Taraxacum officinale agg., Dandelion

Account Summary

Although Dandelions are unmistakable with their smooth, hollow, milky sap-filled, leafless scape, bearing a large, solitary inflorescence-head and they are amongst the most familiar and most ubiquitous of all wildflowers, paradoxically they are also one of the most difficult 'critical' groups of plants to properly identify. This is due to their essentially non-sexual means of short-circuiting seed production (ie apomixis), which results in the creation, maintenance and survival of a multitude of more or less slightly differing forms or 'microspecies'. As Richards (2021, p. 5) points out, "Sexual reproduction in Dandelions, if it occurs at all, is very rare in our islands.". Also, seed that is produced asexually by apomixis, results in seedlings that usually are exact copies of their mother plant. Thus Dandelion populations represent, "a number of genetically invariable mother-daughter lines, which can be thought of as 'seed-clones'. Each of these lines, at least in theory, can be recognised as a species [or 'microspecies'].". Also, "Most [Dandelion species, microspecies or 'lines'], seem to have been formed from hybridisation between genetically distant parents, so that they are fixed heterozygotes for many genes, a feature which tends to give them a measure of 'hybrid vigour'." (Hughes & Richards 1988).

As Richards (2021) has observed, "while Dandelion lines ('species') can generate a small amount of genetic variability,…..for all practical purposes the lines are invariable.". Also, "If the species [ie microspecies] are genetically invariable lines, they might not differ by very much, but they should differ consistently. Sadly, this is far from the case. Dandelions are amongst the most plastic of all plants, the same clone being able to produce amazingly different phenotypes at different ages and times of year, in different soils and under different amounts of moisture stress, shade, grazing etc." (Richards 2021, pp. 6-7). These facts give rise to the range of variation that bedevils the process of making correct identifications. Richards (2021) fully recognises these difficulties, and he advises, "…it is usually only possible to identify material accurately for a short part of the year (in late bud and early flower) and when well grown (but not too well, as in the dreaded 'cowpat-forms'). Plants collected out of season or from grazed, mown, shaded or manured sites can rarely be identified successfully.".

While it might be imagined that this apomictic process could or should create an infinite number of asexual lines that become genetically 'fixed' and described as microspecies, in practice this is not the case since natural selection works on asexual plants just as it does on sexual phenotypes. Thus many less 'fit' potential microspecies genetic lines have not survived competition and have died out (Richards 2021). In Britain and Ireland, the count of microspecies in 2021 reached 239, of which 100 are probably accidental alien introductions and around 40 of the total are considered endemic (T.D. Dines, in: Preston et al. 2002; Richards 2021). Also, Richards (2021) has estimated that around 150 Taraxacum species are native to B & I, but because wind-blown Dandelion seed spreads easily, continental Europe is in close proximity, plus the readiness of the plants to prosper in man-made environments, there is a regular invasion of continental species. Taraxacum seed is very mobile and is readily imported accidently in grass seed, animal feed, on vehicles and on clothing. In many cases, these imports do not persist for long (Richards 2021, p. 9). This multitude of forms requires detailed study to separate and name them, very frequently (or always) requiring subsequent expert verification. In view of this, it is no surprise that the BSBI Atlas 2000 survey that led to the publication of the New Atlas, does not map any of them.

The sixth edition (1977) of Prof David Webb's An Irish Flora, which we (the current author (RSF) and RHN), used for the vast bulk of their field recording, did not treat dandelion variation at all well. Furthermore, publication of the excellent Dandelions of Great Britain and Ireland. BSBI Handbook No. 9 (Dandelion Handbook) (Dudman & Richards 1997) came too late for the bulk of the Fermanagh flora survey. We have, therefore, not yet mutated to become competent Taraxacum specialists or 'taraxacologists', and the Fermanagh dandelions are almost virgin territory for anyone wanting to research this plant group. Thus, apart from periodic forays by P. Hackney from Belfast, this 'species aggregate' still awaits critical study and disassembly into the multitude of apomictic microspecies it undoubtedly contains.

