|28 April 2017||First evidence for adaptive function of red fluorescence in fish|
|Many marine fish show striking red fluorescence, but whether these patterns are adaptive remains elusive. In new work by Ulrike Harant et al. (BMC Ecology), red fluorescent fish were more successful in catching copepods under red fluorescence-friendly ambient light spectra compared to broad-white illumination. This suggests that active photolocation might indeed be present in the tested species, and that red fluorescent colours provide and adaptive benefit in "red-deprived" marine environments.|
|27 March 2017||Red fluorescence contrasts more at depth|
Marine light environments become increasingly blue with depth because long wavelengths such as reds are absorbed by water. One consequence is that red fish lose their colours at depth. Some, however, produce red colours through fluorescence, by converting short wavelengths to longer wavelengths. In this new work, Pierre-Paul Bitton et al. (Roy. Soc. Open Science) characterized the visual system and fluorescent properties of the small benthic triplefin fish, Tripterygion delaisi, to determine how depth would influence their colours as perceived by conspecifics. Fish were found to look redder as depth increases, supporting functionality of fluorescence in this species.
|09 March 2017||A novel form of eyeshine in marine fish|
|Eyeshine is the phenomenon of (seemingly) glowing eyes, e.g. cat eyes at night. Roland Fritsch et al. (Front. Zool.) describe a previously unknown form of eyeshine in the Mediterranean triplefin T. delaisi that is based on transmission of light through the head and optic nerve, thus termed optic-nerve-transmitted (ONT) eyeshine. Factors increasing ONT eyeshine intensity include locally reduced head pigmentation, a thin skull, and the potential light-guiding properties of the optic nerve. The authors suggest that ONT eyeshine is widespread among small fish species, and discuss how ONT eyeshine might affect visual performance and if it could serve a function.|
|24 Nov 2016||Ausgezeichnet! Nachhaltigkeitspreis für Behrend Dellwisch|
In einem Festakt wurde Behrend Dellwisch als einer von sechs Preisträgern heute mit dem Nachhaltigkeitspreis der Universität Tübingen ausgezeichnet. In seiner von Nils Anthes betreuten Bachelorarbeit hatte er die Auswirkungen der durch die EU-Greening-Prämie geförderten landwirtschaftlichen Anbauformen im Winter auf die Habitatnutzung durch Vogelarten des Offenlandes untersucht.
|16 Nov 2016||Best practice in measuring sexual selection|
Sexual selection is a key area of behavioural and evolutionary research. Most studies rely on summarizing metrics that quantify sexual selection, such as the Bateman gradient. Nils Anthes and coworkers (Methods Ecol. Evol.) scrutinize the methodology underlying these metrics, raise attention to systematic biases due to study design, and derive best-practice guidelines for future work.
|19 Oct 2016||Phylogenetic patterns of red fluorescence in fish propose adaptive function|
Red fluorescent colour patterns are widespread among benthic marine fish, but the adaptive function of these patterns largely remains elusive to date. In this new work, Nils Anthes, Jenny Theobald and coworkers (Frontiers in Ecology and Evolution) first desribe the diversity of fluorescent colour patterns across marine fishes, and second, test whether their phylogenetic distribution is consistent with several proposed adaptive functions. The available data are consistent with the idea that fluorescence contributes to camouflage, may be involved in active photolocation, and plays a role in sexual signalling.
>> Feature by Wissenschaftsjahr Meere und Ozeane.
>> Feature on Photonworld.de.
|23 Sep 2016||Infection status but not paternity determine filial cannibalism|
|Martin Vallon et al. (Ecology and Evolution) study the evolutionary conundrum that brood-caring male fish routinely eat their own young. According to their new work egg cannibalism specifically targeted mould-infected eggs, while males could not distinguish eggs sired by themselves vs. sneaker-males. |
|17 Mar 2016||The visual system of fairy wrasses is sensitive to their own fluorescence|
New work by Tobias Gerlach, Nico Michiels and colleagues, published in Frontiers in Zoology, provides a further significant step forward in our understanding of the adaptive role of red fluorescence in marine fishes. The new study first describes the spectral variation in fluorescent patterns in 13 species of pseudocheilinid wrasses. Second, microspectromety of the visual pigments in the model species Cirrhilabrus solorenis reveals possible trichromacy. The study indicates that the visual system of these wrasses is capable to perceive long-wavelength signals that match the emission of their own red fluorescent pigments, thus complementing earlier studies showing a behavioural response to long wavelength stimuli.
|09 Mar 2016||Size and nest quality, not personality, affect female choice in gobies|
|In many fish with male parental care, fathers occasionally eat some of their. Recent work showed that this cannibalistic behavioure is associated with individual "temperament" as captured in animal personality. In this new work, Nadine Kalb and colleagues investigated whether females of common gobies prefer males of a given personality. While personality affected male abilities to monopolize a rare nesting structure, female choice did not respond to personality. Yet, the study found consistent female choice for males of larger size and with more elaborate nest sites. This contributes to a growing body of research understanding the interactions between personality, mate choice and reproductive success in a growing number of animal systems.|
|19 Feb 2016||Marine fish enhance iris fluorescence under dim light|
|A recent study by Ulrike Harant and co-workers demonstrates that the consistent difference in fluorescence brightness across a 15 m depth gradient reported earlier for several marine fish is mediated by the brightness but not the spectral composition of the ambient light. Fish increased the brightness of their red fluorescent iris significantly when held in dim light and decreased it under bright light conditions. Red fluorescence is therefore not only phenotypically flexible but can also be regulated and fine-tuned in a matter of days. This quick adjustment of fluorescence brightness at a microhabitat scales adds to recent evidence supporing an adaptive function of fluorescence in marine fish.|
|18 Feb 2016||Patterns of sexual selection in the animal kingdom consistent with Darwin’s theory|
The primordial characteristic distinguishing males and females – their often substantial size difference in sperm versus egg cells – has long been considered key to understanding the apparent male-bias in mate competition. Recent theory, however, has challenged this view, predicting that sex differences in sexual selection were rather dictated by environmental and social factors. Ines Häderer, Nils Anthes and colleagues now contrasted these predictions in a meta analysis (Science Advances), confirming the Darwinian paradigm of stronger sexual selection on males among animals. Modifications including a complete sex role reversal may occur, though, in very specific breeding systems.
