Search

Many arthropod species are vulnerable to infection by bacteria that kill the male offspring of their female hosts. These male-killing bacteria (MKB) can greatly impact the ecology and evolution of their hosts, particularly when MKB prevalence is high and persistent through time. However, we still do not have a holistic understanding of the key determinants of MKB ecological epidemiology, particularly regarding the interplay between host-MKB traits and environmental conditions. Here, we derived a mathematical model to analyse the role that several intrinsic and extrinsic factors play in determining MKB epidemiology, and how these factors interact with one another. We found that the invasion threshold and prevalence of MKB is determined by transmission rate and the rate at which female hosts recover from MKB infections. The invasion and prevalence of MKB is also highly sensitive to the extent that MKB can reduce intra-brood competition by killing male offspring. Environmentally-induced periodic changes to the epidemiological characteristics of MKB caused a sharp decline and a slow recovery of MKB prevalence and, in some cases, environmental disturbance can drive MKB extinct. Furthermore, the magnitude of the impact that environmental disturbance had on the dynamics of MKB prevalence was heavily modulated by intrinsic factors, particularly intra-brood competition. This is the first study to explore how both intrinsic and extrinsic factors interact to influence the dynamics of MKB infections over large timescales; our findings are central to predicting the current and future impacts of MKB on host populations.

Dietary niche is fundamental for determining species ecology; thus, a detailed understanding of what drives variation in dietary niche is vital for predicting ecological shifts and could have implications for species management. Gut microbiota can be important for determining an organism’s dietary preference, and therefore which food resources they are likely to exploit. Evidence for whether the composition of the gut microbiota is plastic in response to changes in diet is mixed. Also, the extent to which dietary preference can be changed following colonisation by new gut microbiota from different species is unknown. Here, we use Drosophila spp. to show that: (1) the composition of an individual’s gut microbiota can change in response to dietary changes, and (2) ingestion of foreign gut microbes can cause individuals to be attracted to food types they previously had a strong aversion to. Thus, we expose a mechanism for facilitating rapid shifts in dietary niche over short evolutionary timescales.

Understanding the evolution of pathogen niche width is important for predicting disease spread and the probability that pathogens can emerge in novel hosts. Findings from previous theoretical studies often suggest that pathogens will evolve to be specialists in specific host environments. However, several of these studies make unrealistic assumptions regarding demographic stochasticity and the ability of pathogens to select their hosts. Here, an individual-based model was used to predict how population size, virulence and pathogen mutation rate affects the evolution niche specialism in pathogens. Pathogen specialism evolved regardless of virulence or populations size; thus, the findings of this study are somewhat consistent with those of previous work. However, because specialist pathogens had only a weak selective advantage over generalist pathogens, high mutation rates caused random trait variation to accumulate, preventing the evolution of specialism. Mutation rate varies greatly across different species and strains of pathogen. By showing that high mutation rates may prevent pathogen specialism evolving, this study highlights an intrinsic pathogen trait that may influence the evolution of pathogen niche width.

We currently face significant, anthropogenic, global environmental challenges, and the role of ecologists in mitigating these challenges is arguably more important than ever. Consequently there is an urgent need to recruit and train future generations of ecologists, both those whose main area is ecology, but also those involved in the geological, biological, and environmental sciences.Here we present the results of a horizon scanning exercise that identified current and future challenges facing the teaching of ecology, through surveys of teachers, students, and employers of ecologists. Key challenges identified were grouped in terms of the perspectives of three groups: students, for example the increasing disconnect between people and nature; teachers, for example the challenges associated with teaching the quantitative skills that are inherent to the study of ecology; and society, for example poor societal perceptions of the field of ecology.In addition to the challenges identified, we propose a number of solutions developed at a workshop by a team of ecology teaching experts, with supporting evidence of their potential to address many of the problems raised. These proposed solutions include developing living labs, teaching students to be ecological entrepreneurs and influencers, embedding skills‐based learning and coding in the curriculum, an increased role for learned societies in teaching and learning, and using new technology to enhance fieldwork studies including virtual reality, artificial intelligence and real‐time spoken language translation.Our findings are focused towards UK higher education, but they should be informative for students and teachers of a wide range of educational levels, policy makers and professional ecologists worldwide.

Abstract Distinct behaviours can co-vary within individuals. As such, the magnitude of certain behaviours may be partly predicted by other behaviours, rather than the environment. This can constrain behaviours, potentially reducing behavioural variability. Pre-copulatory sexual cannibalism, the consumption of potential mates before copulation, can lead to females remaining unmated, particularly if males are rare. One possible explanation for the persistence of pre-copulatory cannibalism is that sexual cannibalism is correlated with high levels of aggression towards prey. Here, we test this in two species of praying mantis: the highly cannibalistic Miomantis caffra and the less cannibalistic Orthodera novaezealandiae. If cannibalism in M. caffra is linked to aggression towards prey, we predicted that (1) M. caffra would be more aggressive towards prey than O. novaezealandiae, (2) female M. caffra would be more aggressive than males, (3) aggression towards prey would be correlated across juvenile and adult instars for M. caffra but not O. novaezealandiae, and (4) aggression towards prey would be associated with a propensity for sexual cannibalism among individual M. caffra. We found evidence supporting predictions one and two, but not predictions three and four. Surprisingly, aggression was shown to be repeatable and correlated across instars for O. novaezealandiae but not M. caffra. Our results suggest sexual cannibalism is not a product of behavioural co-variation, even in clades where sexual cannibalism is common. This suggests that sexual cannibalism evolves due to the direct benefits it brings to females, rather than being a by-product of high aggression towards heterospecific prey. Significance statement In some animals, different behaviours co-vary within individuals. This may lead to the emergence of costly behaviours and reduce behavioural plasticity. It is theorized that pre-copulatory cannibalism is a costly behavioural by-product of selection for high levels of aggression towards prey. However, there are very few studies that explicitly test this. Here, we provide a behavioural comparison between two species of praying mantis that vary in their propensity to cannibalize and tested whether general aggression is linked cannibalism. We found that aggression towards prey in adults can be linked to juvenile aggression but not a propensity for cannibalism. Although cannibalism rates were higher in the species that was more aggressive towards prey, aggression towards prey was not linked to cannibalism within individuals. This suggests that pre-copulatory cannibalism is not a behavioural by-product but a result of direct selection.

