Direct and indirect effects of environmental temperature on the evolution of reproductive strategies: an information-theoretic approach

For ectotherms, environmental temperature affects the optimal size and number of offspring via multiple mechanisms. First, temperature influences the performance of offspring, which directly affects the optimal size of offspring. Second, temperature influences maternal body size, which indirectly affects the optimal size and/or number of offspring when larger females acquire more energetic resources or provide better parental care. Although traditional statistical approaches might distinguish the relative importance of these effects, an information-theoretic approach enables one to estimate effects more accurately by identifying the best evolutionary model in a set of candidate models. Here, we use the Akaike Information Criterion to calculate the likelihoods of seven path models, each derived from one or more optimality models of reproduction. Variation in reproductive traits among populations of lizards (Sceloporus undulatus) was used to quantify support for the models. Our results overwhelmingly supported a model based on an indirect effect of temperature that is mediated by maternal size. Path coefficients of this model were consistent with the hypotheses that, first, larger females can acquire more energy for reproduction and, second, the survival of offspring depends on both their size and their density. Our analyses exemplify how information theory can identify evolutionary hypotheses that merit experimental testing.     

Direct and indirect effects of land use on floral resources and flower‐visiting insects across an urban landscape

Although urban areas are often considered to have uniformly negative effects on biodiversity, cities are most accurately characterized as heterogeneous mosaics of buildings, streets, parks, and gardens that include both ‘good’ and ‘bad’ areas for wildlife. However, to date, few studies have evaluated how human impacts vary in direction and magnitude across a heterogeneous urban landscape. In this study, we assessed the distribution of floral resources and flower‐visiting insects across a variety of land uses in New York City. We visited both green spaces (e.g. parks, cemeteries) and heavily developed neighborhood blocks (e.g. with high or low density residential zoning) and used structural equation modeling (SEM) to evaluate the direct and indirect effects of median income, vegetation, and development intensity on floral resources and insects in both settings. Abundance and taxonomic richness of flower‐visiting insects was significantly greater in green spaces than neighborhood blocks. The SEM results indicated that heavily‐developed neighborhoods generally had fewer flower‐visiting insects consistent with reductions in floral resources. However, some low‐density residential neighborhoods maintained high levels of floral resources and flower‐visiting insects. We found that the effects of surrounding vegetation on floral resources, and thus indirect effects on insects, varied considerably between green spaces and neighborhood blocks. Along neighborhood blocks, vegetation consisted of a mosaic of open gardens and sparsely distributed trees and had a positive indirect effect on flower‐visiting insects. In contrast, vegetation in urban green spaces was associated with increased canopy cover and thus had a negative indirect effect on flower‐visiting insects through reductions in floral resources. In both neighborhood blocks and green spaces, vegetation had a positive direct effect on flower‐visiting insects independent of the influence of vegetation on floral resources. Our results demonstrate how inter‐related components of an urban ecosystem can vary with respect to one another across a heterogeneous urban landscape, suggesting that it is inappropriate to generalize about urban systems as a whole without first addressing differences among component land use types.     

Direct and indirect effects of grazing on the phytoplankton seasonal succession in an oligotrophic lake

We examined the simultaneous dynamics of phytoplankton and zooplanktonin an oligotrophic lake, as well as the algal response to experimentalmanipulations of herbivore population structure and density.The seasonal succession of phytoplankton is characterized bya shift in dominance from eukaryotic species to prokaryoticcyanobacteria, as in a eutrophic lake. This unusual patternfor an oligotrophic lake is related to the release of zooplanktonphosphorus, rather than to the amount of total phosphorus. Thehighest estimated values of this released phosphorus occur duringthe co-dominance of small-sized species and of one calanoidpopulation, both under natural and experimental conditions.Our experimental results clearly reveal that a blue-green speciesreplaces non-blue-green ones when environmental conditions renderlow or intermediate values for released phosphorus, irrespectiveof the grazing pressure. The absence of predators or high levelsof released phosphorus stimulate non-blue-green growth. Theseresults agree with the successional pattern observed for thealgal assemblage under natural conditions. Nutrient recyclingplays an essential role in the maintenance of the metabolismof the pelagic system, and therefore the prevalence of a topdownregulation mechanism as proposed for such low-nutrient environmentsshould be reconsidered.     

