Showing papers in "American Midland Naturalist in 2008"
395 citations
TL;DR: Woodpeckers spent significantly more time in foraging bouts on ash than on other tree species in EAB-infested areas, suggesting that managers of sites with substantial ash populations maintain conditions that are attractive to woodpecker to encourage predation of EAB.
Abstract: Woodpeckers are a significant source of mortality of emerald ash borer (EAB) (Agrilus planipennis Fairmaire), an Asian phloem-feeding insect first discovered in North America in 2002. However, factors that may influence woodpecker-EAB interactions have not been investigated. We collected data on woodpecker predation, EAB density and tree and site characteristics in southeastern Michigan, where EAB first became established. We tested statistical models to assess the ability of these variables to account for woodpecker predation levels. We observed foraging woodpeckers in the field to determine which species foraged on ash, and to compare the time spent foraging on ash vs. other tree species. Levels of woodpecker predation on EAB were variable, ranging from zero to 26.3 woodpecker attacks per m2 for green ash (n = 15 sites) and from 2.3 to 37.1 attacks per m2 for white ash (n = 7 sites). Woodpecker predation level was positively associated with the EAB density in a tree. White ash had higher pr...
84 citations
TL;DR: In this paper, the authors quantified the spatial, dietary and temporal resource overlap of kit foxes and coyotes on the U.S. Army Dugway Proving Ground, Utah.
Abstract: Successful coexistence of sympatric canid species often relies on the subdominant species' ability to reduce competition through the differential selection of niche space. Information regarding the process of niche selection and its effect on the structure of canid communities in the Great Basin Desert is unavailable. From Dec. 1999 to Aug. 2001, we quantified the spatial, dietary and temporal resource overlap of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) on the U.S. Army Dugway Proving Ground, Utah. Kit foxes and coyotes demonstrated substantial levels of spatial, temporal and dietary overlap. However, where the two species had overlapping home ranges, space use within the home range differed between the two species, with kit foxes using vegetative and landscape ruggedness characteristics not regularly used by coyotes. Although there was little evidence of seasonal change in either canid's use of habitat, in some areas kit foxes made nightly movements to more productive habitats with moderate ruggedness. Regardless of spatial partitioning, incidents of interference competition were high; 56% of known kit fox deaths were attributed to coyotes. In our study, high levels of temporal and dietary overlap, kit fox movement from extreme to moderate topography during foraging and selection for abundant cover demonstrated competitive pressures exerted on the kit fox population by the sympatric coyote population.
68 citations
TL;DR: While carbon application may benefit native plant growth in the presence of A. petiolata, the addition of activated carbon after removal of aboveground biomass, a source of both allelochemicals and light competition, may have little benefit as an understory plant restoration tool.
Abstract: Invasive plants can exert their effects on native plants through both above- and belowground mechanisms. In a fully factorial field study, we examined the effects of activated carbon addition and removal of aboveground biomass (i.e., cutting) on the survival, growth and reproduction of transplanted Impatiens capensis seedlings in habitats dominated by either Lonicera maackii (honeysuckle) or Alliaria petiolata (garlic mustard). Activated carbon can adsorb organic molecules, including potential allelochemicals. Cutting of A. petiolata increased survival and fruit production of I. capensis, while cutting of L. maackii increased survival and tended to increase fruit production. Carbon application tended to increase survival of I. capensis in A. petiolata-dominated plots, but had no effect in L. maackii-dominated plots. The effects of carbon application on growth and fruit production of I. capensis depended upon the cutting treatment in A. petiolata – dominated plots. In plots where A. petiolata was ...
65 citations
TL;DR: Management for multiple species of pond-breeding amphibians in a landscape benefits from the inclusion of wetlands with a variety of hydroperiods as they only required ponds to hold water for as little as 60 d.
Abstract: Knowing the phenologies of species in a region helps guide management and conservation activities in breeding ponds and surrounding terrestrial habitats. We examined the phenology of pond-breeding amphibians in central Missouri oak-hickory forests. Two ponds were monitored for 4 y from 2000–2003 and five other ponds were monitored for 1 y during 2004 using drift fences with pitfall traps. We found 15 species of pond-breeding amphibians, nine of which we captured in sufficient abundance to evaluate breeding phenology. Among the nine species, breeding migrations occur from Feb. to Nov., while subsequent metamorph emigration occurred primarily from May to Oct.. Our ponds were nearly permanent, resulting in salamander-dominated communities in these oak-hickory forests. Pond-use was partitioned by species that differed in their timing of reproduction and post-metamorphic emergence. For example, breeding in the fall gives larval ringed salamanders a potential size advantage over the spring-breeding spo...
