Impacts of hydroperiod on growth and survival of larval amphibians in temporary ponds of Central Pennsylvania,USA

The effects of variable hydroperiod (three levels) and initial density of amphibians (two levels) on survival, growth rate, and time to and mass at metamorphosis were studied for wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and spotted salamanders (A. maculatum). Experiments were carried out in 260-1 mesocosms set up outdoors in a forest. These pond simulations were designed to mimic conditions that occur in palustrine temporary wetlands in central Pennsylvania. No animals reached metamorphosis in the short hydroperiod (56 days). However a greater proportion (66%) of tadpoles of R. sylvatica survived to the end of the 56-day, treatment than the 84- or 158-day treatments (29 and 14%, respectively), from which all survivors metamorphosed. In contrast, neither of the salamanders metamorphosed by 84 days; survival to metamorphosis at 158 days was 15% for A. jeffersonianum and 10% for A. maculatum. Average instantaneous growth rates for A. jeffersonianum decreased with each increase in hydroperiod. Growth of R. sylvatica was greater in the 56-day hydroperiod than in hydroperiods of 84 or 158 days. Initial amphibian density had no effect on growth or survival of any species. It appears that salamander larvae were predatory on tadpoles, since survival of R. sylvatica was negatively correlated with survival of A. jeffersonianum in 84-day treatments and with growth of A. maculatum in 158-day treatments.     

Potential Impact of Filter-feeding Invaders on Temperate Inland Freshwater Environments

Since the 1990s, biological invasions have captured the attention of the scientific community as an important element of global change and a major threat to biodiversity. The inland waters of South America provide two examples of biological invasions. This review examines bivalve invasions in South America, summarizes the research results for two species, the Asian clam (Corbicula fluminea) and the golden mussel (Limnoperna fortunei), and suggests further studies. The rapid expansion of invasive bivalves into these environments involves significant changes. Until now, C. fluminea, the Asian clam, did not produce generalized macrofouling in the Neotropical region, as is common in the Holarctic region. However, the first specific cases of macrofouling by C. fluminea were recently detected in heat interchangers of power stations in Brazil. On the other hand, L. fortunei is provoking new economic impacts in South American freshwaters through macrofouling. Before the invasion by the golden mussel, macrofouling was recorded only in the marine and estuarine environments of the Neotropical region. The impact caused by invasive bivalves in this region is not only economic, however. Rapid changes in the benthic community, favoring the presence of Oligochaeta and Hirudinea, as well as the displacement of native species of mollusks, are among the problems related to the presence of the golden mussel. Another issue is the settlement of golden mussels on native bivalves. This bivalve is now a new element in the diet of some native fish species, being the main food item in some cases.     

Effect of Climate Change on Lyme Disease Risk in North America

An understanding of the influence of climate change on Ixodes scapularis, the main vector of Lyme disease in North America, is a fundamental component in assessing changes in the spatial distribution of human risk for the disease. We used a climate suitability model of I. scapularis to examine the potential effects of global climate change on future Lyme disease risk in North America. A climate-based logistic model was first used to explain the current distribution of I. scapularis in North America. Climate-change scenarios were then applied to extrapolate the model in time and to forecast vector establishment. The spatially modeled relationship between I. scapularis presence and large-scale environmental data generated the current pattern of I. scapularis across North America with an accuracy of 89% (P < 0.0001). Extrapolation of the model revealed a significant expansion of I. scapularis north into Canada with an increase in suitable habitat of 213% by the 2080s. Climate change will also result in a retraction of the vector from the southern U.S. and movement into the central U.S. This report predicts the effect of climate change on Lyme disease risk and specifically forecasts the emergence of a tickborne infectious disease in Canada. Our modeling approach could thus be used to outline where future control strategies and prevention efforts need to be applied.     

Spatial ecology of the Japanese beetle, Popillia japonica

A cornerstone of spatial ecology is the quantification of the patchy nature of animal and plant populations in space. By using spatial covariance, total covariance, and quantile variance, we found that patchiness of Japanese beetle grub populations varied more between years than between fairways at a central New York golf course. We also observed that populations tended to shrink and swell around patches with perennially low density, that locations with perennially low grub density were associated with high soil organic matter content, and that locations with frequently high grub density were associated with intense adult beetle activity in the vicinity.     

