Does Genetic Diversity Predict Health in Humans?

Genetic diversity, especially at genes important for immune functioning within the Major Histocompatibility Complex (MHC), has been associated with fitness-related traits, including disease resistance, in many species. Recently, genetic diversity has been associated with mate preferences in humans. Here we asked whether these preferences are adaptive in terms of obtaining healthier mates. We investigated whether genetic diversity (heterozygosity and standardized mean d²) at MHC and nonMHC microsatellite loci, predicted health in 153 individuals. Individuals with greater allelic diversity (d²) at nonMHC loci and at one MHC locus, linked to HLA-DRB1, reported fewer symptoms over a four-month period than individuals with lower d². In contrast, there were no associations between MHC or nonMHC heterozygosity and health. NonMHC-d² has previously been found to predict male preferences for female faces. Thus, the current findings suggest that nonMHC diversity may play a role in both natural and sexual selection acting on human populations.     

Does Land-Use Intensification Decrease Plant Phylogenetic Diversity in Local Grasslands?

Phylogenetic diversity (PD) has been successfully used as a complement to classical measures of biological diversity such as species richness or functional diversity. By considering the phylogenetic history of species, PD broadly summarizes the trait space within a community. This covers amongst others complex physiological or biochemical traits that are often not considered in estimates of functional diversity, but may be important for the understanding of community assembly and the relationship between diversity and ecosystem functions. In this study we analyzed the relationship between PD of plant communities and land-use intensification in 150 local grassland plots in three regions in Germany. Specifically we asked whether PD decreases with land-use intensification and if so, whether the relationship is robust across different regions. Overall, we found that species richness decreased along land-use gradients the results however differed for common and rare species assemblages. PD only weakly decreased with increasing land-use intensity. The strength of the relationship thereby varied among regions and PD metrics used. From our results we suggest that there is no general relationship between PD and land-use intensification probably due to lack of phylogenetic conservatism in land-use sensitive traits. Nevertheless, we suggest that depending on specific regional idiosyncrasies the consideration of PD as a complement to other measures of diversity can be useful.     

Does Parenteral Nutrition Influence Electrolyte and Fluid Balance in Preterm Infants in the First Days after Birth?

Background

New national guidelines recommend more restricted fluid intake and early initiation of total parenteral nutrition (TPN) in very preterm infants. The aim was study the effect of these guidelines on serum sodium and potassium levels and fluid balance in the first three days after birth.

Methods

Two cohorts of infants <28 weeks gestational age, born at the Leiden University Medical Center in the Netherlands, were compared retrospectively before (2002–2004, late-TPN) and after (2006–2007, early-TPN) introduction of the new Dutch guideline. Outcome measures were serum sodium and potassium levels, diuresis, and changes in body weight in the first three postnatal days.

Results

In the first three postnatal days no differences between late-TPN (N = 70) and early-TPN cohort (N = 73) in mean (SD) serum sodium (141.1 (3.8) vs 141.0 (3.7) mmol/l) or potassium (4.3 (0.5) vs 4.3 (0.5) mmol/l) were found, but in the early-TPN cohort diuresis (4.5 (1.6) vs 3.2 (1.4) ml/kg/h) and loss of body weight were decreased (−6.0% (7.7) vs −0.8% (8.0)).

Conclusions

Initiation of TPN immediately after birth and restricted fluid intake in very preterm infants do not seem to influence serum sodium and potassium levels in first three postnatal days. Further research is needed to see if a decreased diuresis and loss of body weight in the first days is the result of a delayed postnatal adaptation or better energy balance.     

Infection with Murine Norovirus 4 Does Not Alter Helicobacter-Induced Inflammatory Bowel Disease in Il10?/? Mice

