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Local adaptation and life history differentiation in plant populations by Tove von Euler Supervisor: Johan Ehrlén Plants & Ecology Plant Ecology 2009/6 Department of Botany Stockholm University 1 Plants & Ecology Plant Ecology Department of Botany Stockholm University S-106 91 Stockholm Sweden © Plant Ecology ISSN 1651-9248 Printed by Solna Printcenter Cover: Primula farinosa, Dröstorp, Öland. Photo by Tove von Euler 2 Summary Terrestrial plants display a wide range of adaptations to their local environment. Phenotypic responses to environmental conditions select for genetic change and may result in altered patterns of life history, such as increased reproductive investment in response to environmental stochasticity. Regarding the selective agents on life history differentiation, abiotic and biotic components have been found to act on different temporal and spatial scales. Abiotic factors, such as moisture, soil conditions and exposure usually remain largely unchanged over long periods of time and adaptations to climatic features often follow clinal patterns along large geographical scales. Selection by biotic components on the other hand tends to display a more mosaic pattern, both temporally and spatially. In this paper, I will review and discuss some of the work performed on local adaptation to different environmental variables in terms of alterations in life history strategies among plant populations. I will focus on soil properties, climatic effects, and biotic interactions and discuss the relative impact of these factors on different life history traits. I will also discuss possibilities and constraints of the methods used to detect local adaptation in plant populations. Sammanfattning Landväxter uppvisar en rad anpassningar till sin lokala miljö. Fenotypiska responser till den lokala miljön selekterar för genetiska förändringar och kan leda till ändrade livshistoriemönster. Dessa kan ta sig uttryck i t ex ökad satsning på reproduktion kontra tillväxt till följd av stokastiska miljöförhållanden. Selektion för livshistoriestrategier kan ske på olika skala beroende på vilka miljöparametrar som ligger bakom selektionen. Abiotiska faktorer, såsom fuktighet, markförhållanden och exponering är ofta relativt konstanta under lång tid, medan den biotiska miljön ofta ter sig mer mosaisk i tid och rum. Jag kommer i den här uppsatsen att sammanfatta ett antal studier som gjorts av lokal anpassning i livshistorieegenskaper hos växtpopulationer. Jag har valt att fokusera på markförhållanden, klimatfaktorer och biotiska interaktioner och den relativa effekt dessa faktorer har på olika livshistoriekaraktärer. Jag kommer också att diskutera möjligheter och begränsningar med de forskningsmetoder som tillämpas för att studera lokal anpassning hos växtpopulationer. 3 Introduction During the past century, the environment has been exposed to great changes, such as intensified land use and climate change. Although it might be argued that the changes observed today occur at unnatural speed, occasional events of rapid environmental change have been present throughout the earth’s history, altering the conditions and selective pressures on its inhabitants. Thus, from an evolutionary perspective, the ability to adapt to new conditions is crucial for the survival and reproduction of organisms (Niklas 1997). Across the globe, terrestrial plants display a wide range of adaptations to their local environment. Selective factors contributing to these local adaptations include variation in the local abiotic (edaphic, climatic) and biotic (mutualists, pathogens, herbivores) environment, as a consequence of either natural or human induced forces (White 1984; Joshi et al. 2006). Features such as growth, fecundity and mortality may be affected by various environmental factors acting together on the individual plant, shaping the demography and life history of plant populations (Stearns 1992; Kalisz & Wardle 1994). Moreover, abiotic and biotic components of the environment have been found to exert selection at different temporal and spatial scales. Abiotic factors, such as moisture, soil conditions and exposure usually remain largely unchanged over long periods of time, thus acting on long temporal scales. Spatially, however, soil properties, such as nutrients and soil water content, tend to act on relatively small scales. Adaptations to climatic features (temperature, precipitation etc.) often follow clinal patterns along large geographical scales (Olsson & Ågren 2002; Dahlgren et al. 2007; Macel et al. 2007). Here, the temporal scale may be shorter, with large climatic fluctuations among years. Selection by biotic components tends to display more mosaic pattern, both temporally and spatially, because the selective agents are likely to display high dispersal rates, and also because the biotic environment itself may be subject to selection (Agrawal et al. 2006; Crémieux et al. 2008). The selective impact of environmental properties on plant populations will depend on several factors such as genetic diversity within the population, the extent of gene flow, dispersal pattern and demography. Different selection pressures exerted by different environments will result in genetic heterogeneity. Furthermore, abiotic factors such as elevation, exposure, and moisture availability may act as barriers to gene flow, enhancing genetic differentiation among semi-isolated or isolated populations. Together these factors determine the rate at which adaptation can proceed (Davis et al. 2005). 