Fribourg, Switzerland
Fribourg, Switzerland

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Fragniere Y.,Natural History Museum Fribourg | Betrisey S.,University of Fribourg | Cardinaux L.,Natural History Museum Fribourg | Stoffel M.,University of Bern | And 3 more authors.
Journal of Biogeography | Year: 2015

Aim: Gymnosperms are often described as a marginal and threatened group, members of which tend to be out-competed by angiosperms and which therefore preferentially persist at higher latitudes and elevations. The aim of our synthesis was to test these statements by investigating the global latitudinal and elevational distribution of gymnosperms, as well as their conservation status, using all extant gymnosperm groups (cycads, gnetophytes, ginkgophytes and conifers). Location: Worldwide. Methods: We developed a database of 1014 species of gymnosperms containing latitudinal and elevational distribution data, as well as their global conservation status, as described in the literature. The 1014 species comprised 305 cycads, 101 gnetophytes, the only living representative of ginkgophytes, and 607 conifers. Generalized additive models, frequency histograms, kernel density estimations and distribution maps based on Takhtajan's floristic regions were used. Results: Although the diversity of gymnosperms decreases at equatorial latitudes, approximately 50% of the extant species occur primarily between the tropics. More than 43% of gymnosperms can occur at very low elevations (≤ 200 m a.s.l.). Gymnosperms, considering all species together as well as their main taxonomic groups separately, do not exhibit a latitudinal diversity gradient as commonly observed for many other taxa. Gymnosperms, and especially conifers, are on average less threatened at higher and equatorial latitudes. Main conclusions: Gymnosperms display an unusual latitudinal diversity gradient, which we suggest cannot fully be accounted for by angiosperm dominance and competitive superiority. We hypothesize that other factors explain their present distribution, such as the development of centres of endemism in several regions and the adaptation of certain taxa to cold and arid climates. © 2015 John Wiley & Sons Ltd.

Kozlowski G.,Natural History Museum Fribourg | Kozlowski G.,University of Fribourg | Stoffel M.,University of Bern | Stoffel M.,University of Geneva | And 3 more authors.
Ecohydrology | Year: 2015

According to the classical textbooks, the gymnosperms are the only seed plants without aquatic species. Recently, however, a set of virtually complete compilations on gymnosperms has been published, enabling a new evaluation of the putative hydrophobia of gymnosperms. This synthesis aims at portraying the relation of all extant gymnosperm species to aquatic and wetland habitats. We present a database of all 986 extant gymnosperm species with their ecological characteristics including 291 cycads, 80 gnetophytes, one ginkgophyte and 614 conifers. We define four categories reflecting the level of hydrophobia and hydrophily of all species and their possible adaptation to wetlands and/or aquatic habitats. Eighty-two percent (805) of the extant species of gymnosperms are clearly hydrophobic, but 18% (180) are classified as hydrophilic. The podocarp Retrophyllum minus is the only obligate inhabitant of aquatic habitats. This contribution classifies gymnosperms into four categories in reference to their physiological and morphological adaptation to a moisture gradient. It relativizes the putative hydrophobia of gymnosperms and provides new perspectives for research on gymnosperms. © 2014 John Wiley & Sons, Ltd.

Kozlowski G.,Natural History Museum Fribourg | Kozlowski G.,University of Fribourg | Bondallaz L.,University of Fribourg
Urban Ecosystems | Year: 2013

Urban areas are among the most affected by human activities. In Europe, urbanization has essentially occurred since the end of the 19th century. However, the influence of this dramatic process on aquatic ecosystems has rarely been quantified and analyzed using historical data. In this study, we investigate the evolution of the hydrological system and native aquatic macrophytes in urban areas between the end of the 19th century and the beginning of the 21st century. Four urban areas in Switzerland were chosen for the analyses, Zürich, Basel, Lausanne and Fribourg, and we analyzed the changes in aquatic plant diversity based on the historical and recent floristic data available for the same areas and the same time periods. Our results show that a significant proportion (∼30 %) of aquatic habitats has disappeared from the investigated locales during the last 130 years and that the extinction rate of the aquatic plant species is notably higher in the studied cities (28 %) than in Switzerland as a whole (2 %). Thus, between the end of the 19th and the beginning of the 21st centuries, urban development in Swiss cities has prompted a degradation of aquatic habitats that resulted in a significant reduction of the aquatic biodiversity. However, our study shows that urban areas still have the capacity to shelter a large diversity of aquatic organisms, including some of the most threatened species. Thus, it is important to integrate urban areas in the conservation strategies for these species. © 2012 Springer Science+Business Media New York.

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