Petalophyllum ralfsii (Wilson) Nees & Gottsche ex Lehm. Petalwort PETALOPHYLLACEAE (or FOSSOMBRONIACEAE) Status Vulnerable (in Europe) BAP Priority Species Schedule 8 Wildlife & Countryside Act (1981) Lead Partner: Plantlife International Bryophyte RDB - Vulnerable (2001) Annex II of EC Habitats Directive Appendix I of the Bern Convention UK Biodiversity Action Plan These are the current BAP targets following the 2001 Targets Review: T1 - Maintain the population size at all extant sites. T2 - Maintain the geographical range. Progress on targets as reported in the UKBAP 2002 reporting round can be viewed by selecting this species and logging in as a guest on the following web page: http://www.ukbap.org.uk/ The full Action Plan for Petalophyllum ralfsii can be viewed on the following web page: http://www.ukbap.org.uk/UKPlans.aspx?ID=509 Contents 1 Morphology, Identification, Taxonomy & Genetics.............................................. 2 1.1 Morphology & Identification ...................................................................... 2 1.2 Taxonomic Considerations........................................................................ 3 1.3 GeneticImplications ................................................................................. 3 2 Distribution & Current Status ......................................................................... 4 2.1 World .................................................................................................... 4 2.2 Europe .................................................................................................. 4 2.3 United Kingdom ...................................................................................... 6 2.3.1 England ........................................................................................... 9 2.3.2 Northern Ireland................................................................................ 9 2.3.3 Scotland........................................................................................... 9 2.3.4 Wales .............................................................................................. 9 3 Ecology & LifeCycle....................................................................................... 9 4 Habitat Requirements ................................................................................. 12 4.1 The Landscape Perspective..................................................................... 12 4.2 Communities & Vegetation ..................................................................... 14 4.3 Summary of Habitat Requirements (In The Uk) ......................................... 15 5 Management Implications ............................................................................ 15 6 Threats / Factors Leading to Loss or Decline or Limiting Recovery ..................... 16 7 Current Conservation Measures .................................................................... 17 7.1 In Situ Measures.......................................... Error! Bookmark not defined. 7.2 Ex Situ Measures .................................................................................. 17 7.3 Research Data ............................................. Error! Bookmark not defined. 7.4 Monitering Petallophyllum ralfsii & the Common Monitoring Standard ........... 17 1 8 Recommendations for Future Work ............................................................... 22 9 References ................................................................................................ 19 10 Acknowledgements .................................................................................. 21 11 Contacts................................................................................................. 22 12 Links...................................................................................................... 22 13 Appendix ................................................................................................ 22 13.1 Appendix 1: Data on Plants Growing in Association with Petalwort............. 23 13.2 Appendix 2: Population Study at Upton Towans, W. Cornwall, 1997-1999 .. 