Wen Z.,U.S. Food and Drug Administration |
Pollock K.,Murdoch University |
Nichols J.,Patuxent Wildlife Research Center |
Waser P.,Purdue University
Biometrics | Year: 2011
Ecologists applying capture-recapture models to animal populations sometimes have access to additional information about individuals' populations of origin (e.g., information about genetics, stable isotopes, etc.). Tests that assign an individual's genotype to its most likely source population are increasingly used. Here we show how to augment a superpopulation capture-recapture model with such information. We consider a single superpopulation model without age structure, and split each entry probability into separate components due to births in situ and immigration. We show that it is possible to estimate these two probabilities separately. We first consider the case of perfect information about population of origin, where we can distinguish individuals born in situ from immigrants with certainty. Then we consider the more realistic case of imperfect information, where we use genetic or other information to assign probabilities to each individual's origin as in situ or outside the population. We use a resampling approach to impute the true population of origin from imperfect assignment information. The integration of data on population of origin with capture-recapture data allows us to determine the contributions of immigration and in situ reproduction to the growth of the population, an issue of importance to ecologists. We illustrate our new models with capture-recapture and genetic assignment data from a population of banner-tailed kangaroo ratsDipodomys spectabilisin Arizona. © 2010, The International Biometric Society.
Kirwan M.L.,University of Virginia |
Langley J.A.,Villanova University |
Guntenspergen G.R.,Patuxent Wildlife Research Center |
Megonigal J.P.,Smithsonian Environmental Research Center
Biogeosciences | Year: 2013
The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise. © 2013 Author(s).
Chandler R.B.,University of Massachusetts Amherst |
Chandler R.B.,Patuxent Wildlife Research Center |
King D.I.,U.S. Department of Agriculture |
Raudales R.,University of Massachusetts Lowell |
And 3 more authors.
Conservation Biology | Year: 2013
Two contrasting strategies have been proposed for conserving biological diversity while meeting the increasing demand for agricultural products: land sparing and land sharing production systems. Land sparing involves increasing yield to reduce the amount of land needed for agriculture, whereas land-sharing agricultural practices incorporate elements of native ecosystems into the production system itself. Although the conservation value of these systems has been extensively debated, empirical studies are lacking. We compared bird communities in shade coffee, a widely practiced land-sharing system in which shade trees are maintained within the coffee plantation, with bird communities in a novel, small-scale, land-sparing coffee-production system (integrated open canopy or IOC coffee) in which farmers obtain higher yields under little or no shade while conserving an area of forest equal to the area under cultivation. Species richness and diversity of forest-dependent birds were higher in the IOC coffee farms than in the shade coffee farms, and community composition was more similar between IOC coffee and primary forest than between shade coffee and primary forest. Our study represents the first empirical comparison of well-defined land sparing and land sharing production systems. Because IOC coffee farms can be established by allowing forest to regenerate on degraded land, widespread adoption of this system could lead to substantial increases in forest cover and carbon sequestration without compromising agricultural yield or threatening the livelihoods of traditional small farmers. However, we studied small farms (<5 ha); thus, our results may not generalize to large-scale land-sharing systems. Furthermore, rather than concluding that land sparing is generally superior to land sharing, we suggest that the optimal approach depends on the crop, local climate, and existing land-use patterns. © 2013 Society for Conservation Biology.
Hawley D.M.,Virginia Polytechnic Institute and State University |
Osnas E.E.,Princeton University |
Osnas E.E.,Patuxent Wildlife Research Center |
Dobson A.P.,Princeton University |
And 3 more authors.
