ralfsii (Wilson) Nees & Gottsche ex Lehm.

Petalwort PETALOPHYLLACEAE (or FOSSOMBRONIACEAE)

Status Vulnerable (in ) BAP Priority Species Schedule 8 Wildlife & Countryside Act (1981) Lead Partner: Plantlife International 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 can be viewed on the following web page: http://www.ukbap.org.uk/UKPlans.aspx?ID=509

Contents 1 Morphology, Identification, & 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 ...... 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 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 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 , and ) (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 of known populations in Co. Mayo (H27) and Co. Galway (H16) in 1999 confirmed that some of these are the largest populations known anywhere, with estimates of 1.6 million thalli at Garter Hill (H27) and 5.5 million on the Slyne Head Peninsula (H16) (Dr N. Lockhart unpublished; Holyoak 1999c).

Dr Neil Lockhart is preparing a paper describing the status, ecology and conservation of Petalwort in Ireland. He has noted the causes through which four of its stations have been lost: one each to agricultural eutrophication of groundwater, golf course development, land reclamation, and (at the only inland site, Lough Arrow) to competition from vascular plants due to under-grazing in a disused quarry.

AZORES (PORTUGAL) Petalwort has usually been regarded as absent from Macaronesia, but an abstract by Sim-Sim, Jones & Sérgio (1998) reported the species as 'collected in one locality on the Azores (Faial)'. This record was published in more detail by Sérgio (1994) with the following information: ‘AZORES: Island of Faial, Horta, path of Hotel Faial towards Observatory, amongst volcanic rock and soil near to sea, associated with Corsinia coriandrina, Trichostomum sp.’. However, it was later realised that the specimen was based on ‘an uncommon form of Fossombronia angulosa’ (Sim-Sim, Jones & Sérgio 2000). Unfortunately the comparative descriptions (op. cit., pp. 102-103) still fail to point out the most useful differences between these taxa.

PORTUGAL Duell (1983) gives a Portuguese record as: leg. Wigger 1964, det. Frahm. T.L. Blockeel (in litt., 6 July 1998) reports: 'Algarve: on damp sandy ground on bank of stream, Fonte Grande, near Alte, March 1989, Herb. TLB 18/072'. Since then, Sim-Sim, Jones & Sérgio (2000) have recorded several more sites in the Algarve and commented that the 'normal habitat in Algarve shows that Petalophyllum ralfsii could benefit by grazing and some human activities'.

BALEARIC ISLANDS (SPAIN) Thanks are due to Prof. Dra M. Brugués (in litt.) and Mr Tom Blockeel (in litt.) for detailed information on records from the Balearic Islands that were listed by Holyoak (1999a). The records now cover all four of the main islands. An additional record from Mallorca is given by Stern (1997), on damp stony ground in the Parc Natural de s’Albufera.

There has been some confusion about whether Petalwort occurs on the Spanish mainland, probably because some listings for 'Spain' have separated records from the Balearic Islands and others have not (thus Duell (1983) gives separate listings for the Balearics as 'Bl' and Spain as 'Hs', but the European Red Data Book [Stewart, ed., 1995] merely gives 'Hs', which includes the Balearics). However, Prof. Dra M. Brugués (in litt., 24 Nov 1998) mentions that published records of the species in Andalucia are erroneous

5 and that 'In Spain, until now, the only correct localities for this species are in the Balearic Islands'.

ITALY Listed by Duell (1983) for Italy, Sardinia and Sicily. Dr Michele Aleffi (in litt.) kindly supplied details of records from seven localities held in the database of Italian (listed in Holyoak 1999a). Carratello & Aleffi (1999) have added another locality on the island of Linosa in the Pelagian Islands. Prof. Schumacher (in litt.) mentions that sites discovered since 1985 have been lost, especially in Calabria.

MALTA Recently collected here by Dr A.J. Harrington (fide F.J. Rumsey, pers. comm., in Holyoak 1999a).

CRETE (GREECE) Reported as new for Crete and the Aegean region by Dull & Dull-Hermanns (1973). Also reported by Bischler & Jovet-Ast (1979) and listed by Preston (1981) and Duell (1983) (confirmed by correspondent).

GREECE Listed for Peloponnisos by Schiffner & Baumgartner (1919), cited by Preston (1981). Listed for Greece by Duell (1983). Blockeel (1991) gives a record as: 'Peloponnese: Messinia: luxuriant on sandy ground at the archaeological site, Palace of Nestor, nr. Khora, March 1988, Herb. TLB 17/217'.

CYPRUS T. L. Blockeel (in litt., 6 July 1998) gives details of a specimen as: 'Eastern Troodos: on damp soil in bed of small seasonal stream, several km SW of Kapedes, 28 March 1997, Herb. TLB 26/151'.

TURKEY Crundwell & Nyholm (1979) give details of three records and mention three others. They comment that it is 'evidently widely distributed in the south and west at altitudes below 50m'. The species was also listed for Turkey by Duell (1983) (as confirmed by correspondent), and by Hill et al. (1991).

NORTH AFRICA Listed by Duell (1983) and by Hill et al. (1991). Smith (1990) lists Algeria. A recent check-list of the bryophytes of north Africa (Ros et al. 1999) cites literature reporting the species from Algeria (Jelenc 1955, 1967) and Tunisia (Labbe 1953, Jovet-Ast & Bischler 1971).

2.3 UNITED KINGDOM

OVERVIEW Populations of Petalwort still survive in Cornwall and Devon in south-west England, in north-western England on the Sefton Coast, in north-eastern England in north Northumberland, at one site in East Anglia (north Norfolk), at numerous sites on the coast of Wales, and at one site each in Scotland and Northern Ireland (Table 1).

Petalwort has been recorded in a total of 16 vice-counties in Britain and 2 in Northern Ireland, but is thought to now be extinct in 2 English vice-counties and 1 in Northern Ireland. The vice-counties involved are: 1 West Cornwall, 3 South Devon, 4 North Devon, 6 North Somerset (extinct), 28 West Norfolk, 41 Glamorgan, 44 Carmarthenshire, 45 Pembrokeshire, 46 Cardiganshire, 48 Merioneth, 51 Flintshire, 52

6 Anglesey, 59 South Lancashire, 62 North-east Yorks (extinct), 68 North Northumberland, 105 West Ross, H39 Antrim (extinct), H40 Londonderry.

Figure 5 - UK distribution showing extant sites of Petalophyllum ralfsii.

Table 1 - Overview of the location and size of UK populations of Petalophyllum ralfsii. SITE SSSI/ASSI/CSAC POP. VICE COUNTY SITE NAME GRID NO. STATUS SIZE* Upton Towans/ SSSI, cSAC SW 1 West Cornwall Godrevy (mainly in Gwithian- 6 5739 Towans Mexico Towans) SSSI, cSAC SW 2 West Cornwall Gear Sands 3 (in Penhale Dunes) 7655

7 SITE SSSI/ASSI/CSAC POP. VICE COUNTY SITE NAME GRID NO. STATUS SIZE* SX 3 South Devon Dawlish Warren SSSI, cSAC 4 9878 Braunton SS 4 North Devon SSSI, cSAC 4 Burrows 4632 Holme-next- TF 5 West Norfolk SSSI, cSAC 2 the-Sea 7044 Whiteford Burrows- SS 6 Glamorgan Whiteford NNR Landimore Marsh SSSI, ? 4495 Burry Inlet: Dunes cSAC SS 7 Glamorgan Oxwich NNR Oxwich Bay SSSI 3 5086 Merthyr Mawr Warren SS 8 Glamorgan Merthyr Mawr ? SSSI, cSAC 8676 Kenfig Pool and Kenfig Pool and Dunes SS 9 Glamorgan ? Dunes NNR SSSI 7882 Laugharne and Laugharne and Pendine SN 20 10 Carmarthenshire Pendine Burrows SSSI, Burry & SN 4 Burrows Inlet: Dunes cSAC 30 SN 11 Carmarthenshire Towyn Burrows Pembrey Coast SSSI 0 3605 Broomhill SM 12 Pembrokeshire SSSI 3? Burrows 8800 Brownslade Castlemartin Cliffs and SR 13 Pembrokeshire 6 Burrows Dunes SSSI 8998 SN 14 Cardiganshire Ynyslas Dyfi SSSI, Dyfi cSAC 2-4 6093 Morfa Harlech SSSI, Morfa Harlech SH 15 Merioneth Morfa Harlech a Morfa 2? NNR 5534 Dyffryn cSAC Morfa Dyffryn SSSI, Morfa Morfa Dyffryn SH 16 Merioneth Harlech a Morfa Dyffryn ? NNR 5525 cSAC Gronant Dunes SJ 17 Flintshire and Talacre SSSI ? 1184 Warren Rhosneigr SH 18 Anglesey (Cyttir Tywyn not SSSI, not cSAC ? 3174 Trewan) Tywyn Tywyn Aberffraw SSSI, SH 19 Anglesey ? Aberffraw Glannau Mon: Twyni cSAC 3668 Newborough Warren - Newborough Ynys Llanddwyn SSSI, SH 20 Anglesey ? Warren NNR Glannau Mon: Twyni 4263 cSAC) SD South 2912 21 Merseyside Sefton Coast (SSSI, cSAC 4 Lancashire SD 3216 NU North 22 Holy Island SSSI, cSAC 1243 3 Northumberland etc. NC 23 West Ross Achnahaird Bay not SSSI, not cSAC 5 0113

8 SITE SSSI/ASSI/CSAC POP. VICE COUNTY SITE NAME GRID NO. STATUS SIZE* C Ballymaclary 6936 24 Londonderry ASSI, cSAC 2 NNR C 7036 *Maximum counts or estimates of numbers of thalli recorded 1999-2005 are given as orders of magnitude: 1 = 1-10 thalli, 2 = 11-100, 3 = 101-1000, 4 = 1001-10 000, 5 = >10 000, 6 = > 100 000, ? = information insufficient or unavailable.

