Local Adaptation in the Monocarpic Perennial Carlina Vulgaris at Different Spatial Scales Across Europe
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Oecologia (2006) 150:506–518 DOI 10.1007/s00442-006-0534-9 CONSERVATION ECOLOGY Local adaptation in the monocarpic perennial Carlina vulgaris at different spatial scales across Europe Ute Becker Æ Guy Colling Æ Petr Dostal Æ Anna Jakobsson Æ Diethart Matthies Received: 7 December 2005 / Accepted: 3 August 2006 / Published online: 6 September 2006 Ó Springer-Verlag 2006 Abstract Spatial variation in environmental condi- growth and reproduction over three growing periods. tions can lead to local adaptation of plant populations, At the regional scale, several performance traits and particularly if gene flow among populations is low. the individual fitness of C. vulgaris were highest if the Many studies have investigated adaptation to con- plants were grown in their home region and they de- trasting environmental conditions, but little is known creased with increasing transplant distance. The ef- about the spatial scale of adaptive evolution. We fect\s are likely due to climatic differences that studied population differentiation and local adaptation increased with the geographical distance between re- at two spatial scales in the monocarpic grassland gions. At the local scale, there were significant inter- perennial Carlina vulgaris. We reciprocally trans- actions between the effects of the population of origin planted seedlings among five European regions and the transplant site, but these were not due to an (northwestern Czech Republic, central Germany, enhanced performance of plants at their home site and Luxembourg, southern Sweden and northwestern they were not related to the geographical or environ- Switzerland) and among populations of different sizes mental distance between the site of origin and the within three of the regions. We recorded survival, transplant site. The size of the population of origin did not influence the strength of local adaptation. The re- sults of our study suggest that C. vulgaris consists of Communicated by Andrew Watkinson. regionally adapted genotypes, and that distance is a Electronic supplementary material Supplementary material is good predictor of the extent of adaptive differentiation available in the online version of this article at http://dx.doi.org/ at large scales ( > 200 km) but not at small scales. We 10.1007/s00442-006-0534-9 and is accessible for authorized users. conclude that patterns of local adaptation should be taken into account for the efficient preservation of U. Becker (&) Æ D. Matthies Department of Biology, University of Marburg, genetic resources, when assessing the status of a plant 35032 Marburg, Germany species and during conservation planning. e-mail: [email protected] Keywords Plasticity Æ Population differentiation Æ G. Colling Department of Population Biology, Population size Æ Reciprocal transplant experiment Muse´e national d’histoire naturelle, 25 rue Munster, 2160 Munster, Luxembourg Introduction P. Dostal Institute of Botany, Academy of Sciences of the Czech Republic, Many plant species have a large geographical range, 252 43 Pruhonice, Czech Republic over which environmental conditions can vary consid- erably. There are two principal mechanisms that may A. Jakobsson Department of Botany, Stockholm University, explain why a species is able to grow under different 106 91 Stockholm, Sweden conditions: phenotypic plasticity and evolutionary 123 Oecologia (2006) 150:506–518 507 adaptation. Phenotypic plasticity is the capacity of a quantifying the phenotypic differences among plants of genotype to express varying phenotypes depending on different origins; moreover, reciprocal transplant environmental conditions (Rice and Emery 2003). experiments permit the responses to different envi- When phenotypic responses to the environment are ronments to be examined (Linhart and Grant 1996; adaptive, plasticity allows individual genotypes to Briggs and Walters 1997). Most transplant studies have maintain fitness under diverse environmental condi- shown that genotypes grow better at their site of origin tions (Sultan and Spencer 2002). A plant species may than at foreign sites (Smith and Bradshaw 1979; van thus have a general-purpose genotype, which is very Andel 1998; Hufford and Mazer 2003), indicating plastic and able to grow, survive and reproduce under home-site advantages. However, most studies have different conditions. focused on adaptation to contrasting environments, i.e. A plant species may also consist of a number of on ecotypic differentiation (e.g. van Tienderen and van different ecotypes that are adapted to the particular der Toorn 1991; Nagy and Rice 1997; Gauthier et al. environmental conditions at different sites (Bradshaw 1998), and have been carried out at small