Latitudinal and anthropogenic effects on the structuring of networks linking blood-feeding flies and their vertebrate hosts.

Biting flies (Diptera) transmit pathogens that cause many important diseases in humans as well as domestic and wild animals. The networks of feeding interactions linking these insects to their hosts, and how they vary geographically and in response to human land-use, are currently poorly documented but are relevant to understanding cross-species disease transmission. We compiled a database of biting Diptera-host interactions from the literature to investigate how key interaction network metrics vary latitudinally and with human land-use. Interaction evenness and H2' (a measure of the degree of network specificity) did not vary significantly with latitude. Compared to near-natural habitats, interaction evenness was significantly lower in agricultural habitats, where networks were dominated by relatively few species pairs, but there was no evidence that the presence of humans and their domesticated animals within networks led to systematic shifts in network structure. We discuss the epidemiological relevance of these results and the implications for predicting and mitigating future spill-over events.

Recommendations for environmental risk assessment of gene drive applications for malaria vector control.

Building on an exercise that identified potential harms from simulated investigational releases of a population suppression gene drive for malaria vector control, a series of online workshops identified nine recommendations to advance future environmental risk assessment of gene drive applications.

Tropical forest dung beetle-mammal dung interaction networks remain similar across an environmental disturbance gradient.

Conservation outcomes could be greatly enhanced if strategies addressing anthropogenic land-use change considered the impacts of these changes on entire communities as well as on individual species. Examining how species interactions change across gradients of habitat disturbance allows us to predict the cascading consequences of species extinctions and the response of ecological networks to environmental change. We conducted the first detailed study of changes in a commensalist network of mammals and dung beetles across an environmental disturbance gradient, from primary tropical forest to plantations, which varied in above-ground carbon density (ACD) and mammal communities. Mammal diversity changed only slightly across the gradient, remaining high even in oil palm plantations and fragmented forest. Dung beetle species richness, however, declined in response to lower ACD and was particularly low in plantations and the most disturbed forest sites. Three of the five network metrics (nestedness, network specialization and functionality) were significantly affected by changes in dung beetle species richness and ACD, but mammal diversity was not an important predictor of network structure. Overall, the interaction networks remained structurally and functionally similar across the gradient, only becoming simplified (i.e. with fewer dung beetle species and fewer interactions) in the most disturbed sites. We suggest that the high diversity of mammals, even in disturbed forests, combined with the generalist feeding patterns of dung beetles, confer resilience to the commensalist dung beetle-mammal networks. This study highlights the importance of protecting logged and fragmented forests to maintain interaction networks and potentially prevent extinction cascades in human-modified systems.

Effects of distance from semi-natural habitat on fall armyworm (Spodoptera frugiperda, J. E. Smith) and its potential natural enemies in Ghana.

Insect crop pests are a major threat to food security in sub-Saharan Africa. Configuration of semi-natural habitat within agricultural landscapes has the potential to enhance biological pest control, helping to maintain yields whilst minimising the negative effects of pesticide use. Fall armyworm (Spodoptera frugiperda, J. E. Smith) is an increasingly important pest of maize in sub-Saharan Africa, with reports of yield loss between 12 and 45%. We investigated the patterns of fall armyworm leaf damage in maize crops in Ghana, and used pitfall traps and dummy caterpillars to assess the spatial distribution of potential fall armyworm predators. Crop damage from fall armyworm at our study sites increased significantly with distance from the field edge, by up to 4% per m. We found evidence that Araneae activity, richness and diversity correspondingly decreased with distance from semi-natural habitat, although Hymenoptera richness and diversity increased. Our preliminary findings suggest that modifying field configuration to increase the proximity of maize to semi-natural habitat may reduce fall armyworm damage and increase natural enemy activity within crops. Further research is required to determine the level of fall armyworm suppression achievable through natural enemies, and how effectively this could safeguard yields.

Reshaping our understanding of species' roles in landscape-scale networks.

In network ecology, landscape-scale processes are often overlooked, yet there is increasing evidence that species and interactions spill over between habitats, calling for further study of interhabitat dependencies. Here, we investigate how species connect a mosaic of habitats based on the spatial variation of their mutualistic and antagonistic interactions using two multilayer networks, combining pollination, herbivory and parasitism in the UK and New Zealand. Developing novel methods of network analysis for landscape-scale ecological networks, we discovered that few plant and pollinator species acted as connectors or hubs, both within and among habitats, whereas herbivores and parasitoids typically have more peripheral network roles. Insect species' roles depend on factors other than just the abundance of taxa in the lower trophic level, exemplified by larger Hymenoptera connecting networks of different habitats and insects relying on different resources across different habitats. Our findings provide a broader perspective for landscape-scale management and ecological community conservation.

