Showing papers in "American Midland Naturalist in 1994"
TL;DR: Invertebrate responses to water loss were investigated during drying, dry and rewetting phases in Sycamore Creek, an intermittent Sonoran Desert stream as mentioned in this paper, and community shifts occurred at one site when it became isolated from upand downstream reaches; taxa such as beetles, hemipterans, and the snail Physella virgata became dominant.
Abstract: Invertebrate responses to water loss were investigated during drying, dry and rewetting phases in Sycamore Creek, an intermittent Sonoran Desert stream. Some taxa were resistant to drying because they could tolerate rapidly changing water quality and/or move upstream to avoid stranding. Community shifts occurred at one site when it became isolated from upand downstream reaches; taxa such as beetles, hemipterans, and the snail Physella virgata became dominant. No community changes were detected at a second site which remained connected with upstream reaches by surface flow. Mortality after water loss was severe as few individuals survived longer than 10 days. Low resistance during the dry phase was associated with rapid moisture loss from sediments. Invertebrate persistence in intermittent reaches was due to recolonization after rewetting; however, density increases after floods which reestablished flow at dry sites were lower than reported values for perennial sites in Sycamore Creek. Slower rates of recovery may reflect he composition, reduced size and remoteness of macroinvertebrate colonist pools. Nonetheless, invertebrate persistence in desert streams where both flooding and drying are frequent is due largely to their ability to rapidly recolonize disturbed sites.
206Â citations
TL;DR: In this article, the effects of topographic, gap and stand variables on density of wood seedlings were assessed for the southern Appalachian mixed-oak forests, where regeneration was dominated by Acer rubrum L., Q. velutina Lamarck, Liriodendron tulipifera L. and Cornus florida L.
Abstract: -Canopy gaps in southern Appalachian mixed-oak forests were assessed for the effects of topographic, gap and stand variables on density of wood seedlings. Seedling density was significantly correlated with percent slope and positively with gap age (1-5 yr). Density varied substantially among topographic positions and increased with gap size. Species richness decreased over time and increased with gap size. Regeneration was dominated by Acer rubrum L. Other important species included Quercus coccinea Muench., Q. rubra L., Q. velutina Lamarck, Liriodendron tulipifera L. and Cornus florida L. Some known gap species increased in density with increasing gap size. Competitive inhibition effects of the evergreen understory (Rhododendron maximum L. and Kalmia latifolia L.) were also examined. Gaps containing over 50% cover of R. maximum had significantly lower densities than all other gaps, including gaps with >50% K latifolia cover. Height distributions of major regenerating species were skewed away from small (<15 cm) height classes. Species establishment was a function of gap area, gap age, topographic position and cover of R. maximum. In addition, species of varying degrees of tolerance of understory conditions are capable of establishment in small to medium size canopy openings in the absence of an evergreen shrub understory.
156Â citations
TL;DR: It is clear that a combinatior' of host immunity, resource partitioning within infracommunities, patch dynamics associated with parasite transmission, temporal factors involved with snail ontogeny, the presence of autogenic and allogenic parasite species within a given habitat, and the potential for interspecific antagonism operate to create the special nature of trematode communities in molluscan intermediate hosts.
Abstract: -The study of parasite communities has traditionally focussed on helminth communities in vertebrate hosts. However, the literature reveals a substantial body of information which shows that infraand component trematode communities in snails frequently are highly structured and very dynamic in character. A variety of forces, both internal and external to the snail, affect the manner in which these communities are organized and function. While snail-trematode and trematode-trematode interactions are variable, it appears that some generalizations are beginning to emerge. It is clear that a combinatior' of host immunity, resource partitioning within infracommunities, patch dynamics associated with parasite transmission, temporal factors involved with snail ontogeny, the presence of autogenic and allogenic parasite species within a given habitat, and the potential for interspecific antagonism, collectively, operate to create the special nature of trematode communities in molluscan intermediate hosts.
115Â citations
TL;DR: Wedges taken from 24 post oaks growing on a ridge in an oak-hickory stand were used to reconstruct the fire history in the Houston Ranger District in Missouri's Mark Twain National Forest.