61 citations
TL;DR: In this paper, the authors evaluate home range size and movements of raccoons during the avian nesting season, describe patterns of habitat selection at multiple spatial scales and suggest management strategies to reduce the impact of raccoon on nesting birds.
Abstract: Raccoons (Procyon lotor) have been implicated as important predators impacting nesting birds in the Midwest. Raccoon populations have increased dramatically in Illinois during the past 20 y prompting suggestions that lethal control programs may be warranted. Non-lethal approaches that separate avian nesting habitat from raccoon travel corridors may provide an acceptable alternative, but little is known about foraging patterns by raccoons in agricultural landscapes. Therefore, the objectives of this study were to: (1) evaluate home range size and movements of raccoons during the avian nesting season, (2) describe patterns of habitat selection at multiple spatial scales and (3) suggest management strategies to reduce the impact of raccoons on nesting birds. Twenty-one raccoons were radio-tracked at the Richardson Wildlife Foundation in northern Illinois from May through Aug. of 2002 and 2003. The mean 95% kernel home range was 60.5 ha and the mean 50% core area was 8.1 ha. Males moved faster than f...
51 citations
TL;DR: Red deer home ranges in BNP were substantially larger than that reported in previous studies throughout Europe, suggesting that in old-growth forests with large carnivores present (i.e., the historical situation for most of Europe), red deer need large areas to meet their seasonal and annual requirements.
Abstract: We monitored four male and seven female red deer (Cervus elaphus) from Mar. 2001 to Mar. 2003 in Bialowieza National Park (BNP), Poland, to determine their home ranges in one of the best preserved old-growth forests in lowland Europe, and with large (>15 kg) carnivores present. Mean home-range size of adult males (36.0 km2) was significantly larger than adult females (8.4 km2). Seasonal home-range sizes differed significantly among seasons for both males and females, with the largest home ranges being in autumn for males (23.0 km2), and winter for females (7.1 km2). Inter-sexual differences in home ranges appeared to be influenced by differences in reproductive strategies and physiological needs. Both sexes exhibited strong range fidelity, although home ranges in different years overlapped more for individual males (93–100%) than females (71–90%). Home ranges of red deer in BNP were substantially larger than that reported in previous studies throughout Europe, suggesting that in old-growth forest...
45 citations
TL;DR: This study examined various quantitative aspects of this butterfly's biology, including the distributional range, habitat associations, population size and trends, demographic parameters and spatial aspects of population structure, including its dependence on beaver and its multi-tiered metapopulation structure.
Abstract: The endangered St. Francis Satyr (Neonympha mitchellii francisci) is a small sedentary butterfly and one of the rarest in North America. Our study examined various quantitative aspects of this butterfly's biology, including the distributional range, habitat associations, population size and trends, demographic parameters and spatial aspects of population structure. The range of N.m. francisci distribution is restricted to DoD lands at Ft. Bragg, North Carolina, where the butterfly utilizes wetland habitats, predominantly those that have previously been impounded by beaver. In situ habitat associations and captive rearing experiments indicate that multiple sedges in the genus Carex, particularly C. mitchelliana, may be important larval food plants. Subpopulation estimates range between 49–739 individuals at any one site, while cumulative population estimates range between 700–1400 individuals for all accessible areas on Ft. Bragg. Habitats occupied by N.m. francisci are frequently subject to burni...
40 citations
TL;DR: The results demonstrate that even relatively small amounts of woody vegetation in prairie landscapes can alter abundance, biomass and species richness and composition of small mammal communities.
