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71 results on '"Holderegger, Rolf"'

6. Factors determining bryophyte species richness and community composition on insular siliceous erratic boulders in calcareous landscapes

Author

Hepenstrick, Daniel, Bergamini, Ariel, Webster, Clare, Ginzler, Christian, Holderegger, Rolf, Hepenstrick, Daniel, Bergamini, Ariel, Webster, Clare, Ginzler, Christian, and Holderegger, Rolf

Abstract

Aim: Pleistocene erratic boulders are rocks that were relocated by glaciers during the Ice Ages. When their geology differs from the geology of the landscape that surrounds them, erratic boulders form habitat islands for regionally rare, edaphically specialised, rock-dwelling cryptogams (bryophytes, ferns and lichens). Such boulders constitute terrestrial model systems for exploring island biogeographic predictions and the effect of environmental variables on species diversity and community composition, which we studied in order to provide basic knowledge of the ecology, with relevance for the conservation, of these unusual island systems. Location: Siliceous erratic boulders in the calcareous Swiss Plateau and Jura Mountains. Methods: For 160 erratic boulders we recorded all bryophyte species and a diverse set of environmental variables. For all species and for specialist species (acidophile rock-dwellers) separately, we analysed species-area relationships and nestedness, and explored relationships between environmental variables, species diversity and community composition. Results: We found 138 bryophyte species, 19 of which were specialists of erratic boulders. A steeper species-area curve for boulder specialists than for total species richness underlined the island properties of boulders for specialist species. Large boulders were more likely to harbour numerous boulder specialists and communities on small boulders were nested within the communities present on large boulders. However, at the landscape level small boulders contributed more specialist species than a few large boulders of the same surface area. Erratic boulders near settlements were less likely to harbour boulder specialists. Boulders in open land harboured different and more specialist species than boulders in forests. Conclusions: Large undisturbed erratic boulders in open land harbour rare bryophyte communities with a large number of specialist species. Conservation should thus prioritise this

Published
2022

8. The distribution of climbing chalk on climbed boulders and its impact on rock‐dwelling fern and moss species

Author

Hepenstrick, Daniel, Bergamini, Ariel, Holderegger, Rolf, Hepenstrick, Daniel, Bergamini, Ariel, and Holderegger, Rolf

Abstract

Rock climbing is popular, and the number of climbers rises worldwide. Numerous studies on the impact of climbing on rock-dwelling plants have reported negative effects, which were mainly attributed to mechanical disturbances such as trampling and removal of soil and vegetation. However, climbers also use climbing chalk (magnesium carbonate hydroxide) whose potential chemical effects on rock-dwelling species have not been assessed so far. Climbing chalk is expected to alter the pH and nutrient conditions on rocks, which may affect rock-dwelling organisms. We elucidated two fundamental aspects of climbing chalk. (a) Its distribution along nonoverhanging climbing routes was measured on regularly spaced raster points on gneiss boulders used for bouldering (ropeless climbing at low height). These measurements revealed elevated climbing chalk levels even on 65% of sampling points without any visual traces of climbing chalk. (b) The impact of climbing chalk on rock-dwelling plants was assessed with four fern and four moss species in an experimental setup in a climate chamber. The experiment showed significant negative, though varied effects of elevated climbing chalk concentrations on the germination and survival of both ferns and mosses. The study thus suggests that along climbing routes, elevated climbing chalk concentration can occur even were no chalk traces are visible and that climbing chalk can have negative impacts on rock-dwelling organisms.

Published
2021

13. Conservation genetics: Linking science with practice

Author

Holderegger, Rolf, primary, Balkenhol, Niko, additional, Bolliger, Janine, additional, Engler, Jan O., additional, Gugerli, Felix, additional, Hochkirch, Axel, additional, Nowak, Carsten, additional, Segelbacher, Gernot, additional, Widmer, Alex, additional, and Zachos, Frank E., additional

Published
2019
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15. Trait differentiation and adaptation of plants along elevation gradients

Author

Halbritter, Aud H., Fior, Simone, Keller, Irene, Billeter, Regula, Edwards, Peter J., Holderegger, Rolf, Karrenberg, Sophie, Pluess, Andrea R., Widmer, Alex, Alexander, Jake M., Halbritter, Aud H., Fior, Simone, Keller, Irene, Billeter, Regula, Edwards, Peter J., Holderegger, Rolf, Karrenberg, Sophie, Pluess, Andrea R., Widmer, Alex, and Alexander, Jake M.

Abstract

Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta-analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genome-wide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.

Published
2018

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