Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact email@example.com with any questions.
Associations between environmental variables and reproductive condition of six catostomid (family Catostomidae) species were evaluated in the Baraboo River, Wisconsin. Electrofishing and hoop net surveys conducted from Mar. to Jun. of 2001 and 2002 revealed white sucker (Catostomus commersoni) reached spawning condition first, followed by quillback (Carpiodes cyprinus) in both years. These two species were followed by the overlapping spawning times of spotted sucker (Minytrema melanops), golden redhorse (Moxostoma erythrurum), shorthead redhorse (M. macrolepidotum), and silver redhorse (M. anisurum). The first axis of a principal component analysis (PCA; based on six environmental variables) explaining 47% of the variation in the environmental variables represented water temperature, flow, and day of the year. The second axis explaining an additional 26% of variation depicted the magnitude of shorter-term changes in water temperature and flow. The best-fitting multinomial logit model to explain variation in reproductive condition of white sucker, shorthead redhorse, and silver redhorse included the first two PCA axes, species, year, and sex along with several first order interactions as predictor variables. The model predicted general temporal trends in reproductive condition over the spawning season but sampling noise precluded the model from identifying fine-scale temporal variation in spawning. Temporal variation in catostomid reproductive condition appears to be driven by complex interactions among species and environmental cues.
Crayfish of the species Orconectes virilis inhabit two distinct types of hydrodynamic environments: lakes and rivers. Odor cues in these habitats convey chemical information differently due to dispersion by different physical processes. In the laboratory we examined orientation strategies of crayfish collected from lake and river habitats to an odor source dispersed in either a lotic (river) or lentic (lake) manner. Our results showed lake crayfish had variable responses under both flow regimes whereas river crayfish oriented similarly under both flow regimes. Lake crayfish increased walking speeds, decreased heading angles, and decreased turn angles while orienting under lotic versus lentic conditions. Conversely, river crayfish oriented similarly under both flow regimes and reflected lake crayfish behavior in lotic flow. We conclude lake and river crayfish show differences in their orientation strategies due to influences from sensory signals in their source habitat. These results show crayfish show behavioral plasticity with respect to the hydrodynamic and signal structure from their native environments and may be an example of sensory bias.
Ranunculus ficaria is an invasive plant species in the northeastern United States, especially in urban riparian habitats. Changes in the frequency and intensity of flooding events in these urban riparian corridors create patches of heavy litter and patches of bare ground. Many plant species either cannot penetrate deep litter, or they are susceptible to freezing temperatures and drying conditions on bare ground. This can result in competitive advantages for invasive species that are adapted to these varying conditions. We conducted a field experiment to test the effects of leaf litter depth on R. ficaria biomass, bulbil production, flower production, and seed production under deep (20 cm) litter, intermediate (10 cm) litter, shallow (5 cm) litter, and bare ground along an urban stream in Louisville, Kentucky. Deep litter and lack of litter decreased plant biomass compared with shallow litter. Bulbil production was not significantly different across treatments. Flower and seed production were only reduced in deep litter. Ranunculus ficaria's ability to maintain production across a large range of litter depths may provide a competitive advantage over plant species not adapted to varying litter depths.
We quantified the fine root length density of Lonicera maackii (Amur honeysuckle) and native trees at two depths on transects away from individuals of this invasive shrub and tested whether the invasive shrub L. maackii reduced water availability for other forest plants by either of two mechanisms: (1) intercepting rainwater during light rain events or (2) absorbing large amounts of water through its fine roots. To test the two hypothesized mechanisms, we selected plots near large L. maackii shrubs and control plots away from any large L. maackii shrubs in the forest understory. Within each plot we placed a trenched and an untrenched subplot and measured soil water content in each. We also measured precipitation above and below L. maackii canopies. We found that within 2 m of large L. maackii shrubs, this shrub accounted for a large fraction (22–25%) of the fine roots in the top 12 cm of soil. Reduced throughfall and soil moisture below shrubs supported the hypothesis that L. maackii competes with tree seedlings by interception. Findings were inconclusive regarding the hypothesis of competition by water uptake.
