NOTES: RANGE EXTENSION OF THE VIRGINIA OPOSSUM (DIDELPHIS VIRGINIANA) IN NORTH DAKOTA

The Virginia opossum (Didelphis virginiana) is broadly distributed across North America from Costa Rica in the south to southern Ontario in the north and from the southern Great Plains in the west to the eastern United States. The Virginia opossum also was introduced multiple times to thePacific Coast beginning in the late 1800s and has established populations in that region (Gardner and Sunquist 2003). This species is a habitat generalist known to frequent wetland and hardwood habitats but also can be found in grasslands, along forest edges, and in agricultural and suburban settings throughout its range (Gardner and Sunquist 2003, Beatty et al. 2014). However, the Virginia opossum is adapted poorly to winter, limiting its northern distribution to more tolerable warmer climates. It does not hibernate or exhibit torpor, and it will remain in its den rather than forage on nights when temperatures are below freezing or when there is deep snow, risking starvation if more than 54 days of winter are too harsh to forage (Brocke 1970). Despite these limitations, the Virginia opossum has expanded north in recent decades (Myers et al. 2009) and has been documented in novel areas of the Upper Midwest and New England (e.g., Dice 1927, Goodwin 1935, Jackson 1961). Both climate change and human land use alteration have been identified as contributing factors to their current range expansion. A recent study conducted across Michigan and Wisconsin identified reduced days of snow on the ground and increased agricultural land as two key factors facilitating the opossum’s expansion in the Midwest (Walsh and Tucker 2017). As generalist omnivores, opossums benefit from increased road kill and resources provided by agricultural practices (Beatty et al. 2014). Humans are further ameliorating winter conditions by providing shelter and easily accessible food, as evidenced by opossums in urban areas weighing more than individuals in adjacent natural habitats (Kanda 2005, Wright et al. 2012)

Nothing lasts forever: Dominant species decline under rapid environmental change in global grasslands

Dominance often indicates one or a few species being best suited for resource capture and retention in a given environment. Press perturbations that change availability of limiting resources can restructure competitive hierarchies, allowing new species to capture or retain resources and leaving once dominant species fated to decline. However, dominant species may maintain high abundances even when their new environments no longer favour them due to stochastic processes associated with their high abundance, impeding deterministic processes that would otherwise diminish them. Here, we quantify the persistence of dominance by tracking the rate of decline in dominant species at 90 globally distributed grassland sites under experimentally elevated soil nutrient supply and reduced vertebrate consumer pressure. We found that chronic experimental nutrient addition and vertebrate exclusion caused certain subsets of species to lose dominance more quickly than in control plots. In control plots, perennial species and species with high initial cover maintained dominance for longer than annual species and those with low initial cover respectively. In fertilized plots, species with high initial cover maintained dominance at similar rates to control plots, while those with lower initial cover lost dominance even faster than similar species in controls. High initial cover increased the estimated time to dominance loss more strongly in plots with vertebrate exclosures than in controls. Vertebrate exclosures caused a slight decrease in the persistence of dominance for perennials, while fertilization brought perennials' rate of dominance loss in line with those of annuals. Annual species lost dominance at similar rates regardless of treatments. Synthesis. Collectively, these results point to a strong role of a species' historical abundance in maintaining dominance following environmental perturbations. Because dominant species play an outsized role in driving ecosystem processes, their ability to remain dominant—regardless of environmental conditions—is critical to anticipating expected rates of change in the structure and function of grasslands. Species that maintain dominance while no longer competitively favoured following press perturbations due to their historical abundances may result in community compositions that do not maximize resource capture, a key process of system responses to global change.Fil: Wilfahrt, Peter A.. University of Minnesota; Estados UnidosFil: Seabloom, Eric. University of Minnesota; Estados UnidosFil: Bakker, Jonathan. University of Washington; Estados UnidosFil: Biederman, Lori. Iowa State University; Estados UnidosFil: Bugalho, Miguel N.. Universidade Nova de Lisboa; PortugalFil: Cadotte, Marc W.. University of Toronto–Scarborough; Estados UnidosFil: Caldeira, Maria C.. Universidade Nova de Lisboa; PortugalFil: Catford, Jane A.. University of Melbourne; AustraliaFil: Chen, Qingqing. Peking University; China. German Centre for Integrative Biodiversity Research; AlemaniaFil: Donohue, Ian. Trinity College Dublin; IrlandaFil: Ebeling, Anne. University of Jena; AlemaniaFil: Eisenhauer, Nico. German Centre for Integrative Biodiversity Research; Alemania. Leipzig University; AlemaniaFil: Haider, Sylvia. Martin Luther University Halle-Wittenberg; Alemania. Leuphana University of Lüneburg; AlemaniaFil: Heckman, Robert W.. University of Texas; Estados Unidos. United States Forest Service; Estados UnidosFil: Jentsch, Anke. University of Bayreuth; AlemaniaFil: Koerner, Sally E.. University of North Carolina Greensboro; Estados UnidosFil: Komatsu, Kimberly J.. University of North Carolina Greensboro; Estados UnidosFil: Laungani, Ramesh. Poly Prep Country Day School; Estados UnidosFil: MacDougall, Andrew. University of Guelph; CanadáFil: Smith, Nicholas G.. Texas Tech University; Estados UnidosFil: Stevens, Carly J.. Lancaster University; Reino UnidoFil: Sullivan, Lauren L.. Michigan State University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tedder, Michelle. University of KwaZulu-Natal; SudáfricaFil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Tognetti, Pedro Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Veen, Ciska. Netherlands Institute of Ecology; Países BajosFil: Wheeler, George. University of Nebraska-Lincoln; Estados UnidosFil: Young, Alyssa L.. University of North Carolina Greensboro; Estados UnidosFil: Young, Hillary. University of California; Estados UnidosFil: Borer, Elizabeth. University of Minnesota; Estados Unido

