Showing papers in "American Midland Naturalist in 2001"
TL;DR: Whereas deer density is clearly important in determining spatial and temporal variation in the presence and magnitude of deer effects, other factors that may modify the effects of deer density are poorly understood.
Abstract: Large effects of white-tailed deer (Odocoileus virginianus) upon individual plants, plant populations and communities have been documented in a number of studies. However, well-supported experimental measures of the magnitude and geographical extent of these effects are still surprisingly scarce. Deer-caused changes in stem morphology and reductions in plant growth rates are well-documented in some parts of the North America. Furthermore, deer have been shown to affect the composition of several plant communities in the north-central and northeastern United States. There are some documented cases of deer-caused reductions in plant survival; most of these are tree seedlings and saplings. However, many studies have detected no effects on plant survival or fecundity, or have found that negative effects occur only in a fraction of years, seasons, sites or deer densities. Little is known about population-level or ecosystem-level impacts. Many regions and plant communities with large deer populations have not been studied. Whereas deer density is clearly important in determining spatial and temporal variation in the presence and magnitude of deer effects, other factors that may modify the effects of deer density are poorly understood.
429 citations
TL;DR: It is suggested that garlic mustard may reduce the competitive abilities of native plants by interfering with the formation of mycorrhizal associations and root growth.
Abstract: We examined the effects of garlic mustard (Alliaria petiolata) leachates on germination of arbuscular mycorrhizal (AM) fungal spores, colonization of plant roots by AM fungi and germination and root growth of monocot and dicot plants under laboratory conditions. In the field we examined the effect of garlic mustard on AM inoculum potential (MIP). Water leachates of garlic mustard prevented germination of spores of the AM fungus Gigaspora rosea, inhibited the formation of AM associations with tomato (Lycopesicum esculentum) and significantly reduced germination of tomato seeds. Garlic mustard leachates also reduced root length of tomato and sorghum (Sorghum bicolor) seedlings. Under field conditions we found a significant negative correlation between the density of garlic mustard and the mycorrhizal inoculum potential of the soil in which the plants grew. These results suggest that garlic mustard may reduce the competitive abilities of native plants by interfering with the formation of mycorrhizal associations and root growth.
243 citations
TL;DR: The authors investigated the association of grassland birds with field-and landscape-level habitat variables in south-central Wisconsin during 1985-1987 and found that only landscape variables were associated with the density of bobolink (Dolichonyx oryzivorus), eastern meadowlark (Sturnella magna) and all birds that were grassland species of management concern.
Abstract: We investigated the association of grassland birds with field- and landscape-level habitat variables in south-central Wisconsin during 1985–1987. Landscape-level variables were measured and digitized at 200, 400 and 800 m from the perimeter of 38 200 m × 100 m strip transects. A mixture of field and landscape variables was associated with the density of savannah sparrow (Passerculus sandwichensis) and grasshopper sparrow (Ammodramus savannarum). Only landscape variables were associated with the density of bobolink (Dolichonyx oryzivorus), eastern meadowlark (Sturnella magna) and all birds that were grassland species of management concern. Field size was not an important predictor of bird density. Cover-type diversity of the surrounding area was commonly selected in the models for three species and all birds that were grassland species of management concern. Higher bird densities in the transects were associated with landscapes where the cover types were less diverse. Landscapes with low cover typ...
138 citations
TL;DR: The shorter, more diverse, cool-season grass fields were equal or better habitat than taller, more vertically dense, switchgrass-dominated fields for grassland birds, including several species of high conservation concern.