A study was conducted to assess the effects of predicted climate change on seedling emergence, growth, and survival for the federally listed threatened species Cirsium pitcheri in the region proximal to Chicago, Illinois, U.S.A. Three geographically distant extant populations that could potentially serve as donors to re- introduced Illinois populations were tested to determine the influence of local adaptation on seed response to climate scenarios at two future time points. For all three populations, temperature was shown to be the most critical factor impacting future growth. All populations performed worst at the 2095 temperature for four measured growth metrics: length of longest adult leaf, number of adult leaves, dry shoot mass, and dry root mass. Growth performance at the 2095 conditions did not correlate with climate familiarity but did reflect the genetic diversity of the parent population. Predicted changes in average precipitation did not produce a significant effect on any growth metric, possibly reflecting a limitation in the study conditions. Seedling emergence and survival were tied to seed mass, a trait influenced by maternal effects and correlated with the level of inbreeding depression in the parent population. These results suggest managing populations to maintain high genetic diversity could be an important factor in tolerating temperature stress associated with climate change.
I studied pollination of the Arizona hedgehog cactus (Echinocereus arizonicus), an endangered plant species occurring in the Superstition Mountains, Arizona, in order to identify the pollinators of the species, determine whether the species is self-incompatible or pollen-limited, and evaluate whether individuals transplanted to make way for habitat disturbance continue to receive pollination. The flowers of E. arizonicus are large, bright red, and cup-shaped. Important flower visitors included hummingbirds and native halictid bees. Flower visitor guilds were similar between the wild population and the transplanted individuals (located in the Boyce Thompson Arboretum in Pinal County, Arizona), although the Arboretum is located at a low elevation and supports much higher abundances of flowering plants and pollinators than occur in the wild sites. Pollination treatments indicated E. arizonicus is highly self-incompatible but not pollen-limited and hummingbird visitation is relatively more important to seed set than is insect visitation but both contribute to total seed counts.
Nitrogen (N) and phosphorus (P) affect the structure and function of grasslands by altering plant competitive interactions, shifting patterns of above and below ground biomass allocation, and increasing net primary production. However, the influence of N and P on net ecosystem CO2 exchange (NEE) is poorly understood. In a field-based factorial N- and P-addition experiment, we measured shallow soil moisture, leaf area index, and component fluxes of midday ecosystem CO2 exchange throughout the growing season in a restored temperate grassland near Buffalo, New York. Throughout the growing season, N-addition increased gross ecosystem CO2 exchange (GEE) and correspondingly altered NEE to increase ecosystem CO2 uptake. In contrast N-addition caused a seasonally dynamic decline in leaf area adjusted GEE, a pattern consistent with increased photosynthetic light limitation. P-addition did not significantly increase Re, and N- and P-addition interacted to significantly weaken the ecosystem as a midday CO2 sink. Moreover, water limitation and phenological constraints during the middle and late growing season appear to limit plant responses to nutrient addition. These results suggest influences of N- and P-addition on ecosystem processes are seasonally dynamic and by differentially influencing above and below ground components of ecosystems, the availability of N and P in soils may interact to influence ecosystem CO2 exchange.
Fire and grazing are commonly used to manage nonnative grasses in the Northern Great Plains, but the effects of fire frequency and management between fire events on fire behavior in this region are poorly understood. We examined temperature and duration of prescribed spring fires at two locations where plots were treated with two fire frequencies (annual or biennial), simulated grazing (1 mo of weekly clipping in spring) and no simulated grazing. In May 2011 and 2013, soil surface fire temperatures and heat duration were monitored in treatment plots using thermocouples. Probes also were placed at 1, 2, and 3 cm depths to measure soil heat transfer. Lethal heat duration (>60 C) at the surface tended to be longer in plots treated with biennial fires compared to plots treated with annual fires. Fires in 2011 had higher maximum temperatures than 2013. Cooler fires in 2013 were characterized by longer durations of lethal heat. However, simulated grazing increased residence time of lethal temperatures in biennial plots and reduced lethal temperature duration in annual plots. Surface heat did not influence soil temperatures even at the 1 cm depth. Greater fuel loads, characteristic of plots treated with biennial fires, generally were associated with higher maximum temperatures and longer heat durations. Results suggest decreasing fire frequency to once every 2 y, perhaps combined with biennial grazing management, may enhance fire behavior to better meet management objectives.
