The link between host density and parasite population size is well-established. However, while high host density facilitates parasite transmission, it may negatively impact parasites through more intense competition and/or more intense host immune defence. We assessed the performance of individually tagged female salmon lice (Lepeophtheirus salmonis), an ectoparasite of Atlantic salmon (Salmo salar), under experimental low and high host density conditions, the latter mimicking salmon aquaculture conditions. Lice at high density exhibit greater pre-reproductive mortality, reduced growth, delayed maturation, smaller adult sizes and lower fecundity. Adult size in salmon lice correlates negatively with age at maturity and positively with early fecundity, lifetime fecundity and lifespan. Thus, lice in high-density host populations perform poorly across all life-history traits, probably owing to stronger immune responses of hosts initially exposed to higher parasite doses. This study suggests density-dependent regulation of parasites in intensive agriculture, where hosts are farmed at high densities. Our results further suggest that salmon lice in aquaculture may be selected for greater resistance to host immune defence. As host populations now consist overwhelmingly of farmed fish, continued research is essential to understand the implications for wild salmonids, which are frequently infected by lice originating from farms.

Monitoring individuals within populations is a cornerstone in evolutionary ecology, yet individual tracking of invertebrates and particularly parasitic organisms remains rare. To address this gap, we describe here a method for attaching radio frequency identification (RFID) tags to individual adult females of a marine ectoparasite, the salmon louse Lepeophtheirus salmonis. Comparing two alternative types of glue, we found that one of them (2-octyl cyanoacrylate, 2oc) gave a significantly higher tag retention rate than the other (ethyl 2-cyanoacrylate, e2c). This glue comparison test also resulted in a higher loss rate of adult ectoparasites from the population where tagging was done using 2oc, but this included males not tagged and thus could also suggest a mere tank effect. Corroborating this, a more extensive analysis using data collected over two years showed no significant difference in mortality after repeated exposure to the 2oc glue, nor did it show any significant effect of the tagging procedure on the reproduction of female salmon lice. The proportion of RFID-tagged individuals followed a negative exponential decline, with tag retention among the living female population generally high. The projected retention was found to be about 88% after 30 days or 80% after 60 days, although one of the four batches of glue used, purchased from a different supplier, appeared to give significantly lower tag retention and with greater initial loss (74% and 60% respectively). Overall, we find that RFID tagging is a simple and effective technology that enables documenting individual life histories for invertebrates of a suitable size, including marine and parasitic species, and that it can be used over long periods of study.

Using measures of research productivity to assess academic performance puts women at a disadvantage because gender roles and unconscious biases, operating both at home and in academia, can affect research productivity. The impact of the COVID-19 pandemic on research productivity has been the subject of a number of studies, including studies based on surveys and studies based on numbers of articles submitted to and/or published in journals. Here, we combine the results of 55 studies that compared the impact of the pandemic on the research productivity of men and women; 17 of the studies were based on surveys, 38 were based on article counts, and the total number of effect sizes was 130. We find that the gender gap in research productivity increased during the COVID-19 pandemic, with the largest changes occurring in the social sciences and medicine, and the changes in the biological sciences and TEMCP (technology, engineering, mathematics, chemistry and physics) being much smaller.

Atlantic salmon (Salmo salar) is repeatedly exposed to and infected with ectoparasitic salmon lice (Lepeophtheirus salmonis) both in farms and in nature. However, this is not reflected in laboratory experiments where fish typically are infected only once. To investigate if a previous lice infection affects host response to subsequent infections, fish received 4 different experimental treatments; including 2 groups of fish that had previously been infected either with adult or infective salmon lice larvae (copepodids). Thereafter, fish in all treatment groups were infected with either a double or a single dose of copepodids originating from the same cohort. Fish were sampled when lice had developed into the chalimus, the pre-adult and the adult stage, respectively. Both the specific growth rate and cortisol levels (i.e. a proxy for stress) of the fish differed between treatments. Lice success (i.e. ability to infect and survive on the host) was higher in naïve than in previously infected fish (pre-adult stage). The expression of immune and wound healing transcripts in the skin also differed between treatments, and most noticeable was a higher upregulation early in the infection in the group previously infected with copepodids. However, later in the infection, the least upregulation was observed in this group, suggesting that previous exposure to salmon lice affects the response of Atlantic salmon towards subsequent lice infections.

Using a dynamic optimisation model for juvenile fish in stochastic food environments, we investigate optimal hormonal regulation, energy allocation and foraging behaviour of a growing host infected by a parasite that only incurs an energetic cost. We find it optimal for the infected host to have higher levels of orexin, growth and thyroid hormones, resulting in higher activity levels, increased foraging and faster growth. This growth strategy thus displays several of the fingerprints often associated with parasite manipulation: higher levels of metabolic hormones, faster growth, higher allocation to reserves (i.e. parasite-induced gigantism), higher risk-taking and eventually higher predation rate. However, there is no route for manipulation in our model, so these changes reflect adaptive host compensatory responses. Interestingly, several of these changes also increase the fitness of the parasite. Our results call for caution when interpreting observations of gigantism or risky host behaviours as parasite manipulation without further testing.