Spatial variability in mycorrhizal hyphae and nutrient and water availability in a soil-weathered bedrock profile

We documented the spatial distribution, abundance and molecular diversity of mycorrhizal hyphae and physical and chemical properties of soil-weathered bedrock in a chaparral community that experiences seasonal drought. Because plants in this community were known to rely on bedrock-stored water during the summer, the data were used to evaluate the potential role of mycorrhizal hyphae in accessing bedrock-stored water during summer drought. The granitic bedrock was characterized by factures filled with a disaggregated, sandy loam that acted as conduits for water, and matrices composed of soil-weathered granite that retained the fabric and structure of rock. Mycorrhizal hyphae of six ectomycorrhizal taxa (from the Basidiomycota and Ascomycota), and arbuscular mycorrhizal hyphae (Zygomycota) were recovered from both fracture and matrix compartments to depths greater than 200 cm. Our findings also indicated a potential linkage between the abundance of Ascomycete hyphae, substrate physical (bulk density) and chemical properties (total N, N:P, Ca:Mg), and bedrock moisture content, as well as spatial patterning between hyphae and resources at a scale of 25–45 cm. Such linkages suggest that mycorrhizal fungal hyphae may be part of an adaptive mechanism that enables chaparral plants to survive seasonal drought.     

Muscodor albus, a potential biocontrol agent against plant-parasitic nematodes of economically important vegetable crops in Washington State, USA

The fungus, Muscodor albus, was tested for nematicidal and nematostatic potential against four plant-parasitic nematode species with three different feeding modes on economically important vegetable crops in the Pacific Northwest. Meloidogyne chitwoodi, Meloidogyne hapla, Paratrichodorus allius, and Pratylenchus penetrans were exposed for 72 h to volatiles generated by M. albus cultured on rye grain in sealed chambers at 24 °C in the laboratory. In addition, the nematodes were inoculated into soil fumigated with M. albus, and incubated for 7 days prior to the introduction of host plants under greenhouse conditions. The mean percent mortality of nematodes exposed to M. albus in the chamber was 82.7% for P. allius, 82.1% for P. penetrans, and 95% for M. chitwoodi; mortality in the nontreated controls was 5.8%, 7%, and 3.9%, respectively. Only 21.6% of M. hapla juveniles died in comparison to 8.9% in controls. However, 69.5% of the treated juveniles displayed reduced motility and lower response to physical stimulus by probing, in comparison to the control juveniles. This is evidence of nematostasis due to M. albus exposure. The greenhouse study showed that M. albus caused significant reduction to all nematode species in host roots and in rhizosphere soil. The percent mortality caused by M. albus applied at 0.5% and 1.0% w/w in comparison to the controls was as follows: 91% and 100% for P. allius in the soil; 100% for P. penetrans in bean roots and soil; 85% and 95% for M. chitwoodi in potato roots, and 56% and 100% in the soil; 100% for M. hapla both in pepper roots and soil. In this study, M. albus has shown both nematostatic and nematicidal properties.     

Spatial distribution of the cockroach, Blattella germanica, in a swimming-bath facility

A population of Blattella germanica L. was studied in a swimming-bath facility using a sampling method. A set of traps deposited weekly, over a period of 50 weeks, allowed us to follow the variations of the temporal and spatial distributions of the population inside the building. A Factorial Correspondance Analysis, performed on the data, led us to the conclusion that the population was stable in time. The spatial distribution of the insects was contiguous. Inside an aggregate, we were able to define a circular movement from the center towards the periphery and vice versa; this movement can be superimposed up on the biological development on the individuals. After birth in the middle of the aggregate, during development, larvae explore further a field as far as the border of the aggregate; this exploratory phase, related to foraging behavior or search for new shelters when these become limiting factors, could be considered as the spreading phase of the population. Then, with the imminence of the imaginal moult, old larvae tend to gather in high density areas in the middle of the aggregate. Newly molted adults look for a sexual partner. And finally females remain in the shelters during oothecae maturation.

---

Résumé L'étude d'une population de Blattella germanica L. dans une piscine par des piégeages hebdomadaires pendant une période de 50 semaines, nous a permis de suivre l'évolution spatiale et temporelle de cette population. Les résultats des piégeages étudiés par Analyse Factorielle des Correspondances nous permettent de conclure à une certaine stabilité temporelle de la population. Elle se répartit en larges agrégats dans lesquels s'inscrit un mouvement circulaire, allant du centre vers la périphérie et retour, qui se superpose au cycle de développement des individus.

