Bdellovibrio bacteriovorus is an endobiotic bacterial predator that encodes multiple enzymes related to known peptidoglycan (PG) modifiers, which are necessary for predation to occur. Additionally, a ...plethora of cryptic proteins are expressed and upregulated during predation. It has been shown that L,D-transpeptidases (LDTs) are required for bdelloplast formation and stabilisation. These LDTs cluster in six groups in B. bacteriovorus HD100, nevertheless, no further LDT information has been previously described. Here we have determined and analysed the structures of LDTs Bd0566, Bd1075, Bd3334 and Bd3741, showing that even though they share a structurally conserved catalytic domain, they have acquired accessory domains and motifs characteristic to each LDT group. Moreover, we have integrated these novel structures with the previously solved structures of Bd0553, Bd0886 and Bd1402, generating a panel of seven LDTs representing the six groups of B. bacteriovorus HD100, allowing us to propose possible roles and the structural determinants defining the transferase/crosslinking or hydrolytic activities of each group. Further, we report the structure of two predatory NlpC/P60 amidohydrolases/peptidases, Bd0601 and Bd1177. We have determined that Bd0601 is a DUF1460 amidohydrolase, wherein the PG stem peptide binding groove is blocked by a tyrosine residue, suggesting the need of a conformational rearrangement for substrate binding. On the other hand, we have determined that Bd1177 is a bilobular NlpC/P60, wherein the active site is located in the interface between the catalytic N-terminal domain and a novel C-terminal regulatory domain, suggesting that Bd1177 fluctuates to an open conformation upon substrate binding. Finally, we have determined the crystallographic structure of the cryptic secreted protein Bd0675, depicting a novel fold. The solved structure depicts a prominent central acidic and aromatic groove delimited by a conserved disulphide-stabilised loop, suggesting that this protein has ligand binding functions. Based on the solved structure we have tested different candidate ligands; however further experiments are required to propose a function for Bd0675. In addition, due to its novelty, Bd0675 was used as target for multiple structure predicting algorithms in CASP14.
Predators impose a strong selective pressure on the behavioural traits of prey species. Group living, or sociability, allows individuals to reduce their own risk of predation through avoidance, ...dilution, and confusion effects. Another potentially beneficial mechanism is behavioural lateralisation, or "handedness", the asymmetrical expression of cognitive brain functions through a directional bias in visual or motor tasks. In my thesis, I explore the interaction between behavioural lateralisation, sociability, and predation in both natural and captive populations of Trinidadian guppies (Poecilia reticulata). In Chapter Two, I examine the consistency between current behavioural lateralisation methodologies and assess the assumptions behind these methods, including the number of incorporated turn choices and the impact of random chance. In Chapter Three, I present the use of environmental DNA in assessing natural piscine guppy predator communities at six sites across the Northern Range of Trinidad. Using this measure of predation, I assess its viability in predicting differentiation of adaptive anti-predatory behaviours in natural guppies, including sociability, activity, and both visual and motor lateralisation. In Chapter Four, I assess the visual lateralisation of guppies tested either solitarily or in groups in the presence or absence of a live predator, the blue acara (Andinoacara pulcher). Using a repeated measures design, I investigate the repeatability of guppies' visual lateralisation in terms of personality variation across the investigated contexts. In Chapter Five, I assess the visual lateralisation of natural guppies when viewing a social stimulus and their sociability across a gradient of predation risk using nineteen sites in the Northern Range of Trinidad. Overall, my research demonstrates relatively low levels of lateralisation throughout contexts and populations. However, subtle trends in the lateralisation of eye-use when viewing a predatory or social stimulus appear to exist in relation to predation risk, with an apparent social conformity in lateralisation when assessed in groups.
Selection of prey that are small and in poor body condition is a widespread phenomenon in terrestrial predator–prey systems and may benefit prey populations by removing substandard individuals. ...Similar selection is widely assumed to operate in aquatic systems. Indeed, size‐selective predation is a longstanding and central tenet of aquatic food web theory. However, it is not known if aquatic predators select prey based on their condition or state, compared to their size. Surprisingly, no comparable information is available for marine systems because it is exceedingly difficult to make direct observations in this realm. Thus the role of body condition in regulating susceptibility to predation remains a black box in the marine environment. Here we have exploited an ideal model system to evaluate selective predation on pelagic marine fish: comparing characteristics (fork length, mass corrected for fork length) of fresh, whole, intact juvenile Pacific salmon delivered by a seabird to its single nestling with salmon collected concurrently in coastal trawl surveys. Three species of juvenile salmon (Oncorhynchus spp.) are consumed by provisioning Rhinoceros Auklets (Cerorhinca monocerata); an abundant, colonial, pursuit‐diving seabird. Samples were collected from multiple colonies and fisheries surveys in coastal British Columbia in two years. As predicted, Auklets preyed on small individuals in poor condition and consistently selected them at levels higher than their relative availability. This is the first study to provide direct evidence for both size‐ and condition‐selective predation on marine fish in the wild. We anticipate that our results will be a starting point in evaluating how selective predation may structure or influence marine fish populations and bridges a fundamental incongruity between ecological theory and application; although “bigger is better” is considered a fundamental tenet of marine food webs, marine predators are often assumed to consume indiscriminately.