Abstract: -Wedges taken from 24 post oaks (Quercus stellata Wang.) growing on a ridge in an oak-hickory stand were used to reconstruct the fire history in the Houston Ranger District in Missouri's Mark Twain National Forest. A chronology was constructed dating from 1734 to 1991. Fire frequency was greatest between 1740 and 1850 with a mean return interval of 2.8 yr. After 1850, the fire return interval increased to 24 yr. This change in fire return regimes is coincident with settlement of the area by Anglo-Americans.
108Â citations
TL;DR: The number of leopard frogs in Dickinson County has declined by at least two, and probably three, orders of magnitude, and this decline may be due more to the loss of wetland habitat than past market hunting pressure.
Abstract: -In light of the reports of declines in amphibian numbers we have repeated Blanchard's (1923) survey of the amphibians of Dickinson County, Iowa. We found that five species reported by Blanchard persist: the eastern tiger salamander (Ambystoma tigrinum tigrinum), the American toad (Bufo americanus), the western chorus frog (Pseudacris triseriata triseriata), the gray treefrog (Hyla versicolor/chrysoscelis) and the northern leopard frog (Rana pipiens). Two species reported by Blanchard were not found: the mudpuppy (Necturus maculosus) and Blanchard's cricket frog (Acris crepitans blanchardi). We collected two species not found by Blanchard: the Great Plains toad (Bufo cognatus) and the bullfrog (Rana catesbeiana). The Great Plains toad may have migrated into Dickinson County from the west. The bullfrog was introduced by state fisheries biologists. From descriptions of the turn-of-the-century commercial "frogging" industry in Dickinson County, we estimate that the number of leopard frogs has declined by at least two, and probably three, orders of magnitude. This decline may be due more to the loss of wetland habitat than past market hunting pressure. In our opinion, the most immediate threat to the existing populations of native amphibians comes from the impact of the introduced bullfrog.
106Â citations
TL;DR: Results indicate use of nonwoodland habitats by P leucopus and suggest that crop fields and roadside ditches act as dispersal routes, facilitating movements into and out of what were formerly considered isolated woodlots.
Abstract: -Five habitat types in northwestern Ohio-woods, woods' edge, roadside ditches, crop fields and farmsteads-were sampled in order to better understand the effects of agricultural crop development on dispersal and population dynamics of Peromyscus leucopus. White-footed mice were present in all habitat types and moved from one type to another. Favored habitats in spring were woods and woods' edge, but as crops began developing in summer, occurrence in each of the other habitat types increased and lasted until after crop removal in autumn. Reproduction occurred in all habitats, but was highest in woods and woods' edge. These results indicate use of nonwoodland habitats by P leucopus and suggest that crop fields and roadside ditches act as dispersal routes, facilitating movements into and out of what were formerly considered isolated woodlots.
96Â citations
TL;DR: In this paper, the spatial dis- tributions of roots of three plant life forms: a grass (Bouteloua gracilis) (H.B. & Rusby) and a shrub (Atriplex canescens (Pursh.) Nutt.).
Abstract: In water-limited ecosystems such as the shortgrass steppe of North America, the ability of plants to absorb sufficient water for growth and reproduction is dependent upon the characteristics of their root systems. Our objective was to evaluate the spatial dis- tributions of roots of three plant life forms: a grass (Bouteloua gracilis) (H.B.K.) Lag., a dwarf shrub (Gutierrezia sarothrae (Pursh.) Britt. & Rusby) and a shrub (Atriplex canescens (Pursh.) Nutt.). Our interests were in a qualitative evaluation of evidence that different life forms obtained water from different soil layers. Root systems were excavated and evaluated in terms of horizontal and vertical extension, and proportion of total root length in each 10-cm layer of the soil profile. Bouteloua gracilis had over 80% of its roots in the top 50 cm of the soil, whereas the depth at which Atriplex canescens had over 80% of its roots was 100 cm. The corresponding depth for Gutierrezia sarothrae was 80 cm. Both of the woody plants had deeper and more widely spreading root systems than the grass. The environment of the shortgrass steppe is characterized by low and variable water avail- ability. These conditions lead to a distribution of available water that is biased toward the upper soil layers. The greater concentration of roots of Bouteloua gracilis in the soil layers near the surface compared to the two woody species provides a potential explanation for its dominance in the shortgrass steppe.
