ORCID Profile
0000-0003-4612-9937
Current Organisation
University of Zurich
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Publisher: Elsevier BV
Date: 08-2007
Publisher: Elsevier BV
Date: 09-02-2006
Publisher: American Society of Plant Taxonomists
Date: 07-2006
DOI: 10.1600/036364406778388629
Abstract: AFLP and morphological data were used to reconstruct the phylogeny of Polylepis (Rosaceae). Results from the morphological analysis correlate well with earlier hypotheses about the evolution of the genus, showing a transition from tall, thin-leaved trees with large inflorescences to small trees with thick leaves and reduced inflorescences. While a basic phylogenetic signal is also discernible in the AFLP analysis, it is partly eclipsed in that s les from different species sometimes cluster according to geographic proximity rather than systematic affiliation. This structure is interpreted as indicative of frequent hybridization and introgression.
Publisher: Elsevier BV
Date: 06-2006
Publisher: American Society of Plant Taxonomists
Date: 03-2009
DOI: 10.1600/036364409787602276
Abstract: Guided by systematic studies on Melpomene , we tested the monophyly of the genus by analyzing sequences of cpDNA ( atpβ , rbcL ) and morphological characters for 24 of the 29 recognized species. The atpβ data did not yield any resolution of the investigated group. The other data sets each supported the monophyly of the genus, as did all data combined, and indicate it to be sister to the Lellingeria apiculata group as proposed in previous studies. While the morphologically distinct M. leptostoma and M. gracilis are basal lineages with long branch lengths, most of the relationships within the core genus are weakly supported and have very short branch lengths. This indicates a recent radiation of the genus in the northern Andes, its center of ersity, apparently under the influence of the fast up lift of the mountain range and of glacial fluctuations of the vegetation zones, with subsequent dispersals to the Guyana Highlands, the Brazilian shield, and Africa.
Publisher: Springer Science and Business Media LLC
Date: 28-06-2007
Publisher: Wiley
Date: 12-2007
Publisher: Elsevier BV
Date: 15-04-2005
Publisher: Proceedings of the National Academy of Sciences
Date: 05-02-2018
Abstract: Identifying and explaining regional differences in tropical forest dynamics, structure, ersity, and composition are critical for anticipating region-specific responses to global environmental change. Floristic classifications are of fundamental importance for these efforts. Here we provide a global tropical forest classification that is explicitly based on community evolutionary similarity, resulting in identification of five major tropical forest regions and their relationships: ( i ) Indo-Pacific, ( ii ) Subtropical, ( iii ) African, ( iv ) American, and ( v ) Dry forests. African and American forests are grouped, reflecting their former western Gondwanan connection, while Indo-Pacific forests range from eastern Africa and Madagascar to Australia and the Pacific. The connection between northern-hemisphere Asian and American forests is confirmed, while Dry forests are identified as a single tropical biome.
Publisher: Wiley
Date: 27-02-2019
DOI: 10.1111/BTP.12633
Publisher: Wiley
Date: 10-10-2018
DOI: 10.1111/GEB.12803
Abstract: Large tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan‐tropical model to predict plot‐level forest structure properties and biomass from only the largest trees. Pan‐tropical. Early 21st century. Woody plants. Using a dataset of 867 plots distributed among 118 sites across the tropics, we tested the prediction of the quadratic mean diameter, basal area, Lorey's height, community wood density and aboveground biomass (AGB) from the i th largest trees. Measuring the largest trees in tropical forests enables unbiased predictions of plot‐ and site‐level forest structure. The 20 largest trees per hectare predicted quadratic mean diameter, basal area, Lorey's height, community wood density and AGB with 12, 16, 4, 4 and 17.7% of relative error, respectively. Most of the remaining error in biomass prediction is driven by differences in the proportion of total biomass held in medium‐sized trees (50–70 cm diameter at breast height), which shows some continental dependency, with American tropical forests presenting the highest proportion of total biomass in these intermediate‐diameter classes relative to other continents. Our approach provides new information on tropical forest structure and can be used to generate accurate field estimates of tropical forest carbon stocks to support the calibration and validation of current and forthcoming space missions. It will reduce the cost of field inventories and contribute to scientific understanding of tropical forest ecosystems and response to climate change.
