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Abstract The Equatorial African group of lacertids comprises nine species which share a number of derived features and appear to constitute a holophyletic assemblage. Revision of the group using morphological characters analyzed by parsimony and compatibility methods results in the following taxonomic changes: Lacerta jacksoni = Adolfus jacksoni, Lacerta echinata = Gastropholis echinata, Bedriagaia tropidopholis = Gastropholis tropidopholis, Bedriagaia moreavi = Gastropholis prasina, the latter species being validated and removed from the synonymy of Gastropholis vittata. Adolfus jacksoni has most features in common with the hypothetical ancestor of the group, while Holaspis guentheri and the species of Gastropholis are the most derived forms. Geographical variation in Adolfus alleni is described and what is known of the ecology of the Equatorial group summarized. Most are forest dwellers with the majority of the more primitive forms living on tree boles and among litter and timber on the forest floor (Adolfus jacksoni, A. africanus, A. vauereselli). Another, Holaspis guentheri, is confined to tree boles but glides between them, while the species of Gastropholis appear to be climbers in flimsy vegetation and Adolfus alleni is ground-dwelling above the tree line. Many of the morphological features characterizing these lizards appear to be functionally related to their particular habitats.

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Relationships of lacertid lizards were assessed on the basis of 84 primary and 112 binary characters drawn mainly from morphology, including features of the skeleton, external anatomy, various internal soft part systems and two aspects of behaviour. Among features not previously used, or not fully investigated before, are structure of the septomaxilla and nasal passages, arranged of the xiphisternal cartilages, mite pockets, kidney position, ulnar nerve arragement, thoracic fascia, aspects of the hemipenis and its associated muscles, female genitalia and jaw muscles. On the basis of parsimony analysis and compatibilty treatment of this character set, the Lacertidae fall into two main portions: A paraphyletic Palaearctic and Oriental group of primitive forms, from which is derived a holophyletic assemblage of Ethiopian and advanced Saharan and Eurasian taxa. The former group ist not fully resolvable, but Psammodromus and Gallotia appear to be sister groups and are probably related to Lacerta parva and L. fraasi and then L. brandtii, Podarcis appears to be related successively to L. andreanszkyi, the sister species L. dugesii and L. perspicillata, and perhaps L. danfordi and L. laevis. This assemblage may be related to archaeolacertas and Algyroides. The separation of Lacerta lepida, L. pater and L. princeps from the agilis group, based on chemical evidence, is weakly contradicted by morphology. Takydromus may be most closely related to L. vivipara, and L. jayakari and L. cyanura constitute the most likely sister group of the Ethiopian and advanced Saharo-Eurasian assemblage. Taxe in the Ethiopian and advanced SaharoEuroasian assemblage form a long essentially pectinate tree with relatively change between the side branches, except for a strong disjunction separating the more primitive from the more advanced taxa. Most of the former fall on two main branches, with ´Lacerta` australis and ´L.` rupicola possibly basal to them. 1. the Equatorial forest group containing Gastropholis, Bedriagaia, ´Lacerta` echinata, Adolfus, ´Lacerta` jacksoni and Holaspis. The first three of these constitute a holophyletic group and the same is probably true of the remainder. 2. Tropidosaura, Poromera and Nucras, the latter being the sister group of the more advanced forms. These include successively the Ethiopian Philochortus, Latastia, Ichnotropis and Heliobolus, Pseuderemias, Meroles and Aporosaura, and Pedioplanis, and then the Saharo-Eurasian Eremias, Acanthodactylus, Mesalina and Ophisops-Cabrita. It seems probable that the ancestors of modern Lacertidae arose in western Eurasia, where the family is known since the Palaeocene and is still represented there largely by quite primitive forms (89 species and seven nominal genera). The family later invaded Africa, perhaps first in the early or middle Miocene. Relatively primitive lacertids spread widely in largely mesic situations in the Ethiopian region, radiating to some extent (six present genera and 16 species) and producing Nucras and the related series of advaned groups (eight genera and 54 species) whoich show increasing adaptation to xeric environments. These genera tend to have heir most primitive species in the northeast and north of the Ethiopian region. The most advaned gave rise to the Saharo-Eurasian clade, now made up to Eremias, Acanthodactylus, Mesalina and Ophisops-Cabrita. This invaded the arid areas of North Africa and Eurasia, where it is presently represented by 70 species. Many morphological changes in increasingly advanced lacertids may be functionally related to the problems of survival in arid, hot, open environments. Considerable ecological parallelism exists in lacertids, with members of separate stocks occupying similar niches in different geographical areas. Morphological adaptations associated with these niches contribute significantly to the high levels of character homoplasy found in the family. There is also some correlation between the degree of niche differentiation in various groups and the quality of the phylogenies that can be produced from their physical characters. A number of morphological parallels exist between advaned lacertids and New World macroteiids. In the skull at least, advaned lacertids show a complex mixture of paedomorphosis and acceleration. Nomenclatorial changes are as follows: Cabrita is synonymised with Ophisops, necessitating a new name, Ophisops nictans, for Cabrita jerdonii. Aporosaura is synonymised with Meroles, Platyplacopus with Takydromus, and Bedriagaia with Gastropholis. ´Lacerta` (or Centromastyx) echinata is also transferred to the latter genus and Lacerta jacksoni to Adolfus. ´Lacerta` australis and ´L.` rupicola are put in a new genus, Australolacerta. It is recommended that Lacerta dugesii and L. perspicillata should not be placed in the otherwise very uniform genus Podarcis. Although clearly paraphyletic, Lacerta s. lat. Should be retained at least for the present and, if necessary putative relationships within it indicated by informal groups or subgenera.

