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opencc-by-4.0Mar 2022View details →

Ficus trees with upregulated or downregulated defence did not impact predation on their neighbours in a tropical rainforest

Trees can emit volatile organic compounds (VOCs) when under attack by herbivores, and these signals can also be detected by natural enemies and neighbouring trees. There is still limited knowledge of intra- and inter-specific communication in diverse habitats. We studied the effects of induced VOC emissions by three Ficus species on predation on the focal Ficus trees in a lowland tropical rainforest in Papua New Guinea. Further we assessed predation across a phylogenetically diverse set of neighbouring tree species. Two of the focal tree species, Ficus pachyrrhachis and F. hispidioides, have strong alkaloid-based constitutive defences while the third one, F. wassa, is lower in constitutive chemical defences. We experimentally manipulated the jasmonic acid signalling pathway by spraying the focal individuals with either methyl jasmonate (MeJA) or diethyldithiocarbamic acid (DIECA). These treatments induce increases or decreases in VOC emissions, respectively. We tested the possible effects of VOC emissions on each focal Ficus tree and two of its neighbours by measuring the predation rate of plasticine caterpillars. We found that predation increased after the MeJA application in only one focal tree species, F. wassa, while the DIECA application had no effect on any of the three focal species. Further, we did not detect an effect of our treatments on predation rates across neighbouring trees. Neither the phylogenetic distance of the neighbouring tree from the focal tree nor the physical distance from the focal tree had any effect on predation rates for any of the three focal Ficus species. These results suggest that even congeneric tree species vary in their response to the MeJA and DIECA treatment and subsequent response to VOC emissions by predators. Our results also suggest that MeJA effects did not spill over to neighbouring trees in highly diverse tropical rainforest vegetation.

opencc-by-4.0Jun 2023View details →

Food quantity and quality modulates inducible defences in a common predator-prey system

Zooplankton display different inducible defences against invertebrate and vertebrate predators. The response pattern to gape-limited invertebrate predators involves increased somatic growth and offspring body size but delayed maturity and reduced offspring numbers. In contrast to this general pattern, the freshwater model organism Daphnia magna has been reported to exhibit a different response when encountering the gape-limited tadpole shrimp Triops cancriformis. Under laboratory conditions, D. magna showed increased somatic growth, earlier maturation, and an increase in both offspring number and size. We propose here that the discrepancy between the previously observed and the theory-based response patterns against invertebrate predators is due to differences in food availability in the applied laboratory settings and assessed whether the defensive response of D. magna against T. cancriformis is modulated differently by food quantity and quality. We found a strong impact of food quantity and quality on the defence response of D. magna to T. cancriformis kairomones. The prey seem to be able to overcome trade-offs between morphological defence traits and reproductive traits, but distinctly between high food quantity and high food quality. Thereby, reproductive traits were preferred over morphological defences. Furthermore, removal of particles from the T. cancriformis-conditioned water caused a defence pattern in D. magna that was consistent with the general response pattern known from other invertebrate predators, thus explaining the described discrepancy to previous studies with T. cancriformis.  Our study highlights the importance of assessing food-related effects on predator-prey interactions to understand trophic relationships and food web processes.

opencc-by-4.0Sep 2005View details →

Figure 1 in An investigation of predator-induced defence responses in ciliated protozoa

Figure 1. Effect of different predators on Euplotes muscorum. Results are means of three independent replicates for each treatment; ''eaten'', E. muscorum cells ingested by predators; ''cysts'', encysted E. muscorum cells; ''alive'', uningested, trophic E. muscorum cells.

opencc-by-4.0Sep 2005View details →

Figure 2 in An investigation of predator-induced defence responses in ciliated protozoa

Figure 2. Prey width distributions of Colpidium kleini from the experiment described in Table II, i.e. (a) in the absence of predators; (b) in the presence of Euplotes sp. Each distribution was calculated after 24 h and represents the mean of three replicates (n5150).

Fig. 2 in The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators

Fig. 2. Three members of the almost invisible league: Priocharax ariel (top centre), Palaemonetes carteri (bottom left), Microphilypnus amazonicus (bottom right) in aquarium under artificial light. Same specimens as in Fig. 1 except for M. amazonicus (17.8 mm SL, INPA 25244).

Fig. 5. A in The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators

Fig. 5. A juvenile Centropomus mexicanus (12.9 mm SL, ZUEC 6171) gorged with eleotrid fish prey, photographed in field aquarium under artificial light.

