Defining and evaluating exotic species: issues for Yellowstone park policy

Exotics are species that are foreign to an ecological assemblage in the sense that they have not significantly adapted to resident biota or to local abiotic conditions, and resident species have not significantly adapted to them. Although they need not be human introduced nor damaging, when they are, a negative appraisal of such exotic species can be justified. Human introduction of exotics into natural systems typically increases human influence over those systems, thus diminishing their wildness. Valuing nature for its wildness is a rationale for the national parks policy of letting nature take its course. Thus, Yellowstone Park has a strong reason for removing human-introduced exotics and for welcoming naturally migrating exotics. Disvaluing exotics that are neither human introduced nor damaging simply because they are foreign smacks of xenophobia. But given that wanton human mixing of species threatens to homogenize the earths biological communities, biological nativism is justified as a way to preserve the diversity between such communities.     

Annotated checklist of exotic vascular plants in Yellowstone National Park

Documentation of the arrival of exotic vascular plants in Yellowstone National Park has been sporadic. An annotated checklist of exotic vascular plants is presented, with information about the approximate arrival time in the park of each species and the current extent of the infestation. Yellowstones flora includes 187 exotic vascular plant species (14.8% of the flora), and the park has an extrapolated mean number of exotic species per 10 km 2 of 47.3. The situation in Yellowstone is compared with other areas in North America. The increase in exotics mirrors a corresponding increase in visitation.     

New approaches for sampling and modeling native and exotic plant species richness

We demonstrate new multi-phase, multi-scale approaches for sampling and modeling native and exotic plant species to predict the spread of invasive species and aid in control efforts. Our test site is a 54,000-ha portion of Rocky Mountain National Park, Colorado, USA. This work is based on previous research wherein we developed vegetation sampling techniques to identify hot spots of diversity, important rare habitats, and locations of invasive plant species. Here we demonstrate statistical modeling tools to rapidly assess current patterns of native and exotic plant species to determine which habitats are most vulnerable to invasion by exotic species. We use stepwise multiple regression and modified residual kriging to estimate numbers of native species and exotic species, as well as probability of observing an exotic species in 30 × 30-m cells. Final models accounted for 62% of the variability observed in number of native species, 51% of the variability observed in number of exotic species, and 47% of the variability associated with observing an exotic species. Important independent variables used in developing the models include geographical location, elevation, slope, aspect, and Landsat TM bands 1-7. These models can direct resource managers to areas in need of further inventory, monitoring, and exotic species control efforts.     

Plant composition and erosion potential of a grazed wetland in the salmon river subbasin, Idaho

Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition and structure within the study area and attempted to assess potential erosion conditions using the Revised Universal Soil Loss Equation (RUSLE), an empirical approach developed by the U.S. Department of Agriculture—Agricultural Research Service (USDA-ARS). We found no significant spatial variability in species richness and noted a moderate number of exotic species in the total plant composition. Plant cover was higher near slightly entrenched banks, indicating that uncontrolled livestock were primarily occupying gently sloped streambanks and the interior of the meadow. Based on current vegetation composition and RUSLE results, uncontrolled grazing may be negatively impacting the study area. If uncontrolled grazing were excluded or carefully managed in the wetland meadows of the upper portion of the Deer Creek watershed, a reduction in excess sediments to Deer Creek may occur.     

Effects of exotic grasses on soil seed banks in southeastern Arizona grasslands

Species richness in Madrean mixed-grass prairies dominated by native or exotic species in southeastern Arizona was characterized at the community and point scales using ten 1-m 2 quadrats nested within each of eight 1000-m 2 plots. In the 1000-m 2 plots average richness was significantly higher in oak savanna (OS, 121.0 species) than in exotic grassland on mesa tops (EMT, 52.0 species), whereas native grassland on mesa slopes (NMS, 92.5 species) and native grassland on mesa tops (NMT, 77.0 species) did not differ significantly in richness from OS or EMT. When richness was partitioned by life form, EMT was notably poorer than other community types in species of perennial grasses, perennial herbs, and summer annuals. In the 1-m 2 quadrats, OS (21.2 species), NMS (20.9 species), and NMT (20.7 species) were significantly richer than EMT (5.9 species). Cover in 1-m 2 plots was significantly higher in EMT than in NMT, NMS, or OS. Species richness at the point scale showed a unimodal relation to canopy cover, with cover accounting for 30% of the variation in number of species in 1-m2 quadrats. Competitive exclusion and allelopathy have perhaps limited species richness at the point scale in exotic grassland. There was no evidence of a species-pool effect between point and community scales, but such an effect between community and landscape scales was supported. Madrean mixed-grass prairies are landscapes with high species richness in comparison to other grassland types in North America, providing a large pool of potential colonizing species at the community scale. Beta-diversity (between communities) within the landscape of the Appleton-Whittell Research Ranch was consequently high despite a relative lack of habitat diversity.     

