Sperm competition is recognized as an integral component of sexual selection, shaping life-history characteristics such as body size, morphology, physiology and behavior (Birkhead and Parker 1997). Sperm competition occurs when there is... more
Sperm competition is recognized as an integral component of sexual selection, shaping life-history characteristics such as body size, morphology, physiology and behavior (Birkhead and Parker 1997). Sperm competition occurs when there is competition between the ejaculates of different males for the fertilization of a given set of ova (Parker, 1970). Therefore sperm competition can be shown by detecting mixed paternity using molecular methods (Queller et al. 1993; Roberts et al. 1999), by direct observation of multiple male -single female copulations (Jennions and Passmore 1993; Birkhead and Parker 1997) and by comparing relative testis sizes and sperm traits among and within species based on sperm competition theory (Harcourt et al. 1981; Byrne et al. 2002). However, despite the relatively high number of proposed methods it remains difficult to assess sperm competition in external fertilizers, and our knowledge of the occurrence of sperm competition in externally fertilizing anuran t...
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Chemical cues that evoke anti-predator developmental changes have received considerable attention, but it is not known to what extent prey use information from the smell of predators and from cues released through digestion. We conducted... more
Chemical cues that evoke anti-predator developmental changes have received considerable attention, but it is not known to what extent prey use information from the smell of predators and from cues released through digestion. We conducted an experiment to determine the importance of various types of cues for the adjustment of anti-predator defences. We exposed tadpoles (common frog, Rana temporaria) to water originating from predators (caged dragonfly larvae, Aeshna cyanea) that were fed different types and quantities of prey outside of tadpole-rearing containers. Variation among treatments in the magnitude of morphological and behavioural responses was highly consistent. Our results demonstrate that tadpoles can assess the threat posed by predators through digestion-released, prey-borne cues and continually released predator-borne cues. These cues may play an important role in the fine-tuning of anti-predator responses and significantly affect the outcome of interactions between pre...
Research Interests: Perception, Water, Animal Behavior, Ecology, Cues, and 10 moreAnimals, Digestion, Smell, Odonata, Oecologia, Odors, Larva, Predatory Behavior, Food Chain, and Rana temporaria
It has been implied that the application of pesticides is involved in the world-wide decline of biodiversity, but little is known about the influence of these chemicals on key predators of temporary wetlands. The direct impacts were... more
It has been implied that the application of pesticides is involved in the world-wide decline of biodiversity, but little is known about the influence of these chemicals on key predators of temporary wetlands. The direct impacts were examined of a frequently applied glyphosate-based herbicide on larval Aeshna cyanea (Müller, 1764; Odonata, Insecta) and adult male Lissotriton vulgaris (Linnaeus, 1758; Caudata, Amphibia), 2 top predators of Central European ephemeral ponds. The effects of herbicide exposure were measured on survival, behavior, body mass change, and predatory activity in an outdoor mesocosm experiment lasting for 17 d. No significant effects of exposure were observed in either predator species. The results suggest that the herbicide has no immediate effect on the predators studied at environmentally relevant concentrations and that these predators can also fulfill their top-down regulatory role in contaminated ecosystems.
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Research Interests: Evolutionary Biology, Zoology, Geography, Sexual Selection, Life history, and 15 moreEcology, Multidisciplinary, Case Study, Animals, Male, Regression Analysis, tESTIS, Latitudinal Gradient, Environmental Conditions, Body Mass, Directional Asymmetry, Naturwissenschaften, Resource Availability, Rana temporaria, and Cold climate
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Amphibians are globally threatened, but not all species are affected equally by different threatening processes. This is true for the threat posed by the chytridiomycete fungus (Batrachochytrium dendrobatidis). We compiled a European data... more
Amphibians are globally threatened, but not all species are affected equally by different threatening processes. This is true for the threat posed by the chytridiomycete fungus (Batrachochytrium dendrobatidis). We compiled a European data set for B. dendrobatidis to analyze the trends of infection in European amphibians. The risk of infection was not randomly distributed geographically or taxonomically across Europe. Within countries with different prevalence, infection was nonrandom in certain amphibian taxa. Brown frogs of the genus Rana were unlikely to be infected, whereas frogs in the families Alytidae and Bombinatoridae were significantly more likely to be infected than predicted by chance. Frogs in the 2 families susceptible to B. dendrobatidis should form the core of attempts to develop spatial surveillance studies of chytridiomycosis in Europe. Ideally, surveys for B. dendrobatidis should be augmented by sampling the widespread genus Pelophylax because this taxon exhibits geographically inconsistent overinfection with B. dendrobatidis and surveillance of it may facilitate recognition of factors causing spatial variability of infection intensity. Several European amphibian taxa were not represented in our data set; however, surveillance of unsampled species should also occur when warranted.