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The prairie mole cricket (Gryllotalpa major Saussure) is a rare endemic of the tallgrass prairie ecosystem of the south central United States. Males advertise for females using a low frequency acoustic signal from surface burrows aggregated in leks, but much of the spatial variation observed within the lek remains unexplained. This study reports on the relationship between male spacing and grassland habitat structure within the display arena. The data suggest that as grass heights increase within the lek arena, advertising males increase the distance between their burrows and increase the angle of the surface opening of the burrow. The positive correlation between biomass and spacing was not also seen between biomass and angle of the burrow opening. Prairie mole cricket males, thus, exhibit a form of behavioral plasticity that may have evolved in response to the dynamic disturbance regimes that form and maintain the tallgrass prairie ecosystem.
Celastrus orbiculatus is a non-native, invasive liana that was introduced to the United States in the 1860s and has spread rapidly throughout the Northeast. Several attributes contribute to the invasiveness of C. orbiculatus, including tolerance to a wide range of light levels and habitat types. We compared soil characteristics in seven sets of adjacent, paired plots, spanning a range of habitats and soil types, with and without C. orbiculatus. The paired plots were similar other than the presence or absence of Celastrus. Plots with C. orbiculatus had significantly higher soil pH, potassium, calcium and magnesium levels. Furthermore, nitrogen mineralization and litter decomposition rates were higher in plots with C. orbiculatus. Phosphorus levels were not significantly different between the paired plots. The results of this study contribute to the growing body of research of the effects of invasive species on ecosystem processes.
Plant invasions have been hypothesized to proceed at the local scale (i.e., individual patch or stand) according to one of several distinct spatial patterns. However, few studies have attempted to reconstruct the patterns of perennial herbaceous plant invasions at local scales due to difficulty in determining the age of individuals. We used herb chronology to determine the ages of roots within several crown vetch patches in order to characterize the spatial age structure of these patches. Additionally, we examined both sexual and vegetative crown vetch reproduction, with regard to potential impacts on local spread and persistence, through seed bank sampling and greenhouse experiments. We found little distinct spatial age structuring in crown vetch patches, perhaps due to a lack of older roots caused by rapid ramet turnover within patches. We also found no support for the hypothesis, proposed by several land managers, that crown vetch builds up a large seed bank. However, we did find that even small fragments of crown vetch plants are capable of vegetative regeneration, which may be important in explaining this species' persistence in spite of control measures.
Most landscapes are heterogeneous in vegetation composition and thus, in the distribution of nutrients required by herbivores for growth and reproduction. Hispid cotton rats (Sigmodon hispdus) inhabit Texas coastal prairies which are characterized by habitat patches dominated by dicots, monocots or both [mixed] plant types. Hispid cotton rats must obtain nutrients necessary for reproduction by ingesting both dicots and monocots, and reproductive females concentrate their activity in mixed patches. Mixed patches may be selected because they have high nutrient contents or because presence of both monocot and dicot food plants lowers cost of foraging movements. Because hispid cotton rats select a nutritionally complete diet and may detect protein by odor and taste cues, we hypothesized that nutrient concentrations may cue position of foraging paths. We used nutrient maps to measure amount of protein, P and Ca encountered during foraging from radiotracked individuals. We compared these values to those obtained from randomly generated foraging paths. Actual and random paths did not differ in amount of protein, P or Ca encountered. Differences in nutient accumulation between seasons were explained by seasonal differences in availability. We conclude that foraging paths do not respond to nutrient content of plants, but that reproductive females likely occupy mixed habitat patches because presence of both dicot and monocot food plants decreases time and energy spent foraging.
A 1.44 ha plot in a disjunct Tsuga canadensis-dominated forest in southern Wisconsin was mapped and examined for 25 y. Every 5 y between 1981 and 2006, all of the trees ≥ 2.54 cm dbh were measured and mortalities and additions were noted. The stand had a 27.6% overall decline in density and a 5.8% decline in basal area. Tsuga remained the dominant species though it had a 28.2% decline in density and a loss in basal area of 12.6%. It still made up almost half the relative density and relative dominance throughout the study. Diameter distributions for the six leading species were all bell-shaped or skewed unimodal with the exception of Acer saccharum which had an inverse J-shaped curve. Tsuga presented bell-shaped curves due to the lack of recruitment from the seedling stage. Nearly 32% of the original Tsuga trees ≥ 2.54 cm dbh died throughout the study, giving an annual mortality rate of 1.53%/year. The annual mortality rate for Tsuga stems ≥ 30 cm dbh was 0.71%/year, which is higher than a Michigan study using the same sized stems. The long-term outlook for the Tsuga in this isolated stand is uncertain due to its sporadic regeneration, high mortality rate, possible deer browsing effects combined with future potential threats such as land development, climate warming and the hemlock woolly adelgid.