78Â citations
66Â citations
TL;DR: In this article, data from 37 sites in the Transverse Ranges in southern California were used to assess the influence of a variety of environmental variables on among-site variation in riparian vegetation.
Abstract: -Data from 37 sites in the Transverse Ranges in southern California were used to assess the influence of a variety of environmental variables on among-site variation in riparian vegetation. Ordination and regression analyses indicated that elevation, unit stream power, fire history and valley width all have significant impacts on the composition of this vegetation. TWINSPAN classification generated four species groups: a Baccharis glutinosa/Salix laevigata group that appears related to low elevations, high stream power and recent fire; a Populusfremontii/Alnus rhombifolia group associated with high stream power, but longer time since burning and higher elevations; a Salix lasiolepis/Rosa californica group typically found at high elevation sites with low stream power; and a Platanus racemosa/Adenostoma fasciculatum group that did not show a clear environmental preference.
64Â citations
TL;DR: The results suggest that the way an animal captures its food does not necessarily imply an obligate trophic status for it and the value of combining both methods is illustrated for Orthocladius, which is shown to be more a generalist in its diet based on stable isotopes than a specialist based upon analysis of gut contents.
Abstract: -We used both traditional gut analyses and stable isotopes to determine the diets of macroinvertebrates from an alpine wetland at 3593 m (Colorado Front Range). The two methods agreed. The Trichopteran, Asynarchus curtus (Banks) consumed mostly detritus, while chironomid larvae consumed periphyton and/or detritus. Filamentous algae, however, were not consumed by any taxa studied. The value of combining both methods is illustrated for Orthocladius, which is shown to be more a generalist in its diet based on stable isotopes than a specialist based upon analysis of gut contents. The results suggest that the way an animal captures its food (functional feeding group) does not necessarily imply an obligate trophic status for it.
61Â citations
TL;DR: Statistics indicate that preventing snails from ingesting eggs of some parasites had no affect on the recruitment of other parasites, and certain of the microhabitat variables are better predictors of a snail's infection status than others.
Abstract: -A total of 1231 Physa gyrina and 1532 Helisoma anceps were collected over a 12-mo period from Charlie's Pond, in Stokes County, North Carolina. Similarity in the infraand component parasite communities in Helisoma anceps and Physa gyrina provided an opportunity to compare the effects of various life history traits on infection by larval trematodes in a number of different microhabitats. In order to assess the effects of microhabitat partitioning on the infection status of the two snail species, collections were made twice per month. Site location, water depth, snail depth at capture, distance from shore, type of substratum, infection status, and host size were recorded for each snail. Multivariate statistics were used to assess which variables determined a snail's infection status. Data analysis indicated that certain of the microhabitat variables are better predictors of a snail's infection status than others. Comparing uninfected snails to those infected with a specific parasite species, there was much disparity with regard to which microhabitat characteristic varied significantly. Manipulation of infracommunity structure, by excluding certain parasites, allowed examination of the influence of temporal heterogeneity as compared to interspecific trematode interactions in structuring the infraand component communities. Snails were maintained in cages in the field. Enclosures were positioned a few centimeters above the substratum to prevent infection of the snails via egg ingestion and effectively prevented the more prevalent parasite species (Halipegus occidualis in H. anceps and Halipegus eccentricus in P gyrina) from infecting the snails. Statistical analyses indicate that preventing snails from ingesting eggs of some parasites had no affect on the recruitment of other parasites. Parasite prevalences in H. anceps and P gyrina were not different in caged snails compared with those collected from the substrata of the pond.
TL;DR: Differential olfaction could contribute to the invasion success of 0.
