Chromosomal variation in the scincid genus Mabuya and its arboreal relatives (Reptilia: Squamata)

Karyotypes of four East and Southeast Asian species of the genus Mabuya and representatives of three arboreal genera considered to be closely related to the genus (Apterygodon, Dasia and Lamprolepis) are examined. Mabuya rugifera and M. rudis possess 2n=32 karyotypes, whereas M. longicaudata lacks one small chromosome pair, which makes its diploid number 30. The karyotype of M. macularia quadrifasciata from southern Thailand differs from any known scincid karyotypes, including a previously reported karyotype of the conspecific Indian population, in exhibiting a high diploid number (38) and a gradual change in size from large to small chromosomes. This suggests that M. macularia may consist of more than one biological species. Karyotypes of Apterygodon vittatus, Dasia olivacea and Lamprolepis smaragdinus, while exhibiting a close similarity to most Mabuya karyotypes, suggest the occurrence of slight rearrangements involving either the deletion of two small chromosome pairs (A. vittatus), or the change of centromeric positions in medium and small chromosomes (D. olivacea and L. smaragdinus).     

Modulatory complexity of the feeding repertoire in scincid lizards

The kinematics of jaws and tongue, and jaw muscle activity patterns were investigated in the omnivorous lizard Tiliqua rugosa, and the herbivorous Corucia zebrata (Scincidae) during feeding. Small metal markers were inserted into different parts of the skull, the jaws, and the tongue. Video and cineradiographic images were digitized and displacements of the head, jaws, and tongue were quantified. Additionally, muscle activity patterns were recorded, digitized and several variables were determined quantitatively. The effect of food type on the jaw and hyolingual movement patterns and the jaw muscle activity patterns was investigated for both species. The kinematic data indicate that distinct aspects of gape and tongue cycles are modulated in response to the food characteristics. Similarly, in both species, muscle activity patterns are altered in response to the type of food eaten. A comparison of kinematic and electromyographic patterns during intraoral transport cycles for both species shows that these can be related to food characteristics such as toughness and mobility. Differences between both species in the response to changes in food characteristics are minor. Clearly both species are able to fine tune the activation of the jaw muscles, resulting in the appropriate movement patterns for the type of food eaten. Accepted: 30 January 1999     

Lygosomine phylogeny and the origins of Australian scincid lizards

Aim Australian scincid lizards represent three distinct groups within the cosmopolitan clade Lygosominae, the Egernia, Eugongylus and Sphenomorphus groups. This paper presents a time‐calibrated phylogeny for Lygosominae that provides the necessary temporal framework for assessing the contributions of immigration from Asia and of Gondwanan inheritance in the derivation of the Australian scincid fauna. Location Australasia, Asia, Africa. Methods Phylogenetic relationships and divergence times were inferred from novel BDNF, c‐mos and PTPN12 sequences (2408 aligned sites). Results Lygosomine monophyly is well supported, and there is strong support for monophyly of the Egernia, Eugongylus and Sphenomorphus groups. A sister‐group relationship of Tribolonotus (distributed in Melanesia and the Papuan Region) and the Egernia group is strongly supported in both Bayesian and maximum likelihood analyses. Australian representatives of the Sphenomorphus group compose a significantly supported clade estimated to have originated c. 25 Ma. An age of c. 18 Ma is inferred for a strongly supported clade comprising Australian representatives of the Egernia group; this clade diverged from Corucia zebrata (confined to the Solomon Islands) c. 25 Ma and from Tribolonotus c. 54 Ma. A well‐supported clade including all Australian Eugongylus group taxa sampled is estimated to have arisen c. 20 Ma. Main conclusions The Australian Sphenomorphus group is nested within the more inclusive Sphenomorphus group (distributed primarily in Asia and Australasia), suggesting comparatively recent descent from a colonizing Asian ancestor; the divergence times inferred here indicate that colonization occurred during the mid Cenozoic, subsequent to the rifting of Australia from Antarctica. An Oligocene origin of the extant Eugongylus group fauna of Australasia (the basal members of which are distributed in the Southwest Pacific) indicates that Eugongylus group lygosomines also dispersed to Australia relatively recently. The Egernia group diverged from Tribolonotus in the Early Eocene; however, extant Egernia group lygosomines originated only during the Late Oligocene, implying extensive pruning of stem taxa (i.e. extinction). As a result, inferences of the timing of dispersal into Australia are associated with substantial uncertainty, although independent palaeontological evidence suggests that the Egernia group entered Australia prior to the Oligocene, immediately after (or perhaps before) the separation of Australia and Antarctica.     

