Natural enemy composition rather than richness determines pest suppression

Natural enemy (NE) biodiversity is thought to play an important role in agricultural pest suppression. However, the relative importance of the number of NE species (species richness), versus the particular combinations of species (species composition), in determining aphid suppression and ultimately crop yields, remains poorly understood. We tested the effects of NE richness and composition on pea aphids Acyrthosiphon pisum (Harris) and broad bean plants Vicia faba (Linn.). We used the larvae of two predator species, the ladybird Adalia bipunctata (Linn.) and the green lacewing Chrysopa carnea (Stephens), and the parasitic wasp Aphidius ervi (Haliday) as enemies. NEs generally reduced aphid density but did not increase final plant biomass, despite a significant negative correlation between aphid density and plant biomass. Among NE treatments, species richness had an inconsistent effect on aphid density. The composition of NEs within richness levels also affected final aphid density: the ladybird was a key species among the treatments in controlling aphid density and was especially effective in combination with the parasitoid. This ladybird/parasitoid combination also appeared to drive the higher level of suppression observed at the two, relative to three, species richness levels. Although these three species of aphid NEs are commonly used in aphid control, this is the first study, to our knowledge, that simultaneously examined these three species and highlighted the composition effect between the A. bipunctata and A. ervi. In conclusion, increasing NE species richness had an inconsistent effect on aphid density. Meanwhile, the presence of a key species (the ladybird) and its combination with a parasitoid was an important determinant of aphid biological control.     

Effects of velocity-specific training on rate of velocity development, peak torque, and performance

Little is known about the velocity-specific adaptations to training utilizing movement velocities in excess of 300 degrees x s(-1). The purpose of this investigation was to determine the effects of 4 weeks of slow (60 degrees x s(-1)) vs. fast (400 degrees x s(-1)) velocity training on rate of velocity development (RVD), peak torque (PT), and performance. Twenty male kinesiology students (22.0 years +/- 2.72; 178.6 cm +/- 7.1; 82.7 kg +/- 15.5) were tested, before and after 4 weeks of training, for PT production, RVD (at 60, 180, 300, 400, and 450 degrees x s(-1)), standing long jump (SLJ) distance, and 15- and 40-m sprint times. All participants underwent 8 training sessions, performing 5 sets of 5 repetitions of simultaneous, bilateral, concentric knee extension exercises on a Biodex System 3 isokinetic dynamometer at either 60 degrees or 400 degrees per second. Two 5 (speed) x 2 (time) x 2 (group) multivariate repeated measures analyses of variance revealed no significant differences between groups on any measure. Therefore, the groups were collapsed for analysis. There was a significant (p < 0.05) main effect for RVD by time and SLJ distance by time (pre- 227.1 cm +/- 21.2; post- 232.9 cm +/- 20.7) but no significant change in PT or 15- or 40-m sprint times. These results offer support for the suggestion that there is a significant neural adaptation to short-term isokinetic training performed by recreationally trained males, producing changes in limb acceleration and performance with little or no change in strength. Because results were independent of training velocity, it appears as though the intention to move quickly is sufficient stimulus to achieve improvements in limb RVD. Changes in SLJ distance suggest that open kinetic chain training may benefit the performance of a closed kinetic chain activity when movement pattern specificity is optimized.     

History rather than hybridization determines population structure and adaptation in Populus balsamifera

Hybridization between species is known to greatly affect their genetic diversity and, therefore, their evolution. Also, within species, there may be genetic clusters between which gene flow is limited, which may impact natural selection. However, few studies have looked simultaneously at the influence of among‐species and within‐species gene flow. Here, we study the influence of hybridization between Populus balsamifera and Populus trichocarpa on population structure and adaptation in P. balsamifera. We did this by sampling a total of 1517 individuals from across the ranges of these two species, and by genotyping them using a combination of 93 nuclear and 17 cpDNA SNPs. We found that hybridization is mostly limited to the contact zone where the species’ distributions overlap. Within P. balsamifera, we found multiple levels of population structure. Interestingly, the border between the Eastern and Central clusters is very sharp, whereas the border between the Central and Western clusters is diffuse. Outlier analysis revealed that three loci associated with the sharp border were also associated with climate. We hypothesize that the observed clusters derive from three refugia during the Pleistocene ice ages. Between the Central and Western clusters, post‐glacial long‐distance gene flow has led to the diffusion of their border. In the Eastern cluster, we hypothesize that endogenous genomic barriers have developed, leading to the sharp border and a spurious climate association. We conclude that the large‐scale genetic structure of P. balsamifera is mostly shaped by historical factors and the influence of interspecific hybridization is limited.     