Abstract: We examined response of small mammals to woody invasion of tallgrass prairie in northeastern Kansas by sampling sites that ranged from 0 to 100% in woody cover (i.e., frequently burned prairie to unburned closed-canopy gallery forest; woody coverage mapped from satellite imagery). Abundance and biomass of small mammals initially increased with increasing woody vegetation, but then decreased to their lowest level at 100% woody cover. Richness was greatest (an average of seven species) where woody cover was ≤17% and decreased to one species where woody cover was 100%. Abundance of white-footed mice (Peromyscus leucopus) increased as woody cover increased from 0 to 62% cover, but decreased in forested sites (100% cover). Abundance of western harvest mice (Reithrodontomys megalotis) decreased as woody cover increased; they were not recorded in forested sites. Deer mice (P. maniculatus) were present in sites with no to low levels of woody vegetation, but were absent in sites with moderate to high leve...
40 citations
TL;DR: In this paper, birds and vegetation were surveyed in a 9 ha plot in spring 1976 in a 73 y-old jack pine (Pinus banksiana) forest in northeastern Minnesota.
Abstract: Birds and vegetation were surveyed in a 9 ha plot in spring 1976 in a 73 y-old jack pine (Pinus banksiana) – black spruce (Picea mariana) forest in northeastern Minnesota. A 1368 ha wildfire burned across the area that autumn. The plot was resurveyed in 1977 and periodically through 2006. Before the fire, birds with the highest importance values were Blackburnian Warbler (Dendroica fusca), Ovenbird (Seiurus aurocapillus), Red-eyed Vireo (Vireo olivaceus) and Bay-breasted Warbler (D. castanea). Within 7 y following the fire, canopy tree cover decreased to near zero as fire-damaged trees died. Afterwards, the canopy began increasing, reaching 53% cover by 30 y. Shrub cover, 8% before the fire, peaked at over 70% two decades after fire, primarily as a result of dense jack pine and black spruce regeneration, and then decreased to 58% 30 y after fire. The total number of bird species using the area doubled the first year following the fire while the number of bird species with discernable territories decreased 40%. Thereafter, territorial species began increasing and 30 y after the fire the number exceeded the pre-fire richness by 60%. Overall, density of bird territories decreased nearly three-fold the first 3 y after the fire, but by year 30, was over 56% greater than in the pre-burn mature pine forest. Loss of canopy was related to a reduction in warbler and vireo diversity while increases in woody debris and near-ground vegetation were related to an increase in ground-brush foragers such as White-throated Sparrow (Zonotrichia albicollis) and Chipping Sparrow (Spizella passerina). Brown Creeper (Certhia americana) populations increased briefly as trees died, and for five years following fire there was an increase in woodpeckers and secondary cavity nesting species. At 7 to 10 y after fire, White-throated Sparrow, Magnolia Warbler (Dendroica magnolia), Chestnut-sided Warbler (D. pensylvanica), Nashville Warbler (Vermivora ruficapilla) and Mourning Warbler (Oporornis philadelphia) dominated. White-throated Sparrow continued to be the most important bird species through the first two decades, followed by Magnolia Warbler and Red-eyed Vireo. Thirty years after fire, the dominant birds were Nashville Warbler and Ovenbird, followed distantly by Veery (Catharus fuscescens) Swainson's Thrush (Catharus ustulatus), Least Flycatcher (Empidonax minimus) and Black-and-white Warbler (Mniotilta varia). Overall, bird species using the area after 30 y remained over 70% higher than in the mature forest before the fire.
38 citations
TL;DR: There is no evidence that mounds provided safe sites for early successional species, despite their abundance in the soil seed bank, or that diversity peaked on intermediate-aged mounds, but variation in species composition was greater within and among mounds than in adjacent patches of undisturbed vegetation.
Abstract: Pocket gophers have the potential to alter the dynamics of grasslands by creating mounds that bury existing vegetation and locally reset succession. Gopher mounds may provide safe sites for less competitive species, potentially increasing both species diversity and vegetation heterogeneity (spatial variation in species composition). We compared species composition, diversity and heterogeneity among gopher mounds of different ages in three montane meadows in the Cascade Range of Oregon. Cover of graminoids and forbs increased with mound age, as did species richness. Contrary to many studies, we found no evidence that mounds provided safe sites for early successional species, despite their abundance in the soil seed bank, or that diversity peaked on intermediate-aged mounds. However, cover of forbs relative to that of graminoids was greater on mounds than in the adjacent meadow. Variation in species composition was also greater within and among mounds than in adjacent patches of undisturbed vegetation, suggesting that these small-scale disturbances increase heterogeneity within meadows.