Adaptation to a novel food source can have significant evolutionary advantages. The fruit fly, Drosophila sechellia, is a specialist of the toxic plant noni (Morinda citrifolia). Little is known as to how D. sechellia has become resistant to the toxins in the fruit - comprised predominantly of octanoic acid - but to date, the behavioural preferences for the fruit and genetic architecture underlying them, have been well studied. Here, we examine whether the gut microbiota could have played a role in adaptation to the fruit. In the first series of experiments, we examine the gut microbiota of wild-type, laboratory reared flies and characterise the gut microbiota when reared on the natural host plant, versus a standard Drosophila diet. We show a rapid transition in the core bacterial diversity and abundance within this species and discover sole precedence of Lactobacillus plantarum when reared on M. citrifolia. We also discover that flies reared on a laboratory diet are more likely to carry bacterial pathogens such as Bacillus cereus, although their function in Drosophila is unknown. Flies reared on a laboratory diet have a significantly reduced weight but with no impact on the risk of death before adulthood, when compared to the wild noni diet. In the second series of experiments, we examine the potential role of the gut microbiota in adaptation to octanoic acid resistance in this species and its sister species, Drosophila melanogaster, to which the fruit is usually fatal. We use a combination of methods to analyse resistance to octanoic acid by conducting life history analysis, behavioural assays and bacterial analysis in both D. sechellia and D. melanogaster. We find that by creating experimental evolution lines of D. melanogaster supplemented with gut microbiota from D. sechellia, we can decrease D. melanogaster aversion to octanoic acid, with the flies even preferring to feed on food supplemented with the acid. We suggest this represents the first step in the evolutionary and ecological specialisation of D. sechellia to its toxic host plant, and that the gut microbiota, Lactobacillus plantarum in particular, may have played a key role in host specialisation.

Some behaviours that typically increase fitness at the individual level may reduce population persistence, particularly in the face of environmental changes. Sexual cannibalism is an extreme mating behaviour which typically involves a male being devoured by the female immediately before, during or after copulation, and is widespread amongst predatory invertebrates. Although the individual‐level effects of sexual cannibalism are reasonably well understood, very little is known about the population‐level effects. We constructed both a mathematical model and an individual‐based model to predict how sexual cannibalism might affect population growth rate and extinction risk. We found that in the absence of any cannibalism‐derived fecundity benefit, sexual cannibalism is always detrimental to population growth rate and leads to a higher population extinction risk. Increasing the fecundity benefits of sexual cannibalism leads to a consistently higher population growth rate and likely a lower extinction risk. However, even if cannibalism‐derived fecundity benefits are large, very high rates of sexual cannibalism (>70%) can still drive the population to negative growth and potential extinction. Pre‐copulatory cannibalism was particularly damaging for population growth rates and was the main predictor of growth declining below the replacement rate. Surprisingly, post‐copulatory cannibalism had a largely positive effect on population growth rate when fecundity benefits were present. This study is the first to formally estimate the population‐level effects of sexual cannibalism. We highlight the detrimental effect sexual cannibalism may have on population viability if (1) cannibalism rates become high, and/or (2) cannibalism‐derived fecundity benefits become low. Decreased food availability could plausibly both increase the frequency of cannibalism, and reduce the fecundity benefit of cannibalism, suggesting that sexual cannibalism may increase the risk of population collapse in the face of environmental change.

Sexual cannibalism is common in spiders and can be advantageous for female fitness by increasing egg production. However, it is possible that, under low mate density, females will be at risk of consuming all of the males they encounter prior to copulation. Cannibalistic females may be able to mitigate the risk of virgin death if they reduce cannibalism rates in response to low mate availability. Here, we attempted to manipulate perceived mate density and observe whether it affected female aggression towards males in the fen raft spider (Dolomedes fimbriatus). We predicted that female attack rate would increase in response to an increasing number of male encounters. We also recorded male courtship effort. Despite previous literature finding that D. fimbriatus females were highly aggressive towards conspecific males, we found that females only attacked courting males in 14% of encounters. None of these attacks resulted in cannibalism. Moreover, attacks were not associated with how many males the female had previously been exposed to. Male courtship effort decreased in response to repeated exposure to females. Some of the virgin females laid and guarded unfertilized egg cases; this made them unattractive to males, potentially reducing their reproductive lifespan prematurely.