2.3.1 ENGLAND Details of extant sites and recent population estimates are summarised in Table 1 and Figure 5.

Populations appear to have been stable at most sites from 1997-2004, but with significant increases in West Cornwall (along Towans from Phillack to Godrevy) and North Devon (Braunton Burrows). The single population in West Norfolk is small and threatened.

2.3.2 NORTHERN IRELAND The single extant population (Ballymaclary NNR, Co. Londonderry) is small and threatened (Holyoak 1999b).

2.3.3 SCOTLAND The only population known (Achnahaird Bay in W. Ross) is large and protected in a SSSI. Further populations might yet be discovered in machair and dune habitats of Western Scotland, especially in the Inner Hebrides and Outer Hebrides.

2.3.4 WALES Details of extant sites and recent population estimates are summarised in Table 1. Large populations (thousands of thalli) are extant at four or five sites, including very large numbers at Brownslade Burrows, Pembrokeshire (418,186 thalli estimated in March 2002). Small populations at several other sites are potentially threatened.

3 Ecology & LifeCycle There is hardly any published information on the population biology of P. ralfsii, although the standard floras (Smith 1990, Paton 1999) and the account in the national bryophyte Atlas (J.G. Duckett in Hill et al. 1991) give notes on the biology of the species. In England Petalwort usually grows in habitats that are wet or flooded in winter but which dry out in summer. Depending on rainfall, the thalli are usually visible on the surface from autumn to spring but disappear during the summer, when the plants perennate by means of underground tubers packed with lipid. The thalli often grow branches. There are also comments in the literature that numbers vary from year to year and that it can withstand burial under thin layers of blown sand, but details are not given to substantiate those claims. The species is dioecious and sporophytes are regularly produced, maturing from December to June (J.G. Duckett in Hill et al. 1991: 280), although sporophyte maturation from March to May is more usual (pers. obs.).

Several questions that could prove important to conservation management of P. ralfsii were thus left unanswered when the work on this species by Plantlife International began. The most important of these included the relationship between the number of thalli and the number of genetically distinct plants, the relative frequencies of vegetative reproduction and of sexual reproduction from spores, the numerical ratio of the sexes, the conditions required for vegetative and sexual reproduction, along with such life-table

9 parameters as longevity, fecundity, growth rates, age at reproductive maturity and longevity of spores in soils.

Among these questions, answering some of which would involve large programmes of research, the relationship between thallus number and number of distinct plants seemed of obvious importance for population monitoring, as did the sex ratio. In addition, the question of whether flooding is needed for sexual reproduction demanded attention because most colonies of Petalwort grow in sites that flood whereas a few do not.

Data have been obtained from field sites in West Cornwall by three principal methods. At Upton Towans a study plot was investigated once each month over nearly three years (1997-1999). The technique allowed individual thalli to be followed from month to month. Details of the methodology adopted and results are described in a separate section below.

A second method used for more detailed study of individual Petalwort thalli was their cultivation (under licences from EN). In October 1997 erosion of a small ditch-bank in the ‘main colony’ at Upton Towans had begun to cause subsidence of the neighbouring mossy surface on which a subpopulation of Petalworts was growing, so that their loss due to erosion seemed ineviteable when the slack next flooded. Three pieces of this moss carpet, each measuring ca 10 x 15 cm by 3 cm thick, with good groups of Petalwort thalli were cut out using a sharp knife and transported home intact. Two of the pieces (with groups of 10 mainly male and 17 mainly female thalli respectively) were each replanted in the surface of moist sand from the same site filling a 1kg margarine tub. These cultures grew well for more than two years inside a conservatory, allowing regular scrutiny of details of the thalli at x10-x30 (using stereomicroscope with long-arm stand and fibre-optic cold light sources). Observations were also been made for shorter periods on plants from North Devon, South Lancashire, West Norfolk and North Northumberland, which were cultivated under similar conditions in order to maintain material alive for allozyme studies (Rumsey 1999).

The third method used for study of individual Petalwort thalli involved the complete excavation of all 84 thalli in the third of the pieces collected from Upton Towans. This was carried out using the same Stereomicroscope and fine forceps, mounted needles and a pointed scalpel to trace all underground axes or other connections between the thalli, while recording their characteristics and locations on a double-sized tracing of the original surface [based on 200% enlarged colour photocopy]. The excavation proved to be a lengthy process that took some eight hours to complete.

Of the 84 thalli excavated, 15 were evidently female in that archegonia, female bracts, or their ciliate tips could be seen; there were no antheridial thalli. The majority of the thalli (62) and nearly all of the larger ones, had cylindrical, whitish to brownish, concealed, subterranean extensions (rather like roots of teeth) that were shorter or not much longer than their dorsiventrally flattened, green, exposed parts; these did not make contact with underground parts of any other thallus. However, 22 thalli, mainly small ones, had relatively and actually much longer subterranean extensions that were united to underground parts of other thalli; several of them being thus joined in groups of three, with one group of four. The only simple interpretation of these results is that subterranean axes grow branches on the ends of which small surficial thalli grow, then as this new surficial thallus grows larger (and presumably accomplishes sufficient photosynthesis to become nutritionally independent) the subterranean axes or their branches decay without trace. Presumably the new thallus can in turn give rise to another underground axis and repeat this cycle.

On this basis it seems clear that many adjacent surficial thalli of Petalwort will be clonal derivatives of other thalli from which they originated vegetatively, by branching from a subterranean axis that does not persist. Hence, counts of Petalwort thalli must often greatly exceed the numbers of genetically distinct individual plants that are present. This

10 conclusion could to some extent be foreseen in that data from the field plots had shown a strong tendency for male and female thalli to be clustered in separate small groups. See below for further discussion of sex ratios.

The ratio of thallus counts to number of genetically distinct plants thus remains elusive. It presumably varies according to the age of whole colonies and is anyway unlikely to have any constant numerical value.

Fertilisation in this dioecious species must rely on water through which spermatozoids can pass from antheridia to archegonia. Cornish plants studied on field plots and in cultivation consistently had mature antheridia and archegonia at least from October to January (see below) and it seems clear that the winter flooding in many dune-slacks allows fertilisation and leads to development of sporophytes that commonly mature in April or May [although in Cornwall in 1997 a drought in April prevented any of the many immature sporophytes seen in March from maturing successfully]. However, female plants of several small populations near the landward edge of Upton Towans were on low ridges or small mounds in situations where even overland flow following torrential rain would be unlikely to offer any prospect of fertilisation from neighbouring male plants. As expected, no immature sporophytes were seen on these plants during searches in spring 1997 or spring 1999 and there can be little doubt that they have no opportunities for sexual reproduction because of the characteristics of their sites. Experimental fertilisation of plants in cultivation was attempted several times by flooding the male plants with shallow water, then pipetting this water on to the female plants, but it was not possible to confirm the efficacity of this, perhaps because the plants were not at exactly the right stage of development [the same technique is known to sometimes work with Fossombronia spp., fide Mrs J.A. Paton, pers. comm.].

Petalwort has large (40-56 µm diameter) spores. Nothing appears to have been reported of their longevity or germination. The similarly large spores of some Riccia species are known to retain viability for many years in the mud of pools and lakes, allowing germination in drought years when the mud is exposed. Hence, the possibility that Petalwort has a long-lived ‘spore bank’ should be investigated, as should germination of its spores. Preliminary attempts to germinate one collection of spores on moist filter paper have been unsuccessful, both within a month of collecting them and at irregular longer intervals of up to 10 months. It is unclear whether this failure to germinate is due to provision of unsuitable conditions, to dormancy in the spores, or both. A recent study of spores of the winter-annual liverwort Sphaerocarpos texanus disclosed that the species shows a dormancy/nondormancy spore cycle similar to that found in seeds of obligate winter-annual flowering plants (McLetchie 1999). A detailed study would be needed to establish whether the same adaptations occur in Petalwort. Other unsolved problems relate to acquisition of mycorrhizal fungi in young thalli: are they necessary for spore development, or if not, when are they acquired by the developing thallus?

Rumsey (1999) reported results of allozyme studies carried out on behalf of Plantlife International on samples of Petalwort from nine British localities. No allozyme variation was detected either within or between these populations. The lack of electrophoretically detectable variation at the enzyme loci studied does not of course mean that Petalwort is genetically invariable since these loci represent a tiny fraction of the genetic code. Indeed, additional studies using different techniques are still needed to assess whether genetic variability really is low within and between British populations of Petalwort. Rumsey (op. cit.) warns that RAPDs and AFLP techniques may, however, be unsuitable for study of Petalwort because its thalli contain fungal hyphae. Hence, amplification and study of an appropriate region of plastid genome (which cannot be of fungal origin) or of DNA which can safely be characterised as non-fungal is therefore necessary.