Abstract: To determine the relative value of different Conservation Reserve Program (CRP) plantings for breeding grassland and winter birds we measured vegetation structure, avian abundance and reproductive success, and estimated fecundity during 1993–1995 on CP1 (cool-season grass) and CP2 (warm-season grass) plantings in 16 fields in northern Missouri. CP1 fields had been planted to cool-season grasses or cool-season grass-legume mixtures and CP2 fields had been seeded with switchgrass (Panicum virgatum). Species richness, abundance and nesting success of grassland birds during the breeding season and total bird use in the winter did not differ between CPs. During the breeding season CP1 fields had higher abundances of grasshopper sparrow (Ammodramus savannarum), eastern meadowlark (Sturnella magna), Henslow's sparrow (Ammodramus henslowii) and American goldfinches (Carduelis tristis), whereas common yellowthroats (Geothlypis trichas) were more abundant in CP2 fields. Fecundity of dickcissels (Spiza amer...
110 citations
TL;DR: The data indicate that competition for resources both above- and belowground is an important mechanism for inhibition of canopy tree recruitment by R. maximum, and water availability and the ability to accumulate soil nutrients are equally or more important than light to survival of canopy Tree seedlings in the presence of a subcanopy thicket.
Abstract: Subcanopy shrubs and perennial herbs inhibit recruitment of canopy trees in forests around the world. Although this phenomenon is widespread, and can have significant effects on community dynamics, the mechanisms of inhibition are not well understood. In the southern Appalachian region, Rhododendron maximum inhibits the recruitment of canopy trees in forests of northern red oak (Quercus rubra). We have shown, in previous research, that processes occurring before canopy tree seed germination are not responsible for this inhibition. Therefore, post-germination processes, such as competition for resources are most important. In this study we show that the presence of a thicket of R. maximum in the understory reduced the availability of light by 80%, the frequency and duration of sunflecks by 96%, the availability of water by 20% and the availability of several soil nutrients (particularly cations) by variable amounts. Moreover, the survival of Q. rubra seedlings in the understory over 3 y was signif...
102 citations
TL;DR: In this paper, the authors examined the breakdown of cypress and gum leaves in three wetlands with different hydroperiods: (1) flooded exposed (FE), 5 mo flooded/6 mo litter exposed), (2) multiple flooded exposed and permanently flooded (PF), and they hypothesized that within the MFE wetland mic...
Abstract: Many cypress-gum wetlands in the southeast United States are isolated from rivers and streams and are seasonally inundated by rainfall. Organic matter processing in these wetlands is caused primarily by biotic components (i.e., microbes and invertebrates), which are influenced by timing and duration of seasonal inundation, and low dissolved oxygen levels. Using litter bags, we examined breakdown of cypress (Taxodium spp.) and gum (Nyssa sylvatica var. biflora) leaves in three wetlands with different hydroperiods: (1) flooded exposed (FE; 5 mo flooded/6 mo litter exposed), (2) multiple flooded exposed (MFE; 6 mo flooded/exposed/flooded/exposed) and (3) permanently flooded (PF; 11 mo flooded). Breakdown was fastest in the MFE wetland suggesting cycles of wetting and drying accelerated decomposition by promoting microbial activity through aeration. Even though ergosterol content, an indicator of fungal biomass on the litter, was similar among wetlands, we hypothesized that within the MFE wetland mic...
102 citations
TL;DR: It is indicated that restored wetlands are valuable habitat for at least a subset of the amphibian fauna of this region and that wetland size, isolation and habitat suitability all influence colonization success.
Abstract: Twelve wetlands (7 recently restored; 5 reference) in central and southern Minnesota were monitored during the 1998 breeding season to assess colonization of recently restored wetlands by amphibians, compare the amphibian fauna to that of reference wetlands and identify important factors influencing the probability of colonization. Eight amphibian species rapidly colonized recently restored wetlands and established breeding populations. Reference wetlands were inhabited by twelve species, including four not found in restored wetlands (Ambystoma laterale, Notophthalmus viridescens, Pseudacris crucifer and Rana clamitans). Most local habitat variables, such as water chemistry or aquatic vegetation cover, were not influential in determining species richness patterns in recently restored wetlands. Size and spatial isolation of restored wetlands, however, were important predictors of species richness. Habitat suitability also influenced the probability of colonization for some species. The results of ...
