Low genetic divergence obscures phylogeny among populations of Sphenodon, remnant of an ancient reptile lineage (original) (raw)
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Molecular systematics of primary reptilian lineages and the tuatara mitochondrial genome
2003
We provide phylogenetic analyses for primary Reptilia lineages including, for the first time, Sphenodon punctatus (tuatara) using data from whole mitochondrial genomes. Our analyses firmly support a sister relationship between Sphenodon and Squamata, which includes lizards and snakes. Using Sphenodon as an outgroup for select squamates, we found evidence indicating a sister relationship, among our study taxa, between Serpentes (represented by Dinodon) and Varanidae. Our analyses support monophyly of Archosauria, and a sister relationship between turtles and archosaurs. This latter relationship is congruent with a growing set of morphological and molecular analyses placing turtles within crown Diapsida and recognizing them as secondarily anapsid (lacking a skull fenestration). Inclusion of Sphenodon, as the only surviving member of Sphenodontia (with fossils from the mid-Triassic), helps to fill a sampling gap within previous analyses of reptilian phylogeny. We also report a unique configuration for the mitochondrial genome of Sphenodon, including two tRNA Lys copies and an absence of ND5, tRNA His , and tRNA Thr genes.
Molecular Phylogenetics and Evolution, 2010
Archaeolacerta bedriagae is a rock-dwelling lizard endemic to the Corso-Sardinian insular system. We investigated the phylogeography of the species by using the mitochondrial ND4 and flanking tRNAs genes from 94 specimens belonging to 19 populations. Phylogenetic, Barrier, and SAMOVA analyses revealed a highly structured pattern characterized by two levels of discontinuities in the geographical distribution of mtDNA diversity: (i) a deep phylogeographic break in Northern Corsica between Lineage A, restricted to northernmost Corsica, and Lineage B widespread all over the remaining range of the species, and (ii) some minor phylogeographic discontinuities within lineage B, which is sub-structured into six closely related haplotype clades with remarkable concordance with geography. The first evolutionary event concerning the split between the two main lineages from an ancestral population occurred in the Upper Pliocene (5.87-3.68 mya), while the divergence within lineage B would have started from the Upper Pleistocene (2.5-1.6 mya), between Corsican and Sardinian populations. Somewhat later (1.7-1.1 mya), the Sardinian ancestral population underwent fragmentation into population groups inhabiting North, Central, and South Sardinia. As inferred from previous allozyme surveys, the divergence among population groups would be driven by allopatric fragmentation, while the discrepancy concerning the major partition into two lineages inferred from mtDNA but not apparent in analysis of allozymes needs further investigation.
Molecular Phylogenetics and Evolution, 2005
The peninsula of Baja California has a complex geological history that has strongly aVected the regional biota. Genealogical histories of many species have revealed congruent patterns, which suggest that the peninsula was temporarily submerged at two locations. We sequenced a total of 1953 base pairs (bp) of the mitochondrial genome for 42 specimens of the zebra-tailed lizard (Callisaurus draconoides). The resulting maternal genealogy supports the former existence of a mid-peninsular seaway and a Plio-Quaternary seaway across the Isthmus of La Paz. In addition, a genealogical break is revealed in the vicinity of Loreto. This genealogical break may have resulted from prolonged submergence of the Loreto Basin during Pliocene. The mid-peninsular seaway may have occurred as early as late Miocene, at a time signiWcantly earlier than previously hypothesized. Comparison with other genealogies and geological evidence suggests that current models on the evolution of Baja California's fauna are temporally shallow. The deep genealogical patterns of C. draconoides also disagree with the very limited population diVerentiation previously reported for allozyme markers, suggesting that maternal history may not be an appropriate approximation for population diVerentiation.
Conservation Genetics, 2007
Tuatara (Sphenodon spp) populations are restricted to 35 offshore islands in the Hauraki Gulf, Bay of Plenty and Cook Strait of New Zealand. Low levels of genetic variation have previously been revealed by allozyme and mtDNA analyses. In this new study, we show that six polymorphic microsatellite loci display high levels of genetic variation in 14 populations across the geographic range of tuatara. These populations are characterised by disjunct allele frequency spectra with high numbers of private alleles. High F ST (0.26) values indicate marked population structure and assignment tests allocate 96% of all individuals to their source populations. These genetic data confirm that islands support genetically distinct populations. Principal component analysis and allelic sequence data supplied information about genetic relationships between populations. Low numbers of rare alleles and low allelic richness identified populations with reduced genetic diversity. Little Barrier Island has very low numbers of old tuatara which have retained some relictual diversity. North Brother Island's tuatara population is inbred with fixed alleles at 5 of the 6 loci.