11 4 Habitat Requirements

4.1 THE LANDSCAPE PERSPECTIVE

HABITATS IN EUROPE Almost all sites in Britain are closely associated with sand dunes, whereas some of the largest populations in Ireland are on damp sand of machair slopes (Holyoak 1999c). Petalwort especially favours dune-slacks (Figure 6) in Britain, with fewer records in dune areas from near pond edges, along damp pathways, in small hollows and (in West Cornwall) on former industrial sites adjoining dunes. Reports of it occurring in and around Torquay in South Devon on thin reddish clay-soil above limestone close to the edges of sea cliffs have turned out to be based on misidentified Fossombronia spp. (Holyoak 1999a). However, Petalwort has been found on damp soil on limestone at the edge of dunes in Co. Clare, Ireland (Long 1995) and as a few thalli amongst thin turf on blown sand over limestone in Co. Galway, Ireland (pers. obs., 1999). Its occurrence on soil in the Mediterranean region is commoner, e.g. on soil among pine litter in shaded gully 2 km inland at 120 m elevation on Ibiza (Blockeel & Crundwell 1987). All British locations at which Petalwort is known are within ca 2 km of a coast, but one of its former sites in Ireland was ca 20 km inland (in old quarry in calcareous grits in Co. Sligo, where now extinct, fide N. Lockhart, in litt.).

Figure 6 - Typical habitat of Petalophyllum ralfsii on pathway in dune- slack (Photograph by David Holyoak).

In Britain it tolerates only light shading, but several sites in the Mediterranean region have been described as under trees or macchia, although it is also known in dune-slacks, e.g. in Italy (Holyoak 1998a for references and other details). A possible explanation of its occurrence under trees in the Mediterranean region but not in Britain relates to higher evapo-transpiration there, associated with higher summer temperatures and more intense insolation. Thus, sites that combine suitably moist conditions in winter with sufficient insolation all year may occur under trees in the Mediterranean region but only in the open in Britain.

12 HABITATS IN UK As discussed by Holyoak (1998a, 1999a, 2000) there are several recurrent features of the habitats in which Petalwort is found in Britain which taken together may explain the scarcity of sites occupied by the species:

It invariably occurs on calcareous substrates, with a basic reaction (pH 7.4-7.7 in the study by Ratcliffe 1977 at Ainsdale; pH 7.1-7.9 recorded in Cornwall by Rouen (2000); see also data on associated plants below). The species appears to be entirely absent from sand-dune areas with base-poor sand, such as in the Isles of Scilly and over large areas of the dunes on the Sefton Coast and in north- west Cumbria. At Dawlish Warren, where most of the sand is base-poor, the newly found Petalwort colonies are close to concrete, masonry debris or limestone gravel.

It requires firm or compacted substrates, avoiding really loose or mobile sand. Smith (1990) writes of new growth arising from thalli buried by several millimetres of sand, and other authors describe it withstanding burial but being slow growing and not able to grow through deep accretions of sand.

Apparently, it prefers sites that remain stable for several to many years, and this is in accordance with its slow growth and gradual vegetative spread year after year, as described below. Dan Wrench demonstrated plants at Ainsdale which appear to be new colonists on ground recently cleared of scrub and these had presumably arisen from spores (strong colonies were present nearby) (Sefton Coast Life Project 1998). However, without persistent active intervention the ‘new’ Petalwort at this site will probably be lost to renewed scrub growth. In contrast, typical sites with Petalwort have persistently very low vegetation that includes many small perennials. Factors maintaining the low vegetation are usually poverty of nutrients and intense grazing by rabbits, but light trampling pressure also plays a part in some places.

In Britain it tolerates only light shading. Thus there are several records of it being lost when bushes spread to shade dune-slacks, and the sites where it is most shaded at present have encroaching scrub that will presumably soon lead to loss of the Petalwort unless action is taken.

Most sites have some bare substratum exposed, commonly 10-50% of bare humic sand amongst low vegetation. Hughes (1997) found a significant correlation between occurrence of Petalwort and the amount of unvegetated ground exposed in 50 x 50 cm quadrats on the Birkdale coast. Nevertheless, Petalwort can grow over large areas in very thin low cover of grasses and herbs (<1 cm) without discrete patches of bare substrate, implying that lack of shading is the main requirement rather than bare ground per se.

All English sites are dry for large parts of a normal summer and most are wet or flooded in at least some winters. Most major colonies in dune-slacks in Cornwall, South Devon and South Lancashire are known to be at least briefly submerged in some winters. Other colonies in Cornwall are in places where rainwater would flow overland briefly after torrential rain. A small residue of colonies, at least in Cornwall, is in locations that cannot flood: as discussed below, plants in these locations do not produce sporophytes and are probably prevented from reproducing sexually.

Several populations discovered since 1995 at Upton Towans, West Cornwall grow on thin compacted lithosols or in low moss mats which overlie rocky spoil from former metalliferous mining. During the 1939-1945 war the mine-spoil was used to surface trackways through these dunes and Petalwort has also colonised the edges of several tracks, where it grows with low mosses on thin compressed soils

13 that include some blown sand. Several of the large populations of Petalwort over mine-spoil at Upton Towans extend to edges of areas that have high concentrations of copper, to judge from occurrence of pure stands of the moss Hymenostylium recurvirostrum that characterises such places. Chemical analyses of its substrates there show that it can tolerate high levels not only of Cu, but also of Pb and Zn, and indeed presence of all three of these metals simultaneously at high concentrations. Analyses by Rouen (2000) of 7 samples show the following metal concentrations (given as µg/g dry weight): Cu 251- 4499, Pb 31-2242, Zn 354-15287. Another unusual habitat in the same area is of at least 50 thalli in a thin mat of mainly acrocarpous mosses which overlies parts of a horizontal spread of mortared brickwork of a ruined building, just above ground-level.

4.2 COMMUNITIES & VEGETATION

Data were accumulated during 1997-1999 on plants growing in association with Petalwort in order to investigate and document details of the habitats and associations in which it grows (Holyoak 1998a, 1999a, 2000). All of these data were collected from 20 x 20 cm quadrats using a fixed wooden frame. All quadrats were selected so as to be representative of sites at which the P. ralfsii was growing: unusual or atypical sites were avoided, as were places with only a few plants of P. ralfsii. All data are for percentage cover. Comparative information from the Sefton Coast is available in Sefton Coast Life Project (1998).

The resulting body of data on site characteristics and associated plants (a representative part of the data is presented in Appendix 1: Tables 2-6) provides detailed documentation in support of several of the generalisations made in the preceding paragraphs. In particular, the presence of very short vegetation (typically <0.5 cm tall) with incomplete ground cover emerges as a recurrent feature of the sites. Grazing by rabbits was a significant factor contributing to this situation at all of the sites studied in detail.

Ground-cover with many low, calciphilous mosses is a striking feature at all of the sites, with species of Barbula or Didymodon forming much of the bryophyte cover. However, the relative abundance of different Barbula or Didymodon species as the commonest of the close associates of Petalwort varies between sites. Thus D. tophaceus was commonest in the quadrats at Holme-next-the-Sea and Dawlish Warren, D. fallax commonest at Braunton Burrows, D. vinealis at Upton Towans, B. convoluta at Gear Sands, whereas the allied Bryoerythrophyllum recurvirostrum was commonest at Holy Island. Since several of the other Barbula or Didymodon species were usually present in lower abundance at each of these sites, it does not appear that which of the species becomes commonest is important in determining suitability of habitat for the Petalwort.

Although several Bryum species were commonly present, they mainly did not reach high cover values in the quadrats, perhaps because they are, variously, primarily colonists of recently disturbed ground (B. bicolor, B. dunense, both taxa now regarded as conspecific with B. dichotomum), prefer drier substrates (B. algovicum, B. inclinatum [= B. archangelicum]) or are taller plants of ground that is wetter in summer (B. pseudotriquetrum). Syntrichia ruraliformis was also recorded often but at low cover values and this also is mainly a moss of drier ground. Various pleurocarpous mosses occurred at mainly low cover values, but when these larger mosses attain substantial amounts of cover they tend to exclude Petalwort.

Incomplete cover formed of low growth of grasses was a feature of quadrats with Petalwort at several localities, the grass involved being mainly Agrostis stolonifera at some sites (e.g. Holy Island) but at others (e.g. Gear Sands), although both these were well represented at Upton Towans. Among a long list of herbs recorded as associates in the quadrats, coronopus was present most consistently (but

14 not at Holy Island). In study plots at Upton Towans the individual plants of P. coronopus remained alive but tiny and dwarfed for many months, some of them growing very little over 21 months. Other commonly recorded herbaceous associates were Bellis perennis, Cerastium diffusum and Leontodon saxatile. Such taller duneland plants as Ammophila arenaria were rarely recorded in the quadrats although commonly present nearby.

Unpublished research by Professor J.G. Duckett (pers. comm.) has revealed that fungal hyphae are regularly present in the lower parts of Petalwort thalli. He has determined that these are vesicular-arbuscular mycorrhizae. They are believed, by analogy with the situation in other plants where they occur, to play a significant role in the nutrition of the Petalwort. Indeed, the mycorrhizae might link Petalwort into complex nutritional relationships with associated vascular plants, although much further study is needed to ascertain this, and it should be noted that no single vascular (or cryptogam) species appears to be invariably present as an associate of Petalwort.