95 citations
TL;DR: Environmental stimuli, such as human activity, increased the amplitude of the circadian rhythms of coyotes and this increase in amplitude is a result of increased nocturnal activity and decreased diurnal activity.
Abstract: We compared the activity patterns of coyotes (Canis latrans) in a suburban/agricultural area to those in an adjacent undeveloped area in northwest Wyoming from August 1998 to August 1999. Activity patterns were recorded using variable-pulse radio-collars. Correlation of recorded activity and observed activity indicated differences in the sensitivity of the collars. The mean percent of active signals for coyotes in the suburban/agricultural area was significantly lower during diurnal periods and significantly higher during nocturnal periods than the mean percent of active signals in those periods for coyotes in the undeveloped area. No differences between the two areas were observed during crepuscular times. Environmental stimuli, such as human activity, increased the amplitude of the circadian rhythms of coyotes. This increase in amplitude is a result of increased nocturnal activity and decreased diurnal activity.
93 citations
TL;DR: In the cornbelt region of the Midwest, where forests have been extensively cleared and fragmented, large urban trees provide important roosting habitat for red bats, which showed fidelity to roost sites within a small geographic area, but not to particular roosts.
Abstract: To investigate natural roost-site selection by eastern red bats (Lasiurus borealis) in an urban area we equipped 12 bats with radio-transmitters and located them at 75 individual roost sites in central Illinois from 16 July to 30 September 1996. Bats used a diversity of roosts including mature trees, leaf litter, dense grass and the shingles of houses, but the majority of roosts (89%) were in the foliage or on the trunks of large deciduous trees (>45 cm dbh). Sweetgum (Liquidambar syraciflua) and oaks (Quercus spp.) were commonly used. Most roosts were located in foliage, >5 m above the ground, within 1.5 m of the edge of the crown and with few branches beneath to obstruct flight paths. Red bats showed fidelity to roost sites within a small geographic area, but not to particular roosts. Individuals rarely used the same roost on consecutive days, but 82% of roosts used on successive days were within 100 m of each other. In the cornbelt region of the Midwest, where forests have been extensively cle...
83 citations
TL;DR: A technique to germinate seeds and cultivate seedlings of P. leucophaea in vitro using cold treatments and mycorrhizal fungi to make it possible for this threatened orchid to be propagated in soil ex vitro, followed by reintroduction into suitable habitats.
Abstract: The 70% decline of the Federally threatened eastern prairie fringed orchid, Platanthera leucophaea (Nuttall) Lindley, has prompted concern for its recovery through artificial propagation. We describe a technique to germinate seeds and cultivate seedlings of P. leucophaea in vitro using cold treatments (=stratification) and mycorrhizal fungi (=symbiotic seed germination). Five fungal isolates were recovered from mature P. leucophaea plants in Illinois and Michigan and were identified as members of the anamorphic genus Ceratorhiza Moore. Stratified seeds inoculated with mycorrhizal fungi germinated within 25 d of sowing. Leaf-bearing seedlings were obtained by chilling young seedlings (protocorms) for 107 d. Our successful culture of leaf-bearing seedlings with a presumed mycotrophic capability may make it possible for this threatened orchid to be propagated in soil ex vitro, followed by reintroduction into suitable habitats.
69 citations
TL;DR: In this paper, a geographic information system (GIS) was used to relate changes in vegetation and land use to population trends of lesser prairie-chickens in Oklahoma, Texas and New Mexico.
Abstract: Home ranges of lesser prairie-chickens (Tympanuchus pallidicinctus) include up to several thousand ha of several habitat types that are concentrated around leks (traditional display grounds). A geographic information system (GIS) was used to relate changes in vegetation and land use to population trends of lesser prairie-chickens in Oklahoma, Texas and New Mexico. We quantified changes in vegetation within 4.8 km of lesser prairie-chicken leks and examined relationships among those changes and long-term population trends based on the number of displaying males per lek. Five of 13 populations declined between 1959 and 1996. Landscapes in which populations of lesser prairie-chickens declined were characterized by greater rates of landscape change and greater loss of shrubland cover types than landscapes in which populations did not decline. Changes of specific cover types were not as important as the total amount of change occurring on landscapes. Conservation of lesser prairie-chickens should focu...
