Ecological speciation in South Atlantic island finches

Examples of sympatric speciation in nature are rare and hotly debated. We describe the parallel speciation of finches on two small islands in the Tristan da Cunha archipelago in the South Atlantic Ocean. Nesospiza buntings are a classic example of a simple adaptive radiation, with two species on each island: an abundant small-billed dietary generalist and a scarce large-billed specialist. Their morphological diversity closely matches the available spectrum of seed sizes, and genetic evidence suggests that they evolved independently on each island. Speciation is complete on the smaller island, where there is a single habitat with strongly bimodal seed size abundance, but is incomplete on the larger island, where a greater diversity of habitats has resulted in three lineages. Our study suggests that the buntings have undergone parallel ecological speciation.     

The abundance of a threatened arboreal marsupial in relation to anthropogenic disturbances at local and landscape scales in Mediterranean-type forests in south-western Australia

This study investigated associations between the relative abundance of the threatened ngwayir (western ringtail possum, Pseudocheirus occidentalis) and anthropogenic disturbances at local and landscape scales within the publicly-managed jarrah (Eucalyptus marginata) forests of south-western Australia. Logging, fire, fox (Vulpes vulpes) control and forest fragmentation were investigated in relation to the relative abundance of ngwayir at 90 sites within an area of 285,000 ha east of Manjimup; the location of the last remaining substantial population of ngwayir in jarrah forest. Overall, ngwayir abundance was greatest in areas with limited anthropogenic disturbance. At the local-scale, ngwayir abundance was negatively associated with greater fire intensity. At the landscape-scale, it was positively associated with fox control and negatively associated with forest fragmentation and distance from non-remnant vegetation (i.e., agriculture and tree plantations). Abundance was also greatest in predominantly unlogged landscapes and in forests that had been regrowing for an average of 40 years since the landscape was most recently logged, in other words, where logging was historically least intense. Interactions between fox control efforts and forest fragmentation were also important. This study emphasises the importance of conducting research at appropriate spatial scales and to account for the synergistic effects of the causes of decline. An adaptive management approach to the mitigation of the agents of decline is recommended.Indirect evidence indicates that high value habitat for ngwayir has in all likelihood been selectively cleared for agriculture, owing to its fertile and productive nature. Habitat loss is, therefore, also likely to be a major cause of the modern decline of the species. While many jarrah forest areas that support remaining high abundances of the ngwayir have been incorporated into reserves, conservation of ngwayir habitat and populations outside reserves also will be essential for the recovery and long-term viability of the species.     

Degradation of selected polycyclic aromatic hydrocarbons in coastal sediments: Importance of microbes and polychaete worms

Rates of degradation of polycyclic aromatic hydrocarbons (PAH) were examined after addition of crude oil enriched with anthracene, fluoranthene, benz(a)anthracene, and benzo(a)pyrene to coastal sediments in a laboratory (20°) flowing seawater system. Three types of sediment (fine sand, medium sand, and marsh sediment) with and without the benthic polychaete worm, Capitella capitata, were used. After extraction from the sediment, PAH concentrations were measured by liquid chromatography with fluorescent detection. Microbial degradation was studied by incubating sediments with radioactive PAH and measuring subsequent production of ¹⁴C0₂. Concentrations of the four PAH decreased significantly with time in fine and medium sized sands. PAH levels also decreased in marsh sediment but trends were not significant (P < 0.05). C. capitata stimulated PAH degradation. Microbial degradation was more rapid in upper surfaces than in lower layers of the sediments.     

Incorporating LASSO effects into a mixed model for quantitative trait loci detection

The identification of quantitative trait loci (QTL) can be viewed as a subset selection problem. In a simulation study the least absolute selection and shrinkage operator (LASSO) is shown to be a useful and powerful tool for QTL identification. LASSO effects are embedded into a mixed model allowing simultaneous modeling of genetic and experimental effects. This provides the flexibility to model the experiment in conjunction with the power of LASSO QTL identification. Estimation is performed using an approximation to the restricted likelihood and modified Gaussian elimination. The extended mixed model is used to analyze a cattle gene mapping dataset.     

Comparison of a central and a peripheral (cephalic vein) injection site for the measurement of cardiac output using the lithium-dilution cardiac output technique in anesthetized dogs

The objective of this study was to determine the agreement between cardiac output measured by central (cranial vena cava) versus peripheral (cephalic vein) venous injection of lithium chloride for lithium-dilution cardiac output (LiDCO) determination in the dog. Five dogs (2 males, 3 females), anesthetized with halothane, were used. With each dog, 12 alternating central and peripheral LiDCO measurements were made, resulting in 10 paired comparisons. A total of 50 comparisons were obtained, the cardiac output measurements ranging from 1.11 to 2.76 L/min. The LiDCO measurement from the cephalic vein was similar to that obtained from the recommended central venous site: the difference between the central and cephalic vein determinations for all measurements was 0.098 ± 0.336 L/min (mean ± 2 standard deviations). Linear regression analysis demonstrated a slope of 1.050 (95% confidence interval 0.904 to 1.196) and a y intercept of 0.005 (r = 0.902). Therefore, although the central venous site is recommended by the manufacturer, the cephalic vein can be used instead in the dog, eliminating the need for central venous catheterization and thus reducing time and expense.     

Disease,production and culling in Holstein-Friesian cows II. Age,season and sire effects

Effects of age, season and sire on the occurrence of common diseases of Holstein-Friesian cows were evaluated in a two and a half year study. The data were from 2875 lactation records from 2008 cows in 32 commercial dairy herds within a 50 mile radius of Guelph, Ontario.Age patterns for all disease conditions were determined using χ² or quadratic regression analyses. Linear increases with age were observed for milk fever, mastitis requiring local therapy only, cystic ovaries and foot and leg problems. Quadratic relationships with age were observed for ketosis (clinical and subclinical), mastitis requiring systemic therapy, subclinical mastitis, dystocia, respiratory diseases and traumatic reticulo-peritonitis. No consistent age patterns were found for retained placentas, reproductive tract infections, abomasal displacements, teat injuries, digestive disorders and abortions.Seasonal patterns were evaluated using a formal statistical test for the seasonality of events. Significant peaks were found in the risk of ketosis and cystic ovaries during the winter, and in the risk of teat injuries in the late winter or early spring. Seasonal patterns, more complex than a simple unimodal pattern, were observed for mastitis requiring local therapy only, traumatic reticulo-peritonitis and abortions.Heritabilities were determined for 9 disease conditions. All heritabilities were low or 0 with the exception of clinical ketosis (h² = 0.31).