|10 Feb 2016||Selective filial cannibalism based on egg age|
|New work by Martin Vallon and Katja Heubel in Behavioral Ecology and Sociobiology shows that male common gobies, Pomatoschistus microps, do not cannibalize their offspring at random but rather selectively remove eggs of a certain phenotype. Specifically, males cannibalize the younger eggs when caring for mixed-age broods. By focussing on such less-developed offspring with lower reproductive value parents may reduce the cost of filial cannibalism. |
Press releases in German and English.
|01 Feb 2016||Filial cannibalism represents intrinsic male trait|
|Filial cannibalism, where caring parents eat some or even all of their young, still represents an evolutionary puzzle. A new study by Martin Vallon and colleagues, published in Ecology and Evolution, now shows that this apparently maladaptive behaviour is correlated with overall male activity in a small benthic fish. This indicates that - at least to some degree - cannibalism may be part of a behavioural syndrome, so that male fish cannot fully adjust this behaviour to the adaptive optimum.|
|05 Mar 2015||Triplefins can see their own red fluorescence|
|Previous work on the biological relevance of fluorescent colour patterns in marine fish relied on the assumption that the investigated fish are capable to perceive their own long wavelength fluorescence. In this study, Nadine Kalb, Ralf Schneider and colleagues for the first time use a training paradigm to demonstrate that a small cryptic Mediterranean fish, Tripterygion delaisi, can indeed discriminate fluorescent colour hues that match its own fluorescence.|
|01-03 Mar 2015||1st European Conference on Scientific Diving|
|Three researchers from our group attend the 1st European Conference on Scientific Diving (ECSD) held at Stuttgart University. The conference focuses on technical aspects of scientific diving as applied in biological, geological or archaeologial work. We present corresponding information - plus some novel findings - in the context of red fluorescence.|
|22 Oct 2014||Female- rather than male-driven sexual coevolution?|
Sexual selection is considered a driving force of trait diversification in males and females. Typically they underlying trait dynamics are thought to be driven by males that evoke counter-adaptations in female.
A new experimental study on sexual trait co-evolution in nematodes questions this paradigm. Karoline Fritzsche, Nadine Timmermeyer and co-workers found that relaxed versus elevated selection pressures stimulated female but not male traits to evolve. (published today in Proceedings of the Royal Society B)
|13 September 2014||14th "Tropical Marine Ecology" course in Egypt|
A student group lead by Melissa Meadows and Ulrike Harant just returned from this summer's field course "Tropical Marine Ecology" at the Red Sea in Egypt.
For more than 10 years now, this course has offered hands-on experience in Marine Ecology, the diversity of coral reef organisms, and in particular the planning and conduction of hypothesis-driven field experiments in small teams.
Lots of fun guaranteed!
|11 September 2014||Congratulations!|
|Tobias Gerlach successfully defended his PhD thesis on the visual ecology of deep red fluorescence in fairy wrasses.|
|09 September 2014||A meta-analysis of the strength and nature of cytoplasmic genetic effects|
|Conducting a formal meta-analysis (Journal of Evolutionary Biology), Ralph Dobler and co-authors confirmed that cytoplasmic genetic variation is commonly tied to phenotypic expression across animals and plants. Furthermore, their results show that cytoplasmic effects tied to epistatic interactions with the nuclear genome tend to be stronger than additive cytoplasmic effects. This indicates that the cytoplasmic-nuclear interaction is a key unit on which natural selection acts.|
|22 August 2014||Group day out|
|This year's day out of the Animal Evolutionary Ecology group led us to the picturesque village of Haigerloch at the Swabian Alb foothills. Core event: a visit to the small but very intriguing 'Atomic Cellar' museum.|
|16 July 2014||More intense fluorescence at depth supports visual rather than UV-protective function|
|A recent study by Melissa Meadows and co-workers (Proceedings B) demonstrates that 6 out of 8 measured reef fish species show brighter red fluorescence when caught at depths devoid of ambient red sunlight compared to shallow sun-exposed habitats that offer full spectral ambient light. This findings is in line with the idea that red fluorescence primarily serves a visual or communicative function (then more relevant in deep water), but contradicts the alternative propostion that fluorescence may primarily serve UV-protection (then more relevant in shallow water).|
|28 May 2014||Red fluoresence mediates male-male aggression.|
New work by Tobias Gerlach and colleagues (Proceedings of the Royal Society of London) provides first evidence for the functional significance of red fluorescence in marine fish, using the Indopacific Fairy wrasse Cirrhilabrus solorensis. Their finding represents a key step in understanding why many fish possess red fluorescent pigments in an environment that is almost entirely devoid of red light.
|The role of red light is not restricted to this single species of fish. A second recent study led by Christoph Braun (Marine Ecology Progress Series) indicates that red colour signals also play a role in agonistic interactions in the Mediterranean wrasse Coris julis.|