Parallels between Island Lizards Suggests Selection on Mitochondrial DNA and Morphology
Proceedings of the Royal Society B: Biological Sciences, 1994
Parallels between species on historically independent islands have been shown to be a powerful means of testing lor the action of n atural selection on m orphology. M itochondrial DNA evolution is often assumed to be selectively neutral, but this is difficult to test em pirically. Here we show that parallels are present between two species of lizards on the geologically distinct but ecologically sim ilar Lesser Antillean islands of Dom inica and Basse T erre (G uadeloupe). These parallels are found not only in m orphological variation but also in m itochondrial DNA variation and these are correlated with sim ilar ecological gradients. A m orphological cline in Anolis oculatus along the C aribbean coast of Dom inica is com pared to sequence variation in the cytochrom e b gene, which shows exceptionally high variability. Patterns of sequence variation and m orphology (especially scalation) are congruent, and are significantly correlated with m oisture gradients. Anolis marmoratus on the adjacent island of Basse T erre (G uadeloupe) shows parallel patterns of m orphological and cytochrom e b variation along the C aribbean coast, and these are also significantly correlated with m oisture gradients.
2004
Squamate reptiles serve as model systems for evolutionary studies of a variety of morphological and behavioral traits, and phylogeny is crucial to many generalizations derived from such studies. Specifically, the traditional dichotomy between Iguania and Scleroglossa has been correlated with major evolutionary shifts within Squamata. We present a molecular phylogenetic study of squamates using DNA sequence data from the nuclear genes RAG-1 and c-mos and the mitochondrial ND2 region, sampling all major clades and most major subclades. Monophyly of Iguania, Anguimorpha, and almost all currently recognized squamate families is strongly supported. However, monophyly is rejected for Scleroglossa, Varanoidea, and several other higher taxa, and Iguania is highly nested within Squamata. Limblessness evolved independently in snakes, dibamids, and amphisbaenians, suggesting widespread morphological convergence or parallelism in limbless, burrowing forms. Amphisbaenians are the sister group of lacertids, and snakes are grouped with iguanians and anguimorphs. Dibamids diverged early in squamate evolutionary history. Xantusiidae is the sister taxon of Cordylidae. Studies of functional tongue morphology and feeding mode have found significant differences between Scleroglossa and Iguania, and our finding of a nonmonophyletic Scleroglossa and a highly nested Iguania suggest that similar states evolved separately in Sphenodon and Iguania, and that jaw prehension is the ancestral feeding mode in squamates. grants from the National Science Foundation (dissertation improvement grant for T. M. T.; DEB-9726064 to A. L., J. R. M., and T. J. Papenfuss). Jeff Groth generously provided aliquots of his RAG-1 primers for preliminary amplifications. We thank Jim Krenz for unpublished RAG-1 sequence for Chelonia mydas, and Jim Schulte and Jane Melville for unpublished mitochondrial sequences. We thank Aaron Bauer,
The tuatara (Sphenodon punctatus), the only living member of the archaic reptilian order Rhynchocephalia (Sphenodontia) once widespread across Gondwana, is an iconic and enigmatic terrestrial vertebrate endemic to New Zealand. A key link to the now extinct stem reptiles from which dinosaurs, modern reptiles, birds and mammals evolved, the tuatara provides exclusive insights into the ancestral amniotes. The tuatara genome, at ~5 Gbp, is among the largest vertebrate genomes assembled. Analysis of this genome and comparisons to other vertebrates reinforces the uniqueness of the tuatara. Phylogenetic analyses indicate tuatara diverged from the snakes and lizards ~250 MYA. This lineage also shows moderate rates of molecular evolution, with instances of punctuated evolution. Genome sequence analysis identifies expansions of protein, non-protein-coding RNA families, and repeat elements, the latter of which show an extraordinary amalgam of reptilian and mammalian features. Sequencing of thi...