Ralph Tollrian

Ralph Tollrian
Ruhr-Universität Bochum | RUB · Department of Animal Ecology Evolution and Biodiversity

Professor

About

227
Publications
37,662
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8,091
Citations
Citations since 2017
74 Research Items
3509 Citations
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20172018201920202021202220230100200300400500600700
20172018201920202021202220230100200300400500600700

Publications

Publications (227)
Article
Full-text available
Information on diversity indices and abundance of individual species is crucial for the assessment of ecosystem health, especially for endangered ecosystems as coral reefs. The application of environmental DNA (eDNA) to monitor coral biodiversity is, however, just beginning to come into focus for marine biologists. In this study, an eDNA metabarcod...
Article
Full-text available
Every ecosystem shows multiple levels of species interactions, which are often difficult to isolate and to classify regarding their specific nature. For most of the observed interactions, it comes down to either competition or consumption. The modes of consumption are various and defined by the nature of the consumed organism, e.g., carnivory, herb...
Article
Full-text available
Inducible defenses are a wide-spread defensive mechanism in Daphnia. For example, D. cucullata is known to form different adaptive morphologies under changing environmental conditions. In this species, predator presence elicits defensive helmets. Defended animals perform better and survive more frequently in predation attempts. Another peculiarity...
Article
Full-text available
Citation: Langer, S. M., M. Horstmann, L. C. Weiss, W. Junke, S. Herlitze, and R. Tollrian. 2021. On Daphnia's path: a semi-automatic system to analyze three-dimensional movement patterns. Ecosphere 12(12): Abstract. Analyzing movement is essential for understanding complex behavioral interactions. Up to date, there are different movement analysis...
Article
Full-text available
Polyp bailout is a drastic response to acute stress where coral coloniality breaks down and polyps detach. We induced polyp bailout in Pocillopora acuta with heat stress and tested for differential gene expression using RNAseq and a qPCR assay. Furthermore, we induced polyp bailout with hypersalinity and compared the results to identify stressor-in...
Preprint
Full-text available
Water fleas of the family Daphniidae are keystone species in many lentic ecosystems and, as most abundant filter feeders, link the primary production to higher trophic levels. As a response to the high predatory pressures, water fleas have evolved a range of defenses, including inducible defenses against animal predators. Here we show in Ceriodaphn...
Article
Full-text available
Predation is a major selective agent, so that many taxa evolved phenotypically plastic defensive mechanisms. Among them are many species of the microcrustacean genus Daphnia, which respond to an increased predation risk by developing inducible morphological alterations. Some of these features are obvious and easily recognized, e.g., crests in D. lo...
Article
Full-text available
Corals have evolved a variety of stress responses to changing conditions, many of which have been the subject of scientific research. However, polyp bailout has not received widespread scientific attention, despite being described more than 80 years ago. Polyp bailout is a drastic response to acute stress in which coral colonies break down, with in...
Article
Full-text available
Fossil fuel combustion results in rising atmospheric carbon dioxide (CO2), which is known to impact the global climate and the oceans. Latest insights indicate that rising atmospheric CO2 levels also affect CO2 partial pressure (pCO2) in freshwaters, where pCO2 is controlled by a multitude of parameters. However, up to date there is no standardized...
Article
Full-text available
Prey species can respond to the presence of predators by inducing phenotypic plastic traits which form morphological, life history or behavioral defenses. These so-called inducible defenses have evolved within a cost-benefit framework. They are only formed when they are needed, and costs associated with defenses are saved when predators are not pre...
Article
Full-text available
Utricularia multifida is carnivorous bladderwort from Western Australia and belongs to a phylogenetically early-diverging lineage of the genus. We present a prey spectrum analysis resulting from a snapshot sampling of 17 traps–the first of this species to our knowledge. The most abundant prey groups were Ostracoda, Copepoda, and Cladocera. The genu...
Article
Increased carbon dioxide from fossil fuel combustion results in an enrichment of CO2 in the global carbon cycle. Recent evidence indicates that rising atmospheric CO2 impacts the partial pressure of carbon dioxide (pCO2) in freshwaters. This affects freshwater biota by disrupting chemical communication between predator and prey. One such well-descr...
Chapter
Aim: Providing an overview of key concepts related to predator-prey interactions and illustrate them with examples. Main concepts covered: Predation cycle; prey defenses, including inducible defenses, swarming effects, responses against specific vs. multiple predators; predator offenses; predator functional responses; predator-prey interactions in...
Article
Ciliates are unicellular protists of the phylum Ciliophora and found in high abundances in water systemsworld-wide. Today their important ecological role in all aquatic systems is well known. However, morphologicalspecies identification in ciliates is difficult due to sometimes tiny morphological characteristics. We here present asimplified method...