Evolutionary basis of parallelism in North American scincid lizards

This study uses a phylogenetic framework to explore the causes of parallelism in two North American scincid lizard assemblages: the skiltonianus and fasciatus species groups of the genus Plestiodon. Each group consists of several closely related species with conserved neonate morphology; features that distinguish species become accentuated during ontogeny, and these differences often resemble different endpoints along a developmental continuum. This continuum is believed to be an expression of the ancestral ontogeny, and has led to the hypothesis that evolutionary change in development has generated much of the observed morphological diversity. However, progress on understanding these mechanisms is limited by a lack of well-supported phylogenetic data for the fasciatus group, and for Plestiodon in general. Recent phylogenetic studies on the skiltonianus group have revealed previously undetected cases of parallelism, and raise the possibility that similar cases have yet to be discovered in the fasciatus group. Here, I estimate a phylogeny to test the monophyly of the fasciatus group and infer its relationship with other North American Plestiodon using 2537 bp from six mtDNA genes. I use the phylogeny to reconstruct the mode (graduated vs. punctuated) and direction of body size evolution, to map the evolution of two predominant color morphs, and to test whether size and color pattern evolve concertedly. The results show that the morphotypes of the traditional fasciatus group constitute good species, but that the species group is rendered paraphyletic by several geographically overlapping species that deviate from the fasciatus-like ontogeny. Body size evolution has occurred gradually and bi-directionally, and shifts to large body size have been consistently associated with the loss of the striped color pattern during ontogeny. I show that parallelism, a lack of rigorous phylogenetic analysis, and a reliance on shared ontogenetic features for predicting phylogenetic relatedness, has misled the traditional systematics of these lizards, but that general ideas concerning the role of development in their morphological evolution remain supported. I close by proposing that the processes influencing repeated phyletic patterns in the skiltonianus and fasciatus groups represent adherence to an ancestral ground state, and discuss the importance of using phylogenies for the initial characterization of evolutionary changes in development.     

Parallel gigantism and complex colonization patterns in the Cape Verde scincid lizards Mabuya and Macroscincus (Reptilia: Scincidae) revealed by mitochondrial DNA sequences

The scincid lizards of the Cape Verde islands comprise the extinct endemic giant Macroscincus coctei and at least five species of Mabuya, one of which, Mabuya vaillanti, also had populations with large body size. Phylogenetic analysis based on DNA sequences derived from the mitochondrial cytochrome b, cytochrome oxidase I and 12S rRNA genes (711, 498 and 378 base pairs (bp), respectively) corroborates morphological evidence that these species constitute a clade and that Macroscincus is unrelated to very large skinks in other areas. The relationships are ((M. vaillanti and Mabuya delalandii) (Mabuya spinalis and Macroscincus coctei (Mabuya fogoensis nicolauensis (Mabuya fogoensis antaoensis and Mabuya stangeri)))). The Cape Verde archipelago was colonized from West Africa, probably in the Late Miocene or Early Pliocene period. The north-eastern islands were probably occupied first, after which the ancestor of M. vaillanti and M. delalandii may have originated on Boavista, the ancestor of the latter species arriving on Santiago or Fogo later. The M. fogoensis--M. stangeri clade colonized the islands of Branco, Razo, Santa Luzia and São Vicente from São Nicolau and reached Santo Antão after this. Colonization of these northeastern islands was slow, perhaps because the recipient islands had not developed earlier or because colonization cut across the path of the Canary Current and the Northeast Trade Winds, the main dispersing agents in the region. Rapid extension of range into the southwestern islands occurred later in M. spinalis and then in M. vaillanti and M. delalandii. The long apparent delay between the origin of these species and their southwestern dispersal may have been because there were earlier colonizations of the southern islands which excluded later ones until the earlier inhabitants were exterminated by volcanic or climatic events. The evolution of large size in Macroscincus occurred in the northwestern islands and was paralleled in the eastern and southern islands by populations of M. vaillanti. Both cases of size increase in Cape Verde skinks were accompanied by the development of herbivory.     