Fig. 1 in The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators

Fig. 1. The studied igapó habitat in Amazonia (top left) with leaf-litter debris on the bottom; the eleotrid fish Microphilypnus amazonicus camouflaged on a decomposing leaf (17.5 mm SL, INPA 25244, top right), the characid fish Priocharax ariel hovering in the water column close to a dead leaf (14.3 mm SL, INPA 25243, bottom left), and the palaemonid shrimp Palaemonetes carteri crawling on a dead leaf (23. 7 mm TL, INPA 1432, bottom right). The cryptic effect of each species' colour pattern is lessened under artificial light (photographed in aquarium).

Fig. 4. A in The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators

Fig. 4. A larval Eleotris pisonis (8.8 mm SL, ZUEC 6169, left) and a juvenile Eucinostomus melanopterus (11.3 mm SL, ZUEC 5378, right) photographed in field aquarium under artificial light.

publicMay 2024View details →

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Data from: the flashy escape: support for dynamic flash colouration as anti-predator defence

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opencc-zeroSep 2023View details →

Data from: Efficacy of multiple defences of mimics from the golden mimicry complex against two predators

Many prey species employ multiple defences during interactions with predators. Multiple defences can provide a selective advantage against a single predator at different stages of the interaction or attack, as well as against multiple predator types. However, the efficacy of multiple defences both during different sequences of an attack and against multiple predator types, remains poorly understood. We measured and classified defensive traits used by five mimics (Müllerian and Batesian) of the myrmecomorphic golden mimicry complex and one non-mimetic species. We then performed predatory trials using two different predators that differed markedly in their body size, trophic specialisation, and how they handle prey – one being an ant specialist (spider) and the other a generalist which avoided ants (skink). We identified 12 defensive traits and classified them into four groups (primary, chemical, mechanical, behavioural), which were strongly correlated. Skinks were much less likely to attack and capture mimics than the ant-eating spider predators. Our results show that multiple defences (five or six) were used against each predator. The defensive behaviours and features that were most effective against skinks included appendage waving and large body size, whereas the golden 'shine' warning signal, large body size, cuticle thickness, and defensive gland size were most effective against spiders. Most defences appeared to be predator-specific. We conclude that potential prey in the golden mimicry complex have been selected for multiple defences because of their vulnerability to different predator types and consequently, the efficacy of some of these defences likely represents a trade-off.

opencc-zeroSep 2023View details →

Data from: predator-induced defences under tropicalisation: a biogeographic approach

Aim: The biogeography of predator-induced defences is an understudied area of predator-prey dynamics. Range overlap with predators that induce the response and local demographics (e.g., prey abundances) are likely to be important factors for determining the biogeographic distribution of induced defences within species. However, with climate warming, range expanding warm-water predators are increasingly preying upon temperate species. This is a consequence of a wider phenomenon known as tropicalisation. We aim to determine: (i) if individuals of a temperate barnacle with induced defences ("bent morphs") are primarily present where they co-occur with range-expanding warm-water predators (muricid snails) and, (ii) if bent morphs are size-structured within populations. Location: North-eastern Pacific rocky intertidal zone (~26-40ºN) Taxon: Tetraclita rubescens (Nilsson-Cantell, 1931), Balanomorpha Methods: We use photo quadrats from sites across the range of T. rubescens to determine the biogeographic distribution of populations with bent morphs and to assess size-structure. We use a combination of field surveys, literature, and museum occurrences to assess range overlap between cool and warm-water predators of T. rubescens and their association with populations with bent morphs and abundance patterns of T. rubescens. Results: Bent morphs are commonly found within the equatorward portion of the species' range (where abundances are highest), in populations overlapping with range expanding warm-water predators. Bent morphs primarily occur within the smaller size classes. Main conclusions: To be partly resilient to the effects of tropicalisation, temperate prey must acclimatize/adapt to altered predator-prey dynamics. Predator-induced defences are one way to do this. We show that bent morphs within a temperate prey species (T. rubescens) are largely restricted to populations that overlap with large-bodied and range-expanding warm-water predators. This is evidence for the partial resilience of T. rubescens to tropicalisation and provides the rationale for further exploration of the eco-evolutionary consequences of tropicalisation in this study system and others.

publicSep 2023View details →

Data from: predator-induced defences under tropicalisation: a biogeographic approach

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publicSep 2023View details →

Data from: Efficacy of multiple defences of mimics from the golden mimicry complex against two predators

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opencc-zeroDec 2014View details →

Data from: Benefits of coloniality: communal defence saves anti-predator effort in cooperative breeders