Planted grasslands and native sod prairie: equivalent habitat for grassland birds?

Little is known about how avian relationships to tracts of native sod prairie compare with avian relationships to single and multiple species of cool- and warm-season grassland plantings. We compared grassland bird species richness and density in 5 grassland cover types ( n = 97) in the tallgrass prairie region of eastern South Dakota and western Minnesota, 2001–2004. Grassland bird species richness was significantly higher in native sod prairies than it was in all planted cover types except warm-season mixes. Grasslands dominated by exotic species did not support as many grassland bird species or have species densities as high as grasslands containing native species. Intermediate wheatgrass monotypes and cool-season mixes comprised of exotic species contained 40%–60% fewer grassland bird species than native sod prairie. Bobolink ( Dolichonyx oryzivorus ) density was 68% and 51% lower in intermediate wheatgrass monotypes and cool-season mixes, respectively, than it was in switchgrass monotypes. Clay-colored Sparrow ( Spizella pallida ) density was 75%–91% higher in native sod prairies than it was in any other cover type. Savannah Sparrow ( Passerculus sandwichensis ) density was 72% higher in native prairie than it was in grasslands dominated by exotic species. We recommend incorporating a diversity of native plant species into grassland plantings for biomass fuels or wildlife, rather than using monotypes or exotic species, to provide habitat for grassland birds. Although replacing croplands with planted grasslands would benefit grassland bird populations, we caution that replacing existing native sod tracts with planted grasslands would be detrimental to populations of several grassland bird species.     

Plant species richness at different scales in native and exotic grasslands in southeastern Arizona

Species richness in Madrean mixed-grass prairies dominated by native or exotic species in southeastern Arizona was characterized at the community and point scales using ten 1-m 2 quadrats nested within each of eight 1000-m 2 plots. In the 1000-m 2 plots average richness was significantly higher in oak savanna (OS, 121.0 species) than in exotic grassland on mesa tops (EMT, 52.0 species), whereas native grassland on mesa slopes (NMS, 92.5 species) and native grassland on mesa tops (NMT, 77.0 species) did not differ significantly in richness from OS or EMT. When richness was partitioned by life form, EMT was notably poorer than other community types in species of perennial grasses, perennial herbs, and summer annuals. In the 1-m 2 quadrats, OS (21.2 species), NMS (20.9 species), and NMT (20.7 species) were significantly richer than EMT (5.9 species). Cover in 1-m 2 plots was significantly higher in EMT than in NMT, NMS, or OS. Species richness at the point scale showed a unimodal relation to canopy cover, with cover accounting for 30% of the variation in number of species in 1-m2 quadrats. Competitive exclusion and allelopathy have perhaps limited species richness at the point scale in exotic grassland. There was no evidence of a species-pool effect between point and community scales, but such an effect between community and landscape scales was supported. Madrean mixed-grass prairies are landscapes with high species richness in comparison to other grassland types in North America, providing a large pool of potential colonizing species at the community scale. Beta-diversity (between communities) within the landscape of the Appleton-Whittell Research Ranch was consequently high despite a relative lack of habitat diversity.     

Bird use of riparian vegetation along the Truckee River, Califonia and Nevada

The Truckee River in California and Nevada is subject to diverse water regimes and a corresponding variety of flow rates. Original riparian vegetation has been altered by these variable flow rates and by a variety of human uses resulting in loss of native riparian vegetation from its historic extent. We conducted bird surveys along the Truckee River during spring 193 to (1) determine relationships between birds and the present vegetation; (2) determine the importance of different vegetation types to sensitive bird species that have declined recently in the western United States due to competition from exotic plant species, cowbird ( Molothrus ater ) parasitism, reduction in nesting habitat, or other unidentified reasons; and (3) establish a monitoring program and collect baseline data for future comparisons. The most frequently detected bird species throughout the study was the Brown-headed Cowbird. The greatest number of bird species (98 of 116) was found in the native mixed willow ( Salix spp.) riparian scrub vegetation type. We recommend protecting the remaining native riparian vegetation types for bird habitat along the Truckee River.     