In many social animals, females mate with multiple males, but the adaptive value of female extra-pair mating is not fully understood. Here, we tested whether male pied flycatchers (Ficedula hypoleuca) engaging in extra-pair copulations with neighboring females were more likely to assist their neighbors in antipredator defense. We found that extra-pair sires joined predator-mobbing more often, approached predators more closely, and attacked predators more aggressively than males without extra-pair offspring in the neighboring nest. Extra-pair mating may incentivize males to assist in nest defense because of the benefits that this cooperative behavior has on their total offspring production. For females, this mating strategy may help recruit more males to join in antipredator defense, offering better protection and ultimately improving reproductive success. Our results suggest a simple mechanism by which extra-pair mating can improve reproductive success in breeding birds. In summary, males siring extra-pair offspring in neighboring nests assist neighbors in antipredator defense more often than males without extra-pair offspring.

Microbial communities are found throughout the biosphere, from human guts to glaciers, from soil to activated sludge. Understanding the statistical properties of such diverse communities can pave the way to elucidate the common mechanisms ...Multiple ecological forces act together to shape the composition of microbial communities. Phyloecology approaches—which combine phylogenetic relationships between species with community ecology—have the potential to disentangle such forces but are often ...

Increasing awareness that parasitism is an essential component of nearly all aspects of ecosystem functioning, as well as a driver of biodiversity, has led to rising interest in the consequences of climate change in terms of parasitism and disease spread. Yet empirical knowledge on the extent and ways in which climatic factors affect parasite prevalence and intensities remains scarce. In an 18-year, multi-site, correlative study we investigated the contributions of weather variables and other factors to spatio-temporal variation in infestation by blowfly parasitic larvae (Protocalliphora spp.) in nests of Corsican blue tits (Cyanistes caeruleus). We found that ambient temperature during the nestling stage is strongly and positively related to parasite load (number of parasites per chick), both across broods when controlling for year, and across years. In addition, annual mean parasite load also increased with minimal spring temperature, and decreased with increasing average temperature in the previous summer. There was no indication of a dependence of parasite dynamics on host dynamics in this system, likely due in part to the wide host range of blowflies that do not solely rely on blue tit hosts. This suggests a major effect of temperature during the blowfly life cycle, with potential implications for blowfly host interactions across their geographical range as climate keeps warming up. Finally, given that ambient temperature increases throughout the breeding season and that blowflies negatively affect survival and recruitment of blue tits, these results also mean that parasites, along with caterpillar availability, can drive selection for breeding date in this system.

The integration and synthesis of the data in different areas of science is drastically slowed and hindered by a lack of standards and networking programmes. Long-term studies of individually marked animals are not an exception. These studies are especially important as instrumental for understanding evolutionary and ecological processes in the wild. Further, their number and global distribution provides a unique opportunity to assess the generality of patterns and to address broad-scale global issues (e.g. climate change). To solve data integration issues and enable a new scale of ecological and evolutionary research based on long-terms studies of birds, we have created the SPI-Birds Network and Database (www.spibirds.org) – a large-scale initiative that connects data from, and researchers working on, studies of wild populations of individually recognizable (usually ringed) birds. Within a year of the establishment, SPI-Birds counts 120 members working on more than 80 populations, with data concerning breeding attempts of almost a million individual birds over a 1700 cumulative years, and counting. SPI-Birds acts as a data hub and a catalogue of studied populations. It prevents data loss, secures easy data finding, use and integration, and thus facilitates collaboration and synthesis. We provide community-derived data and meta-data standards and improve data integrity guided by of Findable, Accessible, Interoperable, and Reusable (FAIR), and aligned with the existing metadata languages (e.g. ecological meta-data language). The encouraging community involvement stems from SPI-Bird's decentralized approach: research groups retain full control over data use and their way of data management, while SPI-Birds creates tailored pipelines to convert each unique data format into a standard format. We outline the lessons learned, so that other communities (e.g. those working on other taxa) can adapt our successful model. Creating community-specific hubs (such as ours, COMADRE for animal demography, etc.) will aid much-needed large-scale ecological data integration.

