouring insect prey chemical discrimination. However, a more likely alternative is that responses to figs are gustatory, whereas as prey chemical discrimination and plant chemical discrimination are usually mediated by vomerolfaction.

To run or hide? Age‐dependent escape behaviour in the common flat lizard (Platysaurus intermedius wilhelmi)

Flat lizards Platysaurus intermedius wilhelmi occur on small discrete rock outcrops in Mpumalanga Province, South Africa. These rock outcrops are structurally simple and this, combined with the lizard's behaviour (ambush foraging in the open), make them ideal for field studies of anti‐predatory behaviour. Lizards were approached in the field and how escape behaviour was influenced by habitat and age‐sex class was recorded. Juveniles (c. 4 months of age) responded quite differently to an approaching human ‘predator’ compared with adult males and females (which responded similarly). Compared to adults, juveniles allowed a closer approach by the investigator; took longer to find a refuge and therefore fled further; were more likely to remain visible in the open and maintain visual contact with the investigator; and more likely to flee into vegetation when given the opportunity to take refuge in a crevice. We suggest that because a greater suite of predators (including arthropods living in rock crevices) feed on small juvenile lizards, this may affect their choice of refuge and result in the avoidance of crevices when chased. Finally, because juveniles were frequently found on small rock outcrops, the influence of rock outcrop area on anti‐predatory behaviour was tested. Escape behaviour (time to refuge) was independent of rock outcrop area.

Thermal Dependence of Appetite and Digestive Rate in the Flat Lizard, Platysaurus intermedius wilhelmi

We investigated the thermal dependence of appetite and digestive rate in the flat lizard, Platysaurus intermedius wilhelmi, over a wide thermal range (12?-34?C). Because Platysaurus seldom venture off rock outcrops, their body temperatures are determined to a large extent by the thermal characteristics of this microhabitat. Our results demonstrate that appetite, measured as the number of food items eaten in a given time, is clearly temperature-dependent, increasing to a maximum that coincides with the thermal preference of 32?C for the species. Our measures for digestive rate, measured as the time to the first passing of feces after a meal, are temperature-dependent below 22?C but are temperature-independent between 22? and 34?C. Furthermore, our data indicate a critical body temperature of 12?C, below which all feeding ceases. We predict that lizards of this species with TbS below 20?C are effectively excluded from nutritive energy gain under natural conditions.

Use of heterospecific cues by the lizard Platysaurus broadleyi for food location

Flat lizards (Platysaurus broadleyi) at Augrabies Falls National Park, South Africa, are restricted to rocky terrain where the predominant tree is the Namaqua fig (Ficus cordata cordata). P. broadleyi readily feeds on Namaqua figs when they are available, and the lizards sometimes form large (maximum recorded=134) congregations under fruiting fig trees. The distance lizards travel to fruiting trees also exceed normal daily foraging distances. Location of fruiting fig trees by a lizard can have a high pay-off because figs are energetically rich and trees fruit irregularly and asynchronously, resulting in a resource that is available, but unpredictable in time and space. The prediction that bird activity in fig trees provides a cue to the presence of ripe figs was tested experimentally. By placing cages containing birds and empty control cages in trees devoid of fruit, we demonstrated that P. broadleyi are drawn to fig trees with high bird congregations. We also tested if the presence of a fig tree was necessary to draw lizards to bird congregations by placing cages containing birds and empty control cages in a matched-pairs design on rock away from trees. Namaqua fig trees were not necessary to draw lizards to bird congregations.

Is Temperature Independence of Digestive Efficiency an Experimental Artifact in Lizards? A Test Using the Common Flat Lizard (Platysaurus intermedius)

Digestive efficiency has been measured in several species of lizards and appears to be related to temperature and diet quality. We hypothesized that the apparent disagreement in the literature concerning the affect of body temperature on digestive efficiency is the result of the confounding effect of diet quality. Because highquality diets result in very high digestive efficiencies, differences due to body temperature are proportionally small and are thus easily masked by noise. To test this hypothesis, we measured the apparent digestive efficiency in 16 common flat lizards (Platysaurus intermedius) fed a low- and high-quality diet at 31 C and 26 C. We standardized the quantity and controlled the quality of food ingested by force feeding the lizards using a syringe. The digestive efficiencies for the low-quality (52%) and high-quality (88%) diets were significantly different at both temperature regimes, but no significant differences were found between the digestive efficiencies measured at the different temperature regimes for either diet. Thus, our hypothesis that the degree of temperature dependence of apparent digestive efficiency is a function of food quality was falsified. This indicates that the temperature dependence of apparent digestive efficiency is a species-dependent attribute.

THE GENUSPLATYSAURUSA. SMITH 1844 IN THE TRANSVAAL

ABSTRACT Transvaal flat lizards of the genus Platysaurus are re-appraised following a greater sample size and improved coverage of the region. This enabled a more detailed analysis of the morphological characters utilized by previous researchers. Five species with thirteen taxa are recognised; taxonomic changes include; revival of P. orientalis from the synonomy of P. guttatus and relegation of P. fitzsimonsi to a subspecies of P. orientalis; elevation of P. minor to a full species (previously treated as a subspecies of P. guttatus); P. guttatus becomes monotypic; recognition of two new subspecies of P. intermedius from the northern Transvaal; recognition of another new subspecies of P. intermedius from the Lebombo mountains (previously confused with P. i. wilhelmi). Colour illustrations of the new and revived taxa are included (formal taxonomic descriptions of the new subspecies will appear elsewhere). A key to the genus Plalysaurus in the Transvaal, and distribution maps of the taxa are included.

Interspecific aggression in flat lizards suggests poor species recognition

Mistaken identity and competitive exclusion are two alternative hypotheses proposed to explain interspecific aggression between males. We examined agonistic behaviour in males of two lizard species: Platysaurus minor and P. monotropis. In each of nine outdoor field enclosures, we maintained a male and a female of both species (i.e., four total) and observed the dominance relationship between the males. Interspecific aggression was intense and P. monotropis was dominant in eight of nine enclosures. Furthermore, P. minor males received significantly more bite marks than P. monotropis males during the course of the experiment. To distinguish among the two hypotheses for interspecific aggression (mistaken identity and competitive exclusion), we presented P. minor males from sympatry and allopatry with model lizards of both taxa and measured aggressive responses. All trials with models were conducted in field enclosures where males were kept alone for the duration of the experiment. The model experiment revealed that compared to P. minor from sympatry, allopatric P. minor males were no less aggressive towards the heterospecific model than the conspecific model, a finding that supports the mistaken identity hypothesis. Finally, in the same experiment, we included a supernormal stimulus (pink Platysaurus model) to test if males were simply responding to a brightly coloured male lizard. Males showed some aggression towards the supernormal model, but significantly less than towards the two models (P. minor and P. monotropis) combined.