Tallgrass prairies pastures are desirable grazing resources and preferred habitat for some wildlife species. Invasion of cool-season grass into these warm-season dominated grasslands is a common problem, and selectively removing cool-season grasses can be a challenge. In four trials conducted in southeastern Nebraska, we evaluated the effectiveness of the herbicide tebuthiuron, applied at rates between 0.7 and 2.7 kg ai ha−1, on selectively controlling cool-season grasses in tallgrass prairie pastures. We included glyphosate (1.3 kg ae ha−1) and imazapic glyphosate (0.21 0.4 kg ae ha−1) in two of the trials for comparison. In three of the four trials, tebuthiuron at 0.9 kg ha−1 or greater reduced cool-season grass yields by over 60% and increased warm-season grass yields by 50 to 300%. Glyphosate and imazapic glyphosate reduced cool-season grass yields but had no effect on warm-season grass or forb yields.
Historic, wide-spread destruction of native prairies in Minnesota was caused by conversion to agricultural land, disruption of disturbance regimes, and loss of key species. Attempts to restore tall-grass prairies have resulted in a new ecosystem type on the Midwestern landscape, with novel assemblages of both plant and animal species. The mammalian herbivore community, once dominated by bison, is now primarily comprised of white-tailed deer (Odocoileus virginianus), Eastern cottontail rabbits (Sylvilagus floridanus), and small mammals such as meadow voles (Microtus pennsylvanicus). The role of this assemblage of herbivores in restored prairies is not well understood. This study characterizes patterns of mammalian herbivory on five legume species in restored prairie in southern Minnesota. Legumes were sampled along transects that varied in their distance from the prairie-forest boundary and time since prescribed burning. Herbivore selectivity was determined for each legume species using an electivity index based on the total number of stems of each species and the percent of stems grazed. Herbivory was highly variable among legume species: Desmodium canadense was strongly preferred, Dalea candida and Dalea purpurea were moderately preferred, and Amorpha canescens and Lespedeza capitata were avoided. Both Dalea species and Lespedeza experienced increased rates of herbivory in burned sites. Avoided species were characterized by either low tissue nitrogen content or a high proportion of recalcitrant carbon relative to preferred species. These results suggest mammalian herbivores have an important functional role in prairie communities with potential consequences for community dynamics and the success of prairie restorations.
Grasslands enrolled in conservation programs provide important habitat for nesting game birds and waterfowl, but conservation grasslands have been targeted as a source of biomass for bioenergy and this could impact nesting birds. We studied the effects of biomass harvest on nest success and density using 109 blue-winged teal (Anas discors), mallard (Anas platyrhynchos), and ring-necked pheasant (Phasianus colchicus) nests found in southwestern Minnesota during 2009 (pretreatment) and 2010 (posttreatment). Grassland biomass was harvested in late autumn of 2009 with production-scale machinery. Harvest treatments included controls (0% biomass removal), partial harvest (50 or 75% biomass removal), and full harvest (100% biomass removal) from 8 ha plots. Nest success averaged 31% and was not influenced by biomass harvest. Daily survival rates were greater for nests located closer to wetlands. Estimated total nest density (0.42 nests ha−1; corrected for survivorship) was similar across harvest treatments, but within-plot analysis revealed nest density was greater in unharvested refuge regions. Estimated nest density was positively correlated with vegetation height and the spatial extent of wetlands surrounding each plot. Harvesting relatively small-scale patches of conservation grasslands in late autumn does not appear to be detrimental to nesting ducks and pheasants the following spring, but managers should consider leaving unharvested refuges near wetlands when harvesting large continuous tracts.
We investigated season-of-release effects on survivorship and reproductive success of laboratory-bred compared with a native population of golden mice [Ochrotomys nuttalli (Harlan)] within a deciduous forest habitat. We released two sets of 32 adult pairs of laboratory-bred golden mice into eight experimental transects established in forest-edge habitat. Releases were conducted in early spring (7 Mar. 2009) and late autumn (2 Nov. 2009). Population abundance of laboratory-bred and native golden mice was severely reduced in late spring and summer following the spring release due to black rat snake [Elaphe obsoleta (Stejneger and Barbour)] predation. Laboratory-bred golden mice, however, maintained a stable population density of 15–18 individuals following the late autumn release as snake predation diminished during winter months. The native population of golden mice maintained an abundance of 25–28 individuals through mid-Mar. The laboratory-bred and native populations exhibited similar reproductive success following autumn release, even crossbreeding during winter.