PLoS Biology | Year: 2013
The evolution of higher virulence during disease emergence has been predicted by theoretical models, but empirical studies of short-term virulence evolution following pathogen emergence remain rare. Here we examine patterns of short-term virulence evolution using archived isolates of the bacterium Mycoplasma gallisepticum collected during sequential emergence events in two geographically distinct populations of the host, the North American house finch (Haemorhous [formerly Carpodacus] mexicanus). We present results from two complementary experiments, one that examines the trend in pathogen virulence in eastern North American isolates over the course of the eastern epidemic (1994-2008), and the other a parallel experiment on Pacific coast isolates of the pathogen collected after M. gallisepticum established itself in western North American house finch populations (2006-2010). Consistent with theoretical expectations regarding short-term or dynamic evolution of virulence, we show rapid increases in pathogen virulence on both coasts following the pathogen's establishment in each host population. We also find evidence for positive genetic covariation between virulence and pathogen load, a proxy for transmission potential, among isolates of M. gallisepticum. As predicted by theory, indirect selection for increased transmission likely drove the evolutionary increase in virulence in both geographic locations. Our results provide one of the first empirical examples of rapid changes in virulence following pathogen emergence, and both the detected pattern and mechanism of positive genetic covariation between virulence and pathogen load are consistent with theoretical expectations. Our study provides unique empirical insight into the dynamics of short-term virulence evolution that are likely to operate in other emerging pathogens of wildlife and humans. © 2013 Hawley et al.
News Article | February 11, 2016
Wisdom, the oldest known bird in the wild, hatches her 40th chick at Midway Atoll National Wildlife Refuge in Hawaii. The nesting colony, which is part of the Papahānaumokuākea Marine National Monument, witnessed how the formidable Laysan albatross took another shot at motherhood. Wisdom's mate was in charge of incubation duties until Jan. 20 as Wisdom search for food. The mates exchanged places on the said date, when Wisdom returned from the sea with a full belly. On Feb. 1, Wisdom's new chick started showing signs of coming out. After a few more days, the chick came out and was named Kūkini, which literally means "messenger" in Hawaii. "Wisdom is an iconic symbol of inspiration and hope," says refuge manager Robert Peyton. He adds that Wisdom is breaking records in terms of longevity, surpassing previously banded birds by at least 10 years. Wisdom is said to have raised about 40 chicks throughout its life, with at least eight since 2006. Wisdom is not only known for its hatching prowess. The 65-year-old bird is an avid and strong traveler too. Experts say Wisdom has likely flown over 3 million miles since 1956 when it first joined Midway Atoll. Bruce Peterjohn from Patuxent Wildlife Research Center estimates that such mileage equates to about six trips from the Earth to the moon and back. Biologist Chandler Robbins was the one who banded Wisdom back in 1956. Robbins still goes to work occasionally for the love of doing his passion. The interesting thing is he was able to see Wisdom near the same nesting area 46 years later. Peyton goes to explain that albatrosses are vital indicators for the world's oceans, which also sustain human life. Midway Atoll houses more than a million albatrosses, which indicates how much is left to know about nature. In November 2015, hundreds of thousands of species arrived at the Midway Atoll. The following month, volunteers from the U.S. Fish and Wildlife Service were able to count approximately 470,000 active nests across the atoll. Each nest represents two adult birds thus, the total estimated population of the birds was 940,000. Such number does not include those that are non-breeders in other colonies and are active in looking for and dancing with mates.
Beyer W.N.,Patuxent Wildlife Research Center |
Green C.E.,U.S. Department of Agriculture |
Beyer M.,Patuxent Wildlife Research Center |
Chaney R.L.,U.S. Department of Agriculture
Environmental Pollution | Year: 2013
Historic emissions from two zinc smelters have injured the forest on Blue Mountain near Palmerton, Pennsylvania, USA. Seedlings of soybeans and five tree species were grown in a greenhouse in a series of mixtures of smelter-contaminated and reference soils and then phytotoxic thresholds were calculated. As little as 10% Palmerton soil mixed with reference soil killed or greatly stunted seedlings of most species. Zinc was the principal cause of the phytotoxicity to the tree seedlings, although Mn and Cd may also have been phytotoxic in the most contaminated soil mixtures. Calcium deficiency seemed to play a role in the observed phytotoxicity. Exposed soybeans showed symptoms of Mn toxicity. A test of the effect of liming on remediation of the Zn and Mn phytotoxicity caused a striking decrease in Sr-nitrate extractable metals in soils and demonstrated that liming was critical to remediation and restoration. © 2013 Elsevier Ltd. All rights reserved.