TL;DR: Smoke may play a more significant role in maintaining the composition and structure of tallgrass prairie communities than was previously realized.
Abstract: Tallgrass prairie species often require a period of cold stratification to break seed dormancy, but not all species germinate when this occurs. Fire, which has historically played an important role in defining the prairie landscape, may also play some role in breaking dormancy by producing a variety of biologically active smoke substances. The role of smoke as a germination cue was investigated in this study, during which the ex situ germination of 37 prairie species was measured in response to aerosol smoke treatment. Overall, one third of the species responded positively, while others were either inhibited or exhibited no response at all. Smoke may therefore play a more significant role in maintaining the composition and structure of tallgrass prairie communities than was previously realized.
TL;DR: This study is the first to compare characteristics of tree roosts of sympatric populations of Rafinesque's big-eared bats and southeastern myotis, suggesting that these species may have different preferences for roost trees.
Abstract: Rafinesque's big-eared bats (Corynorhinus rafinesquii) and southeastern myotis (Myotis austroriparius) are uncommon throughout their range and are listed (informally) by the U.S. Fish and Wildlife Service as species of management concern. Much of the decline in numbers of these species can be linked to a loss of bottomland hardwood forests throughout their range, resulting in a loss of natural roost structures in many areas. We characterized day roosts of both species and determined differences in characteristics of roost trees in western Tennessee. Radio transmitters were attached to adult females of both species to aid in locating new roosts. Thirty-one roost trees were identified, with most (93.5%) being large hollow water tupelos (Nyssa aquatica). Only two roost trees were used by both species during the survey period and no simultaneous roosting was documented. Roost trees in our study typically had triangular-shaped basal openings and large diameters (129.2 ± 7.3 cm). A significant differen...
TL;DR: Estimates of annual soil disturbance and fossorial habitat created suggest F. gordoni serves important ecological functions within the greater habitat.
Abstract: Foam casts and burrow excavations were used to examine Fallicambarus gordoni burrow occupancy rates, seasonal variation in burrow morphology, correlation between crayfish abundance and burrow abundance and potential ecological effects of burrowing through soil disturbance and the creation of fossorial habitat. Burrow occupancy rates were high (75%) and consistent between active and inactive seasons, although several burrow metrics differed significantly between seasons. Crayfish abundance was strongly correlated with burrow abundance. Estimates of annual soil disturbance (82 metric tons/ha/y) and fossorial habitat created (29–49 km/ha) suggest F. gordoni serves important ecological functions within the greater habitat.
TL;DR: In this paper, the authors found colonies and solitary big-eared bats beneath 38 bridges in 2002 and 54 bridges in 2003, and the majority of occupied bridges (94.7%) were in the Upper and Lower Coastal Plains, but a few bridges (5.3%) were located in the Piedmont.
Abstract: Rafinesque's big-eared bats (Corynorhinus rafinesquii) use bridges as day roosts in parts of their range, but information on bridge use across their range is lacking. From May to Aug. 2002 we surveyed 1129 bridges (12.5%) within all 46 counties of South Carolina to determine use and selection of bridges as day roosts by big-eared bats and to document their distribution across the state. During summer 2003, we visited 235 bridges in previously occupied areas of the state to evaluate short-term fidelity to bridge roosts. We found colonies and solitary big-eared bats beneath 38 bridges in 2002 and 54 bridges in 2003. Construction type and size of bridges strongly influenced use in both years; bats selected large, concrete girder bridges and avoided flat-bottomed slab bridges. The majority of occupied bridges (94.7%) were in the Upper and Lower Coastal Plains, but a few bridges (5.3%) were located in the Piedmont. Rafinesque's big-eared bats were absent beneath bridges in the Blue Ridge Mountains. We...
TL;DR: Survival and cause-specific mortality estimates were 81% and 67%, respectively, and canids caused most mortalities during both time periods and space use of fawn white-tailed deer in an agro-forest ecosystem in south central Michigan was described.
