Portail documentaire

Factors determining bryophyte species richness and community composition on insular siliceous erratic boulders in calcareous landscapes / Daniel Hepenstrick in Journal of vegetation science, 32 (2021) 

Public Citation [article]  inJournal of vegetation science > 32 (2021) . - 1-15 Titre : Factors determining bryophyte species richness and community composition on insular siliceous erratic boulders in calcareous landscapes Type de document : Imprimé Auteurs : Daniel Hepenstrick ; Ariel Bergamini ; Clare Webster ; Christian Ginzler ; Rolf Holderegger (1965-) Année de publication : 2021 Article en page(s) : 1-15 Langues : Français (fre) Catégories : [CBNPMP-Thématique] Bryophytes Résumé : 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 type of boulders. Furthermore, conserving large boulders is logistically easier, and they may function as flagships for small boulders that also contribute to the biodiversity within landscapes. Lien pérenne : DOI : 10.1111/jvs.13094 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=147555 Hepenstrick, Daniel, Bergamini, Ariel, Webster, Clare, Ginzler, Christian, Holderegger, Rolf (1965-) 2021 Factors determining bryophyte species richness and community composition on insular siliceous erratic boulders in calcareous landscapes. Journal of vegetation science, 32: 1-15.

Documents numériques

Consultable Article (2021) URL

Overcoming limitations of modelling rare species by using ensembles of smallmodels / Frank T. Breiner in Methods in ecology and evolution, 6 (2015) 

Public Citation [article]  inMethods in ecology and evolution > 6 (2015) Titre : Overcoming limitations of modelling rare species by using ensembles of smallmodels Type de document : Imprimé Auteurs : Frank T. Breiner ; Antoine Guisan (1966-) ; Ariel Bergamini ; Michael P. Nobis Année de publication : 2015 Langues : Anglais (eng) Catégories : [CBNPMP-Thématique] Messicole Note de contenu : 1- Species distribution models (SDMs) have become a standard tool in ecology and applied conservation biology. Modelling rare and threatened species is particularly important for conservation purposes. However, modelling rare species is difficult because the combination of few occurrences and many predictor variables easily leads to model overfitting. A new strategy using ensembles of small models was recently developed in an attempt to overcome this limitation of rare species modelling and has been tested successfully for only a single species so far. Here, we aim to test the approach more comprehensively on a large number of species including a transferability assessment. 2- For each species, numerous small (here bivariate) models were calibrated, evaluated and averaged to an ensemble weighted by AUC scores. These ‘ensembles of small models’ (ESMs) were compared to standard SDMs using three commonly used modelling techniques (GLM, GBM and Maxent) and their ensemble prediction. We tested 107 rare and under-sampled plant species of conservation concern in Switzerland. 3- We show that ESMs performed significantly better than standard SDMs. The rarer the species, the more pronounced the effects were. ESMs were also superior to standard SDMs and their ensemble when they were evaluated using a transferability assessment. 4- By averaging simple small models to an ensemble, ESMs avoid overfitting without losing explanatory power through reducing the number of predictor variables. They further improve the reliability of species distribution models, especially for rare species, and thus help to overcome limitations of modelling rare species. Lien pérenne : DOI : 10.1111/2041-210X.12403 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=148446 Breiner, Frank T., Guisan, Antoine (1966-), Bergamini, Ariel, Nobis, Michael P. 2015 Overcoming limitations of modelling rare species by using ensembles of smallmodels. Methods in ecology and evolution, 6.

Documents numériques

Consultable Article (2015) URL