Prey capture in pitcher plants has been found to be significantly dependent on pitcher size, but the actual importance of size is not clearly understood. We studied insect capture by the carnivorous plant Sarracenia alata and compared the rate of insect capture per unit capture area of plants with that of nonbiological models and traps. The total mass of insects captured was significantly positively related to capture area for both biological and nonbiological systems. However, the rate of insect capture was significantly greater for plants than for models and traps, which suggests a role of attractants in insect capture in pitcher plants. Odor from decaying insects was found to have a significant effect on insect capture on experimental attraction cups. Further study should focus on the nature of other attractants including nectar, UV reflectance and volatiles to determine their role in insect capture by pitcher plants.
We evaluated the status of remnant prairie patches in the Loess Hills of southeastern South Dakota using three parallel approaches. Aerial photograph analysis, vegetation surveys and stable carbon isotope analysis of soil organic matter all yielded evidence of woody plant encroachment. Time series analysis of aerial photos indicated that forest cover expanded by 37.5% between 1941 and 2000. Vegetation surveys revealed several distinct community types ranging from forested ravines supporting basswood, American elm and black walnut trees to upland prairie remnants and oak savannas that now include encroaching eastern red cedar trees, and/or a dense understory of prickly ash, ironwood and other woodland species moving up from the ravines. Finally, carbon isotope values (δ13C) in soil cores decreased as much as 5–7‰ towards the soil surface consistent with increased prevalence of C3 forest species over C4 prairie species in recent years. One consequence of forest encroachment appears to be an increase of 35% in soil organic carbon (SOC) content in surface soils. At the current rate of encroachment and unless management techniques are employed to keep the forests in check as fires once did, we expect the existing prairie remnants to be completely replaced by forest within the next several decades.
In recent decades, an increasing number of plant species have been negatively affected by anthropogenic habitat fragmentation and disturbance. In many cases, the habitat matrix between populations has been converted from a natural to an urban environment. One such species, Lilium philadelphicum (Liliaceae) a showy perennial with a naturally patchy distribution, currently has populations in parts of its range in North America that persist on highly urbanized and fragmented landscapes. In this study, we used six nuclear microsatellite loci to characterize the amount and apportionment of genetic diversity among 12 remnant populations in the Midwest United States. Genetic diversity was high (7–31 alleles per locus, mean HO = 0.44–0.70). An analysis of molecular variance (AMOVA) detected a low level of genetic structure (FST = 0.06, P < 0.001), and no effect of isolation by distance among sites (r2 = 0.02, P = 0.28). Principle coordinate analysis (PCoA) of inter-individual genetic distances revealed essentially no structuring with PC axes one and two explaining only 22.5 and 19.7% of the observed variation respectively. Moreover, Bayesian exploration of population structure supported this observed lack of structure with a low optimum number of estimated genetic “clusters” (e.g., populations; K = 1). If habitat fragmentation does affect gene flow among populations we cannot yet detect a strong genetic signature of this process; most likely due to the recency of landscape disturbance relative to the long generation time of this species. These results suggest that the genetic composition of these remnant populations is relatively homogenous and as such, provides land managers with a large potential germplasm source with a broad genetic base for use in local restoration activities.
Only 0.02% of historic oak savanna exists today. To provide management recommendations, we characterized age-class structure, measured cover of competing tree species and estimated genetic variation within and among four Quercus macrocarpa Michx (bur oak) populations in the Minnesota River Valley. At each site, few middle-aged bur oaks existed, most were 90–140 y. Quercus macrocarpa had the highest importance value (IV) in the older tree species cohort, but never the highest IV among younger trees suggesting that oak recruitment from 1910–1970 was very low. The four Q. macrocarpa populations and both age cohorts possessed moderate genetic diversity. Genetic distances between pairs of bur oak populations were small, but younger cohorts were more genetically differentiated than older cohorts suggesting that gene flow has declined in the past 100 y. Practices that reintroduce fire, reduce grazing and competition with mesic species, and restoration that introduces acorns from nearby populations have the potential to enhance both oak regeneration and genetic diversity.