Publisher: Springer Science and Business Media LLC
Date: 11-08-2016
DOI: 10.1038/SREP31153
Abstract: Land-use change and intensification threaten bee populations worldwide, imperilling pollination services. Global models are needed to better characterise, project, and mitigate bees' responses to these human impacts. The available data are, however, geographically and taxonomically unrepresentative most data are from North America and Western Europe, overrepresenting bumblebees and raising concerns that model results may not be generalizable to other regions and taxa. To assess whether the geographic and taxonomic biases of data could undermine effectiveness of models for conservation policy, we have collated from the published literature a global dataset of bee ersity at sites facing land-use change and intensification, and assess whether bee responses to these pressures vary across 11 regions (Western, Northern, Eastern and Southern Europe North, Central and South America Australia and New Zealand South East Asia Middle and Southern Africa) and between bumblebees and other bees. Our analyses highlight strong regionally-based responses of total abundance, species richness and Simpson's ersity to land use, caused by variation in the sensitivity of species and potentially in the nature of threats. These results suggest that global extrapolation of models based on geographically and taxonomically restricted data may underestimate the true uncertainty, increasing the risk of ecological surprises.
Publisher: Wiley
Date: 30-06-2016
DOI: 10.1111/ELE.12640
Abstract: We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the erse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor - a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon-specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data s led along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness.
Publisher: Springer Science and Business Media LLC
Date: 04-12-2007
Publisher: Elsevier BV
Date: 02-2007
Publisher: American Fern Society
Date: 2001
Publisher: Springer Science and Business Media LLC
Date: 21-02-2013
Publisher: Wiley
Date: 03-2019
DOI: 10.1111/JVS.12710
Publisher: Wiley
Date: 16-02-2010
DOI: 10.1111/J.1438-8677.2009.00297.X
Abstract: The Andean tree genus Polylepis (Rosaceae) is notorious for the high morphological plasticity of its species and the difficulty in their circumscription. The evolutionary mechanisms that have driven ersification of the genus are still poorly understood, with factors as erse as ecological specialisation, reticulate evolution, polyploidisation and apomixis being proposed to contribute. In the present study, chromosome counts, flow cytometry and stomata guard cell size measurements were employed to document for the first time the presence of polyploidy in the genus and to infer ploidy levels for most species. Inferred ploidy levels show a clear progression from diploidy in cloud forest species to polyploidy (tetra- to octoploidy) in the morphologically and ecologically specialised incana group, indicating that polyploidisation may have played a major role in speciation processes and the colonisation of novel habitats during the Andean uplift. At least two species of Polylepis comprise populations with varying degrees of ploidy. More extensive studies are needed to obtain a better understanding of the prevalence and effects of intraspecific polyploidy in the genus.
Publisher: Wiley
Date: 07-2008
DOI: 10.1111/J.1438-8677.2008.00058.X
Abstract: A first comprehensive dataset of nectar sugar composition and concentration in Bromeliaceae is presented, covering 111 species belonging to all three subfamilies. Based on this dataset, we examined the relationship between nectar traits and pollination syndromes in the family. Sugars in s les were assayed by high pressure liquid chromatography. All s led species were grouped into three broad categories (trochilophilous, chiropterophilous, or lepidopterophilous) according to their main pollination mode. Significant differences between the different pollination syndromes were found in nectar sugar composition as well as concentration. For a total of four genera (Guzmania, Pitcairnia, Tillandsia and Vriesea), a comparison of nectar composition showed significant differences between trochilophilous and chiropterophilous species. Data presented here indicate that the characteristics of nectar in Bromeliaceae are predominantly determined by putative adaptations of nectar sugars to preferences of the pollinators rather than by phylogenetic relations.
Publisher: Springer Science and Business Media LLC
Date: 05-08-2020
No related grants have been discovered for Michael Kessler.