Cerezo A.,University of Buenos Aires |
Perelman S.,University of Buenos Aires |
Perelman S.,CONICET |
Robbins C.S.,Patuxent Wildlife Research Center
Ecological Modelling | Year: 2010
Tropical forest destruction and fragmentation of habitat patches may reduce population persistence at the landscape level. Given the complex nature of simultaneously evaluating the effects of these factors on biotic populations, statistical presence/absence modelling has become an important tool in conservation biology. This study uses logistic regression to evaluate the independent effects of tropical forest cover and fragmentation on bird occurrence in eastern Guatemala. Logistic regression models were constructed for 10 species with varying response to habitat alteration. Predictive variables quantified forest cover, fragmentation and their interaction at three different radii (200, 500 and 1000 m scales) of 112 points where presence of target species was determined. Most species elicited a response to the 1000 m scale, which was greater than most species' reported territory size. Thus, their presence at the landscape scale is probably regulated by extra-territorial phenomena, such as dispersal. Although proportion of forest cover was the most important predictor of species' presence, there was strong evidence of area-independent and -dependent fragmentation effects on species presence, results that contrast with other studies from northernmost latitudes. Species' habitat breadth was positively correlated with AIC model values, indicating a better fit for species more restricted to tropical forest. Species with a narrower habitat breadth also elicited stronger negative responses to forest loss. Habitat breadth is thus a simple measure that can be directly related to species' vulnerability to landscape modification. Model predictive accuracy was acceptable for 4 of 10 species, which were in turn those with narrower habitat breadths. © 2009 Elsevier B.V.
News Article | December 1, 2015
Officials at the United States Fish and Wildlife Service reported that the world's oldest living wild bird named Wisdom is back on American soil where she is expected to lay an egg at the ripe age of 64 years old. The Laysan albatross was spotted with her mate at the Midway Atoll National Wildlife Refuge within Papahānaumokuākea Marine National Monument in Hawaii on Nov. 19. The refuge is known as the world's biggest albatross nesting colony, experts said, and is located about 1500 miles north-west of Hawaii. Midway Atoll National Wildlife Refuge Manager Dan Clark said [pdf] that the seabird population has dropped to about 70 percent since the 1950s, and that Wisdom has become a symbol of inspiration and hope. Clark explained that the refuge is part of Wisdom's fate and that they are glad to see her return. Wisdom was first tagged in 1956 by ornithologist Chandler Robbins, and has since then laid and raised 36 chicks. Laysan albatrosses do not return to breed after they are five years old, and many birds that are tagged lose their bands before they can be replaced. Experts were able to continuously replace Wisdom's bands because of meticulous record-keeping. Laysan albatrosses usually lay one egg a year, and they spend six months taking care of their birdlings. These birds have about a seven-foot-wingspan which helps them travel hundreds of miles out into the sea. Experts said Wisdom may have traveled more than six million ocean miles during her lifetime. Aside from Wisdom, there is another albatross bird that was known to have laid an egg during old age. Grandma, a Northern Royal albatross, laid an egg at the age of 61 years old at a nesting area at Taiaroa Head in New Zealand. However, Grandma has not been seen and experts presume that she has died. Meanwhile, 19 of 21 albatross species are dangerously close to extinction, scientists said. Their demise might be linked to human activity. Bruce Peterjohn of the USGS Patuxent Wildlife Research Center warned that something could happen to Wisdom so bird watchers should keep an eye out on Wisdom to know when she comes back. "Something could happen and they could find her dead on Midway. Someday she's going to fly off the island some spring and never come back," added Peterjohn.