4 In this paper, I will review and discuss some of the work performed on local adaptation to different environmental variables in terms of alterations in demography (population age- or size structure and growth rate) and life history strategies (Age and size at maturity, number and size of offspring, reproductive lifespan and ageing) among plant populations. From the wide range of possible natural and anthropogenic environmental factors selecting for local adaptation, I have chosen to focus on soil properties, climatic effects, and biotic interactions. I will proceed to discuss the relative impact of these factors on different life history traits. Finally I will also discuss possibilities and constraints of the methods used to detect local adaptation in plant populations. Adaptation of life history traits Phenotypic responses to environmental circumstances select for genetic change and may result in altered patterns of life history. For instance, high or variable mortality may generate selective pressure toward early reproduction, high fecundity and few reproductions (Roff 2002). A central part of a species life history strategy is its reproductive pattern. Under selection for increased reproductive investment, many plants face arrested vegetative growth. In the process of allocation to features of growth and reproduction, the meristem of a plant may either differentiate into reproductive tissue, eliminating further growth or continue to grow vegetatively. Thus an increased allocation to one of the two will occur at the expense of the other. This phenomenon is central to life history theory and is referred to as trade-offs (Stearns 1992; Roff 2002). An altered environment may lead to an alteration in the relative parting of resources, changing the life history of the plant population and resulting in local adaptation. Plants display a number of reproductive strategies. At one extreme, some species reproduce only once and then die (semelparity), at the other, there are species that live and reproduce during hundreds of years (iteroparity). This variation in reproductive pattern enables plant populations to persist in many different types of environments. In environments with high or variable size-independent mortality, early reproduction, high fecundity, and few reproductions will be selected for. Furthermore, selection for long life, late maturity and many reproductions may occur in environments where the survival is size-dependent. Under these conditions, it is crucial to rapidly attain a large size to ensure survival before reproducing (Roff 2002). 5 Another important feature of plant life histories is the timing of reproductive events within growing seasons. Particularly in a seasonal environment, the onset and duration of flowering are major determinants of reproductive success. The benefits of flowering early, such as the possibility of having a longer flowering period, must be weighed against the drawbacks, sometimes involving greater risks of pre-reproductive mortality due to unfavorable weather. For species where the generation time is short relative to the growing season, it will be beneficial to have an extra generation within the same growing season (bivoltine species). Also, in areas with large variation in the length of the growing season, some species might display two different strategies; one variety with two generations within the same growing season, and one with only one generation per growing season (partially bivoltine). This pattern will increase fitness in years when the growing season is long, but will decrease fitness by means of high mortality and low reproduction in years with a shorter growing season. Conversely, in species that have long generations relative to season length, variation in development time will be favored when the length of the growing season is variable (Roff 2002). Methods of detecting local adaptation The relationships between biotic or abiotic factors and geographic variation in life-history traits are often used to infer genetic differentiation as an adaptive response to environmental factors (Mazer & LeBuhn 1999). In reviewing a number of articles on the subject of local adaptation in plant populations, I have come across several methods used to detect local adaptation. Many of them are observational, where plant populations have been monitored over spatial and temporal scales, and analyzed with aspect to various life history traits in relation to environmental factors. Using large enough samples, it is possible to draw proper conclusions on plant responses. However, it may be difficult to establish causal relationships based on observation alone. Therefore, these methods might be most useful when predicting possible plant-environment relationships. Using greenhouse or common garden experiments, where plant material is collected from the field and grown under common and controlled conditions, the possibility of detecting local adaptation is greater than in observational studies, since many environmental variables can be excluded