Abstract: -We tested the role of olfaction in response to predators and food by three freshwater crayfishes and the potential importance of olfaction in a species invasion. The crayfish Orconectes rusticus (Girard) is replacing Orconectes virilis (Hagen) and Orconectes propinquus (Girard) in northern Wisconsin lakes. To test whether 0. rusticus differs from congeners in its response to the odors of food and predators, we conducted two laboratory experiments comparing five behavioral responses of these Orconectes spp. to odors of dead fish and to live largemouth bass. As expected, all three species responded to carrion odor, suggesting that olfaction is a part of foraging strategy for all three congeners. Orconectes rusticus, however, responded significantly for all five behavioral responses, whereas 0. propinquus and 0. virilis responded significantly for only two and three, respectively. Only 0. rusticus responded to fish predator odor, but in a way contrary to our expectation. In the presence of fish predator odor, 0. rusticus increased time spent out of the shelter. The larger number of significant responses by 0. rusticus suggests that 0. rusticus responded more strongly to the odors of fish carrion and live predaceous fish (as food) than 0. virilis and 0. propinquus. Thus, differential olfaction could contribute to the invasion success of 0. rusticus.
TL;DR: Snorkeling techniques used to examine patterns of microhabitat use among four species of darters-Etheostoma flabellare, E. blennioides, Percina gymnocephala and the potentially threatened E. osburni-in three West Virginia streams found differences in habitat use may be related to morphological differences between species.
Abstract: -We used snorkeling techniques to examine patterns of microhabitat use among four species of darters-Etheostoma flabellare, E. blennioides, Percina gymnocephala and the potentially threatened E. osburni-in three West Virginia streams. Sympatric darter species were generally segregated in each stream, based on microhabitat use variables of mean depth, current velocity and substrate type. In all three streams-the East Fork of the Greenbrier River, the Cherry River and Laurel Creek-E. osburni was observed in fast current velocities and rock substrate in water depths ranging from 20 to 30 cm. In the East Fork of the Greenbrier River and Laurel Creek, E.fiabellare was common in slower velocities over predominantly cobble substrate. Percina gymnocephala and E. blennioides were spatially segregated from E. osburni on the basis of water column depth. Differences in habitat use may be related to morphological differences between species.
TL;DR: Growth and mycorrhizal colonization of roots of Andropogon gerardii and Schizachyrium scoparium were compared in soil collected from Konza Prairie Research Natural Area and from Sand Ridge State Forest, Illinois and there was no response to inoculation with mycor Rhizal fungi from either source.
Abstract: -Previous research in tallgrass prairie in Kansas indicated that warm-season, C4, grasses are obligate mycotrophs and do not grow normally in the absence of mycorrhizal symbiosis. However, the degree to which such grasses depend on mycorrhizae in other prairie soils has not been examined. Growth and mycorrhizal colonization of roots of Andropogon gerardii and Schizachyrium scoparium were compared in soil collected from Konza Prairie Research Natural Area (KPRNA), Riley County, Kansas and from Sand Ridge State Forest (SRSF), Mason County, Illinois. Plants of both species were grown in the two soils and were inoculated with Glomus etunicatum spores originally collected from KPRNA or colonized root pieces from S. scoparium plants collected from SRSF. Glomus etunicatum inoculum resulted in significantly greater root colonization and biomass of both plant species in steamed KPRNA soil than did root piece inoculum. There was no benefit from inoculation in nonsterile soil which contained indigenous mycorrhizal fungi. In SRSF soil, there was no response to inoculation with mycorrhizal fungi from either source. The lack of mycorrhizal response in SRSF soil is attributed to the greater plant-available P level of this soil. For S. scoparium grown in SRSF soil, plants grown in steamed soil produced more biomass than plants grown in steamed soil amended with nonsterile soil sievings (containing soil organisms other than mycorrhizal fungi), or in nonsterile soil. These differences could be due to competition for inorganic nutrients between soil microbes and the plant or antagonistic relationships between the plant or the mycorrhizal association and the soil microbes. Thus, the mycorrhizal dependence of these plant species is related to both soil and inoculum type or species.
TL;DR: This study is the first to test seeds previously buried and recovered for survival, viability and germination in the herbaceous perennial Coreopsis lanceolata (L.) (Asteraceae), finding that larger seeds had higher survivorship and viability rates but lower germination rates after burial in the field.