Infection of laboratory mice with murine noroviruses (MNV) is widely prevalent. MNV alters various mouse models of disease, including the Helicobacter bilis-induced mouse model of inflammatory bowel disease (IBD) in Mdr1a^−/− mice. To further characterize the effect of MNV on IBD, we used mice deficient in the immunoregulatory cytokine IL10 (Il10^−/− mice). In vitro infection of Il10^−/− bone marrow-derived macrophages (BMDM) with MNV4 cocultured with H. bilis antigens increased the gene expression of the proinflammatory cytokines IL1β, IL6, and TNFα as compared with that of BMDM cultured with H. bilis antigens only. Therefore, to test the hypothesis that MNV4 infection increases inflammation and alters disease phenotype in H. bilis-infected Il10^−/− mice, we compared the amount and extent of inflammation in Il10^−/− mice coinfected with H. bilis and MNV4 with those of mice singly infected with H. bilis. IBD scores, incidence of IBD, or frequency of severe IBD did not differ between mice coinfected with H. bilis and MNV4 and those singly infected with H. bilis. Mice infected with MNV4 only had no appreciable IBD, comparable to uninfected mice. Our findings suggest that, unlike in Mdr1a^−/− mice, the presence of MNV4 in Il10^−/− mouse colonies is unlikely to affect the IBD phenotype in a Helicobacter-induced model. However, because MNV4 altered cytokine expression in vitro, our results highlight the importance of determining the potential influence of MNV on mouse models of inflammatory disease, given that MNV has a tropism for macrophages and dendritic cells and that infection is widely prevalent.Abbreviations: BMDM, bone marrow-derived macrophages; IBD, inflammatory bowel disease; MLN, mesenteric lymph node; MNV, murine norovirusInflammatory bowel disease (IBD), which includes both ulcerative colitis and Crohn disease, is a chronic and relapsing inflammatory disorder of the gastrointestinal tract. In addition, patients with IBD may be at increased risk of developing colorectal cancer.^15,46 Although the exact mechanisms of disease are still not understood fully, the pathogenesis of disease is likely multifactorial, with components of the innate and adaptive immune systems, host genetics, and environmental factors (for example, the commensal gut microflora) all playing a role.^4,37,55Animal models of IBD have been used to advance our knowledge and understanding of IBD pathogenesis and treatment.^{16,20,37,38,52} One such model that has been widely used to elucidate the mechanisms of IBD is the interleukin10–deficient (Il10^−/−) mouse.^{3,5,6,20,21,29,33,57} The antiinflammatory cytokine IL10 modulates both innate and adaptive immune responses.⁴¹ Produced mainly by dendritic cells, monocytes, macrophages, and T regulatory cells, IL10 exerts its immunomodulatory effects by various mechanisms including decreasing secretion of proinflammatory cytokines (for example, interferon γ, IL1, IL2, IL6, IL12 and TNFα) and downregulating important components of innate immune responses and T-cell activation (for example, MHC class II, costimulatory molecules, and nitric oxide production) in antigen presenting cells.^14,41 As a consequence, Il10^−/− mice, which lack the suppressive effects of IL10, develop IBD in response to their commensal gut microflora or to certain microbial triggers such as Helicobacter infections.^{5,6,11,21,29,52,57}Antigen-presenting cells such as macrophages and dendritic cells play key roles in the inflammatory responses in IBD.^32,47,50 In 2003, a newly discovered murine norovirus (MNV) in laboratory mice was shown to infect macrophages and dendritic cells.^27,53 Subsequent studies indicated widespread MNV infection in laboratory mice used for biomedical research, with a serologic prevalence as high as 32%.^25,43 Members of the genus Norovirus are regarded as gastrointestinal pathogens in humans and animals, eliciting both innate and adaptive immune responses.¹⁹ Therefore, in light of the cellular (macrophages and dendritic cells) and tissue (gastrointestinal) tropisms of MNV as well as the high prevalence of MNV infection in laboratory mice, we hypothesized that MNV infection could be a potential confounder in mouse models of inflammatory diseases including IBD. In support of this idea, our laboratory recently reported that MNV infection in Mdr1a^−/− mice (FVB.129P2-Abcb1a^tm1Bor) accelerated weight loss and exacerbated IBD progression initiated by H. bilis infection.³¹ This effect potentially was mediated in part through modulating dendritic cell and cytokine responses. In addition, others have reported gastrointestinal abnormalities as a result of MNV infection in some strains of mice,^7,26,36 whereas others have described the importance of both innate and adaptive immune responses during MNV infection.^{8,9,10,28,34,36,48} Collectively, these data indicate that MNV could alter inflammatory responses in laboratory mice.Here we extended our studies of MNV beyond Mdr1a^−/− mice to Il10^−/− mice, another common animal model of IBD, to further examine the potential effect of MNV on IBD research. Disease was initiated in Il10^−/− mice with H. bilis, and we determined whether coinfection with MNV altered disease development, incidence, and severity and the production of cytokines. We demonstrated that although MNV stimulates a Th1 skewing of cytokines in Il10^−/− bone marrow-derived macrophages (BMDM) in vitro, MNV does not alter the development, incidence, or severity of disease in vivo. Therefore, although MNV may not affect disease in Il10^−/− mouse models, the virus may influence in vitro cytokine phenotypes and thus complicate interpretation of such data. To our knowledge, this report is the first to describe the evaluation of MNV infection in the Helicobacter-induced Il10^−/− mouse model of IBD.     