4.3 SUMMARY OF HABITAT REQUIREMENTS (IN THE UK) Petalwort in the U.K. is closely associated with sand dune areas having calcareous sand, where it occurs mainly in dune-slacks, with fewer records from near pond edges, along damp pathways, in small hollows and on former industrial sites adjoining dunes. All English sites are dry for large parts of a normal summer and most are wet or flooded in at least some winters. It tolerates only light shading, prefers firm or compacted substrata, and prefers sites that remain stable for several to many years. Typical sites with Petalwort have persistently very low vegetation that includes many small perennials. Factors maintaining the low vegetation are usually poverty of nutrients and intense grazing by rabbits, but light trampling pressure also plays a part in some places. Most sites have some bare substrata exposed, commonly 10-50% of bare humic sand amongst low vegetation.

5 Management Implications In 2003 Plantlife International published an illustrated leaflet giving an account of various threatened bryophytes of coastal dune-slacks as part of the 'Back from the Brink Management Series', entitled: Looking after rare mosses and liverworts in coastal dune- slacks. This leaflet is intended to increase awareness of the species along with other dune-slack bryophytes. It describes and illustrates Petalwort, discusses threats to its populations and provides details of contacts able to supply additional information.

SITE SAFEGUARD It is important to:

Ensure that all sites for Petalwort which are not currently SSSIs but which are at all likely to be threatened by any kind of damaging activity are considered for notification as SSSIs.

Ensure the safeguard of all Petalwort sites through the preparation of Site Management Statements and the negotiation of Management Agreements.

Encourage managers of land where conservation is the primary concern to appreciate the importance of this species and to implement action to optimise its chances of survival and encourage expansion of its range. In particular, the needs for a seasonally high water-table, unpolluted ground-water and very short vegetation should be stressed.

15 Prevent disruption or pollution of fresh water sources on Petalwort sites where this may have an adverse affect on populations or on the integrity of the site.

ADVISORY It is important to:

Inform all relevant landowners, statutory authorities and local authorities of the presence of the plant, to ensure that they are aware of and fulfil their responsibilities for its management and safeguard.

Advise relevant landowners and site managers of the requirements of the species and measures needed to prevent damage to its populations. In particular, the needs for a seasonally high water table, unpolluted ground water and very short vegetation should be stressed.

6 Threats / Factors Leading to Loss or Decline or Limiting Recovery

CHANGES TO PATHWAYS AND TRACKS Petalwort growing on pathways and old tracks is sensitive to increased or decreased usage by pedestrians and vehicles and seriously at risk from re-surfacing works.

DIGGING OF DITCHES OR OTHER DRAINAGE WORKS A seasonally high water table is an important feature of many Petalwort sites and survival of the species is unlikely if they are drained.

EUTROPHICATION OF WATER SUPPLIES Low-nutrient status and short vegetation characterise sites with Petalwort. Increase in the nutrient status of waters could threaten Petalwort directly and through causing competing plants to grow taller.

USE OF DUNE-SLACKS FOR SEASIDE CAR PARKING One large colony is in part of a dune slack used for car parking and hence it is at risk from damage to the surface caused by tyres, fuel spillage or fires.

EXCAVATION OR DEEPENING OF PONDS FOR AMPHIBIANS Several locations with Petalwort adjoin pools in which natterjack toads breed. Deepening or other management of these pools could threaten Petalwort. Other threats to Petalwort may arise from trampling around the pools or beside fences designed to screen them.

DEVELOPMENT OF TALLER VEGETATION IN DUNE-SLACKS Petalwort is dependent on very short vegetation persisting at its sites. Reduction in grazing pressure (nowadays mainly from rabbits) could cause large losses of Petalwort populations or its extinction at many sites. Survival of Petalwort at other sites may now be dependent on periodic clearance of scrub and other tall vegetation.

DISTURBANCE DUE TO MOTOR VEHICLES Limited disturbance of the ground surface may be beneficial to Petalwort but if too extensive or too regular it may reduce its populations or destroy its habitat. Motorcycle scrambling has been noted as a potential threat at a few sites. Increased mobility of sand due to vehicles and other disturbance, as well as natural processes, often maintains the open vegetation conditions needed by Petalwort. However, too rapid accretion of sand may result in at least temporary losses of its populations.

16 COLLECTION OF SPECIMENS Although protected under Schedule 8 of the Wildlife & Countryside Act 1981, thoughtless collection of specimens might continue to pose a threat, especially to small populations.

7 Current Conservation Measures

7.1 EX SITU MEASURES None

7.2 MONITORING PETALOPHYLLUM RALFSII & THE COMMON MONITORING STANDARD Management of habitat to benefit Petalwort requires knowledge of the locations of its populations and, ideally, estimates of the abundance of the species. These notes consider various difficulties that arise in estimating numbers of Petalwort plants and then suggest appropriate monitoring methods.

LOCATING PETALWORT On first acquaintance with Petalwort, most non-bryologists are surprised by its small size and the resulting difficulties in finding it at all, let alone in locating it consistently. Monitoring is therefore unlikely to be effective unless it is carried out by people who have become familiar with the plant and are able to locate it reliably.

IDENTIFICATION The structure of Petalwort, comprising a flattened thallus beset with raised lamellae radiating from near the midline, is unique in the British flora. Nonetheless, in the field even experienced bryologists can confuse it with species of Fossombronia, despite the fact that the structure of that genus is radically different with leaves arising each side of a flattened stem, not a leafless thallus. The difficulties arise because leaves of Fossombronia commonly overlap and have raised, crisped margins giving a very similar impression to the crisped, raised lamellae of Petalwort. Using a good x10 hand-lens, careful probing with a needle or forceps should reveal the separate leaves if Fossombronia is involved, whereas it should result in exposure (if not tearing) of the thallus of Petalwort. Other differences that may help are that most Fossombronia have violet rhizoids, whereas Petalwort and Fossombronia husnotii have colourless rhizoids; most Fossombronia have leafy stems narrower than mature Petalwort thalli (not true of F. angulosa). Also, many Fossombronia are monoecious but Petalwort and some Fossombronia are dioecious. Recent fieldwork has emphasised that Petalwort and Fossombronia can occur close together and in similar habitats, so that particular care is needed with identification when large counts are made. Moerckia hibernica can also be confused with Petalwort, particularly its male plants with many scales on a thallus that can have strongly crisped margins.

SIGNIFICANCE OF COUNTS Many if not most individual thalli of Petalwort arise from underground branches of other thalli, although the connections decay as the new thalli grow. Hence, groups of Petalwort thalli are mainly clones of identical individuals, more nearly equivalent to branches of a single plant than to groups of different plants.

Three years of monthly recording of individual thalli at a Cornish colony have shown that those parts of thalli exposed above ground die back during dry weather in late spring and reappear at the same places in autumn, the tuberous bases of the thalli having passed the summer underground. Even from October to April the proportion of thalli showing above ground varied from 0% to 85%. The lowest values for exposed thalli

17 during the winter occurred (1) early and late in the winter, (2) when mosses grew rapidly or a covering of sand appeared due to flooding, or (3) if the ground surface dried. However, there was no time when all the thalli that were known to be present were visible above ground.

BEST MONTHS FOR MONITORING The typical annual cycle of Petalwort involves aestivation underground from about May to September. If ground conditions remain or become wet, small numbers of thalli may be seen on the surface during the summer months, but they are not consistently present (although some thalli are visible throughout a normal summer at the Scottish colony in Wester Ross and the same is apparently true in western Ireland). In order to obtain the highest counts, monitoring visits should therefore be made between October and April, but even in those months periods should be avoided when the weather is unusually dry, when parts of slacks that normally hold Petalwort populations are flooded or have recently been flooded, or when the ground is frozen. Ideally, counts should be made on several visits between late October and mid April and the highest count regarded as the best estimate.

METHODOLOGY FOR COUNTING THALLI Prolonged work in some Petalwort colonies can easily damage the habitat, especially when the ground is wet. Such damage can be kept to an absolute minimum by working alone and making counts while kneeling on a folded plastic fertiliser sack or garden 'kneeler'.

With small populations (50 thalli or fewer) there is little difficulty in recording the highest count of thalli seen, although it may be very time consuming to locate small thalli that are partly concealed amongst patchy grasses, herbs and mosses. Where thalli are small and scattered it is often easier to mark them with cocktail sticks after checking each of them with a hand-lens, then to count the cocktail sticks as they are removed.

If accurate counts are required, larger populations need to be counted systematically to avoid missing some thalli and double-counting others. This can be achieved in various ways, e.g. by stretching a surveyor’s tape through the colony and then repeatedly counting within 50 x 50 cm quadrats placed along the tape and at measured intervals away from it. This takes a great deal of time. Although counts of thousands seem satisfying at the time, for the reasons outlined above they are probably not closely reproducible on future visits and they are likely to give little real indication of the numbers of genetically distinct plants that are present.

The reproductive status of Petalwort plants is worth recording at each visit, the most important information being the presence of antheridia or archegonia, or stage of development of sporophytes (green capsule, dark capsule, seta elongated, capsule dehiscing).

