Suchergebnisse

In the Midlands and on the east coast of Tasmania, the eastern barred
bandicoot, Perameles gunnii, is restricted to a small
number of isolated populations around townships. Comparable sites with similar
habitat, rainfall, geology, soil type and topography were observed not to
support P. gunnii. We examined four such paired sites
around Tasmania, one site in each pair supporting
P. gunnii, the other without
P. gunnii. Using orthophotos and aerial photographs
(scale 1: 5000), various features of the habitat were quantified for all site
pairs, which were then compared. In the Midlands and north-west, sites with
P. gunnii had significantly greater areas of ground
cover, suitable as nests for P. gunnii and as refuges
from predators, than did areas without P. gunnii. This
association was not observed for the paired sites on the east coast. It is
hypothesised that the remnant populations of P. gunnii
found in the Midlands reflect the availability of pockets of suitable habitat,
in particular the presence of significant ground cover for nesting sites and
refugia. This has implications for management of
P. gunnii in cleared agricultural land, where weed
species may provide the principal cover for bandicoots.

The exact timing, route, and process of the initial peopling of the Americas remains uncertain despite much research. Archaeological evidence indicates the presence of humans as far as southern Chile by 14.6 thousand years ago (ka), shortly after the Pleistocene ice sheets blocking access from eastern Beringia began to retreat. Genetic estimates of the timing and route of entry have been constrained by the lack of suitable calibration points and low genetic diversity of Native Americans. We sequenced 92 whole mitochondrial genomes from pre-Columbian South American skeletons dating from 8.6 to 0.5 ka, allowing a detailed, temporally calibrated reconstruction of the peopling of the Americas in a Bayesian coalescent analysis. The data suggest that a small population entered the Americas via a coastal route around 16.0 ka, following previous isolation in eastern Beringia for ~2.4 to 9 thousand years after separation from eastern Siberian populations. Following a rapid movement throughout the Americas, limited gene flow in South America resulted in a marked phylogeographic structure of populations, which persisted through time. All of the ancient mitochondrial lineages detected in this study were absent from modern data sets, suggesting a high extinction rate. To investigate this further, we applied a novel principal components multiple logistic regression test to Bayesian serial coalescent simulations. The analysis supported a scenario in which European colonization caused a substantial loss of pre-Columbian lineages. ; Bastien Llamas, Lars Fehren-Schmitz, Guido Valverde, Julien Soubrier, Swapan Mallick, Nadin Rohland, Susanne Nordenfelt, Cristina Valdiosera, Stephen M. Richards, Adam Rohrlach, Maria Inés Barreto Romero, Isabel Flores Espinoza, Elsa Tomasto Cagigao, Lucía Watson Jiménez, Krzysztof Makowski, Ilán Santiago Leboreiro Reyna, Josefina Mansilla Lory, Julio Alejandro Ballivián Torrez, Mario A. Rivera, Richard L. Burger, Maria Constanza Ceruti, Johan Reinhard, R. Spencer Wells, Gustavo Politis, Calogero M. Santoro, Vivien G. Standen, Colin Smith, David Reich, Simon Y. W. Ho, Alan Cooper and Wolfgang Haak