This is the reason why the recording survey for The Flora of County Fermanagh has accumulated well over a thousand records of this species aggregate from 481 Fermanagh tetrads, representing 91.1% of the VC tetrad total. We have no religious, sectarian or ideological bias against taraxacology, or against any of its practitioners. To date we simply have not had the time to devote to the proper study of the subject and therefore invite those interested, from any part of the world, to visit Fermanagh, where they may add to the meagre knowledge of this plant group on this island. Paul Hackney, the now retired botanical curator at the Ulster Museum, has been recording dandelion segregates in Ulster for many years and all his records of the Taraxacum sections and microspecies listed below have been verified by the BSBI Referee for the group, Prof John Richards. Only a brief examination of the maps in the 1997 Dandelions of Great Britain and Ireland handbook, or the 2021 Field handbook to British and Irish Dandelions is required to appreciate how poor our knowledge is of Irish Taraxacum microspecies, their occurrence, frequency and distribution in comparison with the situation in Britain. Undoubtedly recording has improved in the 25 years between these two BSBI published handbooks, and the advent of digital photography of live specimens taken in the field or shortly after collection, and its very extensive incorporation in the latter book, is certain to be exceptionally helpful to all current and potential newly recruited Dandelion field recorders. However, at present, the map inspection and comparison continues to provide one of the clearest demonstrations of the difference in plant recorder density between the two islands.

It is when the flora of an area has been thoroughly worked, that field recorders seem to turn to critical groups like the Dandelion microspecies in order to 'make their mark'. This situation has not yet arisen anywhere in Ireland, due to the genuine scarcity of active field recorders and the relatively under-worked botanical status of most areas of the country. In Britain, somewhere between 80 to 100 interested botanical recorders have made possible the knowledge of Taraxacum occurrence and distribution that is recorded in publications such as the BSBI Dandelions of Great Britain and Ireland handbook (Dudman & Richards (1997) and the Field handbook to British and Irish Dandelions (Richards 2021). As an indication of just how few published Dandelion experts there are in Europe, the number of authors' names listed in the references in the latter text total a mere 51 individuals, including many that date from the pre-1930s, and one reference that stretches back to 1798. Nowadays, the online BSBI website supplies Dandelion identification keys and a dedicated Dandelion webpage, and there are several associated social media groups devoted to Dandelion identification, all of which represent modern innovations that are bound to help involve and encourage more recorders and should assist and enable them to make their own local mark on the subject, and become 'taraxacologists' (Richards 2021).

Dandelions as an aggregate species are perennial, rosette-forming, hemi-cryptophytes, with a long, stout taproot. They are common in all but aquatic or strongly acidic bog habitats and they are particularly frequent in all forms of disturbed soil, waste ground and especially so on rubble, where the deeply penetrating taproot can reach down to underlying mineral soil (Grime et al. 1988, 2007). Dandelions are all too familiar as tenacious and prolific garden weeds and they seem extremely well adapted to take advantage of human disturbance along roads and paths and on any neglected or waste ground in the countryside. Although they are preferentially grazed by herbivores, Dandelions are tolerant of this pressure and they also cope well with regular trampling in pastures, lawns and paths. This resilience is in part due to possession of contractile roots that protect the apical growing point by keeping it 10-20 mm below the soil surface (Sterk et al. 1983).

Despite the mentioned tolerances, in general dandelions are poor plant competitors and they are chiefly colonisers of bare soil, associated with a degree of habitat disturbance, or with naturally open situations, such as cliffs, fens and flushes on bogs (Dandelion Handbook). Plants begin their vegetative growth as early as February and they flower almost all year round, although with a definite peak in April and May. These features appear to confer at least a temporary competitive advantage over accompanying grasses and other herbs in grassland vegetation.

Unless otherwise stated, all of the following Taraxacum records and voucher collections were made by P. Hackney on a visit to Fermanagh from 27-30 March 1975.

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