Article
Wading birds play an important role in coastal and wetland ecosystems. As a result of anthropogenic disturbances, numbers of wading birds have declined over the past years, and therefore, the monitoring of bird species is crucial to preserve their habitats and counteract this. Due to known limitations of conventional monitoring, molecular approache...
Data
Recurvirostra avosetta voucher Recavo1 cytochrome c oxidase subunit I (COX1) gene, partial cds; mitochondrial NCBI: MT132172
Data
Platalea leucorodia voucher Plaleu1 cytochrome c oxidase subunit I (COX1) gene, partial cds; mitochondrial NCBI: MT132171
Data
Tringa totanus voucher Tritot1 cytochrome c oxidase subunit I (COX1) gene, partial cds; mitochondrial NCBI: MT132173
Article
Full-text available
Limited data are available pertaining to life history and population connectivity of the data deficient southern stingray (Hypanus americanus, Hildebrand & Schroeder, 1928). In order to determine potential vulnerabilities of their populations, this study aimed to analyze their movement patterns and genetic variability. A population of southern stin...
Article
Full-text available
Aquatic acidification is a major consequence of fossil fuel combustion. In marine ecosystems it was shown, that increasing pCO2 levels significantly affect behavioural and sensory capacities in a diversity of species. This can result in altered predator and prey interactions and thereby change community structures. Just recently also CO2 dependent...
Article
Full-text available
We investigated the predator-prey interactions between an Australian ecotype of the carnivorous waterwheel plant (Aldrovanda vesiculosa, Droseraceae) and its potential natural prey, the water flea Daphnia longicephala (Daphniidae), which also occurs in Australia. A. vesiculosa develops snap-traps, which close within ~10–100 ms after mechanical trig...
Article
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In accordance with the Red Queen hypothesis, the lower genotypic diversity in clonally reproducing species should make them easier targets for pathogen infection, especially when closely related sexually reproducing species occur in close proximity. We analyzed two populations of clonal P. formosa and their sexual parental species P. mexicana by co...
Article
Full-text available
Synopsis The critically endangered carnivorous waterwheel plant (Aldrovanda vesiculosa, Droseraceae) possesses underwater snap traps for capturing small aquatic animals, but knowledge on the exact prey species is limited. Such information would be essential for continuing ecological research, drawing conclusions regarding trapping efficiency and tr...
Article
Full-text available
Filter feeding zooplankton are a crucial component of limnic food webs. Copepods and cladocerans are important prey organisms for first-level predators like the common and abundant larvae of phantom midges (Chaoborus sp.). The latter possess a complex catching basket built of head appendages specialized to capture small crustaceans. The predator-pr...
Data
Surface mesh (.stl) of the Chaoborus larva head morphology with closed catching basket. (STL)
Data
Surface mesh (.stl) of the Chaoborus larva head morphology with opened catching basket. (STL)
Data
High-speed footage of a Chaoborus larva attacking a defended daphniid. (MP4)
Data
Animation of the opening catching basket of Chaoborus larvae based on micro-CT data and high-speed footage, multiple angles of view. (MOV)
Data
Animation of the opening catching basket of Chaoborus larvae based on micro-CT data and high-speed footage. (AVI)
Article
Behavioral adaptations play an important role in predator–prey interactions as they reduce predation risk. Prey organisms have therefore evolved a tremendous variability in behavioral adaptations. In case of small crustaceans of the genus Daphnia, which are common and important herbivores transferring energy from primary producers to higher trophic...
Article
Full-text available
Infochemicals play important roles in aquatic ecosystems. They even modify food web interactions, such as by inducing defenses in prey. In one classic but still not fully understood example, the planktonic freshwater crustacean Daphnia pulex forms specific morphological defenses (neckteeth) induced by chemical cues (kairomones) released from its pr...
Article
Full-text available
Quantitative analysis of shape and form is critical in many biological disciplines, as context-dependent morphotypes reflect changes in gene expression and physiology, e.g., in comparisons of environment-dependent phenotypes, forward/reverse genetic assays or shape development during ontogenesis. 3D-shape rendering methods produce models with arbit...
Data
Confidence ellipsoid analysis of permutated treatments Displayed are the results of the usual confidence ellipsoid analysis, conducted with the natural treatments leading to complete non-overlap of all the confidence ellipsoids (black clouring) (A). Figures (B) to (D) show three random permutations among the samples, each keeping the number of anim...
Data
Light microscopic comparison of undefended (A) and defended (B) D. magna K34Q (A) The undefended morphological state is mainly characterised by a comparatively short tail spine, while (B) the one of defended animals is elongated and inserts on an almost circular body outline. Apart from these alterations, no other differences between the shapes can...
Data
