Start Key Amplexicaulia Hieracium Vulgata Tridentata Sabauda Hieracioides Ecology Literature
Hieracium, a difficult genus
Hieracium, hawkweeds in English, is a notoriously difficult genus. The determination proves to be diffucult, and time and again, even the large groups seem difficult to separate even for trained botanists. This website, which replaces a Dutch website at Hieracium.stellaria.nl, is intended as an overview of the state of research on Hieracium in the Netherlands. We want to present the diversity of species, and provide an aid to the determination of the sections and species. Moreover, we would like to help those interested in the determination, ecology and conservation of hawkweeds with links to the literature available on the internet.
An estimated 100 hawkweed species can be found in the Netherlands, belonging to five sections. The major part of these species are apomictic: like for instance brambles (Rubus) and dandelions (Taraxacum) they propagate asexually through seeds. These develop without fertilisation of the eggcell by pollen, so the daughters have the same genetic material as their mother; they form true lines which differ only slightly amongst each other.
Hieracium research in the Netherlands
The most famous Dutchman who studied Hieracium systematically, was Johannes Leendert van Soest (1898-1983). He published a revision of the genus almost a century ago in a four volume series of papers in the 'Nederlandsch Kruidkundig Archief' (Van Soest 1926-1929). He was assisted by the internationally recognised Hieracium specialist Karl-Hermann Zahn from Karlsruhe, who identified material from the herberium of the Dutch Botanical Society for Van Soest. Zahn, and consequently Van Soest too, applied the taxonomy of the Central European school, and the apomictic lineages are presented by them as subspecies (or lower taxonomical levels). In the published papers, numerous new taxa are described. After Van Soest shifted his interest to Taraxacum, no serious taxonomical studies are undertaken to clarify the diversity of hawkweeds in the Nehterlands.
In response to a paper about apomicts in Stratiotes by one of us (Haveman et al. 2002) Eddy Weeda argued for a renewed study of Hieracium, which in the first years mainly consisted of combined taxonomical-phytosociological excursions of the 'Plantensociologische Kring Nederland' (Phytosociological Society of the Netherlands). Much herbarium material was colleced, and herbarium material was studied, after about 2008 by the both of us. At these pages, we want to present the state of research and a detailed account of the Hieracium species that occur in the Netherlands, or are mentioned in earlier studies. We will do so in line with the Nordic school of hieraciology: the apomictic lines are described at species level, and they are grouped in informal aggregates and more formal sections. The aggregates are 'loose' groups of species which have certain characters in common: they are inserted between the apomictic species and the sections to accomodate the level of principal and intermediate species of the Central European school, in order to find a way to make the communication between the two schools a little easier. At these pages all apomictic lines are treates as species for convenience (!), even if the taxon is not (yet) described at species level and only subspecific names are available. A more formal treatment would cause a immense confusing, cluttered presentation with more or less equivalent taxa at species, subspecies, variety or even forma level, and this would hinder a clear presentation. Of course we will also mention the valid name in all cases.
In taxonomy, these apomictic lineages are treated in quite different ways (zie for instance Haveman 2013, and Haveman & De Ronde 2014). In the Central European school of hieraciology, a limited number of principal and intermediate species are distinguished, with numerous subspecies, varieties, and formae. The apomictic lineages are accomodated at the subspecific level. In the Nordic school all (alleged) apomictic lineages are considered as species, which are grouped in sections. The entities in the two schools are difficult to compare, because there are no 1-to-1 relations between the levels in both systems. At this website we try to bridge the gap between the two methods by the application of pragmatic levels between the formal levels. Throughout, we follow the Nordic school, as is usual in Rubus and Taraxacum taxonomy in the Netherlands nowadays.
Apart from this homepage these pages will be in Dutch, initially. The information will be disclosed via the key you can find at the next page: it gives entrance to the information about the sections, and via the sections also about the species. Another way to consult the pages is through the menu at the top of this page. Important references can be consulted at the literature page, where many papers and other references can be downloaded. As soon as new research results or literatur becomes available, it will be disclosed through this page.