Abstract: Many cervids exhibit similar behavior near and following parturition. For example, during their first 2 mo of life, fawn white-tailed deer (Odocoileus virginianus) are relatively sedentary, may be at their highest risk for mortality and are not yet functional ruminants. Relatively few studies describe demographics or space use of fawn white-tailed deer ≤2 mo old despite the potential for mortality through this time period having a relatively large influence on deer population dynamics. Our objectives were to estimate survival, assess cause-specific mortality and describe space use (i.e., cover) of fawn white-tailed deer in an agro-forest ecosystem in south central Michigan. We captured (mid-May to mid-Jun.), radiomarked and monitored 34 fawns during 2004–2006 and pooled data for analyses. Two- and 6-mo survival estimates (Mayfield method) were 81% and 67%, respectively, and canids caused most mortalities during both time periods. Kernel home ranges (95%) during the first 2 mo averaged 40.9 ha (ra...
TL;DR: In this article, the authors examined the relationship between wetland type and the distribution of amphibians in 28 relatively undisturbed, seasonally flooded isolated wetlands in southwestern Georgia, USA.
Abstract: Conservation of isolated wetlands is critical for maintaining regional biodiversity within the southeastern U.S. However, relatively little is known about the ecological communities of these wetland systems, particularly within the karst wetlands of the southeastern Coastal Plain. In southwestern Georgia seasonal isolated wetlands include marshes, cypress savannas and cypress/gum swamps, which have fundamental differences in vegetation and soils, hydrology, water chemistry and invertebrate abundance and diversity. We examined the relationship between wetland type and the distribution of amphibians in 28 relatively undisturbed, seasonally flooded isolated wetlands in southwestern Georgia, USA. We sampled wetlands for amphibians in the winter, spring and summer using aquatic traps, dipnetting, PVC pipe refugia and automated frog call recording devices (frogloggers). Mean amphibian species richness among study wetlands was 12.7 ± 0.5 species (range 7–18). Both species richness and composition varied...
TL;DR: A comparative study to determine if life history differences exist between O. neglectus and O. eupunctus that could contribute to the displacement of O. E upunctus, and to document the under-studied life histories of crayfishes endemic to the southeastern United States.
Abstract: The crayfish Orconectes eupunctus is endemic to the Spring and Eleven Point rivers of Arkansas and Missouri, and appears to have been displaced from a portion of its range by the recently introduced crayfish O. neglectus. Life history can be a factor in crayfish species displacements as earlier reproduction or rapid juvenile growth may provide size advantages in competitive interactions, while higher fecundity might permit an invading species to out reproduce a native. We conducted a comparative study to determine if life history differences exist between O. neglectus and O. eupunctus that could contribute to the displacement of O. eupunctus. Crayfish were collected at three sites (each species alone and both species together) monthly from Jul. 2005 through Dec. 2006 by kick-seining. Timing of reproductive events was recorded, fecundity was evaluated through egg counts, and juvenile growth rates were examined using length-frequency histograms. Sex ratios, length-weight relationships, and adult si...
TL;DR: The results showed that turtles with even moderate carapacial algae can act as vectors in the dispersal of seeds associated with wetlands, and it is concluded that epizoochory is likely to occur in other turtle species.
Abstract: The role of animals in seed dispersal is widely acknowledged and turtles have been reported to act as vectors. All reports of turtles dispersing seeds to date have been via endozoochrony. The first evidence of turtles being epizoochronic dispersers of seeds via their carapacial algal mat is reported here. Chelodina longicollis is widespread and abundant throughout most of the eastern fringe of mainland Australia and throughout the largest inland river system, the Murray Darling Basin. They are the most terrestrially mobile of the Australian freshwater turtles and they are the most indiscriminate in habitat choice, inhabiting the entire range of water bodies from rivers to small ephemeral wetlands. Our results showed that turtles with even moderate carapacial algae can act as vectors in the dispersal of seeds associated with wetlands. However, as C. longicollis is unlikely to be unique among the freshwater turtles in this regard, we conclude that epizoochory is likely to occur in other turtle species.
TL;DR: In this article, the authors examined cavity use during the breeding and non-breeding seasons in old-burned ponderosa pine forests in the Black Hills, South Dakota, between 2002 and 2005.
Abstract: Recently, greater attention has been given to the potential keystone interaction between cavity excavators and the community of animals that use cavities. However, most research has focused on avian use of cavities in the breeding season, with little attention given to other cavity using guilds or cavity use during the non-breeding season. Furthermore, most breeding season studies were in unburned forests containing a mix of conifer and deciduous trees with much less attention given to cavity rich post-burn habitats. The objective of this study was to examine cavity use during the breeding and non-breeding seasons in old-burned ponderosa pine forests in the Black Hills, South Dakota. One hundred seventy nine active cavity nests of nine cavity nesting species were monitored between 2002–2005. We examined the contents of each cavity during the breeding season and twice during each non-breeding season (fall, winter, spring) each year. Additionally, we conducted vegetative surveys to determine the mi...