A whispering bat that screams: bimodal switch of foraging guild from gleaning to aerial hawking in the desert long-eared bat.

Echolocating bats have historically been classified as either loud aerial hawkers or whispering gleaners. Some bat species can forage in multiple ways and others have demonstrated limited flexibility in the amplitude of their echolocation calls. The desert long-eared bat, Otonycteris hemprichii, has been said to be a passive gleaning whispering bat preying on terrestrial arthropods such as scorpions. Using an acoustic tracking system, we recorded individuals flying at foraging and drinking sites and compared their flight height, flight speed, call duration, pulse interval and source levels with those of gleaning individuals previously recorded using the same setup. We found differences in all variables with the strongest difference in source levels, where bats called at a mean of 119 dB peSPL (compared with 75 dB peSPL when gleaning). Bat faecal analysis indicated that their diet differed from previous studies and that prey species were capable of flight. We conclude that the bats switched from passive gleaning to capturing airborne insects (aerial hawking). Although whispering bats have been known to opportunistically catch insects on the wing, in the present study we show a full bimodal switch between foraging guilds with the respective changes in source level to those typical of a true aerial hawker.

Ultrasonic vocalisation rate tracks the diurnal pattern of activity in winter phenotype Djungarian hamsters (Phodopus sungorus).

Vocalisations are increasingly being recognised as an important aspect of normal rodent behaviour yet little is known of how they interact with other spontaneous behaviours such as sleep and torpor, particularly in a social setting. We obtained chronic recordings of the vocal behaviour of adult male and female Djungarian hamsters (Phodopus sungorus) housed under short photoperiod (8 h light, 16 h dark, square wave transitions), in different social contexts. The animals were kept in isolation or in same-sex sibling pairs, separated by a grid which allowed non-physical social interaction. On approximately 20% of days hamsters spontaneously entered torpor, a state of metabolic depression that coincides with the rest phase of many small mammal species in response to actual or predicted energy shortages. Animals produced ultrasonic vocalisations (USVs) with a peak frequency of 57 kHz in both social and asocial conditions and there was a high degree of variability in vocalisation rate between subjects. Vocalisation rate was correlated with locomotor activity across the 24-h light cycle, occurring more frequently during the dark period when the hamsters were more active and peaking around light transitions. Solitary-housed animals did not vocalise whilst torpid and animals remained in torpor despite overlapping with vocalisations in social-housing. Besides a minor decrease in peak USV frequency when isolated hamsters were re-paired with their siblings, changing social contexts did not influence vocalisation behaviour or structure. In rare instances, temporally overlapping USVs occurred when animals were socially-housed and were grouped in such a way that could indicate coordination. We did not observe broadband calls (BBCs) contemporaneous with USVs in this paradigm, corroborating their correlation with physical aggression which was absent from our experiment. Overall, we find little evidence to suggest a direct social function of hamster USVs. We conclude that understanding the effects of vocalisations on spontaneous behaviours, such as sleep and torpor, will inform experimental design of future studies, especially where the role of social interactions is investigated.

Effects of storage conditions and digestion time on DNA amplification of biting midge (Culicoides) blood meals.

BACKGROUND: Molecular analysis of blood meals is increasingly used to identify the hosts of biting insects such as midges and mosquitoes. Successful host identification depends on the availability of sufficient host DNA template for PCR amplification, making it important to understand how amplification success changes under different storage conditions and with different durations of blood meal digestion within the insect gut before being placed into the storage medium. METHOD: We characterised and compared the digestion profile of two species of Culicoides over a 96-h period using a novel set of general vertebrate primers targeting the 16S rRNA gene. A set number of individuals from each species were killed over 13 time points post-blood feeding and preserved in 95% ethanol. Samples were stored either at ambient room temperature or in a - 20 °C freezer to examine the effect of storage condition on the PCR amplification success of host DNA. RESULTS: We found that amplification success across the 96-h sampling period post-feeding was reduced from 96 to 6% and 96% to 14% for Culicoides nubeculosus and Culicoides sonorensis, respectively. We found no effect of storage condition on PCR amplification success, and storage in 95% ethanol was sufficient to maintain high rates of amplifiable host DNA for at least 9 months, even at room temperature. CONCLUSIONS: These findings highlight the limited time frame during which an individual may contain amplifiable host DNA and demonstrate the importance of timely sample capture and processing post-blood feeding. Moreover, storage in 95% ethanol alone is sufficient to limit host DNA degradation. These results are relevant to the design of studies investigating the biting behaviour and disease transmission potential of Culicoides and other biting Diptera.

