Range-wide mtDNA phylogeography yields insights into the origins of Asian elephants

Recent phylogeographic studies of the endangered Asian elephant (Elephas maximus) reveal two highly divergent mitochondrial DNA (mtDNA) lineages, an elucidation of which is central to understanding the species's evolution. Previous explanations for the divergent clades include introgression of mtDNA haplotypes between ancestral species, allopatric divergence of the clades between Sri Lanka or the Sunda region and the mainland, historical trade of elephants, and retention of divergent lineages due to large population sizes. However, these studies lacked data from India and Myanmar, which host approximately 70 per cent of all extant Asian elephants. In this paper, we analyse mtDNA sequence data from 534 Asian elephants across the species's range to explain the current distribution of the two divergent clades. Based on phylogenetic reconstructions, estimates of times of origin of clades, probable ancestral areas of origin inferred from dispersal–vicariance analyses and the available fossil record, we believe both clades originated from Elephas hysudricus. This probably occurred allopatrically in different glacial refugia, the α clade in the Myanmar region and the β clade possibly in southern India–Sri Lanka, 1.6–2.1 Myr ago. Results from nested clade and dispersal–vicariance analyses indicate a subsequent isolation and independent diversification of the β clade in both Sri Lanka and the Sunda region, followed by northward expansion of the clade. We also find more recent population expansions in both clades based on mismatch distributions. We therefore suggest a contraction–expansion scenario during severe climatic oscillations of the Quaternary, with range expansions from different refugia during warmer interglacials leading to the varying geographical overlaps of the two mtDNA clades. We also demonstrate that trade in Asian elephants has not substantially altered the species's mtDNA population genetic structure

Geochemistry of Sandstones from the Upper Cretaceous Sillakkudi Formation, Cauvery Basin, Southern India: Implication for Provenance

Major, trace and rare earth elements (REE) composition of sandstones from the Upper Cretaceous Sillakkudi Formation, Ariyalur Group, Cauvery Basin were studied to decipher their weathering and provenance history. Texturally, these sandstones are immature, poorly sorted and grain supported. Abundance of feldspars especially, plagioclase indicates rapid deposition of sediments from a nearby source rocks. Using the geochemical classification diagram the Sillakkudi sandstones are classified as fe-sand, quartz arenite, litharenite, sub-litharenite, sub-arkose, arkose, and wacke types,which is also supported by the petrography study. The transition trace elements like Co, Ni, and V are higher in theSillakkudi sandstones than upper continental crust (UCC) values. However, the Sillakkudi sandstones are lower in Cr (mean ~21) content than average UCC value (~ 35). The poor correlation between Cr and Ni (r = 0.08, number of samples n = 20) imply that these sandstones were derived from felsic source rocks. Similarly, the Eu/Eu* (0.35-1.73), La/Sc (1.93-9.36), Th/Sc (0.41-6.57), Th/Co (0.14-5.01), Th/Cr (0.23-2.94), and Cr/Th (0.34-4.28) ratios support a felsic source for the Sillakkudi sandstones.The significant enrichment of Zr, Hf, and Th in fe-sand, sub-arkose and litharenite could be related to the presence of heavy minerals, especially zircon. However, the zircon geochemistry did not affectthe REE distribution and its patterns in the Sillakkudi sandstones. The Chondrite normalized REE patterns of Sillakkudi sandstones are characterized by relatively flat HREE (Gd/YbCN = ~ 0.73-2.41; subscript CN refers to chondrite normalized value), enriched LREE (La/SmCN = ~ 3.39-5.82) and negative Eu anomaly (mean value Eu/Eu* = 0.80). The Gd/YbCN ratios (~0.73-2.50) are less than 2.5, which suggest that these Sillakkudi sandstones were derived from the less HREE depleted source rocks. The comparison of REE patterns and its Eu anomalies to the source rocks reveals that the Sillakkudi sandstones received a major contribution of sediments from Dharwar craton