Competition and character displacement in two species of scincid lizards

The role of competition in habitat occupation and character displacement is investigated in two species of alpine lizards (Niveoscincus microlepidotus and N. greeni), using both controlled competition experiments and field‐based ecological work. Competition experiments demonstrate that interspecific aggression occurs between these closely related species, with the larger and more aggressive N. greeni being socially dominant. When these species occur in sympatry, N. microlepidotus was found to shift its habitat occupation to the heathlands, which provide less thermal opportunities. In addition, a reduction in body size occurred in both adult and neonatal N. microlepidotus at sympatric field sites. Differences in body size between N. microlepidotus and N. greeni in sympatry were significantly greater than in allopatry, indicating that character displacement is occurring. Results, combined with previous molecular and biogeographical data, suggest that there is a trend towards a reduction in body size and a restriction in habitat occupation in N. microlepidotus in the north‐east periphery of its distribution, which is shaped by competition with N. greeni.     

The karyotypes of two scincid lizards,and their bearing on relationships in genus Leiolopisma and its relatives (Scincidae: Lygosominae)

Abstract

The karyotypes of the skinks Leiolopisma telfairi (Desjardin) and Cyclodina oliveri (McCann) are presented for the first time, from male spceimens. Metaphase cells from intestinal epithelium (C. oliveri) and testicular material (C. oliveri and L. telfairi) gave the diploid number, 2n = 30, for both species. Heteromorphism of the pair 6 chromosomes was observed in C. oliveri; this is the first published report of male heterogamety in the Scincidae. A common origin is proposed for L. spenceri and L. telfairi, on the basis of chromosome pair 8 morphology. These species may be more closely allied to Cyclodina than previously believed.     

Phylogeny and phylogeography of the genus Patella based on mitochondrial DNA sequence data

Although some molecular phylogenies of Patella species have been published in recent years, unresolved questions concerning the phylogeny and taxonomy of this genus still remain. We sequenced the mitochondrial genes cytochrome c oxidase subunit I, 12S rRNA and 16S rRNA for all Patella species (Patella vulgata, Patella depressa, Patella candei, Patella caerulea, Patella lugubris, Patella ferruginea, Patella pellucida and the continental and Macaronesian forms of Patella ulyssiponensis and Patella rustica) and Cymbula safiana. Our results revealed the occurrence of five strongly supported clades, although relationships between these are not well supported. According to our data P. vulgata is a genetically distinct lineage and the close phylogenetic relationship between this species and P. depressa, found in previous mitochondrial DNA studies, is not supported. The Mediterranean Sea and the Macaronesian Islands seem to have played an important role in the speciation and diversification of this genus, although different clades show different phylogeographic patterns. Our dataset point to the necessity of a taxonomic revision, as P. candei is paraphyletic relative to P. lugubris.     

Partitioned Bayesian analyses, partition choice, and the phylogenetic relationships of scincid lizards

Partitioned Bayesian analyses of approximately 2.2 kb of nucleotide sequence data (mtDNA) were used to elucidate phylogenetic relationships among 30 scincid lizard genera. Few partitioned Bayesian analyses exist in the literature, resulting in a lack of methods to determine the appropriate number of and identity of partitions. Thus, a criterion, based on the Bayes factor, for selecting among competing partitioning strategies is proposed and tested. Improvements in both mean -lnL and estimated posterior probabilities were observed when specific models and parameter estimates were assumed for partitions of the total data set. This result is expected given that the 95% credible intervals of model parameter estimates for numerous partitions do not overlap and it reveals that different data partitions may evolve quite differently. We further demonstrate that how one partitions the data (by gene, codon position, etc.) is shown to be a greater concern than simply the overall number of partitions. Using the criterion of the 2 ln Bayes factor > 10, the phylogenetic analysis employing the largest number of partitions was decisively better than all other strategies. Strategies that partitioned the ND1 gene by codon position performed better than other partition strategies, regardless of the overall number of partitions. Scincidae, Acontinae, Lygosominae, east Asian and North American "Eumeces" + Neoseps; North African Eumeces, Scincus, and Scincopus, and a large group primarily from sub-Saharan Africa, Madagascar, and neighboring islands are monophyletic. Feylinia, a limbless group of previously uncertain relationships, is nested within a "scincine" clade from sub-Saharan Africa. We reject the hypothesis that the nearly limbless dibamids are derived from within the Scincidae, but cannot reject the hypothesis that they represent the sister taxon to skinks. Amphiglossus, Chalcides, the acontines Acontias and Typhlosaurus, and Scincinae are paraphyletic. The globally widespread "Eumeces" is polyphyletic and we make necessary taxonomic changes.     

