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Stuttgart, Germany

Aparicio A.,University of Marburg | Berens D.G.,University of Marburg | Muller J.,National Park Bavarian Forest | Farwig N.,University of Marburg
Acta Oecologica

Geographic variation in the diversity, abundance or composition of plant and frugivore assemblages may have consequences for seed dispersal processes. Such variations may be related to climatic conditions as well as habitat characteristics such as fruit availability and forest complexity. Studying frugivore assemblages and seed dispersal processes along an elevational gradient can help to elucidate the interplay between the extent of dispersal services provided by frugivores and the geographic variability of the food resources. We studied frugivore assemblages on and fruit removal from 28 rowan trees (Sorbus aucuparia) along an elevational gradient in the Bavarian Forest, Germany. Both, the number of frugivore species and the number of frugivore individuals were significantly enhanced by high fruit availability. In both cases we found a slight interaction between elevation and fruit availability indicating a higher attractiveness of fruits for frugivores at lower than at higher elevations. A high number of frugivore individuals in turn significantly increased fruit removal from rowan trees. Here, we found a significant interaction between elevation and the number of frugivore individuals suggesting that the number of frugivores is of major importance for fruit removal particularly at lower elevations. Path analysis corroborated that the number of frugivore individuals indirectly mediated the effect of fruit availability on fruit removal. These findings suggest that fruit removal is rather influenced by changes in habitat characteristics than in climatic conditions across space. © 2013 Elsevier Masson SAS. Source

Tidiere M.,University of Lyon | Gaillard J.-M.,University of Lyon | Gaillard J.-M.,University of Zurich | Muller D.W.H.,University Claude Bernard Lyon 1 | And 5 more authors.
Experimental Gerontology

Patterns of actuarial senescence vary among long-lived species. A proposed explanation of the evolution of species-specific senescence patterns is that increased levels of energy allocation to intra-male competition decrease the amount of energy available for somatic maintenance, leading to earlier or faster actuarial senescence. Previous studies did not provide support for such relationships, but did not focus on the intensity of allocation likely to shape inter-specific variation in actuarial senescence in males. Here, by analyzing data from 56 species of captive large herbivores, we tested whether actuarial senescence is more pronounced in species displaying a well-defined 'rut' period than in species with year-round reproduction. Using an original quantitative metric of the annual duration of reproductive activity, we demonstrated that the length of the mating season has no detectable effect on actuarial senescence. On the other hand, both diet and body mass are important factors shaping actuarial senescence patterns in male captive herbivores. © 2014 Elsevier Inc. Source

Clauss M.,University of Zurich | Steuer P.,University of Bonn | Muller D.W.H.,National Park Bavarian Forest | Codron D.,University of Zurich | And 3 more authors.

Digestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differentiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM. © 2013 Clauss et al. Source

Muller J.,National Park Bavarian Forest | Muller J.,TU Munich | Bassler C.,National Park Bavarian Forest | Essbauer S.,University of Federal Defense Munich | And 5 more authors.
Journal of Biogeography

Aim: We assessed the phenotypic responses of body size and organ weights of two small rodent species (Myodes glareolus and Apodemus flavicollis) to elevation, a surrogate for temperature and other environmental conditions. We expected not only an increase in body size (Bergmann's rule), but also an increase in relative heart weight with increasing elevation (Hesse's rule). Location: The Bohemian Forest, south-eastern Germany. Methods: We measured body length, body mass, and mass of the heart, lung, liver, kidneys and spleen of 386 adult specimens (188 of A flavicollis and 198 of M. glareolus) from 28 localities at 300-1450 m a.s.l., and also recorded the number of ectoparasites. We analysed body length using linear mixed models, with site as a random factor and species, sex, population density and elevation as fixed factors, and included all two-way interactions between species and the remaining fixed variables. For the organ masses, we included body length and body mass in the calculations to account for allometric variation of organ mass with body size. For a subset of individuals, we sequenced the mitochondrial D-loop to analyse genetic variation along the elevational gradient. Results: For both species, we found no support for Bergmann's rule. The body size of A. flavicollis even decreased with elevation. In contrast, the relative heart weight of both species significantly increased with elevation, thereby supporting Hesse's rule. Lung mass also increased with elevation. The mass of other internal organs showed no such consistent relationship with elevation. Neither species showed genetic differentiation across the elevational gradient. Main conclusions: Our results suggest that both rodent species respond to increasing elevation by decreasing overall energy expenditure and by increasing overall aerobic capacity. In the context of climate change, our results indicate that biogeographers should pay more attention to the potential significance of genetic and/or phenotypic plasticity of relative organ mass to environmental heterogeneity. © 2014 John Wiley & Sons Ltd. Source

Lehnert L.W.,University of Marburg | Bassler C.,National Park Bavarian Forest | Brandl R.,University of Marburg | Burton P.J.,University of Northern British Columbia | And 2 more authors.
Journal for Nature Conservation

Heavy natural disturbance in large protected areas of former commercial forests increasingly evokes European parliaments to call for management intervention because a loss of habitats and species is feared. In contrast, natural early successional habitats have recently been recognised as important for conservation. Current knowledge in this field mostly results from studies dealing only with selected taxa. Here we analyse the success of species across 24 lineages of three kingdoms in the Bavarian Forest National Park (Germany) after 15 years of a European spruce bark beetle (Ips typographus L.) outbreak that led to rapid canopy opening. Using indicator species analysis, we found 257 species with a significant preference for open forests and 149 species with a preference for closed forests, but only 82 species with a preference for the stand conditions transitional between open and closed forests. The large number of species with a preference for open forests across lineages supports the role of this bark beetle as a keystone species for a broad array of species. The slowdown of the outbreak after 15 years in the core zone of the national park resulted in less than half of the area being affected, due to variability in stand ages and tree species mixtures. Our case study is representative of the tree species composition and size of many large protected montane areas in Central European countries and illustrates that (1) natural disturbances increase biodiversity in formerly managed forests and (2) a montane protected area spanning 10,000. ha of low range mountains is likely sufficient to allow natural disturbances without a biased loss of closed-forest species. © 2012 Elsevier GmbH. Source

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