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Molecular Dating (molecular + dating)
Selected AbstractsWhen Thailand was an island , the phylogeny and biogeography of mite harvestmen (Opiliones, Cyphophthalmi, Stylocellidae) in Southeast AsiaJOURNAL OF BIOGEOGRAPHY, Issue 6 2010Ronald M. Clouse Abstract Aim, To develop a comprehensive explanation for the biological diversity of Southeast Asia, especially in the Wallacea and Sundaland regions. This study focuses on a group of arachnids, mite harvestmen, which are thought to be an extremely old group of endemic animals that have been present in the region since most of its land supposedly formed part of the northern rim of the supercontinent Gondwana. Location, Eastern Himalayas, Thai-Malay Peninsula, Sumatra, Borneo, Java, Sulawesi, and New Guinea. Methods Approximately 5.6 kb of sequence data were obtained from 110 South-east Asian Cyphophthalmi specimens. Phylogenetic analyses were conducted under a variety of methods and analytical parameters, and the optimal tree was dated using calibration points derived from fossil data. Event based and paralogy-free subtree biogeographical analyses were conducted. Results, The Southeast Asian family Stylocellidae was recovered as monophyletic, arising on what is now the Thai-Malay Peninsula and diversifying into three main clades. One clade (Meghalaya, here formally placed in Stylocellidae) expanded north as far as the eastern Himalayas, a second clade entered Borneo and later expanded back across the Sundaland Peninsula to Sumatra, and a third clade expanded out of Borneo into the entire lower part of Sundaland. Molecular dating suggested that Stylocellidae separated from other Cyphophthalmi 295 Ma and began diversifying 258 Ma, and the lineage that inhabits mostly Borneo today began diversifying between 175 and 150 Ma. Main conclusions, The topology and molecular dating of our phylogenetic hypothesis suggest that Stylocellidae originated on Gondwana, arrived in Southeast Asia via the Cimmerian palaeocontinent, and subsequently diversified north, then south. Their present distribution in the Indo-Malay Archipelago is explained largely by a diversification over the Sundaland Peninsula before western Sulawesi departed and the peninsula was extensively inundated. [source] Phylogenetic Origin of Phyllolobium with a Further Implication for Diversification of Astragalus in ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2009Mingli Zhang Abstract Astragalus is a species-rich genus occurring in the western arid habitats in China and its diversification and infrageneric relationships in this region remain unclear. In the present study, based on molecular data, we aim to (i) test whether Phyllolobium (previously treated as a subgenus Pogonophace in Astragalus) should be warranted; and (ii) date the origin of Phyllolobium and probable diversification of Astragalus sensu stricto (s.s.). We sequenced five species from Phyllolobium first and collected all related sequences from the genus, Astragalus s.s and their close relatives (Oxytropis and Caragana etc.). Our phylogenetic analyses suggested that all species of Phyllolobium comprise a monophyletic sister-group to genera of the subtribe Coluteinae. Molecular dating suggested that Phyllolobium and Astragalus s.s. originated around 8 and 10 million years ago. These two estimates are highly consistent with the intense uplifts of the Qinghai-Tibetan Plateau inferred from geological evidence. In addition, one section of Pogonophace (Sect. Robusti) was estimated to originate 2.5 million years ago and this section with a tendency for dry habitats seems to be evidence of Asian intensified aridity resulting from the intense uplift of the Qinghai-Tibetan Plateau. [source] Genetic variation in Irish pygmy shrews Sorex minutus (Soricomorpha: Soricidae): implications for colonization historyBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009ALLAN D. MCDEVITT The status of the pygmy shrew (Sorex minutus L.) as a native or an introduced species in Ireland has been subject to much debate. To examine this and other aspects of the colonization history of the Irish pygmy shrew, genetic variation was determined in 247 pygmy shrews collected throughout Ireland, using mitochondrial control region sequences and five polymorphic microsatellite loci. Genetic diversity was low for both types of marker. The median-joining network for control region sequences was star-like, suggesting that the colonization of Ireland involved a small number of founders and rapid population expansion thereafter; this was supported by other statistics. Molecular dating with both mitochondrial DNA and microsatellite data is consistent with a human introduction. This would have been several thousand years ago; a recent colonization within historical times can be ruled out. This is the first detailed population genetic study of the pygmy shrew anywhere in its range. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 918,927. [source] When Thailand was an island , the phylogeny and biogeography of mite harvestmen (Opiliones, Cyphophthalmi, Stylocellidae) in Southeast AsiaJOURNAL OF BIOGEOGRAPHY, Issue 6 2010Ronald M. Clouse Abstract Aim, To develop a comprehensive explanation for the biological diversity of Southeast Asia, especially in the Wallacea and Sundaland regions. This study focuses on a group of arachnids, mite harvestmen, which are thought to be an extremely old group of endemic animals that have been present in the region since most of its land supposedly formed part of the northern rim of the supercontinent Gondwana. Location, Eastern Himalayas, Thai-Malay Peninsula, Sumatra, Borneo, Java, Sulawesi, and New Guinea. Methods Approximately 5.6 kb of sequence data were obtained from 110 South-east Asian Cyphophthalmi specimens. Phylogenetic analyses were conducted under a variety of methods and analytical parameters, and the optimal tree was dated using calibration points derived from fossil data. Event based and paralogy-free subtree biogeographical analyses were conducted. Results, The Southeast Asian family Stylocellidae was recovered as monophyletic, arising on what is now the Thai-Malay Peninsula and diversifying into three main clades. One clade (Meghalaya, here formally placed in Stylocellidae) expanded north as far as the eastern Himalayas, a second clade entered Borneo and later expanded back across the Sundaland Peninsula to Sumatra, and a third clade expanded out of Borneo into the entire lower part of Sundaland. Molecular dating suggested that Stylocellidae separated from other Cyphophthalmi 295 Ma and began diversifying 258 Ma, and the lineage that inhabits mostly Borneo today began diversifying between 175 and 150 Ma. Main conclusions, The topology and molecular dating of our phylogenetic hypothesis suggest that Stylocellidae originated on Gondwana, arrived in Southeast Asia via the Cimmerian palaeocontinent, and subsequently diversified north, then south. Their present distribution in the Indo-Malay Archipelago is explained largely by a diversification over the Sundaland Peninsula before western Sulawesi departed and the peninsula was extensively inundated. [source] Near Eastern Neolithic genetic input in a small oasis of the Egyptian Western DesertAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Martina Kujanová Abstract The Egyptian Western Desert lies on an important geographic intersection between Africa and Asia. Genetic diversity of this region has been shaped, in part, by climatic changes in the Late Pleistocene and Holocene epochs marked by oscillating humid and arid periods. We present here a whole genome analysis of mitochondrial DNA (mtDNA) and high-resolution molecular analysis of nonrecombining Y-chromosomal (NRY) gene pools of a demographically small but autochthonous population from the Egyptian Western Desert oasis el-Hayez. Notwithstanding signs of expected genetic drift, we still found clear genetic evidence of a strong Near Eastern input that can be dated into the Neolithic. This is revealed by high frequencies and high internal variability of several mtDNA lineages from haplogroup T. The whole genome sequencing strategy and molecular dating allowed us to detect the accumulation of local mtDNA diversity to 5,138 ± 3,633 YBP. Similarly, theY-chromosome gene pool reveals high frequencies of the Near Eastern J1 and the North African E1b1b1b lineages, both generally known to have expanded within North Africa during the Neolithic. These results provide another piece of evidence of the relatively young population history of North Africa. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||