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Differences in surface structure (ober- hautchen) of body scales of lacertid lizards involve cell size, shape and surface profile, presence or absence of fine pitting, form of cell margins, and the occurrence of longitudinal ridges and pustular projections. Phylogenetic information indicates that the primitive pattern involved narrow strap-shaped cells, with low posteriorly overlapping edges and relatively smooth surfaces. Deviations from this condition produce a more sculptured surface and have developed many times, although subsequent overt reversals are uncommon. Like variations in scale shape, different patterns of dorsal body microornamentation appear to confer different and conflicting performance advantages. The primitive pattern may reduce friction during locomotion and also enhances dirt shedding, especially in ground-dwelling forms from moist habitats. However, this smooth microornamentation generates shine that may compromise cryptic coloration, especially when scales are large. Many derived features show correlation with such large scales and appear to suppress shine. They occur most frequently in forms from dry habitats or forms that climb in vegetation away from the ground, situations where dirt adhesion is less of a problem. Microornamentation differences involving other parts of the body and other squamate groups tend to corroborate this functional interpretation. Microornamentation features can develop on lineages in different orders and appear to act additively in reducing shine. In some cases different combinations may be optimal solutions in particular environments, but lineage effects, such as limited reversibility and different developmental proclivities, may also be important in their genesis. The fine pits often found on cell surfaces are unconnected with shine reduction, as they are smaller than the wavelengths of most visible light.

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A complete catalogue is provided for the type specimens of lacertid lizards in the herpetological collection of the Zoological Museum, Berlin, as of December, 1993. The collection contains a total of 514 type specimens, representing 63 taxa, of which 42 are currently regarded as valid at the specific or subspecific level. Types representing an additional four taxa appear to have been lost from the collection. The collections are especially rich in African lacertid types and in historically significant specimens collected early in the Nineteenth Century by Pallas, Eversmann, and Hemprich & Ehrenberg. Also present are the type series of many subspecies of Podarcis lilfordi and P. pityusensis described by Eisentraut.

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The evolutionary diversification of many terrestrial vertebrate groups is strongly linked to climatic events in the Cenozoic, the period from 65 Million years ago to today when modern animals first appeared. I investigated the effects of Cenozoic climate change on the taxonomic and morphological diversification of the Old World lizard family Lacertidae, with particular emphasis on the African radiation. African lacertids exhibit an unusual pattern of diversification, in which their highest species richness occurs in deserts north and south of the equator, despite being spread throughout the continent. This disparity is particularly surprising given that desert lacertids are thought to be evolutionarily younger than their mesic-dwelling relatives, suggesting increased diversification rates in arid habitats. To identify the evolutionary factors underlying this pattern, I use a combination of phylogenetic, morphological and ecological techniques. In Chapter 1, I apply Bayesian methods and fossil-based calibrations to molecular sequence data to construct a time-calibrated phylogeny for Lacertidae. I estimate that the family arose in the early Cenozoic, with the majority of their African radiation occurring in the Eocene and Oligocene. In Chapter 2, I describe changes in lacertid body shape across biomes and substrates, and find widespread morphological convergence in similar habitat types. I suggest that in addition to foraging demands, fluctuating and extreme climatic conditions, largely driven by precipitation and temperature, contribute to morphological convergence across independent arid-dwelling clades. Finally, I test if ancestral transitions in ecology, morphology, and rates of diversification temporally coincide with paleoclimatic events in the Cenozoic. I use High Resolution X-ray Computed Tomography to characterize changes in the skull related to life in arid habitats, and apply maximum likelihood methods to test if the origins of those traits temporally coincide with significant shifts in habitat, diversification rates and climatic changes. My results show that African lacertids experienced three major peaks in diversification, accompanied by the evolution of suites of arid-adapted morphological traits. These changes coincide with climatic shifts in Africa, including the transition from closed forests to open grasslands and savanna in the late Oligocene, prior to the peak temperatures of the mid-Miocene Climatic Optimum, and following the formation of the Benguela current leading to hyper-aridity in southern Africa. I conclude that deserts are important centers for reptile evolution, but that expected changes in climate due to global warming may outpace the ability of arid-dwelling species to adapt and persist in the future.