TL;DR: In this paper, the topographic variation in habitat affects the nesting ecology of three species: Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum) and Eastern Meadowlark (Sturnella magna).
Abstract: Much of the tallgrass prairie remaining in North America occurs in hilly regions, such as the Flint Hills of Kansas and Oklahoma. Despite the conservation importance of these areas for grassland birds, little is known about how topographic variation in habitat affects the nesting ecology of these species. We examined topographic patterns of nest distribution, daily nest survival and nest-site selection for three species: Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum) and Eastern Meadowlark (Sturnella magna). Dickcissels shifted from nesting more in lowlands to uplands as the season progressed. Grasshopper Sparrows and Eastern Meadowlarks generally nested in midland habitats, but seasonal differences were still evident in the relative proportions of nests found in lowlands vs. uplands. Topography did not affect nest survival of Dickcissels or Grasshopper Sparrows and had only a marginal effect on nest survival for Eastern Meadowlarks. Nest survival for Dickcissels and Grasshopper Sparrows was highly dependent on nest-site vegetation, however. Dickcissels and Eastern Meadowlarks both experienced greater daily nest survival with increasing vertical vegetation structure at nest sites, whereas daily nest survival for Grasshopper Sparrows increased with increasing cover of litter and grass. Although topography may not affect nest survival directly, it may have indirect effects mediated through nest-site vegetation because of selective nest placement. For example, Dickcissels and Eastern Meadowlarks selected sites with greater vertical vegetation structure than generally available, even in upland sites where vegetation structure was reduced. Conservation planning for grassland birds may thus need to consider how topographic variation affects habitat quality within hilly regions where much of the remaining tallgrass prairie occurs.
TL;DR: In this paper, the authors studied initial invasion of cheatgrass (Bromus tectorum) into burned pinon-juniper woodlands to determine if particular features enhance invasion and if particular grasses promote or retard invasion.
Abstract: We studied initial invasion of cheatgrass (Bromus tectorum) into burned pinon-juniper woodlands to determine: (1) if particular features enhance invasion and (2) if particular grasses promote or retard invasion. We compared cheatgrass cover among roads, burn edges, seeded interiors, unseeded interiors and unburned woodlands and quantified grasses present or absent near cheatgrass. Invasion was favored by burn edges, roads and seeded interiors, but not unseeded interiors. Odds of finding cheatgrass were seven times higher near prairie junegrass (Koeleria macrantha), but six times lower near James' galleta (Hilaria jamesii) and two times lower near intermediate wheatgrass (Agropyron intermedium). Invasion may be favored: (1) in burn edges because of higher seed-bank survival, (2) along roads because of moisture, disturbance and dispersal and (3) in seeded interiors because of seed-mix contamination or seeded species that enhance invasion.
TL;DR: It is recommended that careful measurement, recording and photographing of key characteristics as well as genetic analysis of suspected lynx-bobcat hybrids be priorities for natural resource agencies where hybridization between these species may occur.
Abstract: Hybridization between federally threatened Canada lynx (Lynx canadensis) and bobcat (L. rufus) was recently documented in the United States, but little is known regarding physical characteristics of hybrids compared to parent species. We report on the morphology and physical characteristics of five of seven Canada lynx-bobcat hybrids detected near the southern extent of the lynx's geographic range in Maine, Minnesota and New Brunswick. Hybrids displayed a range of physical characteristics, including features common to both lynx and bobcat, or that were intermediate in character. Observation of an adult female hybrid with three kittens, as well as placental scars in the reproductive tract of a second animal, suggest that hybrids may be reproducing successfully. We recommend that careful measurement, recording and photographing of key characteristics as well as genetic analysis of suspected lynx-bobcat hybrids be priorities for natural resource agencies where hybridization between these species may...
TL;DR: This review highlights those methods currently used and most applicable to ecological studies, including assays to study various aspects of the carbon and nitrogen cycles, and methods to directly link community structure to function.
