Ecology and Conservation of Vulpicida Pinastri
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Ecology and Conservation of Vulpicida pinastri Mark Binder & Christopher J. Ellis Royal Botanic Garden Edinburgh Published on-line: 2006 • British populations of the lichen Vulpicida pinastri (Scop.) Gray (synonym Cetraria pinastri ) are considered 'Near threatened' according to a 2003 IUCN assessment [1]. • Rare and locally restricted populations of V. pinastri in Britain occur at its biogeographic range-edge, in a setting that is relatively more temperate and oceanic, compared to its circumboreal-montane distribution in continental Eurasia and America [2, 3: Fig. 1]. Figure 1 : Vulpicida pinastri growing on Pinus mugo at ca 2000 m in the Austrian Tirol. Figure 2: Vulpicida pinastri growing on Juniperus communis at ca 400 m in north-east Scotland. • Populations of V. pinastri at its distributional range-edge in Britain (Fig. 2) may be constrained by a scarcity of suitable habitat [4], i.e. as establishment and growth become restricted to a reduced suite of favourable localities, in a climatically marginal area [5, 6]. • There are two key threats to British populations of V. pinastri : o Climate change : Vulpicida pinastri exemplifies species whose present-day British distribution is centred on the Cairngorm region of north-east Scotland [7]. The relatively continental Cairngorm region includes western-most outliers for lichen species with a boreal-montane distribution. Such species are expected to be threatened by warmer and wetter winters. o Habitat loss : Large areas of juniper provide the habitat for the majority of V. pinastri ’s British populations, including its only large populations [7: Fig. 2], with only rare and fewer thalli recorded elsewhere and on different substrata. Thus, the putative vulnerability of Britain’s range-edge population of V. pinastri , e.g. to climate change or pollution effects, may be exacerbated by the continuing wide-spread decline of juniper [8, 9]. 1 • Our research on V. pinastri has addressed three key themes: 1. Inferred past and present distribution, 2. Present and projected future distribution, and 3. Smaller-scale habitat factors controlling its local occurrence and abundance. > Inferred Past and Present Distribution • We reconstructed the distribution of V. pinastri within three time frames: pre-1900, 1900-1960 and post-1960. • We believe that these data demonstrate the useful application of herbarium specimens and recording schemes in assessing the status of a species, though based on careful caveats and assumptions. Two assumptions are critical to our interpretation of patterns of change in V. pinastri records: o That the range and intensity of lichen recording has been consistently, and across all time- frames, greater in England than in Scotland (and possibly Wales); o That the range and intensity of lichen recording has generally increased across Britain between the pre-1900 era and the post-1960s. • Our results point to an increase in the recorded occurrence of V. pinastri in Scotland, which may be attributed to increased sampling effort (Fig. 3). However, the apparent decline in occurrence of V. pinastri in England compared between the pre-1900 and post-1960 period contrasts with the assumption of increased sampling effort, and may tentatively indicate a regional decline. Figure 3: Change in the number of independent confirmed records for V. pinastri in England and Scotland, compared between three time-frames (data range = 1805-2007). > Present and Projected Future Distribution • We used nonparametric multiplicative regression [10] to examine the climatic response of V. pinastri . • This modelled response was then projected using UKCIP02 data [11], to estimate changes in available 'bioclimatic space' based on climate change scenarios for the 2050s (IPCC low and high greenhouse gas emissions, [12]). • However, the projected range of V. pinastri was further delimited by application of a 'habitat mask' [13]. This habitat mask was equivalent to recorded distribution of V. pinastri 's primary habitat (juniper scrub) during the present-day. For the 2050s scenarios, the habitat mask was equivalent to 2 the present-day distribution of juniper minus a number of sites corresponding to the documented rate of juniper decline [9], i.e. assuming continued loss of juniper. • Our results indicate the potential loss of suitable bioclimatic space for V. pinastri in Britain, in response to warmer winters (Fig. 4). These climate impacts may be augmented by the continued loss of juniper from the wider landscape. Unmodelled Present-day 2050s low 2050s high Lv = 0.53-0.9 Lv = > 0.9 Figure 4: Projected potential distribution of V. pinastri in response to climate (present-day, 2050s low and high emissions scenarios) and the present-day distribution and future loss of juniper (2050s). 