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Population differentiation of Southern Indian male lineages correlates with agricultural expansions predating the caste system

Sat, 31 Dec 2011 13:30:00 GMT

Title: Population differentiation of Southern Indian male lineages correlates with agricultural expansions predating the caste system Author: ArunKumar, GaneshPrasad; ... et al.; Genographic Consortium Abstract: Previous studies that pooled Indian populations from a wide variety of geographical locations, have obtained contradictory conclusions about the processes of the establishment of the Varna caste system and its genetic impact on the origins and demographic histories of Indian populations. To further investigate these questions we took advantage that both Y chromosome and caste designation are paternally inherited, and genotyped 1,680 Y chromosomes representing 12 tribal and 19 non-tribal (caste) endogamous populations from the predominantly Dravidian-speaking Tamil Nadu state in the southernmost part of India. Tribes and castes were both characterized by an overwhelming proportion of putatively Indian autochthonous Y-chromosomal haplogroups (H-M69, F-M89, R1a1-M17, L1-M27, R2-M124, and C5-M356; 81% combined) with a shared genetic heritage dating back to the late Pleistocene (10–30 Kya), suggesting that more recent Holocene migrations from western Eurasia contributed, <20% of the male lineages. We found strong evidence for genetic structure, associated primarily with the current mode of subsistence. Coalescence analysis suggested that the social stratification was established 4–6 Kya and there was little admixture during the last 3 Kya, implying a minimal genetic impact of the Varna(caste) system from the historically-documented Brahmin migrations into the area. In contrast, the overall Y-chromosomal patterns, the time depth of population diversifications and the period of differentiation were best explained by the emergence of agricultural technology in South Asia. These results highlight the utility of detailed local genetic studies within India, without prior assumptions about the importance of Varna rank status for population grouping, to obtain new insights into the relative influences of past demographic events for the population structure of the whole of modern India. Description: Christina J. Adler, Alan Cooper, Clio S.I. Der Sarkissian and Wolfgang Haak are contributors to the Genographic Consortium

Land use changes imperil South-East Asian biodiversity

Sat, 31 Dec 2011 13:30:00 GMT

Title: Land use changes imperil South-East Asian biodiversity Author: Sodhi, Navjot Singh; Posa, Mary Rose C.; Peh, Kelvin S-H.; Koh, Lian Pin; Soh, Malcolm C. K.; Lee, Tien Ming; Lee, Janice S. H.; Wanger, Thomas Cherico; Brook, Barry W.

Identification of rays through DNA barcoding: an application for ecologists

Sat, 31 Dec 2011 13:30:00 GMT

Title: Identification of rays through DNA barcoding: an application for ecologists Author: Cerutti-Pereyra, Florencia; Meekan, Mark G.; Wei, Nu-Wei V.; O'Shea, Owen; Bradshaw, Corey; Austin, Christopher M. Abstract: DNA barcoding potentially offers scientists who are not expert taxonomists a powerful tool to support the accuracy of field studies involving taxa that are diverse and difficult to identify. The taxonomy of rays has received reasonable attention in Australia, although the fauna in remote locations such as Ningaloo Reef, Western Australia is poorly studied and the identification of some species in the field is problematic. Here, we report an application of DNA-barcoding to the identification of 16 species (from 10 genera) of tropical rays as part of an ecological study. Analysis of the dataset combined across all samples grouped sequences into clearly defined operational taxonomic units, with two conspicuous exceptions: the Neotrygon kuhlii species complex and the Aetobatus species complex. In the field, the group that presented the most difficulties for identification was the spotted whiptail rays, referred to as the ‘uarnak’ complex. Two sets of problems limited the successful application of DNA barcoding: (1) the presence of cryptic species, species complexes with unresolved taxonomic status and intra-specific geographical variation, and (2) insufficient numbers of entries in online databases that have been verified taxonomically, and the presence of lodged sequences in databases with inconsistent names. Nevertheless, we demonstrate the potential of the DNA barcoding approach to confirm field identifications and to highlight species complexes where taxonomic uncertainty might confound ecological data.

Critical flow and blooms of the cyanobacterium Anabaena circinalis in the Murray River system

Fri, 31 Dec 1993 13:30:00 GMT

Title: Critical flow and blooms of the cyanobacterium Anabaena circinalis in the Murray River system Author: Burch, Michael David; Steffenson, D. A.; Bursill, D. B.; Bain, D. B,; Ganf, George G.; Brookes, Justin D.