Abstract: -We examined the effects of seed mass on seed survival and germination in the herbaceous perennial Coreopsis lanceolata (L.) (Asteraceae). Seeds were collected from bagged flower heads, weighed and sorted into mass classes. Seed mass variation was 29-fold (range 0.111 to 3.210 mg), almost twice as high as in other species. For seeds buried in soil flats 0, 1, 2, 3 and 4 cm, larger seeds had greater viability, emerged from lower depths, and had higher emergence rates. After 2-yr burial in nylon bags in the field, larger seeds had higher survivorship and viability rates but lower germination rates. The lower germination rates of large seeds after burial in the field may be due to dormancy. This study is the first to test seeds previously buried and recovered for survival, viability and germination. Seedmass variation may be maintained by differential dormancy and germination which results in spreading the risk of recruitment.
TL;DR: Overall, there was little indication that resorption behavior correlated strongly with site fertility, but the drought year had a strong effect on both foliar nutrient dynamics and nutrient Resorption.
Abstract: -The relative importance of site fertility and drought on foliar nutrient dynamics and resorption by the forest understory shrub Viburnum acerifolium L. (maple-leaf viburnum) was determined by sampling leaves monthly through 2 growing seasons from plants in three Ohio deciduous forest sites which differed in soil nutrient availability. Sampling was done during 1985, a year in which growing season precipitation was near the 30-yr average, and during 1991, a year with only ca. 60% of average growing season rainfall. Foliar phosphorus (P) and nitrogen (N) concentrations were higher during 1991 than 1985. Although there were significant intersite differences in fertility, patterns of foliar P differences did not parallel site fertility. Foliar N was inversely proportional to availability in 1985, but not 1991. Resorption of P during senescence was highest at the intermediate fertility site in both years, and P resorption was significantly reduced during the drought year. At the intermediate fertility site, there were no differences in N resorption between years. In contrast, at the highest and lowest fertility sites, foliar N was significantly higher and N resorption significantly lower during the drought year (1991) than the normal precipitation year (1985). Overall, there was little indication that resorption behavior correlated strongly with site fertility. The drought year had a strong effect on both foliar nutrient dynamics and nutrient resorption.
TL;DR: The influence of intensive grazing on canopy microclimate, grass leaf water relations and community evapotranspiration was investigated by comparing a grassland heavily grazed by a colony of black-tailed prairie dogs (Cynomys ludovicianus) with an adjacent lightly-grazed, uncolonized area in a northern-mixed prairie in South Dakota as mentioned in this paper.
Abstract: -The influence of intensive grazing on canopy microclimate, grass leaf water relations and community evapotranspiration was investigated by comparing a grassland heavily grazed by a colony of black-tailed prairie dogs (Cynomys ludovicianus) with an adjacent lightly-grazed, uncolonized area in a northern-mixed prairie in South Dakota. Total aboveground plant biomass was lower on the colony through the growing season. Daytime leaf and air temperatures were higher on the colony. Although daytime air vapor pressure in the canopy was higher on the colony, higher leaf temperatures resulted in higher leaf-to-air vapor-pressure differences on the colony. Along with higher vapor-pressure differences, higher wind speeds within the canopy probably also contributed to higher evaporative demand. In spite of this, the dominant grasses, Agropyron smithii and Bouteloua gracilis, had consistently higher leaf conductances to water vapor and water potentials (4) on the colony, especially later in the day and growing season. Predawn leaf 'p were higher on the colony in July and August, suggesting available soil moisture in the rooting zone was higher there. At the community level, afternoon evapotranspiration rates were lower on the colony in June, but higher on the colony in July and August as soil water became more limiting. While intensive grazing by prairie dogs lead to a warmer canopy microclimate with higher evaporative demand, any detrimental effects on plant water status were apparently offset by greater available soil moisture, especially later in the day and season. Greater soil water availability on the colony was probably the result of smaller transpiring leaf mass (and area), although soil factors such as improved infiltration due to prairie dog burrows can not be ruled out as causative factors.
TL;DR: Indices of habitat fragmentation were used to quantitatively describe the components of habitat assessment now evaluated subjectively by experienced wild turkey biologists, including a proximity index that distinguishes isolated forest patches from those that are part of a cluster of forest patches.