The season-of-release was the most important factor regarding survivorship and reproductive success of released laboratory-bred golden mice and the native population in identical forest-edge habitat.
Conspecific aggression may play an important role in partitioning resources and maintaining territories among beavers (Castor canadensis), yet few studies have examined physical evidence of agonistic encounters. We trapped and examined pelts from 147 beavers harvested between 2006 and 2012 from the Sangamon River (n = 96) and tributary streams (n = 51) in central Illinois. We modeled the influence of sex, age class, season (predispersal or dispersal), and habitat (river or tributary stream) on the number of recent injuries caused by conspecifics. One-third (51/147) of beavers had ≥1 injury; of those, the median number of injuries was 2.0. Kits had fewer injuries than adults (βKit = −2.24 ± 0.63), but yearlings and subadults did not (βyearling = 0.02 ± 0.38, βsubadult = −0.22 ± 0.48). Beavers on small streams had only one-quarter of the injuries recorded for beavers on the river (βStream = −1.34 ± 0.82). We failed to detect differences in injuries between the sexes. Our results suggest both sexes participate in territorial defense through physical confrontations and such encounters can be costly to both dispersing juveniles and resident adults.
Knowledge of fundamental biological characteristics, such as food habits, is essential for conserving wildlife, especially as species distributions shift in response to climate change. We captured wolverines (Gulo gulo) in Greater Yellowstone, one of the southernmost points of the species distribution, where we identified wolverine food items in the field (n = 91) and collected wolverine scats (n = 96) while snow tracking, visiting den and rendezvous sites, and examining concentrated locations from very high frequency (VHF) telemetry and global positioning system (GPS) collars. Similar to other areas of their distribution, wolverines in Greater Yellowstone appeared to focus on scavenging ungulates during winter (χ2 = 20.1, df = 1, P < 0.0001) and preying upon rodents, neonatal ungulates, and other small prey during summer (χ 2 = 2.94, df = 1, P = 0.08). However, our results showed a focus on food species not found across much of the wolverine's circumboreal range, e.g., elk (Cervus elaphus) and yellow-bellied marmots (Marmota Flaviventris). Factors other than prey species composition result in the limit to wolverine distribution and changing distributions of prey species as climate change occurs may not be of great concern for wolverine conservation.
The timing of births in ungulates has significant implications for juvenile survival and population growth. For North American elk (Cervus elaphus), typical parturition season ranges from late May to early Jun., and juveniles born outside of this peak characteristically exhibit lowered survival. We observed abnormally long parturition seasons in free-ranging elk populations in Missouri and South Dakota during 2012. Both populations exhibited late births; the last known births occurred on 26 Sep. in Missouri and 4 Sep. in South Dakota. Duration of parturition season was 112 and 119 d in Missouri and South Dakota, respectively. In Missouri, late births likely resulted from breeding by both yearling females and males. Late parturition in South Dakota may be caused by extended estrous cycles of elk that occurred on high quality range where few adult males were located.
California tiger salamanders (Ambystoma californiense) exhibit an obligate metamorphic life history strategy in which aquatic larvae metamorphose into terrestrial juveniles early each summer. However, we have recently documented two occurrences of populations containing large gilled California tiger salamander larvae during the winter months. Large gilled larvae could be the result of genetic admixture between California tiger salamanders and an introduced congener, the barred tiger salamander (Ambystoma tigrinum mavortium), but the population occurrences we observed are located outside the presumed extent of the A. californiense/A. t. mavortium–hybrid swarm. We used single nucleotide polymorphisms (SNPs) to investigate the possibility the genomes of these atypical larvae have been introgressed by “superinvasive” loci that have escaped from the established hybrid swarm. We also discuss the possibility the overwintering larval phenotypes may be the result of increased prevalence of large, fishless, semipermanent ponds, or of a combination of both introgression and habitat modification.