Information regarding survival and cause-specific mortality of eastern wild turkeys (Meleagris gallopavo silvestris) is vital to their management, especially in small or isolated populations. Between January 2003 and August 2005, we used radio telemetry to investigate survival and cause-specific mortality of 87 [44 male (24 adult and 20 juvenile) and 43 female (34 adult and 9 juvenile)] wild turkeys in northern Indiana. We estimated annual and seasonal survival using the Kaplan-Meier product-limit method. Mean male and female annual survival estimates were 0.257 and 0.777, respectively. Annual survival estimates were different between sexes within years, but were homogenous within sexes between years. Survival estimates did not differ among seasons for either sex. However, differences in survival estimates between sexes were detected in the spring, fall and winter seasons. Hunter harvest (46.2% male mortality) and predation (33.3% female mortality) were the leading known causes of mortality for male and female wild turkeys, respectively. Predators (canids, birds and unknown mammals) were responsible for 28.6% of mortality for both sexes combined. Although predation on adult birds was not severe, high mortality of male turkeys in the form of legal spring harvest, in addition to other causes of mortality, warrants concern for small, exploited populations in highly fragmented landscapes like those of northern Indiana.
In Part I (Livezey, 2009), I presented the chronology and distribution of the range expansion of Barred Owls (Strix varia) from the late 1800s to the present. Here I explore what had prevented Barred Owls from expanding their range westward during recent millennia and what allowed them to do so during the past century. Using strength-of-evidence analysis, I evaluate the plausibility of the five ecological or behavioral changes proposed in the literature to have facilitated the range expansion. From this evaluation, three of these changes appear to be implausible, one appears to be plausible after modifying its location, and one appears to be very plausible. For the very plausible one, I score seven ecological changes that may have affected it using five strength-of-evidence criteria. Overall, it appears the historical lack of trees in the Great Plains acted as a barrier to the range expansion and recent increases in forests broke down this barrier. Increases in forest distribution along the Missouri River and its tributaries apparently provided Barred Owls with sufficient foraging habitat, protection from the weather, and, possibly, concealment from avian predators to allow Barred Owls to move westward. Decades later, increases in forests in the northern Great Plains allowed Barred Owls to connect their eastern and western distributions across southern Canada. These increases in forests evidently were caused by European settlers excluding fires historically set by Native Americans, suppressing fires and planting trees. They apparently were caused, to lesser degrees, by European settlers extirpating bison (Bison bison), overhunting elk (Cervus elaphus) and deer (Odocoileus spp.) and, in some areas, extirpating beaver (Castor canadensis) and replacing native ungulates with livestock. Accordingly, it appears the range expansion was prohibited for millennia by actions of Native Americans and recently facilitated by actions of European settlers.
Overgrazing, weed invasion and wildfire have resulted in the conversion of large areas of shrub steppe to exotic annual grassland in the western United States. This has been accompanied by reduced habitat for native plants and animals, and altered water and nutrient flows. In these landscapes, badgers increase landscape heterogeneity by creating a mosaic of foraging pits and mounds over extensive areas while preying on fossorial animals. The effects of badger-produced mounds on infiltration and surface physical properties were examined in a mixed sagebrush (Artemisia) – winterfat (Krascheninnikovia) site in west-central Idaho. Recently constructed mounds were physically degraded (i.e., more compacted, poorly aggregated, few macropores, erodible by wind) and vascular plant and cryptogamic crust cover increased as mounds aged. Infiltration through younger mounds was about half that through older mounds or inter-mounds. The results indicate that mounds function as water shedding sites, suggesting that the area around the base of the mounds will be moisture-rich, and may be important for recruitment of shrub-steppe plant species.
The purpose of scientific writing is to impart thoughts or ideas and their bases and implications in such a manner that a reading audience, with at least a moderate knowledge of science, can understand the material presented within a paper. This carries the necessity of using words in a manner that clearly impart the intended meaning of the author and not getting off the subject as reflected in the title. Also, the goal of scientific writing is to produce a manuscript written from the perspective of strength, rather than weakness. I discussed appropriate formation of titles such that the intended audience can find the title through bibliographic sources. Also included, to aid in the writing of scientific manuscripts, are discussions of words or sentences with unintended connotations, misuse of words, double entendres, slang, contrived acronyms, jargon, danglers or orphaned clauses, and superfluous words. Finally, remember that the object of the art of scientific writing is to communicate in the most concise and precise manner possible, it is not to paint pretty word pictures.