PRACTICAL MONITORING Many days are needed to locate and count thalli in large populations of Petalwort and the resulting counts are of rather uncertain significance. Hence, where limited time is available it is better to ascertain details of the local distribution of the species and estimate numbers in each carefully defined locality, rather than to leave whole areas unexplored while counting hundreds of thalli at a few locations. Where possible, location of populations should be recorded using hand-held GPS equipment or marked carefully on 1:10,000 maps, with accompanying notes on their exact locations (e.g., ‘ca 20 thalli along west edge of path, 3 metres north of lone sallow’) and on habitat conditions at the sites. Where more time is available but counts are impracticable, rough estimates of population size can be assigned to a scale such as 1-10, 11-50, 51-100, 101-200, 201- 500, 501-1000, 1000+.

18 8 References Anon. 1999. Species Action Plans for plants: Petalwort. London: Plantlife. Appleyard, J. 1970. A bryophyte flora of North Somerset. Transactions of the British Bryological Society 6: 1-40. Bischler, H. & Jovet-Ast, S. 1979. Nouvelles récoltes d’Hépatiques en Crète. Revue bryologie etlichénologie. 45: 45-60. Blockeel, T.L. & Crundwell, A.C. 1987. New bryophyte records from the Balearic Islands. Journal of Bryology 14: 519-522. Blockeel, T.L. 1991. The bryophytes of Greece: new records and observations. Journal of Bryology. 16: 629-640. Blockeel, T.L. & Long, D.G. 1998. A check-list and census catalogue of British and Irish bryophytes. Cardiff: British Bryological Society. Breeds, J. & Rogers, D. 1998. Dune management without grazing: a cautionary tale. Enact, Managing Land for Wildlife 6: 18 -22. Carratello, A. & Aleffi, M. 1999. Fossombronia crozalsii Corb. (Codoniaceae) new to the Italian bryoflora. Cryptogamie, Bryologie 20: 69-71. Cavers, F. 1903. Notes on Yorkshire Bryophytes. 1. Petalophyllum ralfsii. Naturalist [1903]: 327-334. Church, J.M., Hodgetts, N.G., Preston, C.D. & Stewart, N.F. 2001. British Red Data Books. Mosses and liverworts. Peterborough: JNCC. Corley, M.F.V. & Hill, M.O. 1981. Distribution of Bryophytes in the British Isles. A Census Catalogue of their occurrence in Vice-Counties. Cardiff.: British Bryological Society. [p. 29]. Crandall-Stotler, B.J., Stotler, R.E. & Ford, C.H. 2002. Contributions towards a monograph of Petalophyllum (). Novon 12: 334-337. Crundwell, A.C. & Nyholm, E. 1979. Some additions to the bryophyte flora of Turkey. I. Hepaticae. Journal of Bryology. 10: 479-489. Curnow, W. 1843. List of Jungermanniae etc. found near Penzance. Phytologist 1: 609- 610. Curnow, W. 1882. Hepaticae of West Cornwall. Transactions of the Penzance Natural History Society, N.S. 1: 121-125. Duell, R. 1983. Distribution of the European and Macaronesian liverworts (Hepaticophytina). Bryologische Beitraege 2: 1-115. [pp. 26, 84]. Düll, R. & Düll-Hermanns, I. 1973. Ergänzungen und Nachträge zur Bryoflora und Bryogeographie der ostmediterranean Insel Kreta in der Aegaeis. Journal of Bryology. 7:421-437. Ford, C.H. & Crandall-Stotler, B.J. 1999. Petalophyllum in . Poster Abstracts for XVI International Botanical Congress. [Brief abstract indicating that work is in progress on spore germination/dormancy, induction of apical tubers and variations in size/morphology and distribution of sexes. Definitive publication of results is awaited with interest]. Grolle, R. 1983. Hepatics of Europe including the Azores: an annotated list of species, with synonyms from the recent literature. Journal of Bryology 12: 403-459. Hill, M.O., Preston, C.D. & Smith, A.J.E. 1991. Atlas of the Bryophytes of Britain and Ireland. vol. 1. Liverworts (Hepaticae and Anthocerotae). Colchester: Harley Books. [p. 280]. Holyoak, D.T. 1998a. Petalwort Petalophyllum ralfsii: Report to Plantlife on work carried out during 1997. Plantlife Report, 31 pp. Holyoak, D.T. 1998b. Rare plant surveys at Braunton Burrows: Water Germander (Teucrium scordium) and Petalwort (Petalophyllum ralfsii). Report to English Nature on Contract No. F14-01-627, October 1998. Unpublished. 28 pp. Holyoak, D.T. 1998c. Bryoflora Britannica. Plantlife Magazine, Summer 1998, p. 15 (includes colour photos of Petalwort). Holyoak, D.T. 1999a. Petalwort Petalophyllum ralfsii: Report to Plantlife on work carried out during 1998. Plantlife Report no. 109, 45 pp.

19 Holyoak, D.T. 1999b. Research on Biodiversity Priority Bryophyte Species in Northern Ireland: Interim Report on Results of Fieldwork during April 1999. Report to Environment & Heritage Service, 25 pp. Unpublished. Holyoak, D.T. 1999c. Report on surveys of Petalophyllum ralfsii in Co. Mayo and Co. Galway, western Ireland, 16-22 April 1999. Report to National Parks and Wildlife. Unpublished. Holyoak, D.T. 2000. Petalwort Petalophyllum ralfsii. Report on work carried out during 1999 and summary of results of work during 1997 and 1998. Plantlife Report no. 143, 43 pp. Holyoak, D.T. 2002. Petalwort Petalophyllum ralfsii. Report on work carried out in England and Wales during 2001 and 2002. Plantlife Report no. 202, 41 pp. Hughes, K. 1997. The factors which affect the distribution of Petalophyllum ralfsii on the Birkdale Coast. Dissertation for BSc Geographical Studies, Liverpool Hope University College. 42 pp. Unpublished. Hurford, C. 1995. A baseline survey to monitor populations of Petalophyllum ralfsii in young dune-slacks at Kenfig, Merthyr Mawr and Whiteford in September 1993. Unpublished Report. Jelenc, F. 1955. Muscinées de l’Afrique du Nord (Algérie, Tunisie, Maroc, Sahara). Société de Géographie et d’Archéologie de la Province d’Oran 72-76: 1-152. Jelenc, F. 1967. Muscinées de l’Afrique du Nord (Supplément). Revue Bryologique et Lichénologique 35: 186-215. Jovet-Ast, S. & Bischler, H. 1971. Les hépatiques de Tunisie. Énumération, notes ecologiques et biogéographiques. Revue Bryologique et Lichénologique 38: 1-125. Labbe, A. 1953. Contribution à la connaissance des bryophytes de Tunisie. I. Bryophytes nouveaux pour la flore Tunisienne. Revue Bryologique et Lichénologique 22: 200- 201. Long, D.G. 1975. Petalophyllum ralfsii (Wils.) Nees & Gottsche in Scotland. Transactions of the Botanical Society of Edinburgh 42: 521. Long, D.G. 1995. New vice-county records and amendments to the Census Catalogues. Hepaticae. Bulletin of the British Bryological Society 66: 37-40. McLetchie, D.N. 1999. Dormancy/nondormancy cycles in spores of the liverwort Sphaerocarpos texanus. Bryologist 102: 15-21. Martin, P. 1992. The Spring Meeting, Clevedon, 1991. Bulletin of the British Bryological Society 59: 5-7. Newton, M.E. 1995. Survey and monitoring of Petalwort, Petalophyllum ralfsii in Gwynedd and Clwyd, January 1995. Report to Countryside Council for Wales. Unpublished. Nicholson, W.E. 1938. Hepatics in West Cornwall. Annals of Bryology 11: 106-107. Paton, J.A. 1966. Distribution maps of Bryophytes in Britain. Petalophyllum ralfsii. Transactions of the British Bryological Society 5: 152. Paton, J.A. 1969. A bryophyte flora of Cornwall. Transactions of the British Bryological Society 5: 669-756. [p. 693]. Paton, J.A. 1999. The liverwort flora of the British Isles. Colchester: Harley Books. Preston, C.D. 1981. A check-list of Greek liverworts. Journal of Bryology. 11: 537-553. Pryce, R. 1999. Pwll fly-ash lagoon- unique in Britain. Llanelli Naturalists’ Neewsletter 64: 6. [erroneous record of Petalwort]. Ratcliffe, D. 1997. Factors affecting the distribution of the liverwort Petalwort (Petalophyllum ralfsii) in a dune slack at Ainsdale sand dunes, Merseyside. Unpublished typescript, 25 pp. Ratcliffe, D.A. 1968. An ecological account of Atlantic Bryophytes in the British Isles. New Phytologist 67: 365-439. Rilstone, F. 1919. Cornish mosses and hepatics. Journal of Botany, London 57: 3-10. Ros, M.A., Cano, M.J. & Guerra, J. 1999. Bryophyte checklist of Northern Africa. Journal of Bryology 21: 207-244. Rothero, G. 1998. Baseline survey of Petalophyllum ralfsii and preliminary survey of Red Data Book species of Bryum at Achnahaird Bay, Wester Ross. Report to Scottish Natural Heritage, 32 pp. Unpublished.