Does An Asexual Endophyte Symbiont Alter Life Stage and Long-Term Survival in a Perennial Host Grass?

Asexual, seedborne endophytic fungi in perennial grasses are often viewed as strong mutualists because fitness of the symbiont and host grass are closely coupled. However, at least for some native grasses, the asexual endophyte, Neotyphodium, acts parasitically, yet remains at high frequencies in natural populations. Most previous studies of Neotyphodium effects on host survival have been short term relative to the long life span of the perennial grass host. We therefore tested the hypothesis that Neotyphodium alters the survival in various life stages and long-term survival of adult native Arizona fescue (Festuca arizonica). To test the former, we planted 40 infected (E+) and 40 uninfected (E−, endophyte removed) seeds from four different maternal plants in the field under ambient conditions. We followed survival of seeds, seedlings, and adult plants over a 5-year period. To test the latter, we determined the infection of 1633 adult plants and followed their survival over the next 5–7 years. E+ seeds did not differ from uninfected seeds in terms of overall survival from seed germination to seedling to adult. However, the shape of the survival curve differed, with E+ plants showing higher mortality in early life stages. E+ adult plants did not differ from E− plants in long-term survival. Survival was generally very high during the study, which included a severe and prolonged drought. Infection by asexual Neotyphodium does not increase survival in early life stages or that of adult plants. Because asexual, vertically transmitted symbionts are predicted by evolutionary theory to be strong mutualists, the persistence of high infection frequencies in natural populations without long-term benefits to the host remains enigmatic. One possible explanation is that the long life span of the perennial host and low seedling recruitment may obscure either the costs or benefits of endophyte infection.     

Genetic Knockdown of Brain-Derived Neurotrophic Factor in 3xTg-AD Mice Does Not Alter Aβ or Tau Pathology

Brain-derived neurotrophic factor (BDNF) is a neurotrophin critically involved in cell survival, synaptic plasticity, and memory. BDNF has recently garnered significant attention as a potential therapeutic target for neurodegenerative diseases such as Alzheimer disease (AD), but emerging evidence suggests that BDNF may also be mechanistically involved in the pathogenesis of AD. AD patients have substantially reduced BDNF levels, which may be a result of Aβ and tau pathology. Recent evidence, however, indicates reduced BDNF levels may also serve to drive pathology in neuronal cultures, although this has not yet been established in vivo. To further investigate the mechanistic role of BDNF in AD, we generated 3xTg-AD mice with a heterozygous BDNF knockout (BDNF(+/-)) and analyzed Aβ and tau pathology. Aged 3xTg-AD/BDNF(+/-) mice have significantly reduced levels of brain BDNF, but have comparable levels of Aβ and tau pathology to 3xTg-AD/BDNF(+/+) mice. These findings indicate that chronic reduction of BDNF does not exacerbate the development of Aβ and tau pathology, and instead suggests the reduced BDNF levels found in AD patients are a consequence of these pathologies.     

Does Intraspecific Size Variation in a Predator Affect Its Diet Diversity and Top-Down Control of Prey?

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity.     

Diversity in the circumsporozoite protein of Plasmodium vivax: Does it matter?

Since the gene encoding the malarial circumsporozoite surface protein was characterized a decade ago, the corresponding protein has been considered an important vaccine candidate. Victoria Mann, Michael Good and Allan Saul here discuss molecular variation in the circumsporozoite surface protein of Plasmodium vivax in this context. There is still doubt about the degree and importance of polymorphisms in non-repetitive regions of the molecule. The degree of polymorphisms and data on naturally occurring protective responses suggests there has been minimal immunological pressure; the authors contend that antigenic diversity is unlikely to be a major factor in the use of this antigen as a vaccine for P. vivax.     