     

Spatial genetic structure in populations of the terrestrial orchid Orchis cyclochila (Orchidaceae)

Orchid seeds are minute, dust-like, wind-borne and, thus, would seem to have the potential for long-distance dispersal. Based on this perception, one may predict near-random spatial genetic structure within orchid populations. In reality we do not know much about seed dispersal in orchids and the few empirical studies of fine-scale genetic structure have revealed significant genetic structure at short distances (< 5m), suggesting that most seeds of orchids fall close to the maternal plant. To obtain more empirical data on dispersal, Ripley’s L(d)-statistics, spatial autocorrelation analyses (coancestry, f_ij analyses) and Wright’s F statistics were used to examine the distribution of individuals and the genetic structure within two populations of the terrestrial orchid Orchis cyclochila in southern Korea. High levels of genetic diversity (H_e = 0.210) and low between-population variation were found (F_ST = 0.030). Ripley’s L(d)-statistics indicated significant aggregation of individuals, and patterns varied depending on populations. Spatial autocorrelation analysis revealed significant positive genetic correlations among individuals located <1 m, with mean f_ij values expected for half sibs. This genetic structure suggests that many seeds fall in the immediate vicinity of the maternal plant. The finding of significant fine-scale genetic structure, however, does not have to preclude the potential for the long distance dispersal of seeds. Both the existence of fine-scale genetic structure and low F_ST are consistent with a leptokurtic distribution of seed dispersal distances with a very flat tail.     

Spatial and temporal patterns of morel fruiting

The biotic and abiotic factors conditioning morel fruit body production are incompletely known. We examined spatial and temporal patterns of Morchella esculenta fruiting over five years in a wooded site in Missouri, USA. Fruiting onset was inversely correlated with spring air and soil temperatures, whereas abundance was positively correlated with rain events (>10 mm) during the 30 d preceding fruiting. The two years with the greatest fruiting had the shortest fruiting seasons (6–7 d). Fruiting season length was positively correlated with soil warming, suggesting that a narrow range of optimum soil temperatures favour the explosive production of fruit bodies. All woody stems of at least 1 cm diam were mapped and stem diameter and crown condition were noted. Morel fruit bodies were significantly closer to stems of Carya spp., Tilia americana and Ulmus americana than predicted by the frequencies of these woody species or their contribution to the total basal area on the site. Although intra-annual clustering of fruit bodies was often observed, inter-annual clustering was not. The spatial pattern of M. esculenta fruiting appears to be associated with vegetation pattern, whereas the onset and abundance of fruiting are determined by the interaction of spring temperatures with availability of supporting precipitation.     

An NMR Study of the Spatial Structure and Intramolecular Dynamics of Modified Analogues of Steroid Hormones

Special features of the use of homo- and heteronuclear correlation methods of NMR in one and two dimensions for studying the spatial structure and intramolecular dynamics of modified analogues of steroid hormones (MASH) are considered. The application of these methods to the assignment of resonances in the high-field ¹H NMR region and to the determination of the most stereospecifically important parameters, such as the vicinal constants of spin–spin coupling (³J_H–H) and nuclear Overhauser effects (NOE), are discussed using the example of NMR studies of some estrogens and androgens at 300 MHz and on the basis of literature data. The most efficient combination of the methods and the necessary modification of each of them may be chosen considering the spectral and relaxation parameters of MASH in liquid medium, including the anisotropy of the overall diffusive motion. The characteristics of MASH are the wide use of correlations through long-range couplings (COSY-45 and DQF-COSY), the application of the ^4,5J_H–H constants for the determination of spatial structure, and the advantage of heteronuclear HSQC methods with and without ¹³C decoupling over the corresponding HMQC methods in both resolution and sensitivity. In the conformationally rigid MASH molecules, the anisotropy of the MASH diffusive motion in liquid adversely affects the determination of interproton distances by the calibrating processing method for the NOE difference and NOESY spectra: it results in both overestimated and underestimated distance values depending on the polar angle ratios of the reference and the determined distances. Under certain conditions, conformationally mobile MASH demonstrate the additional contribution of the scalar relaxation mechanism between the indirectly (scalarly) bound protons. This mechanism is responsible for the underestimated values of NOE and the corresponding errors in the distance determination.     