TL;DR: The data suggest that the costs of autotomizing one leg are marginal for Pardosa females and, thus, support the “spare leg hypothesis” that has been proposed for other arachnids.
Abstract: A number of animals escape predation by sacrificing a body part. Spiders commonly lose legs in encounters with predators or conspecifics. We investigated the frequency of leg loss and its affect on locomotion and prey capture activities of the wolf spider, Pardosa milvina (Araneae; Lycosidae). In addition, we determined if Pardosa were easier to subdue by the larger wolf spider predator, Hogna helluo (Araneae; Lycosidae), once they had experienced leg loss. A field census demonstrated that Pardosa autotomized members of all pairs of legs with equal frequency but overall leg loss was high and increased significantly late in the season. Laboratory experiments revealed that leg loss had no effect on locomotory behavior or prey capture. However, injured spiders tended to take smaller prey. The ability of Hogna, to attack and subdue 7 or 8-legged Pardosa was not different, although 8-legged Pardosa tended to lose multiple legs as they were killed whereas 7-legged Pardosa only lost one. These data sugg...
TL;DR: In this article, the authors examined patterns of species richness of gall-inducing insects by counting the number of gallinducing insect species and plant species, and measuring soil phosphorus, in replicate dry and mesic plots at five locations along an altitudinal aridity gradient in Big Bend National Park, Texas.
Abstract: Insect-induced galls are observed on plants throughout the world, but patterns of gall-inducing insect species richness are not random. In the USA and Brazil, species richness increases with decreasing altitude, which is associated with increasing temperature and aridity. At a given elevation the number of gall-inducing insect species is also higher in drier habitats than mesic habitats. However, variations in the number of potential host plant species, related to soil fertility, may be the cause of these patterns, not differences in temperature and aridity. We examined patterns of species richness of gall-inducing insects by counting the number of gall-inducing insect species and plant species, and measuring soil phosphorus, in replicate dry and mesic plots at five locations along an altitudinal aridity gradient in Big Bend National Park, Texas. Almost all galls were on woody plant species (trees or shrubs). We found the greatest number of gall-inducing insect species at intermediate elevations,...
TL;DR: Radio-tracked 4 solitary subadult and 3 adult female evening bats (Nycticeius humeralis) to 7 and 14 roost trees, respectively, during the summer of 1997 on the Upper Coastal Plain of South Carolina, finding that evening bats roosts for both age-classes were located in cavities and under exfoliating bark in live trees and dead snags.
Abstract: We radio-tracked 4 solitary subadult (2 male and 2 females) and 3 adult female evening bats (Nycticeius humeralis) to 7 and 14 roost trees, respectively, during the summer of 1997 on the Upper Coastal Plain of South Carolina. Roosts for both age-classes were located in cavities and under exfoliating bark in live trees and dead snags. Based on nightly exit counts, adult female evening bats roosted communally. Some roosts were presumed to be active maternity colonies. Five of six subadult roosts and one adult female roost were located under exfoliating bark on dead snags in beaver (Castor canadensis) ponds. Thirteen of 14 adult female evening bat roosts were located in cavities in live longleaf pines (Pinus palustris) in stands of relatively mature, park-like, pine plantations. One subadult roost was located under exfoliating bark in a live longleaf pine. No evening bats roosted in the more densely canopied, nearby bottomland hardwood stands, mixed pine-hardwood stands or loblolly pine (P. taeda) s...
TL;DR: Preservation of microhabitat characteristics like downed woody debris and understory vegetation, and certain macrohabitats (e.g., old fields), would require minimal management effort and provide suitable habitat for a diverse small mammal fauna in fragmented landscapes.
