Lejeunea Mandonii (Steph.) Müll.Frib
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Lejeunea mandonii (Steph.) Müll.Frib. Atlantic lejeunea LEJEUNEACEAE SYN.: Microlejeunea mandonii Steph., Lejeunea macvicari Pearson, Inflatolejeunea mandonii (Steph.) Perss. Status Bryophyte RDB - Endangered (2001) English Nature Species Recovery Status in Europe: Rare BAP Priority Species Lead Partner: Plantlife International UK Biodiversity Action Plan This is the current BAP target following the 2001 Targets Review: T1 - Maintain at all known, new or re-discovered sites. Progress on targets as reported in the UKBAP 2002 reporting round can be viewed online at: http://www.ukbap.org.uk/2002OnlineReport/mainframe.htm The full Action Plan for Lejeunea mandonii can be viewed on the following web page: http://www.ukbap.org.uk/asp/UKplans.asp?UKListID=406. Plantlife published an Expanded Species Action Plan for Lejeunea mandonii in 1999. Contents 1 Morphology, Identification, Taxonomy & Genetics................................................2 1.1 Morphology & Identification ........................................................................2 1.2 Taxonomic Considerations ..........................................................................4 1.3 Genetic Implications ..................................................................................4 2 Distribution & Current Status ...........................................................................5 2.1 World ......................................................................................................5 2.2 Europe ....................................................................................................5 2.3 United Kingdom ........................................................................................6 2.3.1 England .............................................................................................6 2.3.2 Northern Ireland..................................................................................7 2.3.3 Scotland.............................................................................................7 2.3.4 Wales ................................................................................................7 3 Ecology.........................................................................................................8 4 Habitat Requirements .....................................................................................9 4.1 The Landscape Perspective.........................................................................9 4.2 Communities & Vegetation .......................................................................14 4.3 Dispersal & Strategy................................................................................15 4.4 Habitat Requirements in the UK - Conclusion ..............................................15 5 Threats / Factors Leading to Loss or Decline of Recovery....................................15 6 Management Implications ..............................................................................16 7 Current & Future Conservation Methods...........................................................17 7.1 In Situ Measures....................................................................................17 1 7.2 Ex Situ Measures ...................................................................................18 7.3 Research Data ........................................................................................18 7.4 Monitoring Lejeunea mandonii & the Common Monitoring Standard................18 8 References ..................................................................................................18 9 Acknowledgements .......................................................................................20 10 Contacts...................................................................................................20 11 Links........................................................................................................20 12 Appendix 1. ..................................................................................................21 1 Morphology, Identification, Taxonomy & Genetics 1.1 MORPHOLOGY & IDENTIFICATION ‘Atlantic lejeunea’ (Lejeunea mandonii) is a small leafy liverwort that grows on basic rocks and tree bark. It has been found at only a few sites in Britain, located on the Lizard Peninsula of west Cornwall and in western Scotland. Elsewhere, it has been reported only from Ireland, Madeira, the Canary Islands, Portugal and western Spain. Its stems are very slender, usually less than 10mm long and form low or prostrate, bright yellow-green patches, often growing over low mosses. The leaves are in three ranks, comprising two rows of broadly lingulate leaves that each has a smaller, appressed antical lobe, and one row of much smaller bilobed underleaves. Distinction from allied species relies on careful appraisal of leaf shape, number and size of oil-bodies in the leaf-cells and the smooth perianth. Figure 1 - Photomicrograph of Lejeunea mandonii. (Photograph by Natural History Museum). 