Influence of soil and site characteristics on Palouse prairie plant communties

The structure of grassland communities can vary widely in response to heterogeneous habitat variables. In this study we document plant communities, soil types, and site characteristics for 12 Palouse prairie remnants in southeastern Washington and northern Idaho. We used general linear models to test the predictive value of 6 biophysical variables (slope, aspect, distance from edge, edge type, vegetation structure, and soil type) on 3 plant community metrics: species richness, Simpson’s diversity index, and the dominance of exotic species. From full models including all variables, we used Akaike’s information criterion (AIC) to select the best model for each metric. Aspect and vegetation structure were significant predictors of species richness ( R 2 = 0.08) and diversity ( R 2 = 0.09), while aspect, soil type, distance from edge, and edge type (type of adjacent matrix habitat) influenced the dominance of exotic species ( R 2 = 0.28). Additional soil sampling determined that the depth to a restrictive layer also had significant impacts on the dominance of exotic species ( R 2 = 0.31). This study confirms that biophysical characteristics influence Palouse prairie plant communities and may help set research and conservation priorities for isolated and uninventoried remnants.     

Late Pleistocene mollusks from the southern Black Hills, South Dakota

Pleistocene-age mollusks recovered from the Nelson-Wittenberg Site and Mammoth Site provide information on paleoenvironments of the southern Black Hills, South Dakota. New mollusk records for the Mammoth Site include Vertigo modesta, Catinella sp., and Gyraulus parvus . The presence of V. modesta, Columella columella alticola , and Pupilla muscorum at the Nelson-Wittenberg Site suggests cooler than modern conditions in the Black Hills during the Pleistocene. Although the majority of identified taxa are consistent with previous interpretations of an arid, shrubsteppe environment for the Black Hills during the Wisconsin Glaciation, V. modesta and C. c. alticola suggest the presence of at least some isolated, local mesic areas.     

A rule-based model for mapping potential exotic plant distribution

Wildland managers need a method to predict which portions of the lands under their stewardship are susceptible to invasion by exotic plants. We combined a database listing exotic plant species known to occur in major environmental types (habitat types) throughout the northern Rocky Mountains with a digital vegetation map of environmental types for a major national park in the region (Yellowstone National Park) to produce maps of areas potentially threatened by major exotic species. Such maps should be helpful to managers concerned with monitoring and controlling exotic plants.     

Can Townsend's ground squirrels survive on a diet of exotic annuals?

Southwestern Idaho desert shrub-bunchgrass rangeland is being invaded by fire-prone exotic annuals that permanently dominate the landscape following wildfires. This study was undertaken to describe diets of Townsend's ground squirrels ( Spermophilus townsendii idahoensis ) at four study sites with varying degrees of exotic annual invasion to determine if the squirrels could utilize high proportions of exotic annuals in their diets. Townsend's ground squirrels were collected in March and May of 1987 and 1988, and stomach contents were analyzed using a microhistological technique. Grasses comprised 37-87% of Townsend's ground squirrel diets at the four sites. Native species, especially Sandberg's bluegrass ( Poa secunda ), winterfat ( Ceratoides lanata ), big sagebrush ( Artemisia tridentata ) and six-weeks fescue ( Vulpia octoflora ) constituted 7-96% (x = 47.2%) of the diet, whereas exotic species, especially cheatgrass ( Bromus tectorum ), tumbleweed ( Salsola iberica ), and tansymustards ( Descurainia spp.) made up 4-68% (x = 48.0%) of the diet. At each site 2-4 species comprised >90% of the diet. There was no apparent correlation between the importance values of exotic species at a site and their importance in Townsend's ground squirrel diets.     

Aquatic vertebrate assemblages of the Upper Clear Creek Watershed, California

We sampled streams in the Upper Clear Creek Watershed in northwestern California in fall 2004 and fall 2005 to document assemblages of aquatic vertebrates and to provide resource managers with information on the importance of these assemblages in terms of regional biodiversity. We used single-pass backpack electrofishing to sample 15 sites in fall 2004 and the same 15 sites plus 4 new sites in fall 2005. We captured 10 fish taxa and 2 species of larval amphibians. Seven of the fish taxa were native species. Of the exotic species, only brook trout ( Salvelinus fontinalis ) occurred at more than 1 site. Ordinations by nonmetric multidimensional scaling indicated a gradient from sites with rainbow trout ( Oncorhynchus mykiss ), Pacific giant salamander ( Dicamptodon tenebrosus ), and tailed frog ( Ascaphus truei ) to sites dominated by riffle sculpin ( Cottus gulosus ), California roach ( Hesperoleucas symmetricus ), and Sacramento sucker ( Catostomus occidentalis ). The gradient in species composition was associated with changes in elevation, gradient, discharge, and substrate. The Upper Clear Creek Watershed represents a unique area of overlap between the North Coast California amphibian fauna and the Central Valley fish fauna with a notable paucity of exotic fishes and amphibians. Preservation of the integrity of native aquatic assemblages is an important goal for aquatic resource management in the region; our results provide a critcial baseline to gauge future management actions.     

