Convergence in foraging guild structure of forest breeding bird assemblages across three continents is related to habitat structure and foraging opportunities

Comparisons of community structure across sites allow for the detection of convergent patterns and the selective forces that have produced them. In this study, we examined the foraging guild structure of birds breeding in forests on three continents - Europe, North America, and Australia, with largely phylogenetically distinct avifaunas. We examined two hypotheses: (1) the bird assemblages in the three geographically separated forested study sites should have similar foraging guild patterns to the extent to which environmental resources of these forests are similar, and (2) if bird assemblages in structurally similar forest habitats have undergone adaptive evolution, then radiation of species into guilds should have been caused by analogous selective resource gradients (factors). Bootstrapped cluster analysis (UPGMA) and bootstrapped principal coordinate analysis (BPCoA) of chord distances were employed to determine foraging guild structure for each assemblage, and to extract the significantly different factors responsible for segregation of species into guilds. Cluster analyses identified three analogous foraging guilds (ground and litter foragers, foliage gleaners, and trunk foragers) in each of the bird assemblages, supporting the first hypothesis of guild structure convergence. The BPCoA determined that two environmental factors (vertical resource allocation and spatial tree morphology gradients) were primarily responsible for segregation of species into guilds in these three geographically distant but structurally similar forests. These findings support the hypothesis that guild structures in forest bird assemblages largely reflect the similarities and differences in forest structure and the distribution and abundance of foraging resources, and result from largely adaptive evolution

Convergence in foraging guild structure of forest breeding bird assemblages across three continents is related to habitat structure and foraging opportunities

Comparisons of community structure across sites allow for the detection of convergent patterns and the selective forces that have produced them. In this study, we examined the foraging guild structure of birds breeding in forests on three continents — Europe, North America, and Australia, with largely phylogenetically distinct avifaunas. We examined two hypotheses: (1) the bird assemblages in the three geographically separated forested study sites should have similar foraging guild patterns to the extent to which environmental resources of these forests are similar, and (2) if bird assemblages in structurally similar forest habitats have undergone adaptive evolution, then radiation of species into guilds should have been caused by analogous selective resource gradients (factors). Bootstrapped cluster analysis (UPGMA) and bootstrapped principal coordinate analysis (BPCoA) of chord distances were employed to determine foraging guild structure for each assemblage, and to extract the significantly different factors responsible for segregation of species into guilds. Cluster analyses identified three analogous foraging guilds (ground and litter foragers, foliage gleaners, and trunk foragers) in each of the bird assemblages, supporting the first hypothesis of guild structure convergence. The BPCoA determined that two environmental factors (vertical resource allocation and spatial tree morphology gradients) were primarily responsible for segregation of species into guilds in these three geographically distant but structurally similar forests. These findings support the hypothesis that guild structures in forest bird assemblages largely reflect the similarities and differences in forest structure and the distribution and abundance of foraging resources, and result from largely adaptive evolution

Hybrid (18)F-FDG PET-MRI of the hand in rheumatoid arthritis: initial results

18F-fluorodeoxyglucose PET (18F-FDG PET) is highly sensitive to inflammatory changes within the synovial tissue in rheumatoid arthritis (RA). However, the highest spatial resolution for soft tissue can be achieved with MRI. Here, we report on the first true hybrid PET-MRI examination of the hand in early RA exploiting the advantages of both modalities. PET-MRI was performed with a prototype of an APD-based magneto-insensitive BrainPET detector (Siemens Healthcare, Erlangen, Germany) operated within a standard 3T MR scanner (MAGNETOM Trio, Siemens). PET images were normalized, random, attenuation and scatter-corrected, iteratively reconstructed and calibrated to yield standardized uptake values (SUV) of 18F-FDG uptake. T1-weighted TSE in coronal as well as sagittal orientation prior to and following Gadolinium administration were acquired. Increased 18F-FDG uptake was present in synovitis and tenovaginitis as identified on contrast-enhanced MRI. The tracer distribution was surrounding the metacarpophalangeal joints II and III. Maximum SUV of 3.1 was noted. In RA, true hybrid 18F-FDG PET-MRI of the hand is technically feasible and bears the potential to directly visualize inflammation

Image quality of low-dose CCTA in obese patients: impact of high-definition computed tomography and adaptive statistical iterative reconstruction

The accuracy of coronary computed tomography angiography (CCTA) in obese persons is compromised by increased image noise. We investigated CCTA image quality acquired on a high-definition 64-slice CT scanner using modern adaptive statistical iterative reconstruction (ASIR). Seventy overweight and obese patients (24 males; mean age 57 years, mean body mass index 33 kg/m(2)) were studied with clinically-indicated contrast enhanced CCTA. Thirty-five patients underwent a standard definition protocol with filtered backprojection reconstruction (SD-FBP) while 35 patients matched for gender, age, body mass index and coronary artery calcifications underwent a novel high definition protocol with ASIR (HD-ASIR). Segment by segment image quality was assessed using a four-point scale (1 = excellent, 2 = good, 3 = moderate, 4 = non-diagnostic) and revealed better scores for HD-ASIR compared to SD-FBP (1.5 ± 0.43 vs. 1.8 ± 0.48; p < 0.05). The smallest detectable vessel diameter was also improved, 1.0 ± 0.5 mm for HD-ASIR as compared to 1.4 ± 0.4 mm for SD-FBP (p < 0.001). Average vessel attenuation was higher for HD-ASIR (388.3 ± 109.6 versus 350.6 ± 90.3 Hounsfield Units, HU; p < 0.05), while image noise, signal-to-noise ratio and contrast-to noise ratio did not differ significantly between reconstruction protocols (p = NS). The estimated effective radiation doses were similar, 2.3 ± 0.1 and 2.5 ± 0.1 mSv (HD-ASIR vs. SD-ASIR respectively). Compared to a standard definition backprojection protocol (SD-FBP), a newer high definition scan protocol in combination with ASIR (HD-ASIR) incrementally improved image quality and visualization of distal coronary artery segments in overweight and obese individuals, without increasing image noise and radiation dose