20 Rouen, S. 2000. Substrate metal contamination in relation to rare bryophyte species distribution at former metalliferous mining locations in Cornwall. Research Project Report, submitted as part requirement for the degree of BSc (Hons) in Environmental Studies, University of Hertfordshire. 44 pp. Unpublished. Rumsey, F.J. 1999. Genetic variation in British Petalwort (Petalophyllum ralfsii (Wils.) Nees & Gottsche). Plantlife Report no. 131, 14 pp. Rumsey, F.J., Vogel, J.C. & Russell, S.J. 2001. A study of genetic variation in the threatened hepatic Petalophyllum ralfsii (Wils.) Nees and Gottsche (Fossombroniaceae). Conservation Genetics 2: 271-277. Schiffner, V. & Baumgartner, J. 1919. Beiträge zur Kenntnis der Flora Griechenlands. B. Leber- und Laubmoose. Verh. Zool.-bot. Ges. Wien. 69: 313-341 Schumacker, R. & Martiny, P. 1995. Red Data Book of European Bryophytes. Part 2: Threatened bryophytes in Europe including Macaronesia. Trondheim: European Committee for the Conservation of Bryophytes. Schuster, R.M. 1992. The Hepaticae and Anthocerotae of North America, Vol. 5-6. Chicago. Sefton Coast Life Project. 1998. The Sefton Coast Dune System: Survey of Petalophyllum ralfsii (Petalwort). Unpublished Report. 43 pp. Sérgio, C. 1994. Petalophyllum ralfsii (Wils.) Ness [sic] et Gott. ex Lehm., espécie nova para os Açores e para a Macaronésia. Revista de Biologia 15: 184. Sérgio, C., Casas, C., Brugués, M. & Cros, R.M. 1994. Lista vermelha dos briófitos da Península Ibérica. Lisboa: Instituto da Conservação da Natureza. Sim-Sim, M., Jones, M.P. & Sérgio, C. 1998. Petalophyllum ralfsii (Wils.) Nees & Gott., a threatened liverwort present in Portugal. Morphological and ecological data, directions for future conservation. Abstracts for the 3rd European Conference on the Conservation of Bryophytes, The Scientific Basis for Conservation, p. 28. Sim-Sim, M., Jones, M.P. & Sérgio, C. 2000. Petalophyllum ralfsii (Wils.) Nees & Gott., a threatened liverwort present in Portugal. Morphological and ecological data, directions for future conservation. Lindbergia 25: 101-105. Smith, A.J.E. 1990. The Liverworts of Britain and Ireland. Cambridge: Cambridge University Press. [pp. 287-288]. Stern, R.C. 1997. Briòfits al Parc Natural de s’Albufera. Butlletí del Parc Natural s’Albufera de Mallorca 3: 57-61. Stewart, N.. (ed.) 1995. Red Data Book of European Bryophytes. Part 1: Introductory section & background. European Committee for the Conservation of Bryophytes. Stotler, R.E., Ford, C.H. & Crandall-Stotler, B.J. 2002. Typifications in genus Petalophyllum (Marchantiophyta). Bryologist 105: 400-406. Viney, Michael. 2000. A tiny difference. Another life. Irish Times 25 March 2000.

9 Acknowledgements Thanks to David Thomas Holyoak for his work on the draft of this dossier, and to the following for their cooperation:

Dr M. Aleffi, Major Barry Andrews, Simon Bates, John Blackburn, Tim Blackstock, Tom Blockeel, John Breeds, Prof. Dra M. Brugues, Dr Agneta Burton, James Cadbury, Ms K. Cliffe, Sarah Coles, Shawn Corrin, Steve Crummay, the late Alan Crundwell, Phil Davey, Prof. Jeff Duckett, Ruth Davis, Dr Jenny Duckworth, Peter Gahan, Paul Gainey, Alan Hale, Bob Haycock, Dr J.-P. Hebrard, Gary Hibberd, Nick Hodgetts, Geraldine Holyoak, Mike Hughes, Philippa Hoskin, Yvonne Jackson, Ivan Lakin, Peter Lambley, Dawn Lenn, Dr Neil Lockhart, Dr David Long, Max Montgomery, Ian Morgan, Catriona Neil, Mrs Jean Paton, Roy Perry, R.B. Pierrot, Mark Pool, Ron Porley, Dr Chris Preston, Deb Ratcliffe, Paul Rooney, Gordon Rothero, Simon Rouen, Dr Fred Rumsey, Prof. R. Schumacker, Dr Phil Smith, Dr Tony Smith, Adrian Spalding, Rod Stern, Robin Stevenson, Nick Stewart, Beth Tonkin, Keri Walsh, Richard Weyl, the late Dr Harold Whitehouse, Sally Whyman, Dr Robert Wolton, Dan Wrench; Christie Estates, Cornwall County Council, Ministry of

21 Defence, Spalding Associates; curators of bryophytes at BBSUK, BM, DBN, E, NMW and OXF.

Thanks also to Plantlife International Volunteer James Peat for his editorial work on this dossier.

10 Contacts Plantlife International The Wild Plant Conservation Charity 14 Rollestone Street Or contact enquiries: Salisbury [email protected] Wiltshire SP1 1DX. Tel: 01722 342730

11 Links ARKive species web page for Petalophyllum ralfsii: http://www.arkive.org/species/ARK/plants_and_algae/Petalophyllum_ralfsii/

British Bryological Society http://www.britishbryologicalsociety.org.uk/

Plantlife International wishes to acknowledge the financial support of English Nature, Scottish Natural Heritage and the Countryside Council for Wales for the Back from the Brink (species recovery) programme.

ISBN: 1 904749-22-4

Original draft by David Thomas Holyoak Edited by Plantlife International First draft dated September 2005 Last revised 13 February 2006

12 Recommendations for Future Work

MONITOR POPULATIONS Monitoring of all UK populations should be carried out at three-yearly intervals using the agreed monitoring protocol, i.e. if possible in winters 2004-05, 2007-08, etc.

MAINTAIN CONTACTS WITH SITE-MANAGERS AND LANDOWNERS Ensure that all relevant site-managers and landowners remain aware of populations of Petalwort on land they control, of the conservation needs of the species and of any threats, potential threats or other significant developments.

22 SHARE DATA Information on current population status, threats, ecology, etc. should be supplied to Threatened Bryophyte Database, JNCC and BRC for incorporation into national databases.

It is also necessary to provide information on current status annually or as it becomes available to World Conservation Monitoring Centre.

13 Appendix

13.1 APPENDIX 1: DATA ON PLANTS GROWING IN ASSOCIATION WITH PETALWORT.

Table 2 - Data on plants associated with Petalophyllum ralfsii at Upton Towans, W. Cornwall. QUADRAT NUMBER 1 2 3 4 5 6 7 8 SLOPE (DEGREES) 7 3 5 2-5 2 0-2 0 2 ASPECT S S SSE SE SE E - NNW MEAN VEGETATION HEIGH (CM) <1 <1 <1 <1 <1 <1 <1 <1 MAXIMUM VEGETATION HEIGHT (CM) 2 3 2 3 3 3 2 2 BARE GROUND 12 22 42 36 42 54 58 64 CRYPTOGAMS Barbula convoluta 5 4 - <1 - - - <1 Barbula unguiculata - - - <1 - - - <1 Brachythecium albicans 9 3 <1 <1 - - - - Bryum cf. algovicum+ 8 2 7 2 4 6 9 7 Calliergon cuspidatum <1 ------Cratoneuron filicinum 23 31 20 17 27 3 9 8 Dicranella varia - <1 - - - <1 <1 1 Didymodon insulanus - 2 <1 <1 <1 - - - Didymodon tophaceus 2 1 8 11 11 11 14 12 PETALOPHYLLUM RALFSII <1 1 1 3 2 2 1 2 Pseudocrossidium hornschuchianum - - - <1 - - - - Trichostomum crispulum - - - - - 1 - - PHANEROGAMS* Agrostis stolonifera 3 9 <1 1 - 9 - - Bellis perennis 5 4 2 1 - - - - Carex arenaria - - 1 - 4 - 2 1 Cerastium cf. fontanum 3 9 <1 <1 - - - - Festuca rubra <1 - - 1 8 8 4 2 Leontodon saxatilis 10 - 3 9 - - 1 - Lotus corniculatus 1 ------Ononis repens 1 ------Plantago lanceolata 1 <1 <1 - - - - - Plantago coronopus 15 11 13 18 4 4 2 3 Poa annua 2 1 ------Sagina procumbens - - <1 - - - - - Taraxacum sp. - - 2 - 1 - <1 - Data collected 5 March 1997; quadrats 1-4 were from the eastern part of the main colony (SW 5739, on low bank at edge of path near dune-slack), quadrats 5-8 from its western part (on flat or nearly flat ground beside former path within dune-slack; with higher water-table than for Q1-4). + = Sterile Bryum resembling B. algovicum but perhaps including other species such as B. inclinatum; *Nearly all phanerogams were small plants, mainly immature, and with some species not much more than seedlings.