Direct and indirect effects of an introduced piscivore, <Emphasis Type=Italic>Cichla kelberi</Emphasis> and their modification by aquatic plants

The non-native peacock bass (Cichla kelberi) is causing freshwater fish extinctions in the tropical regions around the world, but there are very few studies on its interaction with native species. This study, based on a mesocosm experiment, examined direct and indirect effects of a non-native peacock bass on the native prey in Paraná River, Brazil, and tested whether these effects were mitigated by aquatic vegetation. Feeding activity of most prey was unaffected by the presence of peacock bass. All prey were consumed in the absence of vegetation; whereas a marginally significant decrease in mortality was observed in the vegetated habitats. Overall, peacock bass had minor indirect effects on prey foraging, but very significant direct effects on prey survival. As aquatic plants provide very limited protection to native prey, vegetated habitats are unlikely to slow down the decline in biodiversity resulting from this invasive species and conservation measures may need to consider other ways to ensure survival of the source populations.     

Direct and indirect effects of a sex-biased antagonist on male and female fertility: consequences for reproductive trait evolution in a gender-dimorphic plant

Gender-dimorphic plants are often subject to sex-differential enemy attack, but whether and how this contributes to trait evolution is unknown. To address this gap, we documented the spatiotemporal prevalence of sex-biased weevil damage in a gynodioecious strawberry. We then conducted path analysis to evaluate the direct and indirect pathways for weevils to affect female and male fertility and to mediate selection in two experimental gardens. Direct effects of weevils significantly reduced fertility and mediated selection on reproductive traits, even in the nonpreferred sex (females). Weevils significantly reduced floral display size in hermaphrodites in both gardens, and this translated into a substantial negative indirect effect on male fertility in the garden where the pathway to fertility via display was stronger. Thus, indirect effects of weevils can contribute to selection in hermaphrodites, which gain the majority of their fitness via male function. Our results also indicate that weevils often play a larger role than pollinators in shaping reproductive phenotype and thus raise the intriguing possibility that antagonists may be drivers of sexual dimorphism. Finally, our results support the view that mutualists, antagonists, and the abiotic environment should be considered when attempting to understand reproductive trait evolution in gender-dimorphic species.     

Direct and indirect effects of two herbivore species on resource allocation in their shared host plant: the rhizome galler Eurosta comma, the folivore Trirhabda canadensis and Solidago missouriensis

We examined the effects of the rhizome galling fly, Eurosta comma (Wiedemann), on rhizome mass and nitrogen allocation in a clone of its goldenrod host plant, Solidago missouriensis Nutt. In comparison to ungalled ramets, galled ramets initiated significantly fewer new rhizomes, and allocated less mass to leaves and stems and more to roots. Galled ramets had lower concentrations of nitrogen in roots and rhizomes but leaf and stem nitrogen concentrations were not affected. In the second year of our study, outbreaks of the leaf-eating beetle, Trirhabda canadensis (Kirby), occurred in three of our four study clones, removing ∼20%, ∼50%, and 100% of leaf area from clones 2–4, respectively. In the most heavily grazed clones, the influence of rhizome galls on plant resource allocation was least pronounced. Despite the overwhelming immediate impact of grazing, the presence of a gall population may be important because they decrease the ability of S. missouriensis clones to initiate new rhizomes and hence to recover from defoliation. Received: 28 December 1997 / Accepted: 28 December 1998     

No evidence for the small‐island effect in avian communities on islands of an inundated lake