Conflict in Protected Areas: Who Says Co-Management Does Not Work?

Natural resource-related conflicts can be extremely destructive and undermine environmental protection. Since the 1990s co-management schemes, whereby the management of resources is shared by public and/or private sector stakeholders, have been a main strategy for reducing these conflicts worldwide. Despite initial high hopes, in recent years co-management has been perceived as falling short of expectations. However, systematic assessments of its role in conflict prevention or mitigation are non-existent. Interviews with 584 residents from ten protected areas in Colombia revealed that co-management can be successful in reducing conflict at grassroots level, as long as some critical enabling conditions, such as effective participation in the co-management process, are fulfilled not only on paper but also by praxis. We hope these findings will re-incentivize global efforts to make co-management work in protected areas and other common pool resource contexts, such as fisheries, agriculture, forestry and water management.     

Does Seeding After Wildfires in Rangelands Reduce Erosion or Invasive Species?

Mitigation of ecological damage caused by rangeland wildfires has historically been an issue restricted to the western United States. It has focused on conservation of ecosystem function through reducing soil erosion and spread of invasive plants. Effectiveness of mitigation treatments has been debated recently. We reviewed recent literature to conduct a meta‐analysis of seeding after wildfires to determine if seedings may (1) protect ecosystems against soil erosion and (2) reduce invasion or abundance of undesirable nonnative plant species. Effectiveness of postfire seedings was examined in 8 erosion and 19 invasive species cases. Seeding has little effect on erosion during the first year after fire and is highly dependent upon initial establishment and coverage of species in successive years. Among all seeding cases, 28% reduced, 67% were neutral, and 5% increased invasive species abundance. Older seedings were more likely to show reductions in invasives than younger seedings. Seedings with high plant establishment were more likely to reduce invasives than those with low establishment. Studies are needed that examine (1) frequency of adequate establishment of postfire seedings and causal factors of success or failure, (2) long‐term impacts of seeding along a range of initial establishment and concomitant plant coverage over time as it relates to erosion and abundance of invasive plant species, and (3) auxiliary treatments designed to increase likelihood of germination and establishment given the inevitable variability of environmental conditions. These studies would aid land managers in deciding when postfire treatments are required and their likely level of success.     

When Does Diversity Trump Ability (and Vice Versa) in Group Decision Making? A Simulation Study

It is often unclear which factor plays a more critical role in determining a group's performance: the diversity among members of the group or their individual abilities. In this study, we addressed this "diversity vs. ability" issue in a decision-making task. We conducted three simulation studies in which we manipulated agents' individual ability (or accuracy, in the context of our investigation) and group diversity by varying (1) the heuristics agents used to search task-relevant information (i.e., cues); (2) the size of their groups; (3) how much they had learned about a good cue search order; and (4) the magnitude of errors in the information they searched. In each study, we found that a manipulation reducing agents' individual accuracy simultaneously increased their group's diversity, leading to a conflict between the two. These conflicts enabled us to identify certain conditions under which diversity trumps individual accuracy, and vice versa. Specifically, we found that individual accuracy is more important in task environments in which cues differ greatly in the quality of their information, and diversity matters more when such differences are relatively small. Changing the size of a group and the amount of learning by an agent had a limited impact on this general effect of task environment. Furthermore, we found that a group achieves its highest accuracy when there is an intermediate amount of errors in the cue information, regardless of the environment and the heuristic used, an effect that we believe has not been previously reported and warrants further investigation.     

Does Isolated Unilateral Hip or Knee Osteoarthritis Lead to Adverse Changes in Extremity Composition?

