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Apeldoorn, Netherlands

Haveman R.,Dienst Vastgoed Defensie
Nordic Journal of Botany | Year: 2013

Apomict groups keep challenging taxonomists, in classifications as well as in more fundamental question about the nature of apomictic species. The latter question is not just an academic one, because the outcome influences practical decisions on biodiversity and conservation. A historical overview over the species problem shows that a period of confusion and proliferation of species concepts between 1940 and 1990 was followed by an increasing consensus at the end of the 20th century that the species category is heterogeneous. Species come in kinds, which is understandable in light of their different evolutional histories. Recently, Wilkins stated that we do not need a generally applicable species concept, because species are not an a priori category into which all biological organisms must fit, but salient phenomena that are to be explained. Not only biparental, but also asexual organisms often form such species-as-phenomena, explained as some combination of adaptation to an ecological niche and reproductive compatibility. The above is illustrated by historical and current studies in three well-studied apomict groups, viz. Ranunculus cassubicus agg., Rubus subgen. Rubus and Hieracium (subgen. Hieracium and Pilosella). Species in the Ranunculus cassubicus aggregate are the few existing sexuals, which are surrounded by a hybrid swarm of only partial apomictic forms, whereas in Rubus subgen. Rubus and Hieracium s.s. sexuals as well as numerous apomicts form well defined species. How species should be circumscribed in Pilosella is yet to be clarified. Largely, the differences between these groups can be contributed to their different modes of apomixis and the associated retained sexuality. From this review it is clear that the question is not so much 'What is a species?', but 'What is a species in this particular group?' To answer this question a thorough knowledge and understanding of the biology of the genus in question is required. © 2013 The Authors.

Haveman R.,Dienst Vastgoed Defensie
Nordic Journal of Botany | Year: 2013

After a short sketch of Dutch hieraciology, three taxa belonging to Hieracium sectt. Vulgata and Tridentata that were described from the Netherlands at the rank of subspecies or variety by Zahn are typified and raised to species rank. Hieracium meppelense (Zahn) Haveman comb. et stat nov. is found in the province of Drenthe in the northeastern part of the country, H. limburgense (Zahn) Haveman comb. et stat nov. in south-Limburg in the southernmost part and H. macrodontophyllum (Van Soest et Zahn) Haveman comb. et stat nov. in the surroundings of Nijmegen and Arnhem, and further north in the central sand area. Photographs of the types as well as maps with the hitherto known distribution of these three species are included. © 2013 The Authors.

Mucher C.A.,Wageningen University | Kooistra L.,Wageningen University | Vermeulen M.,Wageningen University | Borre J.V.,Research Institute for Nature and Forest INBO | And 2 more authors.
Ecological Indicators | Year: 2013

Monitoring of habitat types protected under the Annex I of the EU Habitats Directive requires every 6 years information to be reported on their conservation status (area, range, structure and function) in the member states. Hyperspectral imagery can be an important source of information to assist in the evaluation of the habitats' conservation status, as it can provide continuous maps of habitat quality indicators (e.g., life forms, management activities, grass, shrub and tree encroachment) at the pixel level. Such local level information is highly needed for management purposes, e.g., the location of habitat patches and their sizes and quality within a protected site. This paper focuses on the use of continuous fraction images as derived from spectral mixture analysis of hyperspectral imagery (AHS-160), in combination with segmentation techniques, to facilitate habitat quality assessment in a heathland site in the Netherlands. This combined application of techniques on hyperspectral imagery demonstrates the usefulness of information from continuous fraction maps of grass abundance (Molinia caerulea) in heathlands - at and within the patch level - compared to traditional mapping techniques that assess grass encroachment in a limited number of abundance classes at the patch level. It therefore provides a better basis to monitor large areas for processes such as grass encroachment that largely determine the conservation status of Natura 2000 heathland areas. Timely, accurate and up-to-date spatial information on the encroachment of mosses, grasses, shrubs or trees (dominant species) can help conservation managers to take better decisions and to better evaluate the effect of taken measures. While discrepancies exist between the results of field-based vegetation surveys and the proposed remote sensing approach, we provide a discussion on the uncertainty of determining which of both methods is most accurate in relation to dominant species, which is in our case Molinia caerulea, and set forth several reasons why the remote sensing based approach might form a better basis for the monitoring of abundant species and patch evolution through time. © 2012 Elsevier Ltd. All rights reserved.

Ficetola G.F.,University of Milan Bicocca | Bonardi A.,University of Milan Bicocca | Mucher C.A.,Wageningen University | Gilissen N.L.M.,Dienst Vastgoed Defensie | Padoa-Schioppa E.,University of Milan Bicocca
International Journal of Geographical Information Science | Year: 2014

At the local spatial scale, land-use variables are often employed as predictors for ecological niche models (ENMs). Remote sensing can provide additional synoptic information describing vegetation structure in detail. However, there is limited knowledge on which environmental variables and how many of them should be used to calibrate ENMs. We used an information-theoretic approach to compare the performance of ENMs using different sets of predictors: (1) a full set of land-cover variables (seven, obtained from the LGN6 Dutch National Land Use Database); (2) a reduced set of land-cover variables (three); (3) remotely sensed laser data optimized to measure vegetation structure and canopy height (LiDAR, light detection and ranging); and (4) combinations of land cover and LiDAR. ENMs were built for a set of bird species in the Veluwe Natura 2000 site (the Netherlands); for each species, 26-214 records were available from standardized monitoring. Models were built using MaxEnt, and the best performing models were identified using the Akaike's information criterion corrected for small sample size (AICc). For 78% of the bird species analysed, LiDAR data were included in the best AICc model. The model including LiDAR only was the best performing one in most cases, followed by the model including a reduced set of land-use variables. Models including many land-use variables tended to have limited support. The number of variables included in the best model increased for species with more presence records. For all species with 33 records or less, the best model included LiDAR only. Models with many land-use variables were only selected for species with >150 records. Test area under the curve (AUC) scores ranged between 0.72 and 0.92. Remote sensing data can thus provide regional information useful for modelling at the local and landscape scale, particularly when presence records are limited. ENMs can be optimized through the selection of the number and identity of environmental predictors. Few variables can be sufficient if presence records are limited in number. Synoptic remote sensing data provide a good measure of vegetation structure and may allow a better representation of the available habitat, being extremely useful in this case. Conversely, a larger number of predictors, including land-use variables, can be useful if a large number of presence records are available. © 2014 © 2014 Taylor & Francis.

Haveman R.,Dienst Vastgoed Defensie
Gorteria: Tijdschrift voor Onderzoek aan de Wilde Flora | Year: 2012

Hieracium L. (Hawkweed) is one of the most diverse and challenging genera in the Dutch flora. Historically, two systems were developed to address variation within Hieracium subgen. Hieracium: recognition of numerous subspecies, varieties, and forms with the help of 'Hauptarten' and 'Zwischenarten' (Central-European system), and grouping in sections and series of every apomictic progenitive unit as a separate species (North-European system). The Central-European system has been used in the Netherlands since Van Soest introduced it in the 1920s and 1930s. The taxa in the recent Heukels' Flora6 are the 'Hauptarten' as recognised by Van Soest and they correspond well with the sections of the North-European system. Because Hieracium species are frequently misidentified, this paper presents a new key to the sections of Hieracium subgen. Hieracium. In addition, an overview is provided of the sections of Hieracium subgen. Hieracium in the Netherlands, including the number of species in each sections.

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