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Aim To map and assess the richness patterns of reptiles (and included groups: amphisbaenians, crocodiles, lizards, snakes and turtles) in Africa, quantify the overlap in species richness of reptiles (and included groups) with the other terrestrial vertebrate classes, investigate the environmental correlates underlying these patterns, and evaluate the role of range size on richness patterns. Location Africa. Methods We assembled a data set of distributions of all African reptile species. We tested the spatial congruence of reptile richness with that of amphibians, birds and mammals. We further tested the relative importance of temperature, precipitation, elevation range and net primary productivity for species richness over two spatial scales (ecoregions and 1° grids). We arranged reptile and vertebrate groups into range-size quartiles in order to evaluate the role of range size in producing richness patterns. Results Reptile, amphibian, bird and mammal richness are largely congruent (r = 0.79–0.86) and respond similarly to environmental variables (mainly productivity and precipitation). Ecoregion size accounts for more variation in the richness of reptiles than in that of other groups. Lizard distributions are distinct with several areas of high species richness where other vertebrate groups (including snakes) are species-poor, especially in arid ecoregions. Habitat heterogeneity is the best predictor of narrow-ranging species, but remains relatively important in explaining lizard richness even for species with large range sizes. Main conclusions Reptile richness varies with similar environmental variables as the other vertebrates in Africa, reflecting the disproportionate influence of snakes on reptile richness, a result of their large ranges. Richness gradients of narrow-ranged vertebrates differ from those of widespread taxa, which may demonstrate different centres of endemism for reptile subclades in Africa. Lizard richness varies mostly with habitat heterogeneity independent of range size, which suggests that the difference in response of lizards is due to their ecological characteristics. These results, over two spatial scales and multiple range-size quartiles, allow us to reliably interpret the influence of environmental variables on patterns of reptile richness and congruency.

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Aim Body size is instrumental in influencing animal physiology, morphology, ecology and evolution, as well as extinction risk. I examine several hypotheses regarding the influence of body size on lizard evolution and extinction risk, assessing whether body size influences, or is influenced by, species richness, herbivory, island dwelling and extinction risk. Location World-wide. Methods I used literature data and measurements of museum and live specimens to estimate lizard body size distributions. Results I obtained body size data for 99% of the world`s lizard species. The body size–frequency distribution is highly modal and right skewed and similar distributions characterize most lizard families and lizard assemblages across biogeographical realms. There is a strong negative correlation between mean body size within families and species richness. Herbivorous lizards are larger than omnivorous and carnivorous ones, and aquatic lizards are larger than non-aquatic species. Diurnal activity is associated with small body size. Insular lizards tend towards both extremes of the size spectrum. Extinction risk increases with body size of species for which risk has been assessed. Main conclusions Small size seems to promote fast diversification of disparate body plans. The absence of mammalian predators allows insular lizards to attain larger body sizes by means of release from predation and allows them to evolve into the top predator niche. Island living also promotes a high frequency of herbivory, which is also associated with large size. Aquatic and nocturnal lizards probably evolve large size because of thermal constraints. The association between large size and high extinction risk, however, probably reflects a bias in the species in which risk has been studied.

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Many animals display complex colour patterns that comprise several adjacent, often contrasting colour patches. Combining patches of complementary colours increases the overall conspicuousness of the complex pattern, enhancing signal detection. Therefore, selection for conspicuousness may act not only on the design of single colour patches, but also on their combination. Contrasting long- and short-wavelength colour patches are located on the ventral and lateral surfaces of many lacertid lizards. As the combination of long- and short-wavelength-based colours generates local chromatic contrast, we hypothesized that selection may favour the co-occurrence of lateral and ventral contrasting patches, resulting in complex colour patterns that maximize the overall conspicuousness of the signal. To test this hypothesis we performed a comparative phylogenetic study using a categorical colour classification based on spectral data and descriptive information on lacertid coloration collected from the literature. Our results demonstrate that conspicuous ventral (long wavelength-based) and lateral (short wavelength-based) colour patches co-occur throughout the lacertid phylogeny more often than expected by chance, especially in the subfamily Lacertini. These results suggest that selection promotes the evolution of the complex pattern rather than the acquisition of a single conspicuous colour patch, possibly due to the increased conspicuousness caused by the combination of colours with contrasting spectral properties.

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The herpetofauna of southern Africa is currently receiving an increased amount of attention. The Zoological Society of Southern Africa held a symposium on herpetology and ichthyology in 1975, the proceedings of which have been published in Zoologica Africana, and no less than 17 papers dealt specifically with research carried out recently on southern African amphibians and reptiles. Our aim in this chapter, therefore, can be no more than to sketch the present state of knowledge and thinking in a rapidly changing field.

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This checklist records the 99 species of lizards known at present from Kenya, and which are divided amongst eight families: Gekkonidae 33 species, Agamidae seven, Chamaeleonidae 17, Scincidae 22, Lacertidae 12, Cordylidae five, Varanidae two, Amphisbaenidae one. Brief data on the distribution of all species is given, with some localities, details of habitat and (in some cases) status of subspecies. Some taxonomic notes on certain problematic species/genera are included, plus a brief discussion of the zoogeography of Kenya`s lizards, and a gazetteer of localities.