Abstract: -The evaluation of the spatial configuration of habitat is often difficult due to large geographic areas to be evaluated and the subjective nature of spatial pattern assessment. Habitat quality for wild turkey populations has a spatial component related to the arrangement of habitat elements across large geographic areas. Indices of habitat fragmentation were used to quantitatively describe the components of habitat assessment now evaluated subjectively by experienced wild turkey biologists, including a proximity index that distinguishes isolated forest patches from those that are part of a cluster of forest patches. These indices were used to mathematically classify landscapes into discrete quality categories and the classifications were compared to subjective assessments made by experienced turkey biologists. Mathematical classifications of landscapes agreed with expert judgment when the proximity index and proportion of forest were used to characterize the spatial pattern of forest habitat. None of the indices alone were adequate to correctly classify all test landscape samples. Mean values of the indices were compared between study areas of different quality as wild turkey habitat. Study areas of optimal and suboptimal quality were more different from each other than were suboptimal and poor study sites. The proximity index is a valuable quantitative measure of habitat spatial pattern that provides information related to subjective, expert assessment of landscape suitability for use by wild turkeys. These quantitative measures add objectivity to the assessment of the spatial components of wild turkey habitat, and provide additional information that can be used to help identify the best potential turkey release sites. These methods can be extended to the evaluation of the spatial distribution of habitat for other wildlife species, and can provide quantitative spatial information for hypothesis testing.
TL;DR: The length of time between rains was the main factor influencing the amount of time the turtles required to complete the nesting cycle and all turtles buried themselves after nesting.
Abstract: -Previous research conducted at Ellenton Bay on the Savannah River Site near Aiken, S.C., indicated that gravid mud turtles (Kinosternon subrubrum) leaving the bay to nest remain in the terrestrial habitat for several days. We determined the time required to complete a nesting foray for 68 mud turtles. Nesting forays ranged from 2-29 d (x = 8.7 d, SD = ?5.9 d). To determine why the turtles require so much time to nest, 25 mud turtles were equipped with radio transmitters and followed through the nesting cycle. Gravid mud turtles buried themselves after exiting the bay and most (86%) remained buried until a rainstorm occurred. The turtles nested during rainstorms. All turtles buried themselves after nesting. Most of the buried turtles (67%) then waited for another rainstorm before returning to the bay. The length of time between rains was the main factor influencing the amount of time the turtles required to complete the nesting cycle.
TL;DR: The thermal ecology of Sceloporus jarrovi was studied in the Chiricahua Mountains of southeastern Arizona at different elevations and times of year and pregnant females had lower Tbs than nonpregnant females and males and females had similar Tbs.
Abstract: -The thermal ecology of Sceloporus jarrovi was studied in the Chiricahua Mountains of southeastern Arizona at different elevations and times of year. Mean body temperature (Tb) was 31.8 C (range 6.6-38.8 C). Mean air temperature (Ta) was 20.6 C (range 5.0-36.2 C). The slope of the regression of Tb on Ta was 0.37. Winter Tbs were lower than summer Tbs. Low elevation lizards had higher Tbs than high elevation lizards. Males and females had similar Tbs. Pregnant females had lower Tbs than nonpregnant females. Pregnant females also had a lower slope for the Tb on Ta regression than nonpregnant females. Body temperatures of pregnant females at early stages of pregnancy (November) were not significantly different from pregnant females at late stages of pregnancy (May). Sceloporus jarrovi maintained lower Tbs than the sympatric lizard Sceloporus scalaris. These two species have different Tb on Ta regressions.
TL;DR: Beavers were studied on two Lake Superior islands; one (Stockton) had black bears (Ursus americanus), while the other (Outer) did not; active beaver colonies on Outer Island increased during the study whereas they declined on Stockton Island.