BackgroundWhile muscle atrophy is a function of normal aging, loss of muscle in the setting of hip and knee osteoarthritis (OA) has been observed using radiographic studies. There is limited data available regarding changes in extremity composition using bioimpedance (BIA). The purpose of this study was to assess the changes in extremity composition in patients with isolated, unilateral hip or knee OA using BIA.MethodsPatients presenting to our institution’s adult reconstruction clinic from February 2020 to April 2021 were retrospectively reviewed to identify those with isolated, unilateral hip and knee OA. The InBody 770 Body Composition Analyzer (InBody USA, Cerritos, California) was used to perform a complete body composition assessment, per protocol. Lean extremity mass (LEM), fat mass (FM), intracellular water (ICW), extremity body water (EBW = ICW + extracellular water (ECW)) and phase angle (PA) were determined. Differences between the affected (OA) and unaffected (no OA) extremities were compared using t-tests.Results38 patients had isolated hip OA. The mean age was 60.8 (±11.7) years, mean BMI was 31.7 (±6.8) kg/m2, and 39.5% were female. LEM, FM, EBW, ICW, and PA were significantly decreased in the hip OA extremity (LEM: 20.0 vs. 20.4 kg, p=0.0008, FM: 8.8 vs. 8.9 kg, p=0.0049, EBW: 15.7 vs 16.0, p=0.0011, ICW: 9.5 vs. 9.7 L, p=0.0004, PA: 4.5 vs 4.9º, p<0.0001). There were 25 patients with isolated knee OA. Mean age was 62.8 (±11.3) years, mean BMI was 33.6 (±6.9) kg/m2, and 52.0% were female. FM and PA were significantly lower in the knee OA extremity (11.3 vs 11.4 kg, p=0.0291, 4.5 vs 4.9º, p<0.0001). There were no significant differences in LEM, EBW, and ICW between the knee OA extremity and the unaffected extremity.ConclusionPatients with isolated, unilateral hip OA had decreased LEM, FM, EBW, and ICW in the affected extremity. Both unilateral hip and knee OA was associated with decreased PA, suggestive of greater underlying dysfunction in muscle or cellular performance. Further study is needed to better define when these abnormalities develop, how they progress over time, and the impact of targeted interventions in reversing these changes. Level of Evidence: III     

Female Gender and Differences in Outcome after Isolated Coronary Artery Bypass Graft Surgery: Does Age Play a Role?

Introduction

Female gender is a known risk factor for early and late mortality after coronary artery bypass graft surgery (CABG). Higher age of women at operation may influence outcome, since age per se is also an important risk factor. The purpose of our study was to analyze possible gender differences in outcome after isolated CABG in different age groups to delineate the impact of female gender and age.

Methods

All patients over 60 years of age undergoing isolated CABG at our department during 2001 and 2011 were included and categorized by age into sexagenarians (2266, 16.6% women), septuagenarians (2332, 25.4% women) and octogenarians (374, 32% women) and assessed by gender for 30-day and 180-day mortality.

Results

Thirty-day mortality was significantly higher in women only amongst septuagenarians (7.1 vs. 4.7%, p = 0.033). Same differences apply for 180-day mortality (12.3 vs. 8.2%, p = 0.033) and estimated one-year survival (81.6 ± 4.2 vs. 86.9 ± 2.2%, p = 0.001). Predictive factors for 30-day mortality of septuagenarian were logistic EuroSCORE (ES) (p = 0.003), perioperative myocardial infarction (MI) (p<0.001), pneumonia (p<0.001), abnormal LV-function (p<0.04) and use of LIMA graft (p<0.001), but not female gender. However, female gender was found to be an independent predictor for 180-day mortality (HR 1.632, p = 0.001) in addition to ES, use of LIMA graft, perioperative MI, pneumonia and abnormal LV function (HR 1.013, p = 0.004; HR 0.523, p<0.001; HR 2.710, p<0.001; HR 3.238, p<0.001; HR 2.013, p<0.001).

Conclusion

Women have a higher observed probability of early death after CABG in septuagenarians. However, female gender was not found to be an independent risk factor for 30-day, but for 180-day survival. Therefore, reduction of high impact risk factors such as perioperative MI and enhancement of LIMA use should be future goals. In view of our findings, decision for surgical revascularization should not be based on gender.     

How Does Hemicelluloses Removal Alter Plant Cell Wall Nanoscale Architecture and Correlate with Enzymatic Digestibility?