Contribution to the orchid flora of South Central Africa

11 new taxa (8 new species, 3 new varieties) ofOrchidaceae are described from South Central Africa, including data on their habitat and distribution and discussions of their systematic affinities.     

Spatial patchiness of epilithic biofilm caused by refuge-inhabiting high shore gastropods

Aggregations of Melarhaphe neritoides and Littorina saxatilis are common on the high shore in north-east England. These aggregations are frequently found in crevices which act as a refuge from desiccation. The aggregations are surrounded by patches of epilithic biofilm which are visibly lighter in colour than the biofilm present on the remainder of the high shore. Chlorophyll a levels were lower in regions of close proximity to aggregated littorinids (mean = 4.9 μg cm⁻²) as compared to areas >‰5 cm away from the edge of the visible colour change (mean = 15.9 μg cm⁻²). Manipulations of littorinid density showed that areas of high density had significantly lower levels of chlorophyll a than those where littorinids were excluded. This difference was mainly due to the presence of higher numbers of small grazed areas or an increase in size of grazed areas rather than a homogenous change in chlorophyll a levels across the entire manipulated area. These results are supported by observations showing that only 7% of the total foraging time of littorinids was spent outside visibly lighter patches of biofilm suggesting littorinids only control local biofilm levels through grazing.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Hydrobiologia     

Spatial Segregation of the Sexes and Nutrients affect Reproductive Success in a Dioecious Wind-pollinated Grass

In many dioecious plant species in which spatial distributions of males and females have been examined, the sexes are spatially segregated – usually along an environmental gradient. Unless pollen is uniformly distributed in a population, spatial segregation of the sexes should reduce the average mating success of individuals. In three Californian populations of Distichlis spicata – a wind-pollinated grass species that exhibits spatial segregation of the sexes – I examined patterns of pollen movement and the effects of pollen load and nutrient availability on seed set to determine whether spatial segregation of the sexes actually reduces mating success for both males and females. In two of the populations, pollen dispersal was restricted, and pollen augmentation consistently, significantly increased seed set. However, in the third population – which had the lowest seed set – I found that although there were some indications of pollen limitation, pollen dispersal was not restricted, and seed production was limited primarily by nutrient availability. These results imply that in some populations of D. spicata nutrient limitation on the production of seeds by females may be sufficiently strong that spatial segregation of the sexes causes a fairly low cost to reproductive success compared with a more random distribution of the sexes. However, in other populations, pollen does limit mating success, and the spatial segregation of males and females in these populations is reducing the fecundity of both males and females.     

Spatial distribution of three phytochromes in dark- and light-grown Avena sativa L.

We have addressed two issues regarding the spatial distribution of three phytochromes in 3-d-old oat (Avena sativa L.) seedlings. Three monoclonal antibodies, GO-4, GO-7 and Oat-22, were used as probes. Each antibody detects only one of the phytochromes. The first issue is whether any of the phytochromes might be membrane-bound. To address this issue the abundance of each phytochrome in extracts prepared with either a detergent-free or a detergent-containing buffer was compared by immunoblot assay. The detergent-free buffer was formulated to extract only soluble protein, while the detergent-containing buffer was intended to extract both soluble and membrane proteins. None of the data indicate that any of these three phytochromes is membrane-bound in either a dark- or a light-grown seedling. The second issue is whether these three phytochromes are distributed differentially in 3-d-old dark- and light-grown seedlings. When seedlings were dissected into shoots, scutellums, and roots, all three phytochromes were detected in all three fractions from both dark- and light-grown seedlings. Each of the three phytochromes was most abundant in the shoot and least abundant in the root, except that in light-grown seedlings type I, etiolated-tissue phytochrome was more abundant in the root than in either the shoot or the scutellum. When the equivalent fractions dissected from different seedlings were compared, those dissected from dark-grown seedlings contained a higher quantity of each of the three phytochromes than did those dissected from light-grown seedlings, except that green-tissue, type II phytochromes did not differ significantly in the roots. At this level of resolution, no evidence was obtained to indicate a substantive difference among the three phytochromes in their spatial distribution. We thank Drs. Elizabeth Williams and Tammy Sage (Botany Department, University of Georgia, USA) for generously permitting us to use their image-analysis system. This research was supported by USDA NRICGP grant 91-37100-6490.     