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Table 3 - Data on plants associated with Petalophyllum ralfsii at Upton Towans, W. Cornwall. QUADRAT NUMBER 1 2 3 4 5 SLOPE (DEGREES) 1 0-1 0 0 2 ASPECT S SW - - SW MEAN VEGETATION HEIGHT (CM) <1 1 <1 <1 <1 MAXIMUM VEGETATION HEIGHT (CM) 2 3 3 2 1 BARE GROUND 19 22 8 7 52 BARE ROCK - - 5 1 - CRYPTOGAMS Barbula convoluta 4 1 1 <1 1 Barbula unguiculata <1 <1 - - - Bryoerythrophyllum recurvirostrum 5 - - - 2 Bryum cf. algovicum+ <1 - <1 <1 2 Campyliadelphus chrysophyllus 19 3 21 10 4 Didymodon acutus <1 - 2 1 1 Didymodon fallax 5 4 2 5 - Didymodon insulanus <1 <1 2 1 <1 Didymodon vinealis 4 18 23 25 13 Gymnostomum recurvirostrum 7 4 5 9 <1 Hypnum cupressiforme var. lacunosum - <1 - - - PETALOPHYLLUM RALFSII <1 2 3 1 2 Pseudocrossidium hornschuchianum - - - - <1 Scleropodium purum - - - - <1 Syntrichia ruraliformis <1 <1 - - <1 PHANEROGAMS* Agrostis capillaris 2 4 - - - Agrostis stolonifera 9 15 6 15 6 Aphanes arvensis agg. - <1 - - 1 Bellis perennis - 1 - <1 - Cerastium diffusum <1 <1 1 2 4 Festuca rubra 12 6 6 9 1 Leontodon saxatilis - - - 4 - 9 8 5 5 6 Poa annua 1 10 9 2 2 Rumex cf. acetosa - - - - <1 Sagina procumbens <1 - - - 2 Thymus polytrichus 1 - - 2 - Veronica arvensis 2 1 1 1 1 Data collected 13 March 1997 from chimney colony (SW 5739). All quadrat sites were in diffuse pathway with thin sandy soil overlying old metalliferous mine-spoil. Other notes as for (Table 2) above.

Table 4 - Data on plants associated with Petalophyllum ralfsii at Gear Sands, W. Cornwall. QUADRAT NUMBER 1 2 3 4 5 SLOPE (DEGREES) 4 2 2 3 2 ASPECT SSE E N NNE E MEAN VEGETATION HEIGHT (CM) 1 <1 1 1 <1 MAXIMUM VEGETATION HEIGHT (CM) 4 3 2 4 4 BARE GROUND 39 59 23 51 32 CRYPTOGRAMS Barbula convoluta 5 5 8 2 2 Barbula unguiculata - <1 1 - - Brachythecium albicans - 2 <1 - -

24 QUADRAT NUMBER 1 2 3 4 5 Bryum cf. algovicum 1 2 5 <1 2 Bryum dunense - - - - <1 Dicranella varia - - - <1 - Didymodon acutus 1 <1 - - - Didymodon fallax <1 5 7 1 8 Didymodon vinealis <1 2 8 <1 3 Ditrichum gracile - <1 <1 - 9 Homalothecium lutescens - - 1 - - Hypnum cupressiforme var. lacunosum 6 - 1 <1 - PETALOPHYLLUM RALFSII 3 <1 <1 <1 1 Pleurochaete squarrosa - <1 - - - Pseudocrossidium hornschuchianum <1 <1 - - - Scleropodium purum - - <1 - - Syntrichia ruraliformis - - <1 - - Trichostomum crispulum - <1 <1 - 9 PHANEROGAMS Agrostis stolonifera - <1 3 21 - Ammophila arenaria 1 - - - - Bellis perennis 13 - 2 <1 - Carex arenaria - - - 2 - Carex cf. distans - - <1 - 9 Carex flacca 8 - - 2 - Cerastium cf. fontanum - 1 1 <1 3 Festuca rubra 23 16 28 16 12 Galium verum <1 <1 - - - Leontodon autumnalis - - - <1 - Lotus corniculatus - - - <1 - Luzula campestris - - 3 - - Plantago coronopus - 7 6 4 13 Plantago lanceolata - - 1 - - Thymus polytrichus <1 - 1 - - Data collected 6 March 1997; locations of quadrats as follows: Q1 in East colony (SW 7755), Q2-3 in Sallow Slack (SW 7656), Q4 by Main Drain (SW 7656), Q5 in Fence Corner Slack (SW 7655).

Table 5 - Data on plants associated with Petalophyllum ralfsii at Dawlish Warren, S. Devon (VC slack). QUADRAT NUMBER 1 2 3 4 5 SLOPE (DEGREES) 2 3 1 1 3 ASPECT NW NW N N NW MEAN VEGETATION HEIGHT (CM) 1 1 1 1 1 MAXIMUM VEGETATION HEIGHT (CM) 3 2 2 3 5 BARE SAND 13 21 24 28 23 CRYPTOGAMS Aneura pinguis <1 1 - 1 1 Barbula convoluta <1 - - - - Bryum algovicum type 18 <1 2 3 2 Bryum bicolor - - <1 1 <1 Didymodon tophaceus 26 41 39 33 21 PETALOPHYLLUM RALFSII 1 1 1 <1 <1 PHANEROGAMS Agrostis stolonifera 8 - 4 - 1 Aira caryophyllaea - - <1 - - Bellis perennis <1 - <1 <1 - Carex arenaria - 4 5 3 1

25 QUADRAT NUMBER 1 2 3 4 5 Festuca rubra <1 1 2 3 5 Juncus bufonius agg. <1 1 2 4 2 Leontodon saxatilis - - 2 1 - Plantago coronopus 25 27 19 23 41 Poa annua 4 3 <1 - 4 Trifolium ornithopodioides 5 <1 <1 <1 - Data collected 15 May 1997 from SX 9878.

Table 6 - Data on plants associated with Petalophyllum ralfsii at Ross Links, N. Northumberland. QUADRAT NO. 1 2 3 SLOPE 0-5 5 5-8 ASPECT S, E E SE MEAN VEGETATION HEIGHT (CM) 1 1 1 MAXIMUM VEGETATION HEIGHT (CM) 2 6 2 BARE SAND (% COVER) 42 26 28 BRYOPHYTES (% COVER) Aneura pinguis <1 3 1 Bryum pseudotriquetrum 2 - <1 Campylium stellatum var. stellatum 6 - - Homalothecium lutescens - 2 - Hypnum lacunosum var. lacunosum - - <1 PETALOPHYLLUM RALFSII 1 1 <1 Riccardia chamedryfolia - - 2 Scleropodium purum - 1 2 VASCULAR PLANTS (% COVER) Carex arenaria - - 2 21 9 35 Cerastium fontanum - 3 - Festuca rubra 3 44 12 Juncus articulatus 1 2 3 Leotodon saxatilis 15 5 4 Lotus corniculatus - <1 - Luzula campestris - <1 - Prunella vulgaris - - 2 Salix repens 1 1 3 Selaginella selaginoides <1 2 <1 Spergularia cf. marina 8 - 6 Trifolium repens - 1 - Data collected 31 October 1999, in a small damp sandy hollow at the edge of a dune- slack, close to deflating sand. The site was intensely rabbit grazed.

13.2 APPENDIX 2: POPULATION STUDY AT UPTON TOWANS, W. CORNWALL, 1997-1999 When Plantlife International commenced work on Petalwort in 1996 lack of knowledge of many aspects of the life history, phenology and growth of the species was seen as a handicap to monitoring populations. It was known that the plants often disappeared from the ground surface in the summer when they aestivated as underground tubers, and that although dioecious, they often produced sporophytes from mid-winter to spring. However, details of the timing of the plants’ appearance above ground were lacking, along with information on the relation of this to water tables and other environmental changes. There were no data on longevity of individual thalli, or on rates of recruitment of new thalli from spores or vegetative growth. Also, the sex ratio was unknown and

26 there were no comparative data on size, growth or seasonal appearance of thalli of each sex or of the seasonal appearance of antheridia and archegonia.

METHODS In an attempt to provide information on at least some of these aspects of the biology of the species, a three-year study of part of a population at Upton Towans, West Cornwall was planned. Detailed observations were begun in March 1997 and continued on monthly visits until November 1999, so that they spanned all of three summers, all of two winters and parts of two additional winters. From September to May at least one visit was made each month, on a dry day as close to the 20th of each month as the weather and other work allowed. After it was found that no Petalwort were visible above ground from June to August the visits in these months were occasionally missed and otherwise limited to a quick check to confirm the non-appearance of the plants.

The study was carried out on part of the flat floor of a dune slack at SW 572398, in a situation chosen to be typical and hence representative of the occurrence of Petalwort in W. Cornwall. Observations were mainly made on a rectangular plot of 21.0 x 29.5 cm (A4-size). A rigid sheet of clear plastic glazing material (resembling perspex) slightly larger than the plot was placed over it on each monthly visit and precisely relocated each month by positioning a drilled hole in each corner over the tip of a cocktail stick left pushed into each corner of the plot. An A4 sheet of acetate was secured to the rigid plastic sheet using drafting tape and the exact position of each Petalwort thallus was traced onto it using a waterproof pen, then pens of different colours were used to draw in the outlines of the larger vascular plants present. Each Petalwort thallus was also measured (to within a 1-mm size class) and carefully searched for antheridia or archegonia using a x10 lens.

