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Studies of woodland caribou (Rangifer tarandus caribou) in the Birch Mountains of northeastern Alberta were conducted from January 1976 through June 1978. Twenty-nine caribou were radio collared and repeatedly located from fixed wing aircraft. Eight capture-related deaths were associated with increased stress (hazing and handling time) and slow or incomplete absorption of the immobilizing drug. Young bulls (1.0 to 3.0 years old) and adult, cows (>3.0 years old) were sometimes indistinguishable from the air due to similar body size and antler morphology. Time of antler drop among bulls was related to age. A population survey combining fixed-wing transect flights and helicopter tracking over 1400 km2 yielded a late-winter density of 1 caribou/24km2. Radio-tracking data indicated that adult bulls concentrated in this area in winter; adjusted resident density was 1/33 km2. The total caribou population on the 25 000 km2 Alberta Oil Sands Environmental Research Program study area was estimated at 433. Bulls comprised 42% of animals older than calves. Calves made up 12% of the total fall and winter population. Yearlings comprised 14% of captured caribou, but individuals born from 1972 to 1974 comprised only 15%. This apparently reflected low survival of animals born following winters of deep snow and high food-short lynx (Lynx canadensis) populations. Calving occurred from 7 May to 3 June. The pregnancy rate of adult cows (>3.0 years) was 88%. Calf survival was 42% in the first 2 months of life and 17% annually. Annual survival of radio collared adults averaged 85%. At least two of four radio collared adults which died were killed by wolves (Canis lupus). The calculated finite rate of population growth (A = 0.85) indicated a declining population in years with normal snowfall. Radio collared adult bulls remained solitary in summer, as did cows with calves. Both adult bulls and cows formed mixed groups during the rut in September. Groups of adult bulls remained separated from mixed groups of cows and young bulls in winter. Caribou group sizes were smallest in summer (mean: 1.2) and largest in late fall after the rut (mean: 5.4). Continuous associations of radio collared caribou were longest in late winter. Seasonal ranges and movement patterns varied greatly between individuals, but seemed traditional among adult bulls. The latter made long-distance movements (>11 km) up to five times per year to distinct seasonal ranges. Most cows moved two and sometimes three times per year. The time of such movements by either sex was similar in all years. Seasonal range sizes were similar for bulls and cows, though individual cows were much more sedentary and their seasonal ranges overlapped much more. More annual range size of adult bulls was 1196 km2 and that of cows was 539 km2. Seasonal changes in relative use of habitat types seemed related to availability of food resources, snow depths, and social behaviour. Most locations (69%) were in lowland cover, predominantly black spruce (Picea mariana) muskegs. Caribou used upland deciduous cover types very little in any season. The great variability in winter habitat use reflected habitat availability within individual winter ranges.

Population studies of wolves (Canis lupus) were carried out between October 1975 and June 1978 on two study areas in northern Alberta. Ten adult wolves in four packs and two lone wolves were captured, radio collared and repeatedly located in the Alberta Oil Sands Environmental Research Program (AOSERP) study area; three wolves in two packs were radio collared on the other area (Swan Hills). Telemetry data, observations of unmarked wolves, and trapper surveys indicated a winter wolf density of approximately 1/179 km2, or 140 on the entire 25 000 km2 AOSERP study area. Wolf density between areas varied with available food resources. Numbers appeared to have increased from 1975 to 1977 at a rate of about 21% annually. The wolf density of 1/77 km2 on the Swan Hills study area appeared to be lower than in past years, and the population was probably expanding. Trapping and early pup deaths were likely the major mortality factors. Wolves killed or consumed disproportionately more young, old, and probably debilitated moose (Alces alces), as well as more female calves and adult bulls. Most wolf kills in winter (88%) were made in lowland habitats despite an even distribution of moose in uplands and lowlands. Deeper snow and colder temperatures in 1978 resulted in decreased daily travel (5.7 vs. 9.0 km/day) by one pack whose activities were intensively monitored on the AOSERP study area. The mean kill rate of this pack was the same in both years (1 moose/4.7days); per capita consumption decreased slightly in 1978 (0.12 vs. 0.15 kg prey/kg wolf/day) due to larger mean pack size (9.8 vs. 9.2). The geographic distribution of wolf relocations and wolf kills shifted in 1978 to an area where moose numbers had also increased. An equation was derived for calculating true kill rates when relocation flights were spaced more than one day apart. Summer food habits of wolves, as determined by analysis of 1723 scats (2095 items) collected on cutlines, at densities, and at rendezvous sites indicated that adult moose remained the staple food in all areas. Utilization of beaver (Castor canadensis) was highest where beaver densities were highest. Wolves annually consumed about 11 to 12% of adult moose in the Muskeg River drainage (AOSERP study area); this was 70% of .annual recruitment of calves to the moose population. Wolves captured at dump sites associated with oil development were in poorer physical condition than those captured in undisturbed areas. Two lone wolves and two of the packs on the AOSERP study area were partially dependent on dumps for food during winter; predation rates by these packs were much lower. Wolf densities near disturbed sites were higher than on surrounding areas.