Bionomics of the cone spittlebug, Aphrophora canadensis (Homoptera: Cercopidae) on mugo pine in Idaho

The spittlebug, Aphrophora canadensis Walley (Homoptera: Cercopidae), was discovered at Moscow, Idaho, in 1979 infesting Pinus mugo Turra, an exotic ornamental pine. Masses of spittle, densely populated with nymphs, have continued to be abundant since then. The nymphs congregated and fed mainly on cones and did not cause visible reddening of foliage that is typical of other pine-infesting spittlebugs. Immature stages and behavior are described for the first time and are compared to other nearctic pine-infesting species. Beginning in mid-August, eggs were laid under fascicle sheaths at the bases of needles, where they overwintered. Nymphs appeared in late April and began transforming to adults in mid-July. Mating occurred from early August to late September. Adults lingered in diminishing numbers until mid-October.     

Patterns of trophic relationships between planthoppers (Hemiptera: Fulgoromorpha) and their host plants on the Mascarene Islands

Following an up‐to‐date synopsis on the planthopper fauna and their associated host‐plants in the Mascarene Islands including numerous new data, a study of host plant and Fulgoromorpha interaction patterns illustrates some remarkable specificities. The endemic fauna remains essentially on endemic plants and exotic planthoppers have not shifted to them, remaining on exotic plants. Two fulgoromorph families are strictly associated with monocotyledons: (1) the Delphacidae represented by widespread species maintain the same host as the continental source populations, especially exotic Poaceae and (2) the Derbidae which displayed a food conservatism for woody plants are found mostly on endemic Arecaceae, Pandanaceae and Liliaceae. These relationships differ from continental Derbidae, which are recorded as much on dicotyledons as on monocotyledons. Other island specificity appears with the endemic species of Meenoplidae from La Réunion, which are recorded on endemic dicotyledons whereas the continental species are recorded on monocotyledons. In La Réunion, a positive correlation between endemic planthopper diversity recorded on different host plants and endemic plant diversity within different plant orders was observed. This result suggests a stochastic distribution of the planthoppers on the available botanical taxa at the time of colonization. In the Mascarenes, disparities appear between Cixiidae from La Réunion and Mauritius. On the latter, the Cixiidae seem to be mainly monophagous and the majority of them are recorded on Rubiaceae.     

Vegetation, soils, and hydrogeomorphology of riparian patch types of a dryland river

From a landscape perspective, riparian corridors can be viewed as mosaics of vegetation patches. We delineated 10 patch types within the floodplain of the San Pedro River (Arizona) on the basis of physiognomy, dominant overstory species, and tree size class; and we assessed differences in hydrogeomorphology, vegetation structure, plant species richness, and soil chemistry and texture. Patches of tamarisk ( Tamarix ), an introduced species, fell within the continuum of variation shown by other patch types in the landscape mosaic. Among the tree-dominated types, cottonwood-willow ( Populus-Salix ) and tamarisk patches were inundated more frequently than mesquite ( Prosopis ) patches, while cottonwood-willow patches had shallower groundwater than tamarisk or mesquite patches. Due to the wetter conditions, cottonwood-willow patches had a high relative abundance of wetland and exotic species in the understory. Tamarisk patches and wet shrublands ( Baccharis salicifolia—Salix exigua ) had high woody stem densities while cottonwood-willow patches had dense canopy cover. In association with differences in canopy cover, cottonwood-willow patches had low herbaceous species richness but high woody species richness, while tamarisk patches had high herbaceous and low woody species richness. Soil electrical conductivity, silt content, organic matter content, and available phosphorus increased from young to old stands of both tamarisk and cottonwood-willow, often resulting in greater differences between patches of different size/age class than between patches with different dominant species. Surface soil salinity (electrical conductivity) was low in all patches, including those dominated by tamarisk. Nitrate was abundant in soils of tamarisk patches (perhaps reflecting their high clay content) and wet shrubland patches. Dry shrublands ( Hymenoclea-Ericameria ) and wet shrublands were similar to young forest patches in having coarse soils with little organic matter.     