'Unmodelled’ grid-squares comprise a projected clim ate that is beyond the range of the calibrated model, though are concentrated in south-eastern England, and in a drying and warming climate are unlikely to affect the general pattern of change. Two suitability values are shown, Lv (likelihood of occurrence) > 0.53, and > 0.9. > Local Habitat Factors • Threats to V. pinastr i may be mitigated 120 Structure Life stage through existing efforts to regenerate Number of upland scrub (including juniper) in the thalli 100 Scottish landscape. These efforts might be especially useful if habitat recreation is 80 focussed in north-east Scotland, where V. pinastri may prove most resistant to climate 60 warming (Fig. 4). 40 • We carried out research to examine the response of V. pinastri to variation in 20 juniper stand structure. Our results contribute towards a better understanding 0 d e of local habitat requirements, providing i ht r ad g ing Old e ri ram ild D u Matu Py B guidance for practical conservation action. w Up ed w SpreadingLo Lo Invert Figure 5: The number of V. pinastri thalli recorded from juniper shrubs with contrasting structure and life-stage. There were significantly more thalli on old, low-upright shrubs: tested using a Kruskal-Wallis test, for life-stage H = 14.93, P = 0.002 (3 d.f.), and for structure H = 17.17, P = < 0.001 (2 d.f.). 3 • Our results demonstrated that V. pinastri may be dispersal limited within a local setting, being aggregated amongst clumps of juniper whose individual shrubs occur at distances < 5 m apart. • Furthermore, V. pinastri appears to favour older and degenerate (but not dead) shrubs (Fig. 5). This finding points to the potential for a future bottle-neck in habitat availability, as a present-day cohort of degenerate and declining shrubs die-off, with few young shrubs currently established to replace the present-day old shrub habitat. References: [1] Woods, R.G. & Coppins, B.J. (2003) A Conservation Evaluation of British lichens . British Lichen Society, London. [2] Mattsson, J-E. (1993) A monograph of the genus Vulpicida (Parmeliaceae, Ascomycetes). Opera Botanica , 119: 1-61. [3] Randlane, T. & Saag, A. (2005) Distribution patterns of primary and secondary species in the genus Vulpicida . Folia Cryptogamica Estonica , 41: 89-96. [4] Brown, J.H. (1995) Macroecology . Chicago University Press, Chicago. [5] Lennon, J.J., Kunin, W.E., Corne, S., Carver, S. & Van Hees, W.W.S. (2002) Are Alaskan trees found in locally more favourable sites in marginal areas? Global Ecology and Biogeography , 11: 103-114. [6] Lidén, M. & Hilmo, O. (2005) Population characteristics of the suboceanic lichen Platismatia norvegica in core and fringe habitats: relations to macro-climate, substrate, and proximity to streams. The Bryologist , 108: 506-517. [7] Fryday, A. (2006) Lichens. In, The Nature of the Cairngorms (P. Shaw & D.B.A. Thompson, eds), pp. 177-193. Scottish Natural Heritage, Edinburgh. [8] Preston, C.D., Pearman, D.A. & Dines, T.D. (eds) (2002) New Atlas of the British and Irish Flora . Oxford University Press, Oxford. [9] Braithwaite, M.E., Ellis, R.W. & Preston, C.D. (2006) Change in the British Flora: 1987-2004 . Botanical Society of the British Isles, London. [10] McCune, B. (2006) Non-parametric habitat models with automatic interactions. Journal of Vegetation Science , 17: 819-830. [11] Hulme, M., Jenkins, G.J., Lu, X., Turnpenny, J.R., Mitchell, T.D., Jones, R.G., Lowe, J., Murphey, J.M., Hassell, D., Boorman, P., McDonald, R. & Hill, S., (2002) Climate change scenarios for the United Kingdom: the UKCIP02 scientific report . University of East Anglia, Norwich. [12] Nakicenovic, N. (2000) Special Report on Emissions Scenarios . IPCC III. Cambridge University Press, Cambridge. [13] Pearson, R.G., Dawson, T.P., Liu, C., 2004. Modelling species distributions in Britain: a hierarchical integration of climate and land-cover use. Ecography , 27: 285-298. 4 .