Re-examining extreme sleep duration in bats: implications for sleep phylogeny, ecology, and function.

Bats, quoted as sleeping for up to 20 h a day, are an often used example of extreme sleep duration amongst mammals. Given that duration has historically been one of the primary metrics featured in comparative studies of sleep, it is important that species specific sleep durations are well founded. Here, we re-examined the evidence for the characterization of bats as extreme sleepers and discuss whether it provides a useful representation of the sleep behavior of Chiroptera. Although there are a wealth of activity data to suggest that the diurnal cycle of bats is dominated by rest, estimates of sleep time generated from electrophysiological analyses suggest considerable interspecific variation, ranging from 83% to a more moderate 61% of the 24 h day spent asleep. Temperature-dependent changes in the duration and electroencephalographic profile of sleep suggest that bats represent a unique model for investigating the relationship between sleep and torpor. Further sources of intra-specific variation in sleep duration, including the impact of artificial laboratory environments and sleep intensity, remain unexplored. Future studies conducted in naturalistic environments, using larger sample sizes and relying on a pre-determined set of defining criteria will undoubtedly provide novel insights into sleep in bats and other species.

A Network Perspective on the Vectoring of Human Disease.

Blood-sucking insects are important vectors of disease, with biting Diptera (flies) alone transmitting diseases that cause an estimated 700 000 human deaths a year. Insect vectors also bite nonhuman hosts, linking them into host-biting networks. While the major vectors of prominent diseases, such as malaria, yellow fever, dengue, and Zika, are intensively studied, there has been limited focus on the wider interactions of biting insects with nonhuman hosts. Drawing on network analysis and visualisation approaches from food-web ecology, we discuss the value of a network perspective for understanding host-insect-disease interactions, with a focus on Diptera vectors. Potential applications include highlighting pathways of disease transmission, highlighting reservoirs of infection, and identifying emerging and previously unrecognised vectors.

Research priorities for maintaining biodiversity's contributions to people in Latin America.

Maintaining biodiversity is crucial for ensuring human well-being. The authors participated in a workshop held in Palenque, Mexico, in August 2018, that brought together 30 mostly early-career scientists working in different disciplines (natural, social and economic sciences) with the aim of identifying research priorities for studying the contributions of biodiversity to people and how these contributions might be impacted by environmental change. Five main groups of questions emerged: (1) Enhancing the quantity, quality, and availability of biodiversity data; (2) Integrating different knowledge systems; (3) Improved methods for integrating diverse data; (4) Fundamental questions in ecology and evolution; and (5) Multi-level governance across boundaries. We discuss the need for increased capacity building and investment in research programmes to address these challenges.

The importance of Acacia trees for insectivorous bats and arthropods in the Arava desert.

Anthropogenic habitat modification often has a profound negative impact on the flora and fauna of an ecosystem. In parts of the Middle East, ephemeral rivers (wadis) are characterised by stands of acacia trees. Green, flourishing assemblages of these trees are in decline in several countries, most likely due to human-induced water stress and habitat changes. We examined the importance of healthy acacia stands for bats and their arthropod prey in comparison to other natural and artificial habitats available in the Arava desert of Israel. We assessed bat activity and species richness through acoustic monitoring for entire nights and concurrently collected arthropods using light and pit traps. Dense green stands of acacia trees were the most important natural desert habitat for insectivorous bats. Irrigated gardens and parks in villages and fields of date palms had high arthropod levels but only village sites rivalled acacia trees in bat activity level. We confirmed up to 13 bat species around a single patch of acacia trees; one of the richest sites in any natural desert habitat in Israel. Some bat species utilised artificial sites; others were found almost exclusively in natural habitats. Two rare species (Barbastella leucomelas and Nycteris thebaica) were identified solely around acacia trees. We provide strong evidence that acacia trees are of unique importance to the community of insectivorous desert-dwelling bats, and that the health of the trees is crucial to their value as a foraging resource. Consequently, conservation efforts for acacia habitats, and in particular for the green more densely packed stands of trees, need to increase to protect this vital habitat for an entire community of protected bats.