(Lacerta Agilis) on the Edge of Its Range
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Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 41 Population Dynamics and Conservation of the Sand Lizard (Lacerta agilis) on the Edge of its Range SVEN-ÅKE BERGLIND ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 UPPSALA ISBN 91-554-6218-9 2005 urn:nbn:se:uu:diva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ÖRJAR OM IGEN. VI GER OSS INTE. Lars Gustafsson/En biodlares död List of papers This thesis is based on the following papers, which are referred to in the text by their Roman numerals: I Berglind, S-Å. 2000. Demography and management of relict sand lizard (Lacerta agilis) populations on the edge of extinction. – In: Sjögren-Gulve, P. & Ebenhard, T. (eds), The use of population viability analyses in conservation planning. Ecological Bulletins 48, pp. 123-142. II Berglind, S.-Å. 2004. Sand lizard (Lacerta agilis) in central Swe- den – modeling juvenile reintroduction and spatial management strategies for metapopulation establishment. – In: Akcakaya, H. R. et al. (eds), Species conservation and management: case studies. Oxford Univ. Press, New York, pp 326-339. III Berglind, S.-Å. Habitat tacking and population dynamics of an early successional lizard in a changing pine forest landscape. Manuscript. IV Berglind, S.-Å. 2004. Area-sensitivity of the sand lizard and spider wasps in sandy pine heath forests – umbrella species for early suc- cessional biodiversity conservation? – In: Angelstam, P. et al. (eds), Targets and tools for the maintenance of forest biodiversity. Ecological Bulletins 51, pp. 189-207. Paper I, II and IV are reprinted with kind permission from the publishers: © Munksgaard International Publishers Ltd (paper I) © Oxford University Press (paper II) © Blackwell Science (paper IV) Contents Introduction.....................................................................................................9 Objectives.................................................................................................11 Methods ........................................................................................................12 The sand lizard .........................................................................................12 Population study area ...............................................................................14 Population monitoring (I-III)....................................................................15 Demographic modelling (I and II)............................................................15 Simulation studies (I and II).....................................................................17 Demographic management scenarios (I)..................................................18 Habitat restoration and lizard colonisation (III) .......................................19 Regional and landscape surveys and usefulness as an umbrella species (IV) ..............................................................................................20 Results and Discussion .................................................................................22 Population subdivision and demographic management (I) ......................22 Modelling juvenile introduction and spatial management strategies for metapopulation establishment (II) ......................................................24 Habitat restoration and habitat tracking (III)............................................26 Area-sensitivity and usefulness as an umbrella species for biodiversity conservation (IV)......................................................................................28 Conclusions and long-term conservation .................................................31 Svensk sammanfattning ................................................................................33 Populationsförändringar och bevarande av sandödla (Lacerta agilis) på norra gränsen av utbredningsområdet..................................................33 Tack/Acknowledgements..............................................................................36 References.....................................................................................................38 Introduction "Species are likely to be 'rare' near the margins of their distribution and out- side the distribution they are 'extinct'. Because distribution and abundance are but two aspects of one phenomenon, the study of abundance in different parts of the distribution is itself a study of the causes of rareness and commonness in species." (Andrewartha & Birch 1954, p. 665) Species are not evenly distributed throughout their geographic range. Abun- dance tends to decrease towards the periphery of a species range, but the pattern is normally more complex than a gradual decline (e.g. Brown 1984, Lawton 1995, Brown & Lomolino 1998, Gaston 2003). Relict populations close to the range boundary often exhibit relatively low rates of population increase and low densities, the magnitudes of which can be expected to de- pend on whether the populations have retreated to marginal habitats or into former ”hotspots” (Lawton 1993, 1995). In theory, the conservation of geo- graphically peripheral populations poses particular difficulties since popula- tion densities and number of habitat types occupied are lower (Lawton 1993, Gaston 1994). Peripheral populations are also expected to be particularly liable to environmental and catastrophic variation, which generally have profound effects on extinction probabilities (e.g. Thomas 1990, Lande 1993, Caughley 1994), especially in species with low potential rates of population increase (Menges 1998). However, recently Channel & Lomolino (2000) showed that peripheral populations may be no more "doomed to extinction" than populations in the centre of a species´ range, and in fact often less so. In Scandinavia many species are at the northern limit of their range. A large number of these are included in the national red-lists, and there is a need to know more about their population dynamics for long-term conserva- tion (Berg and Tjernberg 1996, Gärdenfors 2000). The study of relict popu- lations known to have survived since pre-historic times is of particular inter- est since confounding effects of recent long-distance dispersal on population survival can be ruled out. In south-central Sweden, a small number of pe- ripheral populations of the sand lizard (Lacerta agilis) occur (Fig. 1) that are considered to be relicts from the postglacial warm period ca 7000-500 B.C. (Gislén and Kauri 1959, Gullberg et al. 1998). Most of these populations are restricted to large, sandy areas dominated by pine (Pinus sylvestris) forest 9 (Berglind et al. 2004). Berglind (1988) suggested that the survival of these populations in the past was largely dependent on recurrent forest fires and former human activities which may have created suitable early successional, open habitat patches with a mosaic of exposed sand and a rich field layer of heather (Calluna vulgaris). This thesis presents results from a 16-yr study of an isolated relict population of the sand lizard in south-central Sweden that consists of a few local populations. The need for conservation action to save this geographic population was realized some years ago (Berglind 1988), and here I evaluate some alternative conservation actions and management strategies. After Graeme Caughley (1994) pointed out what he saw as two disparate directions in conservation biology, there has been progress in blending the so called ”small-population paradigm” (primarily studying threatened species using stochastic models for small populations) with the ”declining- population paradigm” (empirical investigations of declining populations that tend to be case-specific). Still, much remains to be done (Boyce 2002). Caughley (1994) encouraged a profitable synergism among the two ap- proaches since the small-population paradigm needs more practice, and the declining-population paradigm more theory. This thesis sets out to consider both approaches. I evaluate the consequences of smallness by using population viability analysis (PVA), which can be described as a way to predict the probability of population extinction by using actual life-history information in models and project it forward using stochastic computer simulation (Brook et al. 2000). Although PVAs have become a cornerstone of conservation science (Beissinger 2002), it is essential to bear in mind that predictions of future population sizes can be accurate