Comparison of the fatty-acid compositions of prey items and yolks of Australian insectivorous scincid lizards

The yolk fatty-acid profiles of a range of species of insectivorous scincid lizards generally conform to a common pattern, typified by high proportions of linoleic acid (13.5–18.5% of total fatty acids), substantial proportions of -linolenic acid (2.4–8.2%), and significant amounts of the long-chain polyunsaturated fatty acids, arachidonic (1.6–3.3%), eicosapentaenoic (0.7–1.2%) and docosahexaenoic (0.7–1.6%) acids. We characterised the fatty-acid compositions of ten prey taxa that are eaten by female skinks during vitellogenesis. Linoleic acid is the major polyunsaturated fatty acid in all prey, excepting Orthoptera where -linolenic acid predominates. To varying extents, -linolenic acid is present in all the prey items. Arachidonic acid forms over 1% of total fatty acids for six of the prey items. Four of the prey items contain eicosapentaenoic acid at over 1%. Most notably, docosahexaenoic acid is essentially absent from all the prey items. There is a general similarity between the fatty-acid profiles of prey and yolk, suggesting that the linoleic, -linolenic, arachidonic and eicosapentaenoic acids required for egg formation can be supplied directly from the maternal diet. However, the docosahexaenoic acid of the egg lipids cannot derive from the diet and must, therefore, be formed by biosynthesis in the maternal liver, using dietary -linolenic and eicosapentaenoic acids as precursors.     

Systematics and biogeography of the Neotropical genus Mabuya,with special emphasis on the Amazonian skink Mabuya nigropunctata (Reptilia,Scincidae)

Phylogenetic analyses using up to 1532 base pairs (bp) of mitochondrial DNA from 106 specimens of Neotropical Mabuya, including 18 of the 19 recognized South American and Mesoamerican species, indicate that most species of the genus are monophyletic, including M. nigropunctata that had previously been reported to be paraphyletic. The present results shows that this species includes three highly divergent and largely allopatric lineages restricted to occidental, meridional, and oriental Amazonia. Our dataset demonstrates that previous claims regarding the paraphyletic status of M. nigropunctata and the phylogenetic relationships within this species complex based on the analysis of three mitochondrial and four nuclear genes (approx. 5000 bp) were erroneous and resulted from two contaminated cytochrome b sequences.The phylogenetic results indicate that diversification in the Neotropical genus Mabuya started approximately in the Middle Miocene (15.5–13.4 Ma). The divergence dates estimated for the Mabuya nigropunctata species complex suggest that the major cladogenetic events that produced the three main groups (occidental (oriental + meridional)) occurred during the Late Miocene. These estimations show that diversification within the M. nigropunctata species complex was not triggered by the climatic changes that occurred during the Pleistocene, as has been suggested by several authors. Rather, our data support the hypothesis that the late tertiary (essentially Miocene epoch) was a period that played a very important role in the generation of biological diversity in the Amazonian forests.Speciation between Mabuya carvalhoi, endemic to the coastal mountain range of Venezuela, and M. croizati, restricted to the Guiana Shield, occurred during the Middle Miocene and may have been as the result of a vicariant event produced by the formation of the present day Orinoco river drainage basin and the consequent appearance of the Llanos del Orinoco, which acted as a barrier to dispersal between these two species. The split between M. bistriata and M. altamazonica and between the occidental and (meridional + oriental) clades of M. nigropunctata fits very well with the biogeographic split between the eastern and western Amazon basins reported for several other taxa.     

Specializations of the chorioallantoic placenta in the Brazilian scincid lizard,Mabuya heathi: a new placental morphotype for reptiles

New World skinks of the genus Mabuya exhibit a unique form of viviparity that involves ovulation of tiny (1 mm) eggs and provision of virtually all of the nutrients for embryonic development by placental means. Studies of the Brazilian species M. heathi reveal that the chorioallantoic placenta is unlike those reported in any other squamate genus and exhibits striking specializations for maternal-fetal nutrient transfer. The uterine lining is intimately apposed to the chorioallantois, with no trace of an intervening shell membrane or of epithelial erosion; thus, the placenta is epitheliochorial. The uterus exhibits multicellular glands that secrete organic material into the uterine lumen. Opposite the openings of these glands, the chorion develops areolae, invaginated pits that are lined by absorptive, columnar epithelium. A single, mesometrial placentome develops, formed by radially oriented uterine folds that project into a deep invagination of the chorion. Uterine epithelium of the placentome appears to be syncytial and secretory and overlies a rich vascular supply. The apposed chorionic epithelium is absorptive in morphology and contains giant binucleated cells that bear microvilli. Several specializations of the placental membranes of M. heathi are found among eutherian mammals, signifying evolutionary convergence that extends to histological and cytological levels. The chorioallantoic placenta of M. heathi and its relatives warrants recognition as a new morphotype for reptiles, defined here as the "Type IV" placenta. This is the first new type of chorioallantoic placenta to be defined formally for reptiles in over half a century.     