The nocturnal feeding behavior and zoogeographical habitat of cookiecutter sharks Isistius brasiliensis and Isistius plutodus (Isistius spp.) greatly reduces interaction of this species with live ...humans. Attacks on live humans are exceedingly rare with 7 cases reported worldwide, 6 of them in Hawai?i, and 5 of these occuring among channel swimmers. Published research suggests that periods of bright moonlight may increase Isistius spp. contact with live humans and does not otherwise identify significant trends or risk factors. Yet 5 of the 6 Isistius spp. bites on live humans in Hawai?ian waters occurred with the moon set and after nautical twilight end and before nautical twilight start. From 1961-2023 in Hawai?i, 129 successful solo channel crosses and 5 Isistius spp. related injuries in the habitat of cookiecutter sharks were analyzed across two groups: one where both the moon and sun were set (dark group) and one where the moon and/or sun was in the sky (light group). There was a significant difference for swimmers bitten by Isistius spp. in the dark 4 (12%) versus light groups 1 (1%), p = 0.012, RR 12.6 (95% confidence interval: 1.5-108.9). Swim start time and year was also significant (Pearson correlation 0.566, p <0.001). Swimmer gender and use of shark deterrent devices and artificial illumination were not significant. The growing popularity of channel swimming in Hawai?i and swim start times have contributed to an increasing likelihood of live human and Isistius spp. contact and a moonless night sky is a significant risk factor for this interaction.
ABSTRACT
The impact of increasing vertebrate predator numbers on bird populations is widely debated among the general public, game managers and conservationists across Europe. However, there are few ...systematic reviews of whether predation limits the population sizes of European bird species. Views on the impacts of predation are particularly polarised in the UK, probably because the UK has a globally exceptional culture of intensive, high‐yield gamebird management where predator removal is the norm. In addition, most apex predators have been exterminated or much depleted in numbers, contributing to a widely held perception that the UK has high numbers of mesopredators. This has resulted in many high‐quality studies of mesopredator impacts over several decades. Here we present results from a systematic review of predator trends and abundance, and assess whether predation limits the population sizes of 90 bird species in the UK. Our results confirm that the generalist predators Red Fox (Vulpes vulpes) and Crows (Corvus corone and C. cornix) occur at high densities in the UK compared with other European countries. In addition, some avian and mammalian predators have increased numerically in the UK during recent decades. Despite these high and increasing densities of predators, we found little evidence that predation limits populations of pigeons, woodpeckers and passerines, whereas evidence suggests that ground‐nesting seabirds, waders and gamebirds can be limited by predation. Using life‐history characteristics of prey species, we found that mainly long‐lived species with high adult survival and late onset of breeding were limited by predation. Single‐brooded species were also more likely to be limited by predation than multi‐brooded species. Predators that depredate prey species during all life stages (i.e. from nest to adult stages) limited prey numbers more than predators that depredated only specific life stages (e.g. solely during the nest phase). The Red Fox and non‐native mammals (e.g. the American Mink Neovison vison) were frequently identified as numerically limiting their prey species. Our review has identified predator–prey interactions that are particularly likely to result in population declines of prey species. In the short term, traditional predator‐management techniques (e.g. lethal control or fencing to reduce predation by a small number of predator species) could be used to protect these vulnerable species. However, as these techniques are costly and time‐consuming, we advocate that future research should identify land‐use practices and landscape configurations that would reduce predator numbers and predation rates.
1. Both seed predators and herbivores can have profound effects on individual plant growth, reproduction and survival, but their population-level effects are less well understood. While most plants ...interact with a suite of seed predators and herbivores over their life cycle, few studies incorporate the effects of multiple interacting partners and multiple life stages on plant population growth. 2. We constructed a matrix model using 6 years of data from a rare, seed-producing population of American chestnut (Castanea dentata). We combined field demographic data with published experimental results on the effects of pre-dispersal seed predators (weevils) and post-dispersal seed predators (scatter-hoarding vertebrates) and incorporated the effect of vertebrate herbivores estimated from the field data. We explored the impact of these three different animal interactions for short-term (transient) and long-term (asymptotic) tree population growth. In addition, we used the model to explore the conditions under which scatter hoarding would function as a mutualism. 3. Seed predators had greater effect on both short- and long-term population growth than herbivores. Although weevil infestation can greatly reduce the probability of germination, pre-dispersal seed predators had smaller effects on both short- or long-term population growth than post-dispersal predators. The elasticities of weevil-related parameters were also small. The effect of browsers on both the shortand long-term population growth rate were the smallest of the effects studied. Post-dispersal seed predation affected population growth the most in the interactions studied. The probability of seed removal was among the largest elasticities, similar in magnitude to survival of large trees. 4. Synthesis. Our results indicate that neither weevils nor the intensity of browse damage observed at our study site are likely to hinder tree regeneration or reintroduction, although both reduced population growth. Although researchers and forest managers often assume that seeds are unimportant for long-lived tree populations, our test of this assumption shows that scatterhoarders and other post-dispersal seed consumers can significantly limit natural regeneration. Forest management that alters scatterhoarder behaviour could have significant effects on tree population dynamics that are largely unexplored.
Since the 1960s, primatologists have recognized the impact of predation on the evolution of morphology, the social systems and cognitive behavior of monkeys and apes, but few studies considered its ...impact on the prosimians - lemurs, lorises, galagos and tarsiers. This comprehensive volume, written by experts in the field, narrows this gap by highlighting the effect of predation on the order Primates in general. Theoretical approaches to understanding how primates perceive predation threat, as well as proximate and ultimate causes to address threat and attack, are considered across the primate order. Although this volume concentrates on the least known group in this theoretical area - the prosimians - contributions by researchers on numerous primate taxa across four major geographical regions make this a novel and exciting contribution to students interested in primate evolution and ecology.
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