The Selection of an Isolate of the Hyphomycete Fungus,Metarhizium anisopliae,for Control of Termites in Australia

Ninety-three isolates ofMetarhizium anisopliae,mostly derived from a survey of termite material, were screened for activity againstNasutitermes exitiosusandCoptotermes frenchiorC. acinaciformisusing a grooming assay technique. Twenty-six of the most promising isolates were further evaluated by bioassay againstN. exitiosusandC. acinaciformis.All isolates were pathogenic withCoptotermesspp. being more susceptible thanN. exitiosus.A group of nine isolates, chosen for their level of pathogenicity for one or other genus of termites and to represent a genetically diverse group, was finally compared in a minicolony test using termite colonies in 1 liter jars. The isolate, code-named FI-610 (derived from nest-mound material ofC. lacteusin SE New South Wales), was one of the most effective isolates against termites from both of the two colonies tested. This isolate also grew relatively well on agar plates at 36°C. FI-610 was thus selected for field trials and was found to be effective in killing colonies ofC. acinaciformiswhen 10 g (=3 × 10¹¹conidia) or more of conidial powder was blown into the center of the large mound colonies.     

Establishment and dispersal of the biological control weevil Rhinoncomimus latipes on mile-a-minute weed, Persicaria perfoliata

Mile-a-minute weed, Persicaria perfoliata (L.) H. Gross (Polygonaceae), is an annual vine from Asia that has invaded the eastern US where it can form dense monocultures and outcompete other vegetation in a variety of habitats. The host-specific Asian weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) was first released in the US in 2004 as part of a classical biological control program. The weevil was intensively monitored in three release arrays over 4 years, and field cages at each site were used to determine the number of generations produced. The weevil established at all three sites and produced three to four generations before entering a reproductive diapause in late summer. Weevils dispersed at an average rate of 1.5–2.9 m wk⁻¹ through the 50 m diameter arrays, which had fairly contiguous mile-a-minute cover. Weevils dispersing in the broader, more variable landscape located both large monocultures and small isolated patches of mile-a-minute 600–760 m from the release within 14 months. Weevil density ranged from fewer than 10 to nearly 200 weevils m⁻² mile-a-minute weed. Mile-a-minute cover decreased at the site with the highest weevil density. The production of P. perfoliata seed clusters decreased with increasing weevil populations at two sites, and seedling production declined over time at two sites by 75% and 87%. The ability of the weevil to establish, produce multiple generations per season, disperse to new patches, and likelihood of having an impact on plants in the field suggests that R. latipes has the potential to be a successful biological control agent.     

Sunflower stem weevil and its larval parasitoids in the Central and Northern Plains of the USA

The sunflower stem weevil, Cylindrocopturus adspersus (LeConte) (Coleoptera:Curculionidae), is apest of cultivated sunflower (Helianthusannuus L) from the southern to the northernGreat Plains. The incidence of weevilinfestation in fields from the six differentstates sampled during 1996 and 1997 ranged from33% (Minnesota) to 100% (Kansas, Colorado,Nebraska). Weevil populations in the fieldssampled were statistically greater in thecentral Plains (Colorado, Kansas, Nebraska)with a mean of 12.3 and 19.5 larvae per stalkcompared with the northern Plains (North andSouth Dakota, Minnesota) of 0.7 and 1.3 larvaeper stalk in 1996 and 1997, respectively.Parasitization of weevils varied from field tofield ranging from 1 to 100%, but was usuallyless than 20%. The nine species oflarval parasitoids recovered were allHymenoptera and included: Nealioluscurculionis (Fitch), N. collaris(Brues), Bracon sp. (Braconidae); Neocatolaccus tylodermae (Ashmead), Chlorocytus sp., Pteromalus sp.(Pteromalidae); Quadrastichus ainslieiGahan (Eulophidae), Eurytoma tylodermatisAshmead (Eurytomidae); and Eupelmus sp.(Eupelmidae). Nealiolus curculionis wasthe most prevalent parasitoid reared from C. adspersus, and it was recovered from allstates sampled. Parasitoid species richness wasgreatest in the central Plains. Thereduced number of parasitoid species foundattacking C. adspersus in the northernPlains may be caused by low host populationlevels, slow migration by parasitoids into theregion, or lack of adaptation to climaticconditions. Additional work to understandthe population dynamics of the parasitoidcomplex associated with C. adspersus mayresult in improved biological control of thesunflower stem weevil in cultivatedsunflower.