2 Figure 2 - Photomicrograph of leafy stem of Lejeunea lamacerina, a common species that differs from L. mandonii in larger size and rounder postical leaf lobes. (Photograph by David Holyoak). Figure 3 - Photomicrograph of mid-leaf cells of Lejeunea lamacerina showing four or five oil- bodies per cell. Lejeunea mandonii has more numerous and smaller oil-bodies. (Photograph by David Holyoak). 3 Considerable care is needed to distinguish Lejeunea mandonii from other Lejeunea species and confident field identification only becomes possible after prolonged familiarity with them. ‘The Liverwort Flora of the British Isles’ (Paton, 1999) should be consulted for illustrations and detailed descriptions of all British Lejeuneaceae. Lejeunea (including Lejeunea mandonii) and Microlejeunea species are distinct from other British genera of Lejeuneaceae in the form of the underleaves. Of the Lejeunea species occurring in Cornwall, L. cavifolia differs microscopically in having the oil-bodies in each leaf cell much more numerous, smaller and glistening. L. lamacerina and L. patens have fewer, larger oil-bodies (commonly 4-6, sometimes 10 per cell) much as in Lejeunea mandonii (which has 8-13, rarely up to 23 per cell), but both of those species are larger with the postical leaf-lobe normally more rounded (broadly ovate, compared to broadly lingulate in Lejeunea mandonii) (see Figures 1-3). The perianth of Lejeunea mandonii is smooth whereas those of other Lejeunea species occurring in Cornwall are five-angled or winged above, but no Lejeunea mandonii perianths were seen in Cornwall in 1997-2004. Lejeunea mandonii is considerably larger than Microlejeunea ulicina and Cololejeunea minutissima. Given familiarity with both species, Lejeunea mandonii can be distinguished in the field from L. lamacerina using a x10 (or better, x20) hand lens by its combination of narrower and more curved postical lobes and smaller size. Well-grown plants of L. patens and L. cavifolia tend to resemble L. lamacerina more than the smaller Lejeunea mandonii. Some patches of both L. lamacerina and L. mandonii can have very slender stems with small leaves and when attenuated, shaded stems of all these species tend to produce leaves that are longer than usual. The size and leaf-shape of Harpalejeunea molleri closely resemble those of Lejeunea mandonii, but its underleaves are quite different. In Cornwall both Harpalejeunea molleri and Lejeunea patens are rarities that infrequently confuse identification of Lejeunea mandonii, but this is not the case in Scotland or western Ireland and it is therefore much more difficult if not impossible to obtain reliable field identifications of Lejeunea mandonii in those regions. In recognition of these difficulties, identifications need to be checked microscopically and voucher specimens should be retained. With these Lejeunea it is important that voucher specimens are sufficiently large to show variability in leaf-shape and that counts and descriptions of the ephemeral oil-bodies are made and carefully recorded before the plants are dried. 1.2 TAXONOMIC CONSIDERATIONS Taxonomically, Lejeunea mandonii is the only European species in Subgenus Inflatolejeunea (S. Arn.) Schust. (Grolle 1983: 422). K. Müller published its name as the combination used here in Rabenhorst’s Krypt. -Fl. Deutschl., ed. 3, p. 1281 (1958), shortly before the same combination was proposed by E.W. Jones (1958). The older records in Britain were given as L. macvicari Perss., but Persson noted that this is the same as the earlier Lejeunea mandonii from Madeira (Jones 1958: 373). 1.3 GENETIC IMPLICATIONS There is no information on population genetics of Lejeunea mandonii (e.g. from isozymes) and no genetic data (e.g. from DNA sequences) on its affinities to closely related species. 4 2 Distribution & Current Status 2.1 WORLD Known only in Europe (including Macaronesia). 2.2 EUROPE Restricted to the Atlantic seaboard of western Europe and Macaronesia, with records from southwest England (Cornwall), western Scotland, Ireland, Portugal (mainland and Madeira) and Spain (mainland and Canary Islands). IRELAND Known in the Republic of Ireland only in three hectads (Hill et al, 1991: 262), all the records having been made since 1963, so presumably the species is still likely to be under-recorded. The Irish records are as follows: v.-c. H1: South Kerry: 'among boulders S. of Brandon Mt., Dingle, J. Fitzgerald, Aug. 1967' (Paton 1968: 628). v.-c. H2: North Kerry: 'shaded rock below Torc Cascade, Killarney, J.A. Paton,