This section is placed at the beginning of a manuscript and must convey everything presented: what the research was about, where, why, and how it was conducted, and what it means relative to the current state of knowledge. It should consist of one paragraph of 250 or fewer words (i.e., no more than 3% of length of manuscript). Abstracts always are written in the past tense, thus, the best quality abstracts are written after the remainder of the manuscript is finished. Bibliographic services publish only the title and abstract of manuscripts. When conducting a literature search, researchers may read abstracts of perhaps 100 s of papers in which the titles possibly have bearing on an aspect of their work. Only if the content of the abstract seems relevant, will researchers progress to reading the article from which the abstract was derived. Therefore, great care must be used to write an abstract so it correctly reflects the contents of the manuscript in a precise and concise manner that can stand alone. Furthermore, it must contain no figures, tables, or references to them, or material not presented in the body of the manuscript; except for critique papers, no literature citations should be included. Also, it should not contain acronyms or jargon, even with definitions, not readily known to the general reading audience of the publication in which the manuscript will be published.
Epizoochory is the mode of seed dispersal where a diaspore (disseminating plant propagule) is disseminated on the external surface of an animal. While the structures that facilitate diaspore adherence are diverse, epizoochory is considered to be relatively rare (approximately 10% of angiosperms), but is commonly utilized by several invasive plant species. We experimentally sought species specific associations between the adherence and retention of eight common plant species' diaspores and five mammalian furs, plus human clothing. We sought relationships between both fur and diaspore characteristics in both the adherence and retention of diaspores. Diaspores of Geum aleppicum were the only ones interacting significantly better with one kind of substrate (mouse fur) than diaspores of all other plant species by being retained well in mouse fur. Alternatively, bison fur behaved as a “generalist” disperser, by consistently accommodating the adherence and retention of a wide range of diaspore morphologies. Finally, exotic plant species displayed a higher tendency than natives to adhere to a variety of mammal fur types, indicating a more flexible dispersal strategy for the invasive habit.
The research studied the benthic algal cyanobacterial community and ecological and physical characteristics to determine whether recreational hiking impacts the Virgin River in Zion National Park, Utah. Sampling occurred on 10 August 2001 of three cobblestones from 11 different riffle locations. The null hypothesis is the algal community will change in assemblage structure and function along a hikers gradient. This hypothesis predicts that lower or no visitor use sites will have lower algal species diversity, average cell biovolume, cell density, total biomass, chlorophyll a, AFDM, and ash weight and percentage. There were 99 benthic algal and cyanobacteria species identified from the Virgin River. The benthic flora and ecological/physical parameters were examined to assess the impact of hiking. Canonical correspondence analyses of the species data separated sites into 2-groups (impacted and none to low impact). The first and second axes of the ecological/physical variables explained 67% of the variation. The average cell biovolume and species diversity were positively aligned to the first axis, while cell density was slightly negatively aligned. The data suggests the ecological threshold had been reached lowering the relative abundance of diatoms and increasing cyanobacteria contribution. Further research needs to be accomplished determine exact cause.
Dietary studies of sea otters often focus on the ecological implications of foraging on large, energy rich prey. Although fish eggs and kelp have been documented as part of sea otter diets in the past, their relative importance and ecological implications have often been overlooked. Evidence of a relatively large aggregation of sea otters foraging on fish eggs and kelp is presented in this study with the potential implications for local herring fishery recovery. A gradual increase in the number of individuals using this resource over time also indicated that sea otters were attracted to large feeding aggregations which may increase exploitation of previously under utilized resources.
Inhaled isoflurane is one of many chemical immobilizing agents available for field anesthesia of wildlife. We examined the use of inhaled isoflurane for field immobilization of mesopredators. Five species of mammals were anesthetized in a wetland complex in south-central Nebraska with isoflurane; we developed an induction chamber to use with a portable anesthesia machine to provide anesthesia at the capture location. Sixteen raccoons (Procyon lotor), 20 striped skunks (Mephitis mephitis), 4 Virginia opossums (Didelphis virginiana), 2 American badgers (Taxidea taxus) and 1 mink (Mustela vison) were captured and immobilized; we radio-marked 11 raccoons and 9 skunks. Induction was smooth and uneventful for all species immobilized. Mean induction times for raccoons and skunks were 10.7 min (SD = 1.1) and 11.0 min (SD = 2.4) respectively. Mean handling times (post-induction) were 7.1 min (SD = 3.9) for raccoons and 7.3 min (SD = 4.8) for skunks. All animals, with the exception of opossums, were fully recovered within 15 min (raccoon mean recovery: 11.1 min, SD = 3.5; skunk mean recovery: 10.9 min, SD = 3.7). Recovery times for radio-collared animals and uncollared animals did not differ, and individuals with longer handling times did not require longer recovery times. Although isoflurane requires more equipment than injectable anesthesia methods, its short recovery time and wide safety margins deem it practical for use in a variety of field applications.