Abstract: We analyzed macrohabitat and microhabitat associations of four soricid and five rodent species in five macrohabitats on the Coastal Plain of Virginia. There were no significant differences in total small mammal abundance among macrohabitat types based on total captures/unit effort. However, abundances of four species, Cryptotis parva, Reithrodontomys humulis, Microtus pennsylvanicus and Zapus hudsonius, were significantly higher (P < 0.05) in old fields than in four forested habitats. Canonical correspondence analysis revealed that 27% of the variation in small mammal distributions was attributable to microhabitat characteristics. Three characteristics that had a particular influence on small mammal presence in forested habitats were shrub frequency (Sorex longirostris), canopy openness (S. hoyi) and diameter of downed woody debris (S. hoyi, Blarina brevicauda, Microtus pinetorum). Correlations between small mammals and microhabitat characteristics are due to local moisture gradients and structur...
TL;DR: It is demonstrated that relatively small differences in hydroperiod length may have large effects on juvenile recruitment in R. sphenocephala, similar to results of experimental investigations of closely related ranid frogs.
Abstract: Hydroperiod, the time a temporary pond holds water, is an important factor influencing recruitment in amphibian populations and structuring amphibian communities. We conducted an experiment to test the effect of hydroperiod on metamorphic traits of the southern leopard frog (Rana sphenocephala), a common amphibian in the southeastern United States. We reared larval R. sphenocephala in artificial ponds at a density of 32 larvae per tank (initial volume = approximately 650 liter). We dried the tanks according to natural patterns, using three different hydroperiods (60, 75 and 90 d). Experimental hydroperiods had a significant effect on the number of metamorphs and the length of the larval period, but not on overall survival (larvae + metamorphs) nor size at metamorphosis. Our findings confirm a pattern observed in field studies and are similar to results of experimental investigations of closely related ranid frogs. Our results demonstrate that relatively small differences in hydroperiod length (i....
TL;DR: Since spiders with one leg autotomized are slower than spiders with all legs intact, they may be more susceptible to predation.
Abstract: The effects of leg autotomy on running speed and foraging ability were examined in two species of wolf spider (Schizocosa ocreata and Varacosa terricola). Both species run slower following leg autotomy. However, foraging ability was not affected in either species. Since spiders with one leg autotomized are slower than spiders with all legs intact, they may be more susceptible to predation.
TL;DR: Predation on marmots is cryptic; none of the predation events were observed and, in most cases, the marmot was consumed or removed so quickly and completely that searching for carcass remains would have been fruitless.
Abstract: I determined cause-specific mortality of yellow-bellied marmots (Marmota flaviventris) to assess the importance of predation as a mortality factor. Contrary to earlier findings based on visual observation, almost all (98%) mortality during the summer active season was caused by predation. Coyotes (Canis latrans) were the most important predators, followed by badgers (Taxidea taxus), American martens (Martes americana), black bears (Ursus americanus) and raptors, probably golden eagles (Aguila chrysaetos). Predation on marmots is cryptic; none of the predation events were observed and, in most cases, the marmot was consumed or removed so quickly and completely that searching for carcass remains would have been fruitless.
TL;DR: In this paper, the effect of nitrogen, phosphorus and nitrogen and phosphorus (N and P) additions on density, biomass and nutrient dynamics of Typha latifolia L. and the sedge Schoenoplectus tabernaemontani (C.C. Gmel) Palla (a.k.a. Scirpus validus Vahl.) grown in size and density-symmetric and in size-and density-asymmetric mixtures.