1. Many anti-predator benefits of group living are predicted to scale with prey density. Nevertheless, evidence for a general density-dependent increase of prey survival is scarce. A possible reason for this discrepancy is the reduction of costly anti-predator behaviour of prey with increasing density, which may offset density-dependent survival gains. Benefits of group living might hence accrue by saved investment into anti-predator behaviours rather than by increased survival rates. 2. Here, we experimentally presented predators in a colony of the cooperatively breeding cichlid fish Neolamprologus pulcher to study density dependence of their anti-predator defences. Predation is a driver of the formation and stability of breeding groups in this species, but potential benefits of coloniality are yet unclear. We hypothesised that increased density of breeding groups would either increase total anti-predator behaviour or allow individuals to reduce their anti-predator effort due to enhanced predator deterrence from neighbours. 3. Confirming predictions from the second hypothesis, our results show that focal groups invested less into anti-predator behaviour at higher densities, while neighbouring groups' behaviour compensated for this reduced effort. This resulted in stable levels of anti-predator behaviours over the entire range of natural densities. Thus, aggregating in colonies allows these fish to save investment in anti-predator behaviour. 4. These results suggest that the formation of both breeding groups and colonies reflects adaptive responses to high predation pressure in this species. Two different levels of sociality seem to be favoured by the same selective force. 5. Our study provides experimental evidence in nature for an important benefit of coloniality that may explain the concomitant existence of different levels of sociality in many highly social taxa.

opencc-zeroDec 2019View details →

Data from: Defence versus defence: are crucian carp trading off immune function against predator-induced morphology?

1. Numerous species adopt inducible defence strategies, i.e. they have phenotypically plastic traits that decrease the risk of capture and consumption by potential predators. The benefits of expressing alternative phenotypes in high- versus low-risk environments are well documented. However, inducible anti-predator traits are also expected to incur costs, as they are not expressed when predators are absent, yet empirical evidence of such costs remains scarce. 2. Virtually all animals in nature are simultaneously under strong selection to evade both capture by predators and infection by parasites or pathogens, and, hence, display a diverse arsenal of defences to combat these threats, raising the possibility of trade-offs between defences. A classic example of a predator-induced morphological defence is the deep-bodied shape of crucian carp that reduces risk of predation from gape-size limited predators. The goal of this study was to examine if predator exposure affects also immune function in crucian carp, and if the degree of expressed morphological defence is traded off against immune function in individuals. 3. Following exposure to manipulations of perceived risk (predator presence/absence) in a long-term experiment (eight months), key aspects of innate immune function and individual differences in the expression of inducible morphological defence were quantified. 4. Predator-exposed individuals showed lower haptoglobin levels and complement activity, but higher natural antibody titres than fish from predator-free conditions. When experimentally challenged with a mimicked bacterial infection (LPS injection), fish reared in the presence of a natural predator showed a weaker immune response. Moreover, among predator-exposed individuals, the magnitude of morphological defence expression correlated with both baseline immune function and the ability to mount an immune response. However, these relationships were not consistently supportive of a general trade-off among defences. 5. Our results suggest that fish exposed to predators on average reduce investment in immune function and, further, the observed relationships among defences in predator-exposed individuals can best be explained from individual fitness and pace-of-life perspectives.

opencc-zeroDec 2013View details →

Data from: Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant-plant mutualism

In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant–plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output.

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Figure 3 in Size, spines and crochets: defences of luna moth caterpillars against predation by brown anoles

Figure 3. Close-ups of luna moth caterpillars sporting scoli equipped with spines that are effective as defence against anoles. Scoli may deliver an aposematic signal as they can vary in colour from green (freshly molted fourth instar, top left) and black (late fourth instar, bottom left) to blue (freshly molted fifth instar, top right) and red (late fifth instar, bottom right).

opennotspecifiedFeb 2018View details →

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Figure 2 in Size, spines and crochets: defences of luna moth caterpillars against predation by brown anoles

Figure 2. Top and middle: caterpillars of the luna moth, Actias luna; bottom: caterpillar of the io moth, Automeris io (Saturniidae).

opennotspecifiedFeb 2018View details →

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Figure 1 in Size, spines and crochets: defences of luna moth caterpillars against predation by brown anoles

Figure 1. Left: the brown anole (Anolis sagrei); right: the green anole (Anolis carolinensis). Both species are common in Florida and exhibit excellent climbing abilities, which allow them to hunt for caterpillars on plants.

opennotspecifiedFeb 2018View details →