spatial scales 1984; Schlichting and Pigliucci 1998). The evolution of (e.g. McGraw and Antonovics 1983; Waser and Price locally adapted genotypes requires consistent geo- 1985). In contrast, little is known about patterns of graphic variation in selection regimes that cause adaptation at larger geographical scales (Schmidt and directional trait changes, as well as limited gene flow Levin 1985; Galloway and Fenster 2000; Santamaria among populations. Differences in selection pressures et al. 2003). Because environmental differences are that can result in locally specialised ecotypes can be likely to increase and gene flow is likely to decrease due to heterogeneity in abiotic factors like climate with geographical distance, it may be expected that the (Joshi et al. 2001; McKay et al. 2001) and soil condi- extent of adaptive differentiation increases with the tions (Snaydon and Davies 1982; Gauthier et al. 1998), geographical distance between populations (Montalvo and due to differences in biotic factors like competi- and Ellstrand 2000; Joshi et al. 2001). Understanding tors, parasites, pathogens or mutualists (Parker 1995; the geographical scale over which plant species are Linhart and Grant 1996; Prati and Schmid 2000; Gil- adapted is of fundamental interest to evolutionary bert 2002). Genetic differentiation in response to biologists and biogeographists, and has recently be- physical environments typically occurs in a compara- come even more important because of concerns arising tively simple, contiguous fashion, whereas differentia- from ongoing restoration efforts (McKay et al. 2005). tion in response to biotic factors frequently shows fine- Habitat fragmentation, which results in decreased scale mosaic patterns (Linhart and Grant 1996; population size and increased isolation of populations, Thompson and Cunningham 2002). may influence the extent of local adaptation. However, It has been suggested that phenotypic plasticity and the effects of this can be difficult to predict. On the one genotypic variation are alternative means of adapta- hand, fragmentation might be expected to increase tion to heterogeneous environments in plants, because local adaptation, because gene flow (which could dilute phenotypic plasticity may reduce the effectiveness of local adaptations) is lower among isolated populations. selection in eliminating maladapted genotypes (Mar- On the other hand, the effects of random genetic drift in shall and Jain 1968; Sultan and Spencer 2002; Rice and small populations could become more important than Emery 2003). However, phenotypic plasticity does not those of selection and thus reduce or eliminate existing necessarily preclude local adaptation (Schlichting 1986; local adaptations (Frankham et al. 2002) and reduce the Hangelbroek et al. 2003). Because the costs of plas- ability to adapt to future changes in local environmental ticity are often high (DeWitt et al. 1998), dispersal conditions (Barrett and Kohn 1991; Helenurm 1998; distances in plants are typically low and most species Frankham 1999). However, little is known about show large genetic variation, local genetic differentia- the effects of population size and isolation on local tion is common in plants, and most species probably adaptation (Helenurm 1998; Hooftman et al. 2003). consist of many specialised genotypes that are adapted Improving our understanding of the extent of local to the particular conditions at a site or even within a adaptation and its spatial scale has become an specific site (van Tienderen 1990; Linhart and Grant increasingly important task (van Andel 1998; van 1996). Groenendael et al. 1998; Hufford and Mazer 2003; A useful approach to investigate local adaptation is McKay et al. 2005), because the introduction of foreign provided by reciprocal transplant experiments (Nagy seed material to restore populations and to increase and Rice 1997; Kawecki and Ebert 2004). Under the the biodiversity in intensively managed farmlands has environmental conditions at a transplant site, genetic become a frequent practice in modern landscape differences between populations can be studied by management (Keller et al. 2000). Moreover, the 123 508 Oecologia (2006) 150:506–518 reintroduction of endangered plants into sites where flowering plants varies between 2 and at least 11 years they have become extinct and the reinforcement of (Watt 1981; Klinkhamer et al. 1996; Rose et al. 2002). small populations are increasingly being discussed as From the end of June to September, reproducing potential conservation measures. The right choice of plants produce one to several flower heads, each with seed or plant material is crucial to the success of such up to 300 violet or yellow florets. In most plants, the projects, because if the plants are adapted to specific first flower head produced is the largest one. The flo-