Abstract: Loss of plant species diversity in wetlands has been linked to high nutrient conditions. In particular, Typha spp. are known to form monotypic stands in fertile wetland systems. In this study marsh mesocosms were used to study the effect of nitrogen (N), phosphorus (P) and nitrogen and phosphorus (N and P) additions on density, biomass and nutrient dynamics of Typha latifolia L. and the sedge Schoenoplectus tabernaemontani (C.C. Gmel) Palla (a.k.a. Scirpus validus Vahl.) grown in size- and density-symmetric and in size- and density-asymmetric mixtures. Dynamics of Typha and Schoenoplectus mixtures were also estimated along a nutrient gradient in a created wetland. Typha responded with increased growth to higher nutrient conditions more than Schoenoplectus in the first year, but Schoenoplectus responded more than Typha in the second year when nutrient additions were stopped. Typha grew better compared to the control with the addition of nitrogen and phosphorus in both the asymmetric and symmetric ...
TL;DR: An unusual pattern of spatial organization for bobcats is reported such that, although male and female annual home-range sizes were similar to other regional populations, it is suggested that core areas confer benefits to bobcats by reducing competition for resources and may represent areas of more aggressive territoriality within the home range.
Abstract: Many aspects of spatial organization in solitary carnivores remain unknown due to prohibitively low sample sizes and reliance on only annual home range and overlap data. We estimated size, overlap and fidelity of annual and seasonal home ranges and core areas of 52 (22 male, 30 female) adult bobcats (Lynx rufus) in southern Illinois during 1995–1999 and quantified temporal spacing. We report an unusual pattern of spatial organization for bobcats such that, although male and female annual home-range sizes were similar to other regional populations, we found relatively high levels of intrasexual home-range overlap for males and females. Although intrasexual home-range overlap was extensive, core areas were nearly exclusive, implying that core areas confer benefits to bobcats by reducing competition for resources and may represent areas of more aggressive territoriality within the home range. Only 4 of 52 (8%) bobcats shifted annual home ranges, indicating stable spatial organization in the absence ...
TL;DR: Given the importance in the study area of human related food items like the Jaliscan cotton rat, mango and papaya, it is expected the expansion of coyote populations due to deforestation of the tropical deciduous forest.
Abstract: We studied the food habits of the coyote (Canis latrans) in a tropical deciduous forest along the Mexican Pacific coast during 1996 and 1997. Small mammals, chiefly the Jaliscan cotton rat (Sigmodon mascotensis), were the main prey items during the dry season. Cultivated fruits, like mango and papaya, were the most important food for coyotes during the wet season. Given the importance in our study area of human related food items like the Jaliscan cotton rat, mango and papaya, we expect the expansion of coyote populations due to deforestation of the tropical deciduous forest.
TL;DR: Investigation of sexual dimorphism in feeding behavior and morphological characteristics associated with prey capture in the wolf spider, Rabidosa rabida, suggests that differences between the sexes in the relationship between fitness and foraging result in a dichotomy between male and female foraging behavior and differences in morphology.
Abstract: We investigated sexual dimorphism in feeding behavior and morphological characteristics associated with prey capture in the wolf spider, Rabidosa rabida (Araneae, Lycosidae). Female R. rabida attack and consume more prey than do males. In addition to behavioral differences between males and females, morphological features such as chelicerae size and venom gland size are also larger in females. These morphological differences are significant even after accounting for their positive correlation with body size. These data suggest that differences between the sexes in the relationship between fitness and foraging result in a dichotomy between male and female foraging behavior and differences in morphology associated with prey capture.
TL;DR: The Pipe Creek sinkhole local fauna as mentioned in this paper contains frogs and pond turtles, but fishes, birds, snakes and small and large mammals are also present; both extinct and extant taxa are represented.
Abstract: Quarrying in east-central Indiana has uncovered richly fossiliferous unconsolidated sediment buried beneath Pleistocene glacial till. The fossiliferous layer is part of a sedimentary deposit that accumulated in a sinkhole developed in the limestone flank beds of a Paleozoic reef. Plant and animal (mostly vertebrate) remains are abundant in the fossil assemblage. Plants are represented by a diversity of terrestrial and wetland forms, all of extant species. The vertebrate assemblage (here designated the Pipe Creek Sinkhole local fauna) is dominated by frogs and pond turtles, but fishes, birds, snakes and small and large mammals are also present; both extinct and extant taxa are represented. The mammalian assemblage indicates an early Pliocene age (latest Hemphillian or earliest Blancan North American Land Mammal Age). This is the first Tertiary continental biota discovered in the interior of the eastern half of North America.
