Main current projects
Updated in September 2017
Species and range evolution in Amazonian amphibians
It is challenging to explain amphibian history and diversity in Amazonia. Our molecular-, field- and model-based research contributes towards a better understanding of the role of long distance dispersal, how elevation and secondary contact contribute to evolutionary change within or between species, in particular the identification of cryptic species diversity (and also not forgetting to formally name them). Additionally, we contribute to the neglected question why indeed there are wide-spread species.
Involved researchers from our lab: Michael Mayer, Luis Fernando Marin da Fonte, Daniela C. Rößler (all are doctorate candidates of Stefan Lötters), Stefan Lötters.
Photo: Ameerega trivittata, a fellow found over most of Amazonia. By Denise J. Ellwein.
Functional aspects and evolution of aposematism
Harlequin toads (Atelopus) greatly vary between cryptic and brilliant colorations and some just have flash marks. All Atelopus are toxic. They contain tetrodotoxin (TTX) which is puzzling, as this highly venomous substance is, other than in amphibians, known from many marine organisms including puffer fish, a delicacy in Japan. In a phylogenetic context, we study the evolution and function of visual conspicuousness with regard to toxicity.
Involved researchers from our lab: Daniela C. Rößler, Max N. Lorentz (both are doctorate candidates of Stefan Lötters), Denise J. Ellwein, Diego Ellis Soto, Stefan Lötters.
Photo: An undescribed toxic Atelopus species from Ecuador. By Jos Kielgast.
Ecology, evolution and systematics of amphibians in an instable
Floating meadows ('flotantes') on the Amazon river and its tributaries are an interesting but so far largely overlooked habitat to frogs. We explore their diversity and how the high mobility of these instable pieces of vegetation influence species and within-species dispersal and evolution.
Involved researchers from our lab: Luis Fernando Marin da Fonte (doctorate candidate of Stefan Lötters), Philipp Böning, Stefan Lötters.
Photos: Dendropsophus triangulum, a typical but otherwise arboreal frog in floating meadows. By Stefan Lötters.
Effects of environmental contaminants in amphibians and reptiles
Changing land use practices in agriculture may increase the contamination risk to amphibians and reptiles with pesticides. For instance, this may simply be related to the expansion of previously uncultivated areas due to the demand for energy crops, but also the cultivation of genetically manipulated crops. We investigate direct and indirect effects of environmentally (and legally) pesticide concentrations on the survival of individuals, populations and species. (i) We perform lab experiments on an amphibian standard model organism (Clawed frogs, Xenopus), with a strong focus on potential effects from glyphosate-based herbicides. (ii) Wild frogs, newts, lizards and snakes are investigated in the field. Here, we aim at studying at e.g. avoidance of differently contaminated water bodies and the detection of unusual deformation rates in larvae or individual degrees of contamination, for instance, via arthropod food sources. We also use GIS-based approaches in risk analyses.
Involved researchers from our lab: Norman Wagner, Valentin Mingo (former and current doctorate candidates of Stefan Lötters), Stefan Lötters.
How do emerging infectious diseases affect amphibian diversity?
Emerging infectious diseases are one of the main threats to global biodiversity. Amphibians, a group severely declining at the global scale, suffer from spreading fungal diseases, in particular the amphibian chytrid fungus, Batrachochytrium dendrobatidis. We have studied this pathogen in the wild in the Alps and in East Africa and have made a risk assessment for all global amphibian species, based on distribution models.
Involved researchers from our lab: Michael Veith, Norman Wagner, Jos Kielgast, Dennis Rödder (past), Stefan Lötters.
Photo: Fire salamander (Salamandra salamandra):
Right hand side is a global model of the potential
Species, time and space — Biogeography of the Congo Basin
Africa's 'green heart' is among the least explored rainforests, remarkably huge in size. We are interested in understanding past and on-going distributional patterns and processes. Our key groups comprise different anurans that can be attributed to distinct 'functional guilds' and show variable adaptabilities. Apart from the collection of basics (including the description of new species), we study dispersal, vicariance and identify potential refuges, making use of molecular phylogenetic data as well as species distribution models.
Involved researchers from our lab: Daniela C. Rößler, Stefan Lötters.
Photo: Beautiful rainforests in DRC. By Jos Kielgast.