Abstract: -Beavers (Castor canadensis) were studied on two Lake Superior islands; one (Stockton) had black bears (Ursus americanus), while the other (Outer) did not. Both islands were colonized by beavers during the late 1940s or early 1950s in the absence of bears, and bears immigrated to Stockton Island in the 1970s. Active beaver colonies on Outer Island increased during the study whereas they declined on Stockton Island. Bears ate five beavers in live-traps and disturbed twelve other sets. Six of 90 bear scats found had beaver hair in them, and 18 of 26 beaver lodges were dug into by bears. Compared to Outer Island, beavers on Stockton Island cut fewer food trees relative to their availability, and cut few trees >30 m from water, whereas beavers on Outer Island traveled >200 m inland to forage. Mainland studies have not reported such intense beaver/bear interactions, nor is the behavioral or population response of beavers as significant where they are preyed upon by wolves (Canis lupus), a more typical beaver predator.
TL;DR: Imbibed seeds subjected to 5 C entered a secondary dormancy that could not be broken by subsequent warmer temperatures, light/dark cycles or freezing temperatures, and may be a mechanism for spreading the risk of disease in herbaceous perennial C. lanceolata.
Abstract: -We examined physical and physiological factors that control germination in the herbaceous perennial, Coreopsis lanceolata L. (Asteraceae). Seeds stored in paper envelopes for 6 to 18 months at room temperature were tested for germination on moistened filter paper in petri dishes. Germination percentages were greatest at 15 and 25 C and 12 h light/ dark cycles. Germination percentages of imbibed seeds were not affected by previous storage at -10 C. Imbibed seeds subjected to 5 C entered a secondary dormancy that could not be broken by subsequent warmer temperatures, light/dark cycles or freezing temperatures. This study is the first of which we are aware documenting secondary dormancy in a perennial species. Secondary dormancy in C. lanceolata may be a mechanism for spreading the risk of
TL;DR: The inquiline communities found in the leaves of the purple pitcher plant Sarracenia purpurea L.purpurea are investigated, finding no general patterns were found among the abundances of common species or in correlations between biotic and abiotic variables.
Abstract: -We investigated the inquiline communities found in the leaves of the purple pitcher plant Sarracenia purpurea L. No general patterns were found among the abundances of common species or in correlations between biotic and abiotic variables (pitcher volume, sediment volume, pH). Further, no support was found for successional patterns within the pitchers when leaf number was used as an estimate of pitcher age. Experiments were conducted to quantify the effects of two size classes of the mosquito Wyeomyia smithii (Coq.) (Culicidae) and cladocerans (family Daphnidae, subfamily Eurycerinae, species undetermined) on the growth and survival of the small-mosquito size class. In simulated pitchers maintained in growth chambers for 14 days, small mosquitoes and large mosquitoes suppressed small-mosquito growth, and large mosquitoes decreased small-mosquito survivorship. Cladocerans had no effect on small-mosquito growth or survival. In simultaneous experiments conducted in natural pitchers in the field, large mosquitoes suppressed smallmosquito abundance and growth; no other significant interactions were found.
TL;DR: The ecological differences found between seeds and bulbils are small relative to the differences found among dimorphic propagules of other species, and do not fit the predictions of models for the conditions necessary to maintain the production of heteromorphic propagules.
Abstract: -The ecological characteristics of two propagule types of Allium vineale (sexually produced seeds and asexually produced bulbils) were studied to identify factors which could lead to the maintenance of both propagule types as reproductive mechanisms. Ecological traits studied were dispersal patterns, predation rates and longevity of propagules. Seeds and bulbils dispersed to the same average distance from the parent, but seeds occasionally traveled 10-30 cm further than bulbils. In addition, some bulbil infructescences were observed dispersing as a unit. Predation rates were significantly higher for seeds, but the density of propagules in an area had no effect on removal rates. Seeds and bulbils buried in the field were no longer viable after 1 yr. However, seeds stored in the laboratory for up to 3 yr had higher viability percentages than bulbils. Overall, the ecological differences found between seeds and bulbils are small relative to the differences found among dimorphic propagules of other species, and do not fit the predictions of models for the conditions necessary to maintain the production of heteromorphic propagules.
TL;DR: The ability of more than two individuals to produce a larger brood than that of pairs may decrease the costs of communal breeding on larger carcasses, but by itself is not sufficient to explain the evolution of breeding associations consisting of multiple females.