TL;DR: In this paper, the authors examined patterns of spatial heterogeneity in the Spring River basin fish community along with environmental correlates to assess the relative importance of geographic distances and habitat differences among sites in explaining community structure.
Abstract: We examined patterns of spatial heterogeneity in the Spring River basin fish community along with environmental correlates to assess the relative importance of geographic distances and habitat differences among sites in explaining community structure. Spatial patterns of the fish community and environmental correlates, as indicated by results of Mantel tests and correlograms, were consistent with the hypothesis that environmental factors were the primary factors organizing the community at the basinwide scale. However, a linkage between mainstream and tributary communites, along with spatial autocorrelation in species composition, suggested contagious biotic processes were important in maintaining community structure, particularly at the interface between the mainstream and its tributaries. Space-constrained cluster analysis and principal coordinates analysis revealed three primary groups of sites, reflecting relatively distinct fish faunas within the Ozark Highlands, Central Plains and mainstrea...
TL;DR: The results indicate that perennial graminoids predominate in the rapid recovery of vegetation on pocket gopher mounds and burrows, which preempts the establishment of less frequent forbs and decreases plant community richness.
Abstract: Our objective was to evaluate the effects of soil disturbances created by the plains pocket gopher (Geomys bursarius) on the structure of a tallgrass-prairie plant community. We predicted that soil mounds and burrows would provide sites for the establishment of subordinate plant species, thereby increasing regional plant community richness in this ecosystem that is highly dominated by perennial C4 tallgrasses. Our results, however, revealed that plant species richness and biomass were temporarily decreased or unaffected in areas disturbed by gophers. Moreover, the species found locally on mounds and burrows were a subset of the dominant plants present in the undisturbed plant community and graminoids were more frequent on disturbances than forbs. Our results indicate that perennial graminoids predominate in the rapid recovery of vegetation on pocket gopher mounds and burrows. This preempts the establishment of less frequent forbs and, contrary to our predictions, decreases plant community richness.
TL;DR: It is concluded that Ni can be transferred from a high-Ni herbivore to its predators; predators varied in their sensitivity to the Ni contained in M. boydi, and Ni can poison predators which specialize upon high- Ni herbivores and thus may act as an elemental Herbivore defense.
Abstract: The recent discovery of herbivores that feed on Ni-hyperaccumulating plants and contain elevated Ni concentrations in their bodies suggests that Ni may be transferred to their predators. We tested this hypothesis using the high-Ni herbivore Melanotrichus boydi and four predator species: the spiders Pholcus phalangioides and Misumena vatia, the mantid Stagmomantis californica and the lacewing Chrysoperla carnea. Survival of each predator species was compared when individuals were fed either M. boydi or low-Ni prey. No significant survival difference between diets was observed for P. phalangioides or S. californica, although individuals fed M. boydi contained significantly elevated Ni concentrations (470 μg Ni g−1 for P. phalangioides and 460 μg Ni g−1 for S. californica). No significant difference in survival to adulthood was observed for C. carnea: adult production was 45% for high-Ni and 55% for low-Ni diets. In contrast, survival of M. vatia was significantly decreased when fed high-Ni prey: on...
TL;DR: If net photosynthesis is positively related to plant productivity, as has been shown for tallgrass prairie species, the differential photosynthetic responses of these two grasses suggests that their patterns of abundance may change in the future if resource availability is altered.