Associations of Small Mammals Occurring in a Pluvial Lake Basin, Ruby Lake, Nevada

Ruby Lake is a highly mesic and vegetationally diverse pluvial lake basin of east central Nevada. Small mammal associations were examined in six plant communities at Ruby Lake using transects of live traps. Small mammal activity was recorded for these six habitats plus an additional three other specialized habitats. A total of 11 species of small mammals were trapped from the six habitat types; from the entire study area 26 species were trapped or observed. Two greasewood shrub habitats and a shadscale-spiny hopsage habitat held the highest number of trapped species, 6, 5, and 7, respectively. The mesic haymeadow and spring habitats, as well as the big sagebrush-antelope bitterbrush habitat held 4 trapped species each. Peromyscus maniculatus and Perognathus parvus made up 76% of the total captures and were found in all habitat types except marshlands. Eutamius minimus was found in four of the six habitat types, while Dipodomys ordii , Dipodomys microps , Perognathus parvus , and Microtus montanus were limited to specialized habitats. Mesic adapted, wetland species such as Mustela vison , Ondatra zibethicus , and Sorex vagrans possibly dispersed into Ruby Valley from the northeastern drainages and valleys during the late Pleistocene or Holocene.     

Managing a complex exotic vegetation program in Yellowstone National Park

The number of documented exotic plants in Yellowstone National Park has increased from 85 known in 1986 to over 185 today. Exotic plants are substantially impacting the parks natural and cultural resources and are a high management priority. We have adopted an integrated weed management approach with regard to exotic vegetation, emphasizing prevention, education, early detection and eradication, control, and, to a lesser degree, monitoring. The program involves over 140 staff with program expenditures averaging approximately $190,000 annually. Prevention actions include requiring approved gravel on construction projects; banning hay in the backcountry and allowing transport of only certified weed-seed-free hay through Yellowstone; requiring construction equipment to be pressurecleaned prior to entering the park; and native species revegetation after road, housing, and other construction projects have disturbed ground. Over 4500 acres, primarily along roadsides and in developed areas, are surveyed annually in early detection efforts with emphasis placed on eradicating small, new infestations of highly invasive species such as sulfur cinquefoil ( Potentilla recta L.) and leafy spurge ( Euphorbia esula L.). Control efforts focus on about 30 priority species, such as spotted knapweed ( Centaurea maculosa Lam.), oxeye daisy ( Chrysanthemum leucanthemum L.), and hoary cress ( Cardaria draba [L.] Desv.) using chemical, mechanical, and cultural techniques. A total of 2027 acres were treated during 1998, whereas control efforts for 12 species occurred on 2596 acres during the previous 3-year period, 1995-1997. Strong and expanding partnerships with other federal, state, and local agencies and private companies contribute to management efforts within the park. Future program goals emphasize increases in base funding to ensure continued weed management efforts as well as expanding survey, monitoring, and reclamation efforts. Ultimately, a more rigorous assessment of program effectiveness is desired.     

Anurans of Turvo State Park: testing the validity of Seasonal Forest as a new biome in Brazil

The composition of the anuran community of Turvo State Park was compared with that of other localities of Mesophytic semideciduous Forest, aiming to test the hypothesis that localities situated nearest the Misiones nucleus support the new phytogeographic unit, known as Tropical Seasonal Forests Region. In total 32 amphibian species were recorded in the park area and surroundings: Anura, 30 native species and one exotic; Gymnophiona, one species. The ordination among the 20 localities of Seasonal Forest showed the formation of three groups with 45% similarity: group 1, composed of localities of south-eastern and central western regions; group 2, composed of the localities of the transitional portion with the Atlantic Forest sensu stricto and group 3, composed of the southern localities. The consolidation of the second group, which includes the occurrence of endemic species, supports the proposal of a new phytogeographic unit.     

Aquatic Oligochaeta (Annelida: Lumbriculidae, Haplotaxidae, Naididae, Tubificidae) of Utah

Thirty-six species of aquatic Oligochaeta (Lumbriculidae, Haplotaxidae, Naididae, Tubificidae) are now known form Utah. Aquatic habitats in 27 counties were sampled, with 32 oligochaete species identified. An additional 4 species were added from other published investigations. The majority of species are cosmopolitan and occur in other areas of North America. Nais barbata, N. alpina, and N. pardalis are reported from the western United States for the first time. Ilyodrilus frantzi was found to be a major component of the oliogochaete fauna in the Great Basin lentic environment. The North American distribution of Telmatodrilus vejdovskyi is extended significantly eastward. Tow undetermined species of Tubificidae are discussed.