Evolution and systematics of Afrotropical reed frogs
Location: Sub-Saharan Africa.
Taxon: Anura: Hyperoliidae.
Funding: BIOLOG; lab resources.
Collaboration: Daniel Portik, Berkeley; Alan Channing, Bellville; Rayna Bell, Ithaca; Jos Kielgast, Copenhagen; Zoltan T. Nagy, Brussels; Václav Gvoždík, Prague; Michael Veith, Trier;
Mark-Oliver Rödel, Berlin; Max Dehling, Koblenz; and more.
Hyperoliid frogs comprise several hundred species with exclusively sub-Saharan African and Madagascan distributions. These so called Reed frogs are highly sexually dichromatic. Using ancestral character reconstructions on phylogenies, we found that this trait has independently developed multiple times even within one genus. In the course of the on-going research, we intend to contribute to a more complete picture of (i) the phlogeny and taxonomy and (ii) trait evolution in these mainly arboricol frogs. This generally gives some insight how plesimorphic, synapomorphic and convergent adaptations evolve within large clades.
Involved researcher from our lab: Stefan Lötters.
Important publications: Bell, R.C. et al. (2017): Idiosyncratic responses to climate-driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands. — Molecular Ecology, in press.
Channing, A. et al.(2013): Taxonomy of the super-cryptic Hyperolius nasutus group of long reed frogs of Africa (Anura: Hyperoliidae), with descriptions of six new species. — Zootaxa, 3620: 301-350.
Schick, S., et al. (2010): New species of reed frog from the Congo basin with discussion of paraphyly in Cinnamon-belly reed frogs. — Zootaxa, 2501: 23-36.
Veith, M. et al. (2009): Multiple evolution of sexual dichromatism in African reed frogs. — Molecular Phylogenetics and Evolution, 51: 388-393. Photos: Sexual dichromatism in Hyperolius viridiflavus from Kenya: females are green-yellow, males have the same color or are brownish. By Stefan Lötters.
Main past projects
Intra- and interspecific signalling in poison frogs
This species lays eggs on land and transports its larvae singly into water pools in leaf axils (phytotelms). We found that nurse frogs do avoid pools occupied by conspecific tadpoels on the basis of chemical recognition. Phytotelms do provide limited resources only and tadpoles are cannibalistic. We have been able to show that sometimes tadpoels of other frog species are avoided, too (e.g. Hyloxalus azureiventris), but that occasionally pools with (chemical compounds of) tadpoles of heterospecifics are 'preferred'. The latter especially applies to non-cannibalistic tadpoles (e.g. Rhinella poeppigii). Interestingly, nurse frogs are unable to detect insect predators in phytotelms on the basis on chemical compounds.
Combining chemical analyses with in-situ bioassays, we identified the molecular formulas of the chemical compounds triggering the nurse frog's behavior. Ranitomeya variabilis and Hyloxalus azureiventris both produce distinct chemical compound combinations. This leads us to conclude that two separate communication systems are at work. In an ecological context, we classify the conspecific R. variabilis compounds as chemical cues - that is, they are only advantageous to the receiver (nurse frog), not the emitters (tadpoles). The heterospecific compounds, we suggest are chemical signals. These are advantageous to the emitters (heterospecific tadpoles) and likely also to the receivers (nurse frog). Due to these assumed receiver benefits, the heterospecific compounds are possibly synomones which are advantageous to both emitter and receiver. This would be a very rare communication system between animal species, especially vertebrates.
Involved researchers from our lab: Lisa M. Schulte (former doctorate cnadidate of Stefan Lötters), Stefan Lötters.
Photo: Male Ranitomeya variabilis carrying a tadpole on its back. By Lisa M. Schulte.
Contact zones in the parapatric Alpine and Fire salamanders
Parapatric species which meet in small contact zones pose interesting questions. With the aim to to identify the determinants
Involved researchers from our lab: Philine Werner (former doctorate candidate of Stefan Lötters), Stefan Lötters.
Photo: Amazing Alpine salamander portrait. By Ulrich Schulte.
Modelling range shifts in Foraminifera
Involved researcher from our lab: Stefan Lötters.
Above is shown the potential New World distribution of Amphistegina spp. under current and future climatic conditions (for the year 2050, right). Warmer colors suggest higher suitability; that is a trend to decrease with anthropogenic warming.