Results from successive monthly visits could be compared by overlaying successive acetates, allowing each thallus to be numbered and its growth and reproduction to be followed. By carefully replacing cocktail sticks at intervals (and pushing them back into the ground between visits) it proved possible to position the rigid plastic sheet and hence the acetates to within ± 1 mm through the three-year period of observation and hence to identify individual thalli. Branching to produce new thalli normally occurred beneath the surface of the substrate, so that each ‘new’ thallus that appeared was separately numbered even when its proximity to an existing thallus implied that it might only be a branch. On the other hand, when a thallus ‘reappeared’ in exactly the same location as one seen earlier in the same winter or in the same year it was assumed for purposes of analysis to be the same thallus, an assumption that was evidently well founded because it was clear that loose sand sometimes buried individual thalli for several months or that others died back from the ground surface then grew up again. When thalli ‘reappeared’ at longer than 12-month intervals they were assumed to be ‘new’ thalli for purposes of analysis.

RESULTS In March 1997 the study plot had about 35% of bare substrate exposed, mainly humic sand. Its vegetation was very short, mainly under 1 cm tall, kept low by intense grazing by rabbits. The vegetation cover was predominantly of Plantago coronopus (40%) and Festuca rubra (20%). Through successive winters up to late 1999 the amount of bare substrate decreased to about 15% as a result of increased cover from the herbaceous plants, so that by November 1999 Plantago coronopus occupied 45%, Festuca rubra 25% and Leontodon saxatilis 10%. Numbers of Petalwort thalli visible on the plot showed a progressive decrease from maximum monthly counts of 48 in 1997 to 16 in late 1999 (Table 7). This decrease was undoubtedly caused by reduction in open habitat as the cover increased.

Water levels were recorded each month in a shallow ‘ditch’ within 1 m of the plot. The ditch was always dry (water-level >12 cm below plot surface) from May to October and

27 always contained at least some [stagnant] water from December to February. In January 1998 the whole plot was flooded to a depth of 5 cm and through January and February 1999 it was flooded to about 1 cm depth. Although normally within 0-12 cm below ground-level, the level of the water-table in November, March and April varied between years, more or less according to rainfall variations.

Table 7 - Total numbers of thalli counted on the ground surface in each month.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 199 ? ? 46 35 28 0 0 0 0 48 42 37 7 199 0 7 17 28 5 0 0 0 0 18 22 20 8 199 0 0 8 8 0 0 0 0 9 14 16 ? 9

The absence of thalli at the surface in the summer of each year is associated with dry ground conditions. It is evident that exposed parts of individual thalli die back in late spring and that renewed growth from surviving underground parts of the same thalli commonly recommences in autumn.

Absence of visible thalli in winter months of some years (January 1998, January and February 1999) coincides with inundation of the study plot by shallow water, which rapidly covered the exposed parts of Petalwort thalli with a thin film of alluvial sand. Low counts immediately after the floodwater falls (February and March 1998, March and April 1999) result mainly from a proportion of the ‘old’ thalli growing through the alluvial sand. Disappearance of thalli from the surface in May tended to be associated with a seasonal burst of activity by ants, which bring light coloured buried sand to the surface in this month.

The proportion of thalli visible on the ground surface clearly varied widely between months, falling to 0% by mid-summer of each year (Table 8). The methodology adopted allowed estimates for most months of the total numbers of living thalli present, i.e. of the number of visible thalli plus the number of living thalli ‘hidden’ beneath the ground. ‘Hidden’ thalli were those recorded at a given location on both an earlier and a later monthly visit (within the same winter or the same year, but not over a longer interval). Thus estimates of numbers of ‘hidden’ thalli cannot be obtained for the first and last months of the study. The estimates for other months will be minima, since some thalli presumably remain alive underground for a month or more before dying without ever appearing again above the surface.

Table 8 - The numbers of thalli + additional ‘hidden’ thalli deduced for each month of the study, where additional thalli are preceded by a plus sign.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 199 46 35 28 0 0 0 0 48 42 37 ? ? 7 +? +13 +15 +43 +43 +43 +43 +10 +10 +9 199 0 7 17 28 5 0 0 0 0 18 22 20 8 +35 +28 +19 +6 +14 +19 +19 +19 +19 +8 +4 +4 199 0 0 8 8 0 0 0 0 9 14 16 ? 9 +16 +16 +8 +5 +7 +7 +7 +7 +1 +2 +?

28 These results show that a proportion of thalli remain alive but ‘hidden’ beneath the ground surface in all months, including winter months when numbers visible on the surface are highest. Thus in October 1997 the highest count of 48 visible thalli was accompanied by at least another 10 hidden thalli (i.e. at least 17% of thalli were then hidden). From this it is clear that ‘quantitative’ monitoring of Petalwort thalli based on counts from any single visit under ‘ideal’ conditions will always yield underestimates of the numbers present.

Analysis of the data shows that the overall decline in numbers on the study plot from 1997-1999 is much clearer when ‘total’ numbers of thalli are considered rather than just the ‘visible’ thalli (Holyoak 2000 p. 27). It would also appear that some mortality of thalli occurred between spring and autumn of each year. It may be unwise to assume that similar ‘summer mortality’ would occur in a population that was not in long-term decline, since effects of competing vascular plants on this study plot might have been greatest from late spring to early autumn. However, ‘summer mortality’ was evident in 1997 and there was little or no overall population decline that year.

In one year or another ‘new’ thalli (representing growth of new branches or growth of new plants from spores) appeared in all months when thalli were present above the ground surface. Nevertheless, the numbers of ‘new’ thalli in individual months were consistently higher in October (14 in 1997, 7 in 1998, 6 in 1999) and November (4, 5, 5) than in other months, except for a high total in April of 1997 (8, 0, 1). These data suggest that most new growth was made in the autumn but that there was sometimes a second burst of activity in spring. Plants cultivated indoors showed a similar pattern, but by artificially maintaining a high water level in the pots, they could be induced to continue vigorous growth into early summer or to start growth again in mid- or late summer.

There is little information on sex ratios in Petalwort. The sex of thalli could only be established when antheridia, archegonia, involucres or sporophytes are clearly seen to be present (Paton 1999, pp. 523-524). Hence only a minority of thalli could be assigned reliably to either sex at any one time. Confusion can easily arise in distinguishing ‘male bracts’ from the lobes of immature involucres so that sex determinations based only on these structures can be misleading. A general impression gained while visiting many British and Irish populations of the plant is that both sexes normally occur together, although many thalli often lack gametoecia. More detailed studies of several populations in Cornwall suggest both sexes normally occur together in roughly equal numbers or with some predominance of males. Dr T.H. Blackstock (pers. comm.) has stressed that such apparently consistent presence of both sexes in most if not all populations of Petalwort presumably implies regular if not frequent development of the plants from spores, since exclusively vegetative propagation would most likely result in local populations often consisting of clones of one sex or the other. Nevertheless, there are good reasons to believe that very many individual thalli derive from underground branches of existing thalli (Holyoak 1998a). Hence, British populations of Petalwort must presumably achieve both sexual and vegetative reproduction.

Observations on cultivated Petalwort imply that male plants produce more numerous, smaller thalli (i.e. they branch more often) than female thalli, although there is much overlap. The cultivated male plants also produce antheridia over a longer season (September - May) than that in which most female plants produce archegonia (October - January, rarely later).

In the study plot at Upton Towans information recorded on the presence of antheridia or archegonia eventually allowed the sex to be determined for just over one-third of all the thalli which were observed during the three years of study. No gametoecia were ever seen on the remaining almost two-thirds of thalli. When the data are set out for each month the numbers of thalli known to be male (M) almost always exceeded numbers of

29 those known to be female (F), but the imbalance varied from month to month in a rather inconsistent manner (Table 9).

Table 9 – Total numbers of thalli and numbers known to be male (M) or female (F) counted on the ground surface in each month.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 199 ? ? 46 35 28 0 0 0 0 48 42 37 7 ? ? 13 5 9 0 0 0 0 28 17 17 M ? ? 9 6 5 0 0 0 0 5 4 2 F 199 0 7 17 28 5 0 0 0 0 18 22 20 8 0 3 6 15 2 0 0 0 0 6 5 5 M 0 1 0 2 0 0 0 0 0 2 2 2 F 199 0 0 8 8 0 0 0 0 9 14 16 ? 9 0 0 3 1 0 0 0 0 2 3 4 ? M 0 0 1 0 0 0 0 0 1 2 2 ? F

It is apparent that simple ‘simultaneous’ counts of male and female thalli are likely to be of little value in elucidating more detail of sex ratios in Petalwort populations. Only a small fraction of thalli show gametoecia at any one time, male plants show them over a longer season than female plants and not all thalli are visible above ground simultaneously. The apparent excess of male thalli often noted (as in the Upton Towans study plot) may simply result from male plants branching more than female plants.

One may speculate that combinations of sexual selection and natural selection have acted differently in the evolution of male and female Petalwort plants. The males having been selected to produce numerous antheridia from more numerous, smaller and more widely scattered thalli over a long season, the females having been selected to withstand the nutritional demands of the largely parasitic sporophyte so that female thalli are few, large, and have development of archegonia timed to allow over-winter development of the sporophyte. Nevertheless, rigorous proof of such evolutionary speculations would be extremely difficult to obtain, requiring much detailed genetic and physiological information.

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