Immune response to leishmania: paradox rather than paradigm

The leishmaniases are a group of diseases caused by protozoan parasites of the genus Leishmania. Various Leishmania species can cause human infection, producing a spectrum of clinical manifestations. It is estimated that 350 million people are at risk, with a global yearly incidence of 1-1.5 million for cutaneous and 500,000 for visceral leishmaniasis (VL). VL is a major cause of morbidity and mortality in East Africa and the Indian subcontinent. Coinfection with HIV enhances the risk of the disease. The only control measure currently available in India is case detection and treatment with antimonial drugs, which are expensive, not always available and cannot be self-administered. Newer drugs like oral miltefosine have not become widely available. Vector and reservoir control is difficult due to the elusive nature of the vector and the diversity of the animal reservoir. A detailed knowledge of immune response to the parasite would help in designing prophylactic and therapeutic strategies against this infection.     

Local environment rather than past climate determines community composition of mountain stream macroinvertebrates across Europe

Community assembly is determined by a combination of historical events and contemporary processes that are difficult to disentangle, but eco‐evolutionary mechanisms may be uncovered by the joint analysis of species and genetic diversity across multiple sites. Mountain streams across Europe harbour highly diverse macroinvertebrate communities whose composition and turnover (replacement of taxa) among sites and regions remain poorly known. We studied whole‐community biodiversity within and among six mountain regions along a latitudinal transect from Morocco to Scandinavia at three levels of taxonomic hierarchy: genus, species and haplotypes. Using DNA barcoding of four insect families (>3100 individuals, 118 species) across 62 streams, we found that measures of local and regional diversity and intraregional turnover generally declined slightly towards northern latitudes. However, at all hierarchical levels we found complete (haplotype) or high (species, genus) turnover among regions (and even among sites within regions), which counters the expectations of Pleistocene postglacial northward expansion from southern refugia. Species distributions were mostly correlated with environmental conditions, suggesting a strong role of lineage‐ or species‐specific traits in determining local and latitudinal community composition, lineage diversification and phylogenetic community structure (e.g., loss of Coleoptera, but not Ephemeroptera, at northern sites). High intraspecific genetic structure within regions, even in northernmost sites, reflects species‐specific dispersal and demographic histories and indicates postglacial migration from geographically scattered refugia, rather than from only southern areas. Overall, patterns were not strongly concordant across hierarchical levels, but consistent with the overriding influence of environmental factors determining community composition at the species and genus levels.     

Epithelial entry rather than the ensuing systemic immune response determines the pathogenicity of two Salmonella enterica serovar Typhimurium strains in a mouse model

Most studies of Salmonella enterica serovar Typhimurium infection focus only on the pathogenicity of one strain. We investigated whether differences in pathogenicity of two wild-type S. Typhimurium strains; DT120 and SL1344, were related to gut invasion or the resulting immune response.Oral administration of a ten-fold lower number of SL1344 (10⁶ CFU) as compared to DT120 (10⁷ CFU) resulted in higher bacterial counts in liver and lymph nodes, and led to massive neutrophil infiltration of the spleen, while DT120 administration did not. In contrast, administration of the same dose (10³ CFU) of the two strains intravenously resulted in the same levels of bacteria and neutrophils in spleen and bone marrow. Oral administration of SL1344 led to an increase in neutrophil apoptosis in both spleen and the bone marrow and four out of five mice died before Day 8, while in DT120 mice, no increase in neutrophil apoptosis was observed and all mice survived until Day 8. This study reveals that two wild-type S. Typhimurium strains, despite evoking highly comparable immune responses upon intravenous injection, exhibit diverse pathogenicity in mice and thus suggests that differences in their invasiveness and survival during gut passage determines the success of the ensuing immune response.     

Sexual differences rather than flight performance underlie movement and exploration in a tropical butterfly

1. Individual movement behaviour governs several routine processes, and may scale up to important ecological processes, including dispersal. However, movement is affected by a wealth of factors, including abiotic conditions, flight performance, and behavioural traits. Although it has been historically assumed that insect flight is in the first place ruled by physiology and morphology, researchers have only recently begun to understand the potentially important role of behavioural traits. 2. This study aims to disentangle the relative importance of thermal conditions during development, and especially flight performance (capacity), versus behaviour (intrinsic motivation) in relation to movement attributes (i.e. time until take‐off, number of positions visited) under controlled laboratory conditions in the tropical butterfly Bicyclus anynana. 3. As predicted, links were found between flight performance (forced flight) and morphological traits (body size). However, this link was less pronounced for movement and exploratory behaviour, suggesting a more pronounced role of intrinsic motivation on the actual decision to move, or not. Thus, flight performance and movement may not be intimately associated. 4. Flight behaviour was mainly determined by sexual differences, with males showing better flight performance, higher mobility, and enhanced exploration than females. 5. Lower developmental temperatures increased thorax–abdomen ratio, thorax mass, and exploratory behaviour, and decreased wing loading. This may potentially aid flight capacity under thermally challenging conditions. 6. This study adds to the growing evidence that behavioural traits should not be neglected when investigating movement and dispersal, as they may well play a crucially important role.     