The purpose of this study was to prospectively determine the immunogenicity of nonvalved allograft tissue used to repair congenital heart defects.We prospectively analyzed the immune response of 11 children, 1.4 months to 10 years of age, who required nonvalved allografts to alleviate stenosis during repair of congenital heart defects. In 7 patients, pulmonary arterial grafts were used; in 3 patients, monocusp pulmonary artery grafts were used; and in 1 patient, a section of glutaraldehyde-preserved allograft pericardium was used. We measured the level of HLA panel-reactive antibody (PRA) before surgery, 1 week after, 1 month after, and 3 months after surgery. PRA was determined by the antiglobulin technique and flow cytometry. HLA class I and class II antibodies measured by either technique were negligible before and 1 week after surgery. Nine of 11 patients (82%) exhibited a significant immune response at 1 month after surgery that further increased at 3 months. The measured PRA for class I antibodies with the antiglobulin technique increased to 43+/-36% at 1 month and to 69+/-38% at 3 months after surgery. Flow cytometry class I PRA measurements were similar. Class II PRA increased to 26+/-34% at 1 month and to 41+/-36% at 3 months. Age negatively correlated with the degree of elevation of PRA, but neither allograft area nor the area indexed to patient body surface area correlated with PRA.Cryopreserved nonvalved allografts induce a strong HLA antibody response in the majority of children.

How and when the Americas were populated remains contentious. Using ancient and modern genome wide data we found that the ancestors of all present day Native Americans including Athabascans and Amerindians entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (ka) and after no more than an 8000 year isolation period in Beringia. After their arrival to the Americas ancestral Native Americans diversified into two basal genetic branches around 13 ka one that is now dispersed across North and South America and the other restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present day East Asians (including Siberians) and more distantly Australo Melanesians. Putative “Paleoamerican” relict populations including the historical Mexican Pericúes and South American Fuego Patagonians are not directly related to modern Australo Melanesians as suggested by the Paleoamerican Model. INTRODUCTION The consensus view on the peopling of the Americas is that ancestors of modern Native Americans entered the Americas from Siberia via the Bering Land Bridge and that this occurred at least {\textasciitilde}14.6 thousand years ago (ka). However the number and timing of migrations into the Americas remain controversial with conflicting interpretations based on anatomical and genetic evidence. RATIONALE In this study we address four major unresolved issues regarding the Pleistocene and recent population history of Native Americans: (i) the timing of their divergence from their ancestral group (ii) the number of migrations into the Americas (iii) whether there was {\textasciitilde}15000 years of isolation of ancestral Native Americans in Beringia (Beringian Incubation Model) and (iv) whether there was post Pleistocene survival of relict populations in the Americas related to Australo Melanesians as suggested by apparent differences in cranial morphologies between some early (“Paleoamerican”) remains and those of more recent Native Americans. We generated 31 high coverage modern genomes from the Americas Siberia and Oceania; 23 ancient genomic sequences from the Americas dating between {\textasciitilde}0.2 and 6 ka; and SNP chip genotype data from 79 present day individuals belonging to 28 populations from the Americas and Siberia. The above data sets were analyzed together with published modern and ancient genomic data from worldwide populations after masking some present day Native Americans for recent European admixture. RESULTS Using three different methods we determined the divergence time for all Native Americans (Athabascans and Amerindians) from their Siberian ancestors to be {\textasciitilde}20 ka and no earlier than {\textasciitilde}23 ka. Furthermore we dated the divergence between Athabascans (northern Native American branch together with northern North American Amerindians) and southern North Americans and South and Central Americans (southern Native American branch) to be {\textasciitilde}13 ka. Similar divergence times from East Asian populations and a divergence time between the two branches that is close in age to the earliest well established archaeological sites in the Americas suggest that the split between the branches occurred within the Americas. We additionally found that several sequenced Holocene individuals from the Americas are related to present day populations from the same geographical regions implying genetic continuity of ancient and modern populations in some parts of the Americas over at least the past 8500 years. Moreover our results suggest that there has been gene flow between some Native Americans from both North and South America and groups related to East Asians and Australo Melanesians the latter possibly through an East Asian route that might have included ancestors of modern Aleutian Islanders. Last using both genomic and morphometric analyses we found that historical Native American groups such as the Pericúes and Fuego Patagonians were not “relicts” of Paleoamericans and hence our results do not support an early migration of populations directly related to Australo Melanesians into the Americas. CONCLUSION Our results provide an upper bound of {\textasciitilde}23 ka on the initial divergence of ancestral Native Americans from their East Asian ancestors followed by a short isolation period of no more than {\textasciitilde}8000 years and subsequent entrance and spread across the Americas. The data presented are consistent with a single migration model for all Native Americans with later gene flow from sources related to East Asians and indirectly Australo Melanesians. The single wave diversified {\textasciitilde}13 ka likely within the Americas giving rise to the northern and southern branches of present day Native Americans. View larger version: In this page In a new window Download PowerPoint Slide for Teaching Population history of present day Native Americans.The ancestors of all Native Americans entered the Americas as a single migration wave from Siberia (purple) no earlier than {\textasciitilde}23 ka separate from the Inuit (green) and diversified into “northern” and “southern” Native American branches {\textasciitilde}13 ka. There is evidence of post divergence gene flow between some Native Americans and groups related to East Asians/Inuit and Australo Melanesians (yellow). Genetic history of Native Americans Several theories have been put forth as to the origin and timing of when Native American ancestors entered the Americas. To clarify this controversy Raghavan et al. examined the genomic variation among ancient and modern individuals from Asia and the Americas. There is no evidence for multiple waves of entry or recurrent gene flow with Asians in northern populations. The earliest migrations occurred no earlier than 23000 years ago from Siberian ancestors. Amerindians and Athabascans originated from a single population splitting approximately 13000 years ago. Science this issue 10.1126/science.aab3884