Abstract: The availability and distribution of essential resources such as water and nitrogen are changing on a global scale and it is important to determine the effects of such alterations on dominant and subdominant species in ecosystems. We examined the effects of long-term additions of water and nitrogen on leaf-level ecophysiological characteristics of the tallgrass prairie codominants Andropogon gerardii (big bluestem) and Sorghastrum nutans (Indian grass). Both species responded to irrigation with increased water potentials and to fertilization with decreased water potentials. Only in S. nutans, however, were net photosynthesis and stomatal conductance greater in response to both water and nitrogen addition. In contrast, A. gerardii, which currently is more abundant than S. nutans, was relatively unresponsive to resource manipulations. If net photosynthesis is positively related to plant productivity, as has been shown for tallgrass prairie species, the differential photosynthetic responses of these...
TL;DR: The 1998 emergence of 17-y periodical cicada (Magicicada cassini) on Konza Prairie Research Natural Area, Kansas, was quantified using emergence trap transects and counts of emergence holes, and it is suggested that insects generally do not represent important resource pools at the ecosystem level may be an exception.
Abstract: The 1998 emergence of 17-y periodical cicadas (Magicicada cassini) on Konza Prairie Research Natural Area (KPRNA), Kansas, was quantified using emergence trap transects and counts of emergence holes. Emergence density, biomass (emergence production) and associated nitrogen flux were estimated for the entire 100 ha gallery forest of Kings Creek, the major drainage network on KPRNA. Emergence commenced on 22 May 1998 and lasted for 24 d, with 87% of the individuals emerging within the first 9 d. Males dominated early during the emergence, and the sex ratio for the entire population was estimated at 54:46 male:female. Average emergence abundance and biomass estimated from trap transects located in low areas where cicadas were most abundant were 152/m2 and 34.9 g ash-free dry mass (AFDM)/m2, respectively. Based on emergence hole counts, average density and biomass for the 59 ha of gallery forest where cicadas emerged were 27.2 individuals/m2 and 6.3 g AFDM/m2, and emergence hole densities >100/m2 wer...
TL;DR: The food habits of swift foxes (Vulpes velox) occupying two distinct landscapes (dominated by cropland versus rangeland) in western Kansas were determined by analysis of scats collected in 1993 and 1996 as mentioned in this paper.
Abstract: Food habits of swift foxes (Vulpes velox) occupying two distinct landscapes (dominated by cropland versus rangeland) in western Kansas were determined by analysis of scats collected in 1993 and 1996. Frequencies of occurrence of prey items in scats were compared between cropland and rangeland areas by season. Overall, the most frequently occurring foods of swift foxes were mammals (92% of all scats) and arthropods (87%), followed by birds (24%), carrion (23%), plants (15%) and reptiles (4%). No differences were detected between landscapes for occurrence of mammals, arthropods or carrion in any season (P ≥ 0.100). Plants, specifically commercial sunflower seeds, were consumed more frequently in cropland than in rangeland in spring (P = 0.004) and fall (P = 0.001). Birds were more common in the swift fox diet in cropland than in rangeland during the fall (P = 0.008), whereas reptiles occurred more frequently in the diet in rangeland than in cropland during spring (P = 0.042). Variation in the diet ...
TL;DR: Effects of physiological condition and experience influenced home-range size in female wild turkeys in westcentral Arkansas, with the largest reproductive period home range reported for the eastern subspecies.
Abstract: Eastern wild turkeys (Meleagris gallopavo silvestris) in the Ouachita Highland Province of westcentral Arkansas have some of the largest reported home ranges for this subspecies. Previous research on wild turkeys has generally attributed large home-range size to forage abundance or quality. However, limitations in reproduction by wild turkeys in the Ouachitas may influence home-range size and habitat selection. To discern factors governing home-range size, I examined habitat use by 54 female wild turkeys from 1993 to 1996. Shortleaf pine (Pinus echinata) and mixed pine–hardwood sawtimber were selected over other overstory cover types, whereas blackgum (Nyssa sylvatica), red maple (Acer rubrum) and white oak (Quercus alba) were favored in the understory. Mean fixed kernel home-range size during the breeding season was 18.9 km2, the largest reproductive period home range reported for the eastern subspecies. Home-range size varied as a function of age, body mass, reproductive status and the structur...