Abstract: Interest in the relationships between soil microbial communities and ecosystem functions is growing with increasing recognition of the key roles microorganisms play in a variety of ecosystems. With a wealth of microbial methods now available, selecting the most appropriate method can be daunting, especially to those new to the field of microbial ecology. In this review, we highlight those methods currently used and most applicable to ecological studies, including assays to study various aspects of the carbon and nitrogen cycles (e.g., pool dilution, acetylene reduction, enzyme analyses, among others), methods to assess microbial community composition (e.g., phospholipid fatty acid analysis (PLFA), denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism analysis (TRFLP), quantitative polymerase chain reaction (qPCR)) and methods to directly link community structure to function (e.g., stable isotope probing (SIP)). In our discussion of these methods, we describe the information each method provides, as well as some of their strengths and weaknesses. Using a case study, we illustrate how these methods can be applied to investigate relationships between microbial communities and the processes they perform in wetland ecosystems. We end our discussion with a series of questions to consider prior to designing experiments, in the hope that these questions will help guide ecologists in selecting the most appropriate method(s) for their research.
TL;DR: Despite large initial clutch size, burrowing owls in the Imperial Valley may have adapted to nest predation by both dispersal and the ability to renest frequently, regardless of dispersal.
Abstract: Nest predation is considered a primary factor affecting the life-history characteristics and particularly dispersal of many avian species. We tested the hypothesis that nest predation would increase dispersal probability, dispersal distance and the frequency of renesting. We removed eggs from burrowing owl (Athene cunicularia) nests to simulate nest predation in southeastern California. Owls responded to egg removal with increased dispersal probability, nesting attempts and egg production. We found that nest predation tended to increase dispersal probability (50% depredated nests vs. 14% control nests), which occurred fairly soon after nest predation (0–25 d). Dispersal distance was highly variable among owls (range: 148–13,012 m). Following experimental nest predation, burrowing owls increased the number of nesting attempts and thus the total number of eggs produced in a season, regardless of dispersal. Clutch size, however, decreased as the number of breeding attempts increased. Despite large i...
TL;DR: Competition for food between these species is minimal, given the abundance and diversity of prey species available, and the transient nature of mergansers on Lake Erie during migration, it is concluded.
Abstract: Although published studies indicate the contrary, there is concern among many sport anglers that migrating red-breasted mergansers (Mergus serrator) and other waterbirds pose a competitive threat to sport fish species such as walleye (Sander vitreus) in Lake Erie. We quantified the diet of autumn-migrant mergansers and walleye during 1998–2000 in Sandusky Bay and adjacent waters of western Lake Erie. We hypothesized that the diets of both predators would be similar in species composition, but because of different foraging ecologies their diets would differ markedly in size of prey consumed. In addition to predator samples, we used trawl data from the same general area as an index of prey availability. We found that mergansers fed almost exclusively on fish (nine species). Gizzard shad (Dorosoma cepedianum), emerald shiner (Notropis atherinoides) and round goby (Neogobius melanostomus) were consumed in the greatest numbers, most frequently and comprised the greatest biomass. Walleye fed exclusively on fish: gizzard shad, alewife (Alosa psuedoharengus) and emerald shiner were consumed in the greatest numbers, most frequently and comprised the greatest biomass. Diet overlap between mergansers and walleye was 67% by weight and 66% by species frequency. Mean total lengths of gizzard shad, emerald shiner and round goby found in walleye stomachs exceeded those captured in trawls by 47%, on average. Mean total lengths of gizzard shad, emerald shiner and round goby were greater in walleye stomachs than in merganser stomachs. Mean total lengths of emerald shiner and round goby were less in merganser stomachs than in trawls. Our results suggest that although the diets of walleye and mergansers overlapped considerably, mergansers generally consumed smaller fish than walleye. Given the abundance and diversity of prey species available, and the transient nature of mergansers on Lake Erie during migration, we conclude that competition for food between these species is minimal.
TL;DR: The response of fish and aquatic insect assemblage properties to seasonal desiccation and habitat fragmentation is quantified to support findings at larger space and time scales and call attention to the importance of rapid changes in habitat quality, size and connectivity on stream communities.
