Conservation of Britain’s biodiversity: distribution and status of the Welsh endemic Hieracium apheles, Hepste

The conservation status of Hieracium apheles P.D. Sell (Asteraceae), Hepste hawkweed, has been assessed. A lectotype for the basionym H. septentrionale Arv.-Touv. var. simplex Ley has been designated. It is a rare endemic restricted to the Hepste Glen in the Brecon Beacons (v.c.42), Wales. Only one population of five plants is known. It is assessed as ‘Critically Endangered’ under IUCN (2001) threat criteria.


Introduction
Hieracium apheles P.D. Sell (Asteraceae), Hepste hawkweed, is a rare UK endemic restricted to the Brecon Beacons in Wales (Sell & Murrell, 2006;McCosh & Rich, 2018;Rich, 2020). Rich (2010Rich ( , 2011 reviewed information about it for Natural Resources Wales and further field work has been done up to 2013. The aim of this paper is to summarise what is known about it to enable a conservation plan to be drawn up and implemented. Hieracium apheles was first described as a distinct species in Sell & Murrell (2006), though it has had a long history during which it has been allied with several other species.
It was first collected by A. Ley from the Hepste Glen in 1890. Ley (1895a) named it as H. diaphanum var. cacuminum Ley, but cultivated specimens were shortly afterwards distributed through the Botanical Exchange Club in 1894 as H. diaphanum var. stenolepis (Ley, 1895b), with comments from the Swedish expert Elfstrand that it was a variety of H. diaphanum Fr., and from the English expert F.J. Hanbury who thought that it was close to H. euprepes F.J. Hanbury. In 1904 more plants were distributed through the Botanical Exchange Club as H. scoticum F.J. Hanbury on the authority of W.R. Linton (Ley, 1905), and the Linton brothers distributed 1897 specimens with their Set of British hawkweeds (1896 etc.) as no. 166 H. scoticum. Further material was distributed in 1907 (with the locality again cited as the Mellte Glen) with a comment that the name H. scoticum remained doubtful, and that W.R. Linton "does not favour the suggestion that it can be placed under H. sparsifolium" (Ley, 1908 (Ley, 1909). Pugsley (1948) disagreed with the suggestions it should be under H. septentrionale and included it back under H. scoticum with the comment it was a distinct form worthy of further investigation. Finally, it was named as a distinct species H. apheles by P.D. Sell (Sell & Murrell, 2006).
The basionym for H. apheles is H. septentrionale Arv.-Touv. var. simplex Ley (Ley 1909, page 50;Sell & Murrell, 2006); a lectotype has been selected for the basionym and is hereby designated as the sheet in herb. F.J. Hanbury labelled "Rocks in and by the Hepste River near Penderyn, 30 July 1890, collected by the Rev, Augustin Ley" (BM; accession barcode number BM001187536); it should be noted that Ley (1909) cited the locality as Mellte Glen, but all specimens are from the Hepste Glen and this is thought to be a simple confusion.
characterised by the 2-5(-7), lanceolate to elliptical stems leaves with large teeth and cuneate bases, the few-flowered inflorescences with 2-9 capitula on long peduncles, the involucral bracts with numerous stellate and simple hairs but few glandular hairs, and the yellow styles ( Figs. 1 and 2). Other species in the Hepste Glen/Mellte Glen area with which it could be confused are H. charitodon and H. nidense in section Tridentata; both these species have more stem leaves with larger teeth.
Following rediscovery of the population in the Hepste Glen (see below), the description by Sell & Murrell (2006) has been revised as it was based on only a limited sample of cultivated plants in CGE. The major difference was that Sell & Murrell (2006) described H. apheles in both the text and key as having numerous stellate hairs on the involucral bracts, whereas the wild plants and other herbarium material had virtually no stellate hairs except on the lowest outer bracts. A revised description is as follows:   The Hepste Glen was searched on 13 July 2010 from Sgwd yr Eira SN928100 to Bryn-cul SN940105 (Rich & Thomas, 2010). Below Sgwd yr Eira, the Afon Hepste is quite shaded in tall woodland. Between Sgwd yr Eira and Caerhowell, the Afon Hepste was relatively shaded and had mainly acidic rock, and very few hawkweeds were seen. Above Caerhowell, the banks were more open with rocks and a series of small waterfalls had H. argillaceum, H. sabaudum, H. strigosum and H. subcrocatum. Five plants of H. apheles were found on low rocks by a pool below a small waterfall and gorge at SN941101. This site is probably further north than Ley's 'rock in the Hepste Glen at the point nearest to Penderyn'. Above Bryn-cul, the Afon Hepste runs through farmland, is densely shaded with trees and is unsuitable.

Life cycle and Ecology
Hieracium apheles is a perennial which is probably quite long-lived and the five wild plants were seen for at least four years 2010-2013. It is probably a polyploid apomict like most other British Hieracium species; Sell & Murrell (2006) stated it is apomictic but this was not actually tested. The main flowering period is from June to July. Most seed is ripe by August, the seeds have a small pappus and are wind-dispersed or perhaps washed along the Afon Hepste. The H. apheles plants were rooted in clefts in the Twrch Sandstone Formation rocks which are interbedded sandstones and conglomerates of Carboniferous age (Fig. 4). The plants were about 0.5 m above the summer water levels, but were within the flood zone which is probably important to maintain relatively open conditions, however in August 2010 a flash flood washed away all seed from the plants. It is associated with Anthoxanthum odoratum (occasional), Athyrium filix-femina (rare to abundant), Dryopteris dilatata (rare), Geranium robertianum (rare), Geum urbanum (rare), Hieracium cf. subcrocatum (rare), Hieracium sabaudum (rare), Luzula campestris (rare), Nardus stricta (rare), Poa trivialis (rare), Potentilla sterilis (rare), Schedonorus gigantea (rare), Solidago virgaurea (occasional), Sorbus aucuparia (one small shrub) and Succisa pratensis (rare).
The altitude is 250 m.
In 2010 the plants were located out of the reach of sheep, as like, most hawkweeds, they are susceptible to grazing. In 2013 the river was fenced on the east side and was only lightly grazed by sheep thereafter. Plants were still present on 24 May 2021, and a population count on 18 August by Andy Shaw indicated five plants were still present, two of which were vegetative.

Discussion
Hieracium apheles is assessed as 'Critically Endangered' under IUCN (2001) threat criteria based on the occurrence of five plants in one locality. The site has no protection or designation. There is no indication of the population size during Ley's time, but it is now extremely vulnerable. A small collection of seeds from two plants was deposited in the Millennium Seed Bank in 2013 and population reinforcement programme was begun in 2021 by Andy Shaw.