Grassland productivity limited by multiple nutrients

Terrestrial ecosystem productivity is widely accepted to be nutrient limited1. Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)2,3, the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized4,​5,​6,​7,​8. However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment

Herbivores and nutrients control grassland plant diversity via light limitation

Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light

Herbivores and nutrients control grassland plant diversity via light limitation

Human alterations to nutrient cycles[superscript 1,2] and herbivore communities³⁻⁷ are affecting global biodiversity dramatically². Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems[superscript 8,9]. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.This is the publisher’s final pdf. The published article is copyrighted by the Nature Publishing Group and can be found at: http://www.nature.com/nature/index.htm

Remembering Paul B. Kannowski

I am saddened to report that Dr. Paul Kannowski passed away 3 September 2015, succumbing to cancer. He was 88. A native of Grand Forks, Paul attended the University of North Dakota for his B.S. and M.S. degrees, and the University of Michigan for his Ph.D. He joined the University of North Dakota Biology Department in 1957, retiring in 1990 after 33 years of service Paul chaired UND’s Biology Department twice, totaling 13 years, considered to be a remarkable achievement by many of us who have been exposed to that task! His leadership was instrumental in the nearly exponential growth of our department’s faculty and student enrollment, including its new Fishery and Wildlife program

Remembering Paul B. Kannowski

I am saddened to report that Dr. Paul Kannowski passed away 3 September 2015, succumbing to cancer. He was 88. A native of Grand Forks, Paul attended the University of North Dakota for his B.S. and M.S. degrees, and the University of Michigan for his Ph.D. He joined the University of North Dakota Biology Department in 1957, retiring in 1990 after 33 years of service Paul chaired UND’s Biology Department twice, totaling 13 years, considered to be a remarkable achievement by many of us who have been exposed to that task! His leadership was instrumental in the nearly exponential growth of our department’s faculty and student enrollment, including its new Fishery and Wildlife program

Plains Harvest Mouse in North Dakota

The plains harvest mouse (Reithrodontomys montanus) is primarily a species of the central and southern plains of North America (Hall 1981, Wilkins 1986). Its published distribution extends from northwestern South Dakota south to the Mexican states of Chihuahua, Sonora, and Durango. To the west, it occurs in eastern Wyoming, Colorado, New Mexico, and southeastern Arizona, while its eastern limits are in eastern Nebraska, Kansas, Oklahoma, Texas, and southwestern Missouri. In South Dakota, R. montanus has been reported as far north as the vicinity of Ludlow, Harding County, which is the most northerly published location recorded for the species (Andersen and Jones 1971, Higgins et al. 2000). There have been no published reports of plains harvest mice in North Dakota, although Andersen and Jones (1971) cited a previously unreported specimen from 18 km south of Mandan, Morton County, in the collection of the University of Michigan Museum of Zoology. This specimen, a study skin and incomplete skull, falls within the range of measurements of R. montanus (Priscilla Tucker, Curator, University of Michigan, Museum of Zoology, personal communication)

An Incident of Fenthion Mosquito Control and Subsequent Avian Mortality

Mass mortality among migratory birds at Grand Forks, North Dakota, was attributed to a mosquito control operation employing the insecticide fenthion. The factors involved may have included the toxicity of the pesticide for birds, the method of application and coincidence with the peak of the spring warbler migration

NOTES: RANGE EXTENSION OF THE VIRGINIA OPOSSUM (DIDELPHIS VIRGINIANA) IN NORTH DAKOTA

The Virginia opossum (Didelphis virginiana) is broadly distributed across North America from Costa Rica in the south to southern Ontario in the north and from the southern Great Plains in the west to the eastern United States. The Virginia opossum also was introduced multiple times to thePacific Coast beginning in the late 1800s and has established populations in that region (Gardner and Sunquist 2003). This species is a habitat generalist known to frequent wetland and hardwood habitats but also can be found in grasslands, along forest edges, and in agricultural and suburban settings throughout its range (Gardner and Sunquist 2003, Beatty et al. 2014). However, the Virginia opossum is adapted poorly to winter, limiting its northern distribution to more tolerable warmer climates. It does not hibernate or exhibit torpor, and it will remain in its den rather than forage on nights when temperatures are below freezing or when there is deep snow, risking starvation if more than 54 days of winter are too harsh to forage (Brocke 1970). Despite these limitations, the Virginia opossum has expanded north in recent decades (Myers et al. 2009) and has been documented in novel areas of the Upper Midwest and New England (e.g., Dice 1927, Goodwin 1935, Jackson 1961). Both climate change and human land use alteration have been identified as contributing factors to their current range expansion. A recent study conducted across Michigan and Wisconsin identified reduced days of snow on the ground and increased agricultural land as two key factors facilitating the opossum’s expansion in the Midwest (Walsh and Tucker 2017). As generalist omnivores, opossums benefit from increased road kill and resources provided by agricultural practices (Beatty et al. 2014). Humans are further ameliorating winter conditions by providing shelter and easily accessible food, as evidenced by opossums in urban areas weighing more than individuals in adjacent natural habitats (Kanda 2005, Wright et al. 2012)