Abstract: We sampled fishes and aquatic insects monthly (Jun.–Sept. 2002) from intermittent tributaries of the Alum Fork of the Saline River (Arkansas, U.S.A.) to quantify the response of fish and aquatic insect assemblage properties to seasonal desiccation and habitat fragmentation. We collected a total of 4219 individuals, representing 18 species of fishes and 27 families of aquatic insects. Changes in the composition of fish assemblages were significantly related to temporal variability in pool volume and location in the watershed. Smaller, upstream pools varied in volume more than downstream pools. Fish assemblages were significantly more similar through summer in downstream, larger pool habitats. Changes in the composition of aquatic insect families were related to variation in water quality conditions. Highly eutrophied sites were typically dominated by midge larvae (Chironomidae), resulting in highly similar assemblages over time. Our results support findings at larger space and time scales and call...
TL;DR: For one of two Artemisia species considered, evidence for volatile communication between stems that affected their tissue losses to herbivores is found, suggesting that volatile communication among stems or individuals may not be an unusual phenomenon, at least within the genus Artemisia.
Abstract: Recent work has demonstrated that communication between plants in natural settings can increase resistance against herbivores. However, this phenomenon has been found convincingly for only two species, alder (Alnus glutinosa) and sagebrush (Artemisia tridentata), and recent reviews have questioned the commonness of this phenomenon. Results from experiments involving sagebrush suggest that vascular signaling among branches within an individual is limited and that sagebrush may use external volatile cues instead. Communication among individuals may be a byproduct of volatile communication among branches of a single individual. We tested this hypothesis by examining systemic induced resistance and communication between individuals for two naturally occurring species of Artemisia. Artemisia cana exhibited systemic induced resistance without volatile cues. Assay branches on plants with experimentally clipped treatment branches experienced less herbivory than assay branches on unclipped controls even when air contact was blocked. We found no evidence of airborne communication between A. cana individuals that affected herbivory. Branches of A. douglasiana appeared to exhibit systemic induced resistance to experimental clipping. In addition, assay branches on plants with experimentally clipped neighbors received 45% less chewing damage than assay branches with unclipped neighbors. Although stems may have been connected by rhizomes, communication between stems required air contact. In summary, for one of two Artemisia species considered, we found evidence for volatile communication between stems that affected their tissue losses to herbivores. These results suggest that volatile communication among stems or individuals may not be an unusual phenomenon, at least within the genus Artemisia.
TL;DR: This work used historical and current fish assemblage data in conjunction with current habitat information to assess influences on an endemic Great Plains stream fish, the plains topminnow.
Abstract: Native fishes of the Great Plains are at risk of decline due to disturbances to physical habitat caused by changes in land and water use, as well as shifts in species assemblages driven by the invasion of introduced species with the loss of natives. We used historical and current fish assemblage data in conjunction with current habitat information to assess these influences on an endemic Great Plains stream fish, the plains topminnow (Fundulus sciadicus). Of the 31 sites where the plains topminnow occurred historically (1939–1940), it was found in only seven of those sites in 2003–2005. Our results demonstrate a shift in fish assemblage over time that coincides with the loss of plains topminnow. Changes in fish assemblages were characterized by increases in occurrence of exotic, invasive and generalist species with declines in occurrences of native fishes. An information theoretic approach was used to evaluate candidate models of current fish assemblage and physical/chemical habitat on the presen...
TL;DR: The clipping treatment was most successful at reducing fecundity, but also resulted in the highest survivorship of co-occurring juveniles, highlighting the necessity of examining fitness of plants in the non-targeted life stage in order to fully evaluate the effectiveness of different management techniques.
Abstract: Management of invasive species often targets a particular life stage in structured populations. Evaluating the success of management requires measuring the survivorship and reproductive success of the targeted stage class, as well as assessing the possibility for increased fitness in the non-targeted stage class due to a release from density dependence. Management of the invasive biennial, Alliaria petiolata (garlic mustard) focuses on removing adults by pulling or clipping and is applied early or late in the reproductive season. We evaluated the effectiveness of different management types (unmanaged, clipped, pulled) and timing (early or late) on survival and fitness of targeted adult plants and non-targeted, co-occurring juveniles. Viable seeds were produced by adults that were unmanaged, pulled early in the season and clipped at midheight early in the season. Unmanaged and pulled adults produced significantly more seeds than clipped plants; unmanaged plants produced seeds that were significant...