Comparative phylogeography allow us to understand how shared historical circumstances have shaped the formation of lineages, by examining a broad spectrum of co-distributed populations of different taxa. However, these types of studies are scarce in the Neotropics, a region that is characterized by high diversity, complex geology, and poorly understood biogeography. Here, we investigate the div...

We present phylogenetic analyses of the lizard genus Ctenophorus using 1,639 aligned positions of mitochondrial DNA sequences containing 799 parsimony-informative characters for samples of 22 species of Ctenophorus and 12 additional Australian agamid genera. Sequences from three protein-coding genes (ND1, ND2, and COI) and eight intervening tRNA genes are examined using both parsimony and maxim...

Although substantial uncertainty typically surrounds the choice of the best model in most phylogenetic analyses, little is known about how accommodating this uncertainty affects phylogenetic inference. Here we explore the influence of Bayesian model averaging on the phylogenetic inference of the triggerfishes (Family: Balistidae), a charismatic group of reef fishes. We focus on clade support as...

fractionation studies on the sediment samples provide valuable information on the nature of the metals bound to the sediments. thirty three sediment samples of river adyar were collected during two seasons and speciation study was carried out. the industrial and domestic effluents are directed into the river course at many points in the middle and lower of the adyar river. to ascertain the exte...

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and...

Eldredge and Gould (1972)advanced an exciting hypothesis to account for the evolutionary diversification of life. They propose that the great majority of organismal divergence accompanies the splitting of lineages (cladogenesis), and that new species once formed represent well-buffered homeostatic systems, resistant to within-lineage change (anagenesis) until the next round of splitting occurs....

Lizards and snakes putatively arose between the early Jurassic and late Triassic; they diversified worldwide and now occupy many different ecological niches, making them ideal for testing theories on the origin of ecological traits. We propose and test the "deep history hypothesis," which claims that differences in ecological traits among species arose early in evolutionary history of major cla...

Intercontinental distributions in the southern hemisphere can either be the result of Gondwanan vicariance or more recent transoceanic dispersal. Transoceanic dispersal has come into vogue for explaining many intercontinental distributions; however, it has been used mainly for organisms that can float or raft between the continents. Despite their name, the Sea Catfishes (Ariidae) have limited d...

The Dobzhansky–Muller model posits that incompatibilities between alleles at different loci cause speciation. However, it is known that if the alleles involved in a Dobzhansky–Muller incompatibility (DMI) between two loci are neutral, the resulting reproductive isolation cannot be maintained in the presence of either mutation or gene flow. Here we show that speciation can emerge through the col...

The biogeography of speciation remains a controversial issue and the process of allopatric speciation reigns. Sympatric speciation differs from allopatric speciation in terms of geographic setting and the role of selection in bringing about reproductive isolating mechanisms, making it a particularly fascinating and controversial subject for evolutionary biologists. Mayr (1947) explained the dif...