Abstract Evolutionary theory predicts that infection by a parasite that reduces future host survival or fecundity should select for increased investment in current reproduction. In this study, we use the cestode Ligula intestinalis and its intermediate fish host Engraulicypris sardella in Wissman Bay, Lake Nyasa (Tanzania), as a model system. Using data about infection of E. sardella fish hosts by L. intestinalis collected for a period of 10 years, we explored whether parasite infection affects the fecundity of the fish host E. sardella, and whether host reproductive investment has increased at the expense of somatic growth. We found that L. intestinalis had a strong negative effect on the fecundity of its intermediate fish host. For the noninfected fish, we observed an increase in relative gonadal weight at maturity over the study period, while size at maturity decreased. These findings suggest that the life history of E. sardella has been shifting toward earlier reproduction. Further studies are warranted to assess whether these changes reflect plastic or evolutionary responses. We also discuss the interaction between parasite and fishery‐mediated selection as a possible explanation for the decline of E. sardella stock in the lake.

Planter, dyr, sopp, bakterier eller lav ... Hver organisme som blir til eller dør mens du leser dette, er etterkommer av en lang rekke forfedre som kan spores tilbake helt til begynnelsen av livet på kloden vår. Bak livets tre ligger det individer, akkurat som i et familietre – bare over mange, mange flere generasjoner. Vi er i slekt med alt som lever på jorden. Evolusjonær forskning lar oss forstå hvordan og hvorfor livets mangfold har eksplodert, kollapset, og utviklet seg videre gjennom geologiske perioder.

A recommendation of: Tougeron K., Brodeur J., van Baaren J., Renault D. and Le Lann C. Sex makes them sleepy: host reproductive status induces diapause in a parasitoid population experiencing harsh winters https://doi.org/10.1101/371385

A recommendation of: Amalia Rataud, Marlène Dupraz, Céline Toty, Thomas Blanchon, Marion Vittecoq, Rémi Choquet, Karen D. McCoy Evaluating functional dispersal and its eco-epidemiological implications in a nest ectoparasite https://doi.org/10.5281/zenodo.2592114

Behavioural ecologists have for decades investigated the adaptive value of extra‐pair copulation (EPC) for females of socially monogamous species. Despite extensive effort testing for genetic benefits, there now seems to be a consensus that the so‐called ‘good genes’ effects are at most weak. In parallel the search for direct benefits has mostly focused on the period surrounding egg laying, thus neglecting potential correlates of EPC that might be expressed at later stages in the breeding cycle. Here we used Bayesian methods to analyse data collected over four years in a population of blue tits Cyanistes caeruleus , where no support was previously found for ‘good genes’ effects. We found that broods with mixed paternity experienced less brood failure at the nestling stage than broods with single paternity, and that females having experienced complete brood failure in their previous breeding attempt had higher rates of mixed paternity than either yearling or previously successful females. To better understand these observations we also explored relationships between extra‐pair mating, male and female phenotype, and local breeding density. We found that in almost all cases the sires of extra‐pair offspring were close neighbours, and that within those close neighbourhoods extra‐pair sires were older than other males not siring extra‐pair offspring. Also, females did not display consistent EPC status across years. Taken together our results suggest that multiple mating might be a flexible female behaviour influenced by previous breeding experience, and motivate further experimental tests of causal links between extra‐pair copulation and predation.

Aggregation is commonly observed for macroparasites, but its adaptive value remains unclear. Heavy infestations intensities may lead to a decrease in some fitness-related traits of parasites (e.g. parasite fecundity or survival). However, to a dioecious parasite, increased aggregation could also increase the chance of finding individuals of the opposite sex. In a laboratory experiment, we tested if previous experience with salmon lice (Lepeophtheirus salmonis) affected susceptibility of Atlantic salmon (Salmo salar) to later exposure to the same parasite species. We found that currently infected fish got higher intensities of new lice than naive fish. This suggests that hosts already carrying parasites are more susceptible to new lice infections. For this dioecious parasite, such positive density dependence might be adaptive, ensuring successful reproduction under conditions of low lice densities by increasing the probability of both sexes infecting the same host.

Organisms are expected to respond to alterations in their survival by evolutionary changes in their life history traits. As agriculture and aquaculture have become increasingly intensive in the past decades, there has been growing interest in their evolutionary effects on the life histories of agri- and aquacultural pests, parasites, and pathogens. In this study, we used salmon lice (Lepeophtheirus salmonis) to explore how modern farming might have affected life history evolution in parasites. We infected salmon hosts with lice from either farmed or unfarmed locations, and monitored life history traits of those parasites in laboratory conditions. Our results show that compared to salmon lice from areas unaffected by salmon farming, those from farmed areas produced more eggs in their first clutch, and less eggs later on; they achieved higher infestation intensities in early adulthood, but suffered higher adult mortality. These results suggest that salmon lice on farms may have been selected for increased investment in early reproduction, at the expense of later fecundity and survival. This call for further empirical studies of the extent to which farming practices may alter the virulence of agricultural parasites.