The diploid Festuca ovina subsp. ovina (Poaceae) confirmed cytologically for Ireland

Abstract

Two subspecies of Festuca ovina L. (Sheep’s-fescue) (Poaceae) are known to occur in Ireland, namely subsp. hirtula (Hack. ex Travis) M.J. Wilk. and subsp. ophioliticola (Kerguélen) M.J. Wilk. Festuca ovina subsp. hirtula is also known as F. tenuifolia var. hirtula (Hack. ex Travis) Howarth, and F. ophioliticola subsp. hirtula (Hack. ex Travis) Auquier. Festuca ovina subsp. ophioliticola is also known as F. ophioliticola Kerguélen. Both subspecies are tetraploid with 2n= 28 chromosomes (Wilkinson & Stace, 1991). Debate still remains over whether Festuca ovina L. subsp. ovina occurs in Ireland. Both Sell & Murrell (1996) and Stace (2010) cast some doubt as to the existence of the diploid ssp. ovina (2n = 14) in Ireland. This is a reflection of the fact that Watson (1958) only recorded tetraploid plants from Ireland, from cytologically determined samples obtained in West Cork (v.c. H3), Co. Wicklow (v.c. H20) and Co. Londonderry (v.c. H40). Furthermore, Wilkinson & Stace (1991) did not cytologically confirm the existence of diploid plants in Ireland. Cope & Gray (2009) state that F. ovina is a ‘complex of intergrading cytological and ecological races for which suitable discriminating morphological characters are not readily available’ and on that basis, therefore, only cytological analysis (including evaluation of ploidy levels) can confirm subspecies status. Watson (1958) discussed the possibility that the tetraploids of Festuca ovina had a local centre of distribution in (southern) Ireland, from where it was dispersed northwards across Britain and Ireland in the late-glacial period. Furthermore,Watson (1958) claimed that tetraploid plants tend to outcompete anddisplace diploids in vacant habitats where they occur together. All of this begged the question, does the diploid F. ovina subsp. ovina in fact occur on the island of Ireland? Attention was focussed by the first author on one particular site in Co. Monaghan (v.c. H32), where F. ovina subsp. ovina was recorded (using morphological characters only) by A. Hill and I. McNeill on 5th June 2008 on dry, rocky, acid heathland at Lemgare Rocks (Irish Grid reference H80149.27972). On 22nd May 2017, fresh material of the plant was collected by A.F. and was sent off to the BSBI Festuca Referee, A. Copping, for morphological confirmation. Cope & Gray (2009) (as per Wilkinson & Stace 1991) cite the morphological characters for subsp. ovina as follows, ‘spikelets 5.3–6.3 mm, scabrid lemmas 3.1–4.2 mm, awns 0–1.2 mm and glabrous blades with stomata < 31.5 μm’. The collected plant had spikelets 6.0 mm in length, scabrid lemmas 4.0 mm in length and glabrous leaf blades with stomata mostly <31.5 μm. All of the measured characters aligned with those of ssp. ovina. Confirmation was received from A. Copping on 27th May 2017, with the caveat that cytological confirmation would be required. Some of the collected material was therefore cultivated to generate fresh, growing root tips for chromosome counting. One centimetre sections of fresh actively growing root tips were removed from the plant and placed directly in ice-cold water for 24 hours as a pre-treatment. The roots were then fixed in 3:1 ethanol:acetic acid and stored. The roots were later hydrolysed in 1M hydrochloric acid at 60°C for 8 minutes, after which they were removed and placed directly in Feulgen solution (Schiff’s reagent, Sigma) in the dark for 30 minutes. The pink-stained root meristems were then separated from the root pieces and were cut into smaller pieces using clean syringe needles, applying one drop of 45% acetic acid to avoid desiccation of the material. The cut root tip pieces were covered with a coverslip and strong thumb pressure was applied, over a Whatman’s No. 1 filter paper pad, to squash the material into a monolayer of cells. Nail varnish was applied to *Corresponding author: A. FitzGerald Email: alexisfitzgerald434@gmail. com