Miller D.A.,Iowa State University |
Miller D.A.,Patuxent Wildlife Research Center |
Otis D.L.,Iowa State University
Journal of Wildlife Management | Year: 2010
We examined results from the first national-scale effort to estimate mourning dove (Zenaida macroura) age ratios and developed a simple, efficient, and generalizable methodology for calibrating estimates. Our method predicted age classes of unknown-age wings based on backward projection of molt distributions from fall harvest collections to preseason banding. We estimated 1) the proportion of late-molt individuals in each age class, and 2) the molt rates of juvenile and adult birds. Monte Carlo simulations demonstrated our estimator was minimally biased. We estimated model parameters using 96,811 wings collected from hunters and 42,189 birds banded during preseason from 68 collection blocks in 22 states during the 2005-2007 hunting seasons. We also used estimates to derive a correction factor, based on latitude and longitude of samples, which can be applied to future surveys. We estimated differential vulnerability of age classes to harvest using data from banded birds and applied that to harvest age ratios to estimate population age ratios. Average, uncorrected age ratio of known-age wings for states that allow hunting was 2.25 (SD 0.85) juvenilesadult, and average, corrected ratio was 1.91 (SD 0.68), as determined from harvest age ratios from an independent sample of 41,084 wings collected from random hunters in 2007 and 2008. We used an independent estimate of differential vulnerability to adjust corrected harvest age ratios and estimated the average population age ratio as 1.45 (SD 0.52), a direct measure of recruitment rates. Average annual recruitment rates were highest east of the Mississippi River and in the northwestern United States, with lower rates between. Our results demonstrate a robust methodology for calibrating recruitment estimates for mourning doves and represent the first large-scale estimates of recruitment for the species. Our methods can be used by managers to correct future harvest survey data to generate recruitment estimates for use in formulating harvest management strategies. © 2010 The Wildlife Society.
Heinz G.H.,Patuxent Wildlife Research Center |
Hoffman D.J.,Patuxent Wildlife Research Center |
Klimstra J.D.,Patuxent Wildlife Research Center |
Stebbins K.R.,Patuxent Wildlife Research Center
Archives of Environmental Contamination and Toxicology | Year: 2012
Methylmercury chloride and seleno-L-methionine were injected separately or in combinations into the fertile eggs of mallards (Anas platyrhynchos), chickens (Gallus gallus), and double-crested cormorants (Phala-crocorax auritus), and the incidence and types of teratogenic effects were recorded. For all three species, selenomethionine alone caused more deformities than did methylmercury alone. When mallard eggs were injected with the lowest dose of selenium (Se) alone (0.1 μg/g), 28 of 44 embryos and hatchlings were deformed, whereas when eggs were injected with the lowest dose of mercury (Hg) alone (0.2 μg/g), only 1 of 56 embryos or hatchlings was deformed. Mallard embryos seemed to be more sensitive to the teratogenic effects of Se than chicken embryos: 0 of 15 chicken embryos or hatchlings from eggs injected with 0.1 μg/g Se exhibited deformities. Sample sizes were small with double-crested cormorant eggs, but they also seemed to be less sensitive to the teratogenic effects of Se than mallard eggs. There were no obvious differences among species regarding Hg-induced deformities. Overall, few interactions were apparent between methylmercury and selenomethionine with respect to the types of deformities observed. However, the deformities spina bifida and craniorachischisis were observed only when Hg and Se were injected in combination. One paradoxical finding was that some doses of methylmercury seemed to counteract the negative effect selenomethionine had on hatching of eggs while at the same time enhancing the negative effect selenomethionine had on creating deformities. When either methylmercury or selenomethionine is injected into avian eggs, deformities start to occur at much lower concentrations than when the Hg or Se is deposited naturally in the egg by the mother. © Springer Science+Business Media, LLC (outside the USA) 2011.