The small‐island effect (SIE), i.e. the hypothesis that species richness on islands below a certain threshold area varies independently of area, has become more and more part of the theoretical framework of biogeography and biodiversity research. However, existing SIE studies are extraordinarily biased taxonomically: plants and other animal taxonomic groups are predominantly studied, while birds are almost completely overlooked. Furthermore, previous methods for the detection of SIE are flawed in one or another way, including not accounting for model complexity, not comparing all relevant models, not including islands with no species, and ignoring the effects of logarithmic data transformations and habitat diversity in generating SIE. Therefore, the existence and the prevalence of the SIE may be dubious. In this study, after controlling for all these methodological shortcomings in detecting the SIE, we test for the existence of the SIE using bird data collected on islands in the Thousand Island Lake, China. We used the line‐transect method to survey bird occupancy and abundance on 42 islands from 2007 to 2011. We used three broad sets of analyses, regression‐based analyses, path analyses and null model analyses, to overcome potential methodological problems in detecting the SIE. We found no evidence for an SIE in avian communities in the Thousand Island Lake. Model selection based on AIC_c identified the simple power model without SIE as the most parsimonious model. In contrast, there was little support for the three breakpoint regression models with SIE. Path analyses and null model analyses also did not detect an SIE. We conclude that, for the robust detection of SIE, future study should carefully take all these methodological pitfalls into account.     

In vitro rearing of Edovum puttleri,an egg parasitoid of the Colorado potato beetle,on artificial diets: Effects of insect cell line‐conditioned medium

Effects of conditioned media prepared from cell lines derived from 11 insect species (six families, three orders) on the in vitro growth and development of the egg parasitoid Edovum puttleri were investigated. The parasitoid exhibited significantly different responses to the various insect cell line‐conditioned media that were incorporated into the artificial diets. When cell lines were derived from embryos, higher percentages of 3rd instars and prepupae were observed than when cell lines were derived from fat body or ovaries. Medium conditioned with cell line IPLB‐CPB2 derived from the embryos of the Colorado potato beetle produced the best result. Preconditioning time was important. In general, 5 days of preconditioning appeared to be optimal. The growth‐ and development‐promoting effect may have resulted from growth factors or growth‐supporting factors produced/ released by the insect cell lines into the culture medium. Upon storage at 0–4°C for 7–14 days, the ability of cell line‐conditioned medium to promote development beyond the second instar was greatly reduced (approximately 10–55%). Our studies demonstrated that to support the in vitro growth and development of E. puttleri, insect hemolymph could be successfully replaced with insect cell line‐conditioned medium. These findings should facilitate the development of a cost‐effective mass‐rearing system for E. puttleri and/or other parasitoids. Arch. Insect Biochem. Physiol. 40:173–182, 1999. Published 1999 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.     

The effects of organic solvents on the efficiency and regioselectivity of N‐acetyl‐lactosamine synthesis,using the β‐galactosidase from Bacillus circulans in hydro‐organic media

The enzymatic synthesis of N‐acetyl‐lactosamine (LacNAc) by the transgalactosylation of N‐acetyl‐D ‐glucosamine (GlcNAc), catalyzed by the β‐galactosidase from Bacillus circulans (BcβGal), was studied in hydro‐organic media, starting from o‐nitrophenyl‐β‐D ‐galactopyranoside (oNPG) as a galactosyl donor. Thermal stability and synthesis activity of BcβGal were shown to depend on the organic solvent polarity, characterized by its Log P value. BcβGal was thus most stable in 10% (v/v) t‐BuOH, an organic solvent found to have a stabilizing and/or weakly denaturing property, which was confirmed for high t‐BuOH concentrations. In the same manner, the optimal synthesis yield increased as the Log P value of the organic solvent increased. The best results were obtained for reactions carried out in 10% (v/v) pyridine or 2‐methyl‐2‐butanol, which gave 47% GlcNAc transgalactosylation yield based on starting oNPG, of which 23% (11 mM; 4.3 g/L) consisted in LacNAc synthesis. Furthermore, it was also established that both the GlcNAc transgalactosylation yield and the enzyme regioselectivity depended on the percentage of organic solvent used, the optimal percentage varying from 10 to 40% (v/v), depending on the solvent. This phenomenon was found to correlate mainly with the thermodynamic activity of water (a_w) in the aqueous organic solvent mixture, which was found to be optimal when close to 0.96, whatever the organic solvent used. Finally, this study highlighted the fact that the regioselectivity of BcβGal for 1‐4 linkage formation could be advantageously managed by controlling the a_w parameter. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Modeling effects of environment,insect damage,and <Emphasis Type="Italic">Bt</Emphasis> genotypes on fumonisin accumulation in maize in Argentina and the Philippines

Fumonisins are common contaminants of maize (Zea mays L.) grain products, especially in countries where maize is a major constituent of the diet and are harmful to human and animal health. There is a need to better define environmental conditions that favor fumonisin accumulation in the grain of maize. The impacts of biotic and abiotic factors, and hybrids containing the Cry1Ab protein from Bacillus thuringiensis (Bt), were associated with fumonisin accumulation in the grain of maize across contrasting environments in Argentina and the Philippines between 2000 and 2002. Average fumonisin concentrations in grain samples varied from 0.5 to 12 μg g⁻¹ across field locations in Argentina, and from 0.3 to 1.8 μg g⁻¹ across locations in the Philippines. The ratio of fumonisin B1 to fumonisin B2 was <3.0 in four of nine locations in Argentina, which proved to be due to a higher prevalence of Fusarium proliferatum in those locations. Most of the variability of total fumonisins among maize grain samples was explained by location or weather (47%), followed by insect damage severity in mature ears (17%), hybrid (14%), and with the use of Bt hybrids (11%). In Argentina, where conditions were more favorable for accumulation of fumonisin in the years considered, fumonisin concentrations were lower in Bt hybrids compared to their genetic isolines by an average of 40%. A model was developed to predict fumonisin concentration using insect damage to ears and weather variables as predictors in the model. Four periods of weather around silking were identified as critical for fumonisin concentrations at harvest. The model accounted for 82% of the variability of total fumonisin across all locations in 2 years of the study.     

Distance decay of similarity,effects of environmental noise and ecological heterogeneity among species in the spatio‐temporal dynamics of a dispersal‐limited community

The joint spatial and temporal fluctuations in community structure may be due to dispersal, variation in environmental conditions, ecological heterogeneity among species and demographic stochasticity. These factors are not mutually exclusive, and their relative contribution towards shaping species abundance distributions and in causing species fluctuations have been hard to disentangle. To better understand community dynamics when the exchange of individuals between localities is very low, we studied the dynamics of the freshwater zooplankton communities in 17 lakes located in independent catchment areas, sampled at end of summer from 2002 to 2008 in Norway. We analysed the joint spatial and temporal fluctuations in the community structure by fitting the two‐dimensional Poisson lognormal model under a two‐stage sampling scheme. We partitioned the variance of the distribution of log abundance for a random species at a random time and location into components of demographic stochasticity, ecological heterogeneity among species, and independent environmental noise components for the different species. Non‐neutral mechanisms such as ecological heterogeneity among species (20%) and spatiotemporal variation in the environment (75%) explained the majority of the variance in log abundances. Overdispersion relative to Poisson sampling and demographic stochasticity had a small contribution to the variance (5%). Among a set of environmental variables, lake acidity was the environmental variable that was most strongly related to decay of community similarity in space and time.     

Re‐Evaluation of the EUK516 Probe for the Domain Eukarya Results in a Suitable Probe for the Detection of Kinetoplastids,an Important Group of Parasitic and Free‐Living Flagellates

ABSTRACT. Two frequently used universal eukaryote probes, EUK1209 and EUK516, are not consistent with one branch of the eukaryotic phylogenetic tree, the Kinetoplastida, which has undergone rapid evolution of their small subunit rRNA gene. Kinetoplastids include medically important parasitic organisms (e.g. Trypanosoma, Leishmania) and free‐living flagellates that occur in all aquatic environments and in soils (e.g. Bodo, Neobodo, Rhynchomonas). A modified probe presented here as KIN516, now based on the kinetoplastid sequence, provides a strong signal with Neobodo designis, Leishmania donovani, and Trypanosoma cruzi using the catalyzed reporter deposition protocol. EUK516 and KIN516 function as competitor probes, thereby greatly increasing discriminatory power when used in combination. The probe pair was tested in field samples collected in a freshwater pond in Norfolk, the mesohaline Elizabeth River, Norfolk, Virginia, and a tropical lagoon in Belize. The combined probes bound to 58–84% of organisms identified as eukaryotic based on having large DAPI‐stained nuclei. The contribution of kinetoplastids to total eukaryotes (positive signal of EUK516+KIN516) was much higher in marine samples (ca. 17%) than in either the freshwater or brackish water sites (<0.2%).     

For an anthropology of the demoralized: state pay,mock‐labour,and unfreedom in a Serbian firm

Recently, the leitmotif of much anthropological writing became that of the virtue of precarity: the belief that people continue to exercise their ethical imagination in the most trying circumstances. While refreshingly non‐deterministic, the Foucauldian approach to freedom that guides this vision neglects those situations in which people see their ability to be moral as irreparable, and structurally compromised. Such is the case of a Serbian firm selling spare car parts, where policies of financing unprofitable employment gradually involved workers in everyday, ritualized performances of productivity for the state – what I call mock‐labour. Unable either to meaningfully fulfil or to renounce the ethos of work, workers remain in an affective blend of nonchalance and failure, experiencing mock‐labour as both a source of material security and an abandonment of their creative capacities – a mocking of moral self. I call for a reconciliation of the anthropologies of ethics and precarity through the notion of demoralization, as a state in which the deficits of structural agency and the limits of reflective freedom overlap.     

Inter‐annual variation in the breeding chronology of arctic shorebirds: effects of weather,snow melt and predators

Arctic breeding shorebirds travel thousands of kilometres between their wintering and breeding grounds, yet the period over which they arrive and begin to initiate nests spans only several weeks. We investigated the role of local conditions such as weather, snow cover and predator abundance on the timing of arrival and breeding for shorebirds at four sites in the eastern Canadian arctic. Over 11 years, we monitored the arrival of 12 species and found 821 nests. Weather was highly variable over the course of this study, and the date of 50% snow cover varied by up to three weeks between years. In contrast, timing of arrival varied by one week or less at our sites, and was not well predicted by local conditions such as temperature, wind or snow melt. Timing of breeding was related to the date of 50% snow melt, with later snow melt resulting in delayed breeding. Higher predator abundance resulted in earlier nesting than would be predicted by snow cover alone. We hypothesise that when predation risk is high, the value of potential re‐nesting exceeds the energetic risks of early breeding. Synchrony of breeding was significantly higher in late breeding years suggesting a relatively fixed date for the termination of nest initiation, after which nesting is no longer profitable.     

Direct and indirect methods for the quantification of leg volume: comparison between water displacement volumetry,the disk model method and the frustum sign model method,using the correlation coefficient and the limits of agreement

Volume changes can be measured either directly by water-displacement volumetry or by various indirect methods in which calculation of the volume is based on circumference measurements. The aim of the present study was to determine the most appropriate indirect method for lower leg volume calculation using water displacement volumetry as a ‘golden standard’. For 20 male volunteers, age range: 20–35 years, the volume of both lower legs was determined directly by water-displacement volumetry, and indirectly by the frustum sign model method and the disc model method. Calculation of the correlation coefficient and the limits of agreement showed that water-displacement volumetry and the disc model method are interchangeable (r = + 0.99, mean ± 2s = − 45 ± 78 ml), whereas this does not hold for the frustum sign model (r = + 0.93, mean ± 2s = 521 ± 238 ml). In the clinical situation volume measurement can be valuable for monitoring of the severity of oedema or haematoma occurrence after surgery or severe trauma. This non-invasive diagnostic aid may be a valuable adjuvant means of diagnosis for several volume dependent disorders of the extremities.