26 1 Morphology, Identification, Taxonomy & Genetics 1.1 MORPHOLOGY & IDENTIFICATION Petalwort (Petalophyllum ralfsii) is a small thallose liverwort (Figures 1 & 2) that mainly grows on calcareous dune-slacks. It is sparsely distributed in the U.K., currently with about 17 sites (or groups of sites), although at least 9 others have been lost due to destruction of habitats. It is known in the U.K. only from coastal locations, with most localities in south-west, north-west and north-east England and in Wales, with one locality each in Scotland and Northern Ireland. Figure 1 – Petalophyllum ralfsii (Drawing by Fred Rumsey). Figure 2 - Petalophyllum ralfsii (Photograph by David Holyoak). P. ralfsii is one of the most distinctive of all European liverworts, but considerable care is nevertheless needed to ensure correct identification in the field. The structure of its 2 thallus is unique in our flora (Paton 1999), with erect, unistratose lamellae radiating from midrib to margin. Difficulties in identification arise mainly with small thalli (Figure 3) that do not show the radial pattern of the lamellae clearly. These can be confused with small plants of Fossombronia spp., especially the very small F. incurva which grows in dune-slacks in some localities. However, all British Fossombronia, except for the robust cliff-top species F. husnotii, have purple rhizoids whereas the rhizoids of P. ralfsii are colourless or brownish. Confusion with F. husnotii is all too easy when small, prostrate plants grow on pathways, but the Fossombronia has overlapping leaves arranged each side of a stem, not a thallus with raised lamellae. Confusion with Moerckia hibernica can also provide a trap for the unwary. Figure 3 - Male thalli of Petalophyllum ralfsii showing antheridia - the small spherical structures (Photograph by David Holyoak). 1.2 TAXONOMIC CONSIDERATIONS The genus Petalophyllum has five or six species worldwide, but only P. ralfsii occurs in Europe. Stotler et al. (2002) have established that the correct author citation for the species is Petalophyllum ralfsii (Wilson) Nees & Gottsche ex Lehm. Crandall-Stotler et al. (2002) subdivided the family Fossombroniaceae to place Petalophyllum in a newly described family Petalophyllaceae. 1.3 GENETICIMPLICATIONS P. ralfsii is dioecious and often produces capsules (Figure 4) with fertile spores so that it may be assumed to be an out-breeding species, although vegetative reproduction can also occur from thallus fragments. Rumsey et al. (2001) found no genetic variation whatsoever in a study of allozymes from British material. Samples were taken throughout the British range; 178 individual thalli from 24 colonies in nine localities were scored for variation in 11 enzyme systems and 16 putative loci. The authors note, however, that allozymes represent a tiny fraction of the genome and care should thus be taken in assuming that allozymic invariability equates to a total lack of genetic variation. 3 Figure 4 - Mature capsules of Petalophyllum ralfsii (Photograph by David Holyoak). 2 Distribution & Current Status 2.1 WORLD Petalwort is widespread in the Mediterranean region including north Africa and Turkey, extending northwards to Portugal (Algarve), then reappearing along the Atlantic coasts of Europe in Ireland, England, Wales and north-western Scotland. The standard floras also list the species for the southern U.S.A. (in Texas, Louisiana and Arkansas) (Schuster 1992, Paton 1999) but American populations are now separated as P. americanum (Crandall-Stotler et al. 2002). 2.2 EUROPE Outside the U.K. detailed knowledge of the range and status of Petalwort currently exists for the Republic of Ireland, the Balearic Islands (Spain) and at least some parts of Italy, but other areas are very poorly covered, especially in the Balkans and North Africa (Holyoak 1999a, 2000). The apparent absence of records of Petalwort from anywhere in France (including Corsica) appears to be correct (Dr J.-P. Hebrard in litt., Monsieur R.B. Pierrot in litt.), as does the absence of records from the mainland of Spain (Prof. Dra M. Brugués in litt.; see notes below). The European Red Data Book (Schumacher & Martiny, in Stewart 1995) listed the species as Vulnerable in Europe. However, Professor Schumacher, who was one of the authors of that account, now advocates that it should be treated as Endangered using the new IUCN criteria, especially since sites for the species are still being lost (e.g. since 1985 in Calabria, southern Italy). 4 REPUBLIC OF IRELAND Petalwort has (or had) widely scattered localities, most of them coastal, on both eastern and western coasts of Ireland. Corley & Hill (1981) gave records for six vice-counties in the Republic (H1, 2, 21, 27, 28, 35). By 1990 it was known from post-1950 records in 6 ten km squares in the Republic, with additional pre-1950 records from 5 ten-km squares there (Hill et al. 1991). In 1994 D.G. Long found it at Fanore, Co. Clare, adding another ten-kilometre square and another vice-county (H9; Long 1995). By 1998 Dr Neil Lockhart of National Parks & Wildlife Service (in litt., 18 Nov 1998) had found another nine new sites in Ireland. Fieldwork carried out during 1999 by the National Parks and Wildlife Service resulted in discovery of three additional small populations of Petalwort in Co. Donegal (vc H35), so that the species was by then known at a total of six sites in the county. Re-survey