Abstract: -Size of breeding groups and resource quality (carcass mass) were varied independently in experiments using the burying beetle, Nicrophorus defodiens, to examine reproductive output of beetles using carcasses exposed to carrion competitors. Male-female pairs experienced the same rate of brood failure as groups of four beetles (two males and two females). Groups of four produced more total larvae and a greater brood mass than pairs on large but not small carcasses, whereas reproductive output per female was lower for groups. Carcasses prepared by groups of two males and two females attracted similar numbers of free-flying congeners as carcasses prepared by pairs. The ability of more than two individuals to produce a larger brood than that of pairs may decrease the costs of communal breeding on larger carcasses, but by itself, is not sufficient to explain the evolution of breeding associations consisting of multiple females.
TL;DR: Observations suggest the possibility of a social function of night roosting in pallid bats in central Oregon, where many bats spend a significant part of the nocturnal activity period roosted.
Abstract: -Many bats spend a significant part of the nocturnal activity period roosting, but little is known about the ecology of night roosts. Here, I report on the night roosting ecology of pallid bats (Antrozous pallidus) in central Oregon. Night roosts were located in buildings, under rock overhangs and under bridges. Roosts were protected from rain and wind and were spacious enough to allow free flight into and out of the roost. Eighty-five female pallid bats were captured in mist nets at night roosts in 2 yr (1990-1991). Up to six bats were caught entering a roost simultaneously. Recaptures of banded bats suggest bats are faithful to particular night roosts both within and between years. Radio-tracked bats captured at the same night roost did not necessarily roost together subsequently in diurnal roosts. Bats began entering the night roosts almost immediately after the onset of emergence from the day roosts. Activity at the roost was characterized by peaks, with many bats entering and leaving, and lulls, with few or no bats at the roost. These observations suggest the possibility of a social function of night roosting.
TL;DR: Histological examination of the nasolabial groove indicates that chigger attachment in the snout area can occlude the groove, and host tissue response and positioning of the chigger in the dermis was similar to that reported in other amphibian hosts.
Abstract: -In the Ouachita Mountains of Oklahoma and Arkansas, the trombiculid mite, Hannemania dunni, infests five endemic salamander species (Plethodon ouachitae, P caddoensis, P fourchensis, P kiamichi and Desmognathus brimleyorum). Plethodon albagula, which is widely distributed throughout much of Arkansas and southern Missouri, is rarely infested. In a field survey of 322 salamanders, 80.2% of P ouachitae, 26.3% of P caddoensis and 0% of P albagula were infested with chiggers (larval mites). Males of P ouachitae and P caddoensis had significantly more chiggers than females, and site of infestation differed significantly between species. Histological examination of the nasolabial groove (a chemosensory structure) indicates that chigger attachment in the snout area can occlude the groove. Loss of chemosensory function in plethodontids has been shown to impair foraging ability and may adversely affect a salamander's ability to find mates and/or defend a territory. Host tissue response and positioning of the chigger in the dermis was similar to that reported in other amphibian hosts.
TL;DR: Eurasian tree willows will likely continue to spread vegetatively in high plains riparian areas, and the potential for spread through hybridization could increase if males of compatible Salix spp.
Abstract: -Several Eurasian tree willows (Salix spp.) have become naturalized in riparian areas outside of their native range. Salix X rubens is a Eurasian willow that is conspicuous along streams in the high plains of Colorado. We examined establishment of seedlings and cuttings, the sex structure and the breeding system of S. Xrubens. An experiment was conducted on establishment and growth of seedlings and cuttings under a range of hydrologic conditions. Seedlings became established under all conditions except when flooded, although many fewer seedlings became established where soil surface conditions were relatively dry. Cuttings became established under all experimental conditions, but most frequently where soil moisture was highest. The sex structure of S. X rubens was determined along several streams in the Colorado high plains. Of 2175 trees surveyed, >99% (2172) were female. Salix X rubens produce viable seed apparently as a result of hybridization with another Eurasian willow, S. alba var. vitellina. Salix X rubens often reproduces vegetatively, which, combined with low hybrid seedling survival in the field, may explain the unusual sex structure. Salix Xrubens will likely continue to spread vegetatively in high plains riparian areas, and the potential for spread through hybridization could increase if males of compatible Salix spp. are planted near extant S. X rubens.