Thorough understanding of how hemicelluloses removal influences cell wall nanoscale architecture and cellulose digestion is of crucial importance for enabling low-cost industrial conversion of lignocellulosic biomass to renewable biofuels. In this work, delignified poplar cell walls, after various degrees of hemicelluloses removal, were characterized by Fourier transform infrared imaging spectroscopy and atomic force microscopy to evaluate enhancement in cell wall digestibility. There was a gradual decrease in hemicelluloses content with dilute alkali treatment, which resulted in alterations in the nanoscale architecture and crystallinity of cell walls. Removal of hemicelluloses did not disrupt the integrity of microfibrils but resulted in exposure of microfibrils and a decrease in the diameter of microfibrils. X-ray analysis indicated that the increase in crystallinity beyond natural variations in the crystallinity of cellulose was mainly attributable to removal of hemicelluloses. In conclusion, alterations in the architecture and crystallinity of cell walls facilitated enzymatic digestion of delignified poplar, enhancing cellulose conversion from 68.24 to 75.16 %.     

Exposure to Bacterial Signals Does Not Alter Pea Aphids’ Survival upon a Second Challenge or Investment in Production of Winged Offspring

Pea aphids have an obligate nutritional symbiosis with the bacteria Buchnera aphidicola and frequently also harbor one or more facultative symbionts. Aphids are also susceptible to bacterial pathogen infections, and it has been suggested that aphids have a limited immune response towards such pathogen infections compared to other, more well-studied insects. However, aphids do possess at least some of the genes known to be involved in bacterial immune responses in other insects, and immune-competent hemocytes. One possibility is that immune priming with microbial elicitors could stimulate immune protection against subsequent bacterial infections, as has been observed in several other insect systems. To address this hypothesis we challenged aphids with bacterial immune elicitors twenty-four hours prior to live bacterial pathogen infections and then compared their survival rates to aphids that were not pre-exposed to bacterial signals. Using two aphid genotypes, we found no evidence for immune protection conferred by immune priming during infections with either Serratia marcescens or with Escherichia coli. Immune priming was not altered by the presence of facultative, beneficial symbionts in the aphids. In the absence of inducible immune protection, aphids may allocate energy towards other defense traits, including production of offspring with wings that could escape deteriorating conditions. To test this, we monitored the ratio of winged to unwinged offspring produced by adult mothers of a single clone that had been exposed to bacterial immune elicitors, to live E. coli infections or to no challenge. We found no correlation between immune challenge and winged offspring production, suggesting that this mechanism of defense, which functions upon exposure to fungal pathogens, is not central to aphid responses to bacterial infections.     

Does biogeographical history matter? Diversity and distribution of lotic midges (Diptera: Chironomidae) in the Australian Wet Tropics

Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal gradients within the Wet Tropics revealed a fauna of 87 species‐level taxa in 49 genera comprising three main elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an enduring effect of the historical rainforest contractions on current‐day distribution patterns. These findings contrast with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity gradient does not apply to the Australian chironomid fauna.     

Habitats as Complex Odour Environments: How Does Plant Diversity Affect Herbivore and Parasitoid Orientation?

Plant diversity is known to affect success of host location by pest insects, but its effect on olfactory orientation of non-pest insect species has hardly been addressed. First, we tested in laboratory experiments the hypothesis that non-host plants, which increase odour complexity in habitats, affect the host location ability of herbivores and parasitoids. Furthermore, we recorded field data of plant diversity in addition to herbivore and parasitoid abundance at 77 grassland sites in three different regions in Germany in order to elucidate whether our laboratory results reflect the field situation. As a model system we used the herb Plantago lanceolata, the herbivorous weevil Mecinus pascuorum, and its larval parasitoid Mesopolobus incultus. The laboratory bioassays revealed that both the herbivorous weevil and its larval parasitoid can locate their host plant and host via olfactory cues even in the presence of non-host odour. In a newly established two-circle olfactometer, the weeviĺs capability to detect host plant odour was not affected by odours from non-host plants. However, addition of non-host plant odours to host plant odour enhanced the weeviĺs foraging activity. The parasitoid was attracted by a combination of host plant and host volatiles in both the absence and presence of non-host plant volatiles in a Y-tube olfactometer. In dual choice tests the parasitoid preferred the blend of host plant and host volatiles over its combination with non-host plant volatiles. In the field, no indication was found that high plant diversity disturbs host (plant) location by the weevil and its parasitoid. In contrast, plant diversity was positively correlated with weevil abundance, whereas parasitoid abundance was independent of plant diversity. Therefore, we conclude that weevils and parasitoids showed the sensory capacity to successfully cope with complex vegetation odours when searching for hosts.