Gentianella campestris

Taxonomy 

Seemingly uncontroversial, though there is much taxonomic confusion amongst the rest of the genus in the British Isles. However, some continental botanists (cf. Hultén & Fries 1986) separate our species into subsp. campestris and subsp. baltica, both with very similar ranges and both mapped as occurring here.

 

Accepted name: Gentianella campestris (L.) Börner, Field Gentian.

 

Syn: Gentiana campestris L.

 

Hybrids – none known.

 

Chromosome No.: 2n = 36 (Stace 2010). 

Gentianella campestris

Photograph: K.J. Walker

 

Identification 

Distinguished from all others in the genus by the very unequal calyx lobes – the outer much larger than the inner and enclosing them.

 

Distribution 

Gentianella campestris is widespread in Scotland, in northern England and North Wales, and in north and west Ireland, but now very rare indeed in England south of the Lake District and the adjacent Pennines.

Generally lowland, but reaching 915 m at Cairnwell (E. Perth, S. Aberdeen).

European Boreo-temperate element. It is quite widespread in northern Europe, extending southwards at least to the Alps, but more rare in the Pyrenees and the Picos de Europa.

 

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

 

Ecology 

A biennial, occasionally annual, herb of mildly acidic to neutral, infertile (Ellenberg Value for N = 3), soils in a variety of open habitats, including pastures, hill grassland, grassy heaths, sand dunes, machair and road verges (Preston et al. 2002). The flowers are typically purple but sometimes white (Scott & Palmer 1987).

 

In Cornwall it grows in brown earths over serpentine, in North Hampshire on the junction of the chalk and the Reading beds, and in the New Forest on the Headon clays. On limestone it probably indicates surface leaching or the presence of non-calcareous superficial deposits (Halliday 1997). At least in Cornwall and Hampshire Carex montana grows in the same habitat. In Pembrokeshire it grows in maritime heaths overlaying Jurassic limestones.

 

In NW Scotland it is usually a an acid grassland plant, often growing on machair, fixed dunes and road verges where the drainage is sharp, though it does occur in a variety of other habitats, such as grassy sea-cliffs on granite and gabbro on Rum.

 

It is listed for the following NVC communities, CG1, CG2, CG10, CG14and MC10, but as it rarely occurs in abundance, and it was present in small quantities in a small number of quadrats collected for the NVC, these might not be particularly representative of its habitats.

 

In Local Change (Braithwaite et al. 2004) there is an interesting angle to its ecology, based on its distribution in 2 km squares throughout Britain. They found it to be a component of a calcareous upland vegetation, associated with Selaginella selaginoides. This is one of the more rapidly declining suites of species.

 

Flowers are hermaphrodite, pseudo-cleistogamous and markedly protandrous. Flowering is usually between 7-10 but can be variable especially in dry summers when populations tend to be small (Crawley 2005). The flowers are visited by humble-bees and lepidoptera, sometimes selfed (Clapham et al. 1987). In Scandinavia a decrease in populations and increasing fragmentation may have lead to a reduction in gene flow between populations and a decrease in cross-pollination within populations (Lennartsson & Oostermeijer 2001). Plants are monocarpic and regeneration is exclusively by seed. Seeds germinate in the spring but it is not known whether they have a dormancy mechanism or form a persistent seedbank.

 

Status 

A Vulnerable Red Data List species (Cheffings & Farrell 2005) added to the list of UK Biodiversity Action Plan priority species in 2007; not previously listed as threatened. G. campestris had already suffered a marked decline before 1930, but sites are still being lost through overgrazing in the uplands and the neglect of lowland pastures. In its English stronghold, Cumbria, it has disappeared from half the 10 km squares for which there are post-1930 records. It is now extremely rare in southern England, apart from in the New Forest, where it is stable and even possibly increasing; it has recently been reported from three sites on The Lizard and only one each in E. Cornwall, S. Devon, N. Hampshire, E. Sussex, W. Norfolk, Staffordshire and Derbyshire.

 

It is apparently extinct in many counties including Berkshire and Shropshire. Most of the historical losses must have been from agricultural improvement, though many of the recent losses have arisen from relaxation of grazing and invasion by heather and other shrubs. The extent to which acid grassland and heathland populations have declined as a result of atmospheric pollution is unknown but may account for at least some of the losses in S.E. England. Elsewhere in Britain and Ireland there is only evidence of local losses.

 

It is regarded as in serious decline in Scandinavia with a 90% reduction in the last 50 years (Eriksson & Kiviniemi 1999) and the West German plant atlas (Haupler & Schonfelder 1988) shows very large losses.

 

 

Further Work 

Due to its low stature and lifecycle Gentianella campestris appears unable to persist in closed communities and probably requires frequent (micro) disturbance to create suitable conditions for regeneration (for example, plants are often confined to faint sheep/animal tracks in closed heathland). Research into these microhabitats would make an excellent project and would help us to understand why this species persists on some sites but not on other apparently suitable sites closeby.

 

Why does it appear to be flourishing in the New Forest but not elsewhere in southern Britain?

 

What are the effects of increasing atmospheric deposition of nutrients?

 

Is increasing fragmentation leading to a reduction in gene flow between and within populations?

 

Are these same factors affecting populations in the north and west?

 

What is the status of subsp. balticus?

 

Although it is still frequent in the north, it may be declining within its range - a process that is difficult to detect from 10 km maps. Detailed records collected by the Threatened Plants Project will help to monitor its status in future.

 

References 

  • Clapham, A. R., Tutin, T. G. & Moore, D. M. 1987. Flora of the British Isles, 3rd ed. Cambridge: Cambridge University Press.
  • Crawley, M.J. 2005. The Flora of Berkshire. Brambleby Books, Harpenden
  • Eriksson, O. & Kiviniemi, K. 1999. Site occupancy, recruitment and extinction thresholds in grassland plants: an experimental study. Biological Conservation 87(3):  319-325.
  • Halliday, G. 1997. A Flora of Cumbria. Centre for North-West Regional Studies, University of Lancaster.
  • Haupler, H.  & Schonfelder, P. (eds) (1988). Atlas der Farn- und Blütenpflanzen der Bundersrepublik Deutschland. Stuttgart: Eugen Ulmer.
  • Hultén, E. & Fries, M. 1986. Atlas of north European vascular plants: north of the Tropic of Cancer. 3 vols. Königstein: Koeltz Scientific Books.
  • Lennartsson, T. & Oostermeijer, J.G.B. 2001. Demographic variation and population viability in Gentianella campestris: effects of grassland management and environmental stochasticity. Journal of Ecology 89(3): 451–463.

 

Citation 
Pearman, D.A. (date accessed). Species account: Gentianella campestris. Botanical Society of the British Isles, www.bsbi.org.uk.

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