Q-values against their respective p-values Given are p- q-plots for the x- (A), y-(B) and z-dimension (C). Figure S3 (D) gives an exemplary λ–π (λ)-plot for the z-coordinates, calculated with Matlab, to determine π0 and therefore indirectly π1, which is the lower bound on the proportion of test decisions correctly following the alternative hypothes...
Data
Overall displacement, size adjusted By applying a Procrustes-fit with adjustment of size, most alterations, as the ones visualised in Fig. 3C, disappear. Therefore, the true changes of shape become obvious, which are mainly located at the tail spine, which is elongated non-proportionally to body length in defended specimens. Further shape alteratio...
Chapter
The capacity of an organism with a given genotype to respond to changing environmental conditions by the expression of an alternative phenotype is a fascinating biological phenomenon. Plasticity enables organisms to cope with environmental challenges by altering their morphology, behavior, physiology, and life history. Especially, predation is a ma...
Article
Anthropogenically released CO2 accumulates in the global carbon cycle and is anticipated to imbalance global carbon fluxes [1]. For example, increased atmospheric CO2 induces a net air-to-sea flux where the oceans take up large amounts of atmospheric CO2 (i.e., ocean acidification [2-5]). Research on ocean acidification is ongoing, and studies have...
Article
Cladocerans serve as prey for several aquatic predators like fish and Chaoborus larvae. However, because different predators consume different sized prey, cladocerans may display differing life-history responses depending on predator type. Although most studies use the genus Daphnia to evaluate phenotypic plasticity in cladocerans, other genera mig...
Article
Full-text available
Background: Scavenger guilds are composed of a variety of species, co-existing in the same habitat and sharing the same niche in the food web. Niche partitioning among them can manifest in different feeding strategies, e.g. during carcass feeding. In the bentho-pelagic realm of the Southern Ocean, scavenging amphipods (Lysianassoidea) are ubiquitou...
Article
Full-text available
The freshwater crustacean Daphnia is known for its ability to develop inducible morphological defences that thwart predators. These defences are developed only in the presence of predators and are realized as morphological shape alterations e.g. 'neckteeth' in D. pulex and 'crests' in D. longicephala. Both are discussed to hamper capture, handling...
Article
Full-text available
We recorded capture events (CEs) of the daphniid Ceriodaphnia dubia by the carnivorous Southern bladderwort with suction traps (Utricularia australis). Independent to orientation and behavior during trap triggering, the animals were successfully captured within 9 ms on average and sucked in with velocities of up to 4 m/s and accelerations of up to...
Article
Full-text available
Bioluminescence is a fascinating phenomenon occurring in numerous animal taxa in the ocean. The reef dwelling splitfin flashlight fish (Anomalops katoptron) can be found in large schools during moonless nights in the shallow water of coral reefs and in the open surrounding water. Anomalops katoptron produce striking blink patterns with symbiotic ba...
Data
Blink frequency dim light dl i2. (AVI)
Data
Blink behaviour in A. katoptron during the day (3 dim light conditions), night (darkness) and feeding in darkness (frozen plankton). (TIF)
Data
Schooling behaviour Banda Islands. (AVI)
Data
Blink frequency dim light dl i3. (AVI)
Data
Blink frequency dim light dl i1. (AVI)
Data
Blink frequency darkness. (AVI)
Data
Blink frequency frozen plankton. (AVI)
Data
Supporting Information. (DOCX)
Data
Blink frequency feeding cleaner shrimp larvae. (AVI)
Article
Genetic diversity is the basis for adaptation and therefore of primary scientific interest, especially in species that are threatened by anthropogenic challenges, e.g. climate change and/or pollution. Coral reefs are among the most threatened but also the most diverse ecosystems and have therefore been studied quite extensively. So far, most invest...
Article
Full-text available
In recent years, corals have faced increasing anthropogenic disturbances, leading to regional or local reduction in coral species diversity and reduction in genetic variation. The ability of corals to withstand anthropogenic stress, however, differs between genotypes. To be able to estimate survival and recovery potentials, understanding coral gene...
Article
Full-text available
The micro-crustacean Daphnia pulex is a model species for studying predator-induced defenses. When exposed to chemical cues released by its predator, the phantom midge larvae Chaoborus (Diptera), it develops protective neckteeth that reduce the predator’s success of predation in the juvenile instars. Defensive traits need to be expressed as soon as...
Article
Daphnia (Crustacea, Cladocera) are well known for their ability to form morphological adaptations to defend against predators. In addition to spines and helmets, the carapace itself is a protective structure encapsulating the main body, but not the head. It is formed by a double layer of the integument interconnected by small pillars and hemolympha...
Article
Full-text available
Tag-Seq is a high-throughput approach used for discovering SNPs and characterizing gene expression. In comparison to RNA-Seq, Tag-Seq eases data processing and allows detection of rare mRNA species using only one tag per transcript molecule. However, reduced library complexity raises the issue of PCR duplicates, which distort gene expression levels...