Plausibility of inferred ancestral phenotypes and the evaluation of alternative models of limb evolution in scincid lizards

Phylogenetic approaches to inferring ancestral character states are becoming increasingly sophisticated; however, the potential remains for available methods to yield strongly supported but inaccurate ancestral state estimates. The consistency of ancestral states inferred for two or more characters affords a useful criterion for evaluating ancestral trait reconstructions. Ancestral state estimates for multiple characters that entail plausible phenotypes when considered together may reasonably be assumed to be reliable. However, the accuracy of inferred ancestral states for one or more characters may be questionable where combined reconstructions imply implausible phenotypes for a proportion of internal nodes. This criterion for assessing reconstructed ancestral states is applied here in evaluating inferences of ancestral limb morphology in the scincid lizard clade Lerista. Ancestral numbers of digits for the manus and pes inferred assuming the models that best fit the data entail ancestral digit configurations for many nodes that differ fundamentally from configurations observed among known species. However, when an alternative model is assumed for the pes, inferred ancestral digit configurations are invariably represented among observed phenotypes. This indicates that a suboptimal model for the pes (and not the model providing the best fit to the data) yields accurate ancestral state estimates.     

Body size evolution simultaneously creates and collapses species boundaries in a clade of scincid lizards

Speciation is generally viewed as an irreversible process, although habitat alterations can erase reproductive barriers if divergence between ecologically differentiated species is recent. Reversed speciation might also occur if geographical contact is established between species that have evolved the same reproductive isolating barrier in parallel. Here, we demonstrate a loss of intrinsic reproductive isolation in a clade of scincid lizards as a result of parallel body size evolution, which has allowed for gene flow where large-bodied lineages are in secondary contact. An mtDNA phylogeny confirms the monophyly of the Plestiodon skiltonianus species complex, but rejects that of two size-differentiated ecomorphs. Mate compatibility experiments show that the high degree of body size divergence imposes a strong reproductive barrier between the two morphs; however, the strength of the barrier is greatly diminished between parallel-evolved forms. Since two large-bodied lineages are in geographical contact in the Sierra Nevada Mountains of California, we were also able to test for postzygotic isolation under natural conditions. Analyses of amplified fragment length polymorphisms show that extensive gene exchange is occurring across the contact zone, resulting in an overall pattern consistent with isolation by distance. These results provide evidence of reversed speciation between clades that diverged from a common ancestor more than 12Myr ago.     

Species delimitation and phylogeography of the Abies chensiensis complex inferred from morphological and molecular data

Species delimitation in the Abies chensiensis complex, consisting of A. chensiensis, A. recurvata, A. ernestii and A. ernestii var. salouenensis, has been the subject of a long‐term dispute, as various taxonomic combinations have been proposed. We combined different lines of evidence, including morphological characters and mitochondrial and plastid DNA sequence data, to assess species delimitation. Plastid DNA sequence variation was highly consistent with the morphological result and separated A. recurvata from the other three taxa, but the mitochondrial DNA genealogy was more strongly related to geographical distribution rather than species delimitation, as proposed in previous studies. On the basis of morphological characters and plastid DNA sequence variation, the current species status of A. recurvata was well supported, and we also accepted A. ernestii and A. ernestii var. salouenensis as varieties of A. chensiensis. Furthermore, the phylogeographical history of A. chensiensis was surveyed by molecular data and ecological niche modelling. On the basis of molecular data, the current phylogeographical pattern of the A. chensiensis complex was probably shaped by recent rapid expansions from multiple refugia in the Hengduan Mountains and habitat contraction after the last glaciation. This hypothesis was supported by the results of ecological niche modelling and previous fossil records. Our findings suggest that these fir taxa might have continued to expand their range after the largest glaciation until the end of the last glaciation, but have contracted since then with the increasing temperature and habitat changes. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 175–188.