Effects of moderate-velocity strength training on peak muscle power and movement velocity: do women respond differently than men?

The effects of a 10-wk unilateral knee extension strength training (ST) program on peak power (PP) and peak movement velocity (PV), at given absolute (force load) and relative (same % of 1 repetition maximum) resistances (loads), were examined in 30 older men [64 yr (7 SD)] and 32 older women [62 yr (6 SD)]. PP increased significantly in both men and women at the same absolute (P < 0.001) and relative loads (P < 0.01) with ST. Men had a significantly greater increase in relative PP than women with ST at 60% (P < 0.01) and 70% (P < 0.001) of 1 repetition maximum when covarying for baseline differences and age. However, when each subject was tested at the same absolute load and when PP was normalized for the muscle volume of the trained knee extensors (i.e., absolute muscle power quality), women increased by 9% (P < 0.05), whereas men did not change. Both men and women increased their absolute PV (P < 0.001) but decreased their relative PV significantly with ST (P < 0.05). However, when baseline values and age were covaried, women had significantly less of a decrease in relative PV quality with ST than men (P < 0.01), although the difference was small. These normalized data suggest that ST-induced increases in PP depend on muscular hypertrophy in men, but not in women, providing further support for the hypothesis developed from our previous report (Ivey FM, Tracy BL, Lemmer JT, NessAiver M, Metter EJ, Fozard JL and Hurley BF. J Gerontol A Biol Sci Med Sci 55: B152-B157, 2000) that improvements in muscle function with ST result from nonmuscle mass adaptations to a greater extent in women than men.     

Suprazero cooling rate,rather than freezing rate,determines post thaw quality of rhesus macaque sperm

Sperm become most sensitive to cold shock when cooled from 37 °C to 5 °C at rates that are too fast or too slow; cold shock increases the susceptibility to oxidative damage owing to its influence on reactive oxygen species (ROS) production, which are significant stress factors generated during cooling and low temperature storage. In addition, ROS may be a main cause of decreased motility and fertility upon warming. They have been shown to change cellular function through the disruption of the sperm plasma membrane and through damage to proteins and DNA. The objective of this study was to determine which cryopreservation rates result in the lowest degree of oxidative damage and greatest sperm quality. In the rhesus model, it has not been determined whether suprazero cooling or subzero freezing rates causes a significant amount of ROS damage to sperm. Semen samples were collected from male rhesus macaques, washed, and resuspended in TEST-yolk cryopreservation buffer to 100 × 10⁶ sperm/mL. Sperm were frozen in 0.5-mL straws at four different combinations of suprazero and subzero rates. Three different suprazero rates were used between 22 °C and 0 °C: 0.5 °C/min (slow), 45 °C/min (medium), and 93 °C/min (fast). These suprazero rates were used in combination with two different subzero rates for temperatures 0 °C to −110 °C: 42 °C/min (medium) and 87 °C/min (fast). The different freezing groups were as follows: slow-med (SM), slow-fast (SF), med-med (MM), and fast-fast (FF). Flow cytometry was used to detect lipid peroxidation (LPO), a result of ROS generation. Motility was evaluated using a computer assisted sperm motion analyzer. The MM and FF treated sperm had less viable (P < 0.0001) and motile sperm (P < 0.001) than the SM, SF, or fresh sperm. Sperm exposed to MM and FF treatments demonstrated significantly higher oxidative damage than SM, SF, or fresh sperm (P < 0.05). The SM- and SF-treated sperm showed decreased motility, membrane integrity, and LPO compared with fresh semen (P < 0.001). Slow cooling from room temperature promotes higher membrane integrity and motility post thaw, compared with medium or fast cooling rates. Cells exposed to similar cooling rates with differing freezing rates were not different in motility and membrane integrity, whereas comparison of cells exposed to differing cooling rates with similar freezing rates indicated significant differences in motility, membrane integrity, and LPO. These data suggest that sperm quality seems to be more sensitive to the cooling, rather than freezing rate and highlight the role of the suprazero cooling rate in post thaw sperm quality.     

Predictability rather than amplitude of temperature fluctuations determines stress resistance in a natural population of Drosophila simulans

The adaptability of organisms to novel environmental conditions depends on the amount of genetic variance present in the population as well as on the ability of individuals to adjust their phenotype through phenotypic plasticity. Here, we investigated the phenotypic plasticity induced by a single generation's exposure to three different temperature regimes with respect to several life‐history and stress‐resistance traits in a natural population of Drosophila simulans. We studied a constant as well as a predictably and an unpredictably fluctuating temperature regime. We found high levels of phenotypic plasticity among all temperature regimes, suggesting a strong influence of both temperature fluctuations and their predictability. Increased heat tolerance was observed for flies developed in both types of fluctuating thermal environments compared with flies developed in a constant environment. We suggest that this was due to beneficial hardening when developing in either fluctuating temperature environment. To our surprise, flies that developed in constant and predictably changing environments were similar to each other in most traits when compared to flies from the unpredictably fluctuating environment. The unpredictably changing thermal environment imposed the most stressful condition, resulting in the lowest performance for stress‐related traits, even though the absolute temperature changes never exceeded that of the predictably fluctuating environment. The overall decreased stress resistance of flies in the unpredictably fluctuating environment may be the consequence of maladaptive phenotypic plasticity in this setting, indicating that the adaptive value of plasticity depends on the predictability of the environment.     

Dual induction rather than intermediate daylength response of flowering in Echinacea purpurea

Echinacea purpurea cv. Bravado and Magnus have been reported to be intermediate daylength plants (IDP) which flower in response to photoperiods between 13 and 16 h. The present experiments with E. purpurea cv. Bravado show that E. purpurea is actually a dual induction short-long-day plant which flowers promptly and consistently when grown in short day (SD) followed by long day (LD) conditions, but not with the reverse sequence of photoperiods. The flowering response increased with increasing duration of both the SD and the LD treatments. A minimum of 4 weeks of SD followed by 12 LD was required for complete flowering. No flowering occurred in continuous SD or LD, whereas a high proportion of plants flowered in continuous 14-h daylength. However, flowering was more variable in intermediate daylength than after transition from SD to LD. Furthermore, photoperiods between 13 and 16 h could satisfy both the primary SD induction and the secondary LD induction requirements. As a number of dual induction plants, both short-long-day and long-short-day plants, have such an overlapping window of effective photoperiods that can trigger both the SD and LD responses, the rationale for maintaining IDP as a separate and genuine flowering response group is seriously challenged.     

Prior knowledge about spatial pattern affects patch assessment rather than movement between patches in tactile-feeding mallard

1. Heterogeneity in food abundance allows a forager to concentrate foraging effort in patches that are rich in food. This might be problematic when food is cryptic, as the content of patches is unknown prior to foraging. In such case knowledge about the spatial pattern in the distribution of food might be beneficial as this enables a forager to estimate the content of surrounding patches. A forager can benefit from this pre-harvest information about the food distribution by regulating time in patches and/or movement between patches. 2. We conducted an experiment with mallard Anas platyrhynchos foraging in environments with random, regular, and clumped spatial configurations of full and empty patches. An assessment model was used to predict the time in patches for different spatial distributions, in which a mallard is predicted to remain in a patch until its potential intake rate drops to the average intake rate that can be achieved in the environment. A movement model was used to predict lengths of interpatch movements for different spatial distributions, in which a mallard is predicted to travel to the patch where it expects the highest intake rate. 3. Consistent with predictions, in the clumped distribution mallard spent less time in an empty patch when the previously visited neighbouring patch had been empty than when it had been full. This effect was not observed for the random distribution. This shows that mallard use pre-harvest information on spatial pattern to improve patch assessment. Patch assessment could not be evaluated for the regular distribution. 4. Movements that started in an empty patch were longer than movements that started in a full patch. Contrary to model predictions this effect was observed for all spatial distributions, rather than for the clumped distribution only. In this experiment mallard did not regulate movement in relation to pattern. 5. An explanation for the result that pre-harvest information on spatial pattern affected patch assessment rather than movement is that mallard move to the nearest patch where the expected intake rate is higher than the critical value, rather than to the patch where the highest intake rate is expected.     

Functional composition rather than species richness determines root characteristics of experimental grasslands grown at different light and nutrient availability

Plant and Soil - Results from many biodiversity experiments have established evidence for positive effects of diversity on aboveground plant productivity. However, less is known about the...     

History,rather than contemporary processes,determines variation in macroinvertebrate diversity in artesian springs: the expansion hypothesis

1. The relative importance of contemporary and historical processes is a fundamental question in understanding patterns of biodiversity. We tested the hypothesis that species‐sorting into different habitats (limnocrenes, rheocrenes, helocrenes), rather than history, would account for the greatest variation in macroinvertebrate diversity in desert artesian springs of The Bonneville Basin, U.S.A. These springs were isolated at the valley scale c. 9000 years ago by aridity and high salinity. Thus, the valley scale will account for the greatest variation in community composition if history and dispersal limitation are important, whereas niche‐based sorting processes will be most important if habitat accounts for the greatest variation in community composition. 2. We identified 302 taxa from 280 sites and used a partial redundancy analysis, additive partitioning and classification strength (CS) to partition the variability in diversity among the springs. The valley scale accounted for more variation in community composition in limnocrene habitats (32.5%) than all other spatial and environmental variables combined. Valleys also accounted for 58% (additive partitioning) and 83% (CS) of the regional variation in diversity in analyses that included all three habitat types. That is, the average community similarity was 25% across the region, but increased to 41% within valleys. By contrast, habitat filtering did not account for significant variation in community composition in any of the analyses. Our study is one of the few suggesting the over‐riding importance of neutral processes in determining patterns of diversity (history and dispersal limitation). 3. The ‘expansion’ hypothesis suggests that the youthful age of a region, combined with slow dispersal by a fauna dominated by generalists, will maximise the imprint of history. These communities appear to exist in a pre‐equilibrial state, where the maximum carrying capacity has not been reached and niche space is plentiful. With time, we predict that local richness will increase while β‐diversity decreases as species expand their distribution across the region. Consequently, the importance of niche‐based processes may increase with time as the imprint of history fades.     

Circular reasoning rather than cyclic expression

A response to Combined analysis reveals a core set of cycling genes by Y Lu, S Mahony, PV Benos, R Rosenfeld, I Simon, LL Breeden and Z Bar-Joseph. Genome Biol 2007, 8:R146.     

Interfacial binding of cutinase rather than its catalytic activity determines the steady state interfacial tension during oil drop lipid hydrolysis

Hydrolysis of triglycerides by cutinase from Fusarium solani pisi causes in oil drop tensiometer experiments a decrease of the interfacial tension. A series of cutinase variants with amino acid substitutions at its molecular surface yielded different values of the steady state interfacial tension. This tension value poorly correlated with the specific activity as such nor with the total activity (defined as the specific activity multiplied by the amount of enzyme bound) of the cutinase variants. Moreover, it appeared that at activity levels above 15% of that of wild type cutinase the contribution of hydrolysis to the decrease of the tension is saturating. A clear positive correlation was found between the interfacial tension plateau value and the interfacial binding of cutinase, as determined with attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR). These results indicate that the interfacial steady state level is not determined by the rate of hydrolysis, but mainly by the interfacial binding of cutinase.     

Learning new gait patterns is enhanced by specificity of training rather than progression of task difficulty

The use of motor learning strategies may enhance rehabilitation outcomes of individuals with neurological injuries (e.g., stroke or cerebral palsy). A common strategy to facilitate learning of challenging tasks is to use sequential progression – i.e., initially reduce task difficulty and slowly increase task difficulty until the desired difficulty level is reached. However, the evidence related to the use of such sequential progressions to improve learning is mixed for functional skill learning tasks, especially considering situations where practice duration is limited. Here, we studied the benefits of sequential progression using a functional motor learning task that has been previously used in gait rehabilitation. Three groups of participants (N = 43) learned a novel motor task during treadmill walking using different learning strategies. Participants in the specific group (n = 21) practiced only the criterion task (i.e., matching a target template that was scaled-up by 30%) throughout the training. Participants in the sequential group (n = 11) gradually progressed to the criterion task (from 3% to 30% in increments of 3%), whereas participants in the random group (n = 11) started at 3% and progressed in random increments (involving both increases and decreases in task difficulty) to the criterion task. At the end of training, kinematic tracking performance on the criterion task was evaluated in all participants both with and without visual feedback. Results indicated that the tracking error was significantly lower in the specific group, and no differences were observed between the sequential and the random progression groups. The findings indicate that the amount of practice in the criterion task is more critical than the difficulty and variations of task practice when learning new gait patterns during treadmill walking.     

Local habitat condition rather than geographic distance determines the genetic structure of Tamarix chinensis populations in Yellow River Delta,China

Tree Genetics &; Genomes - To breed a new variety of coffee (Coffea arabica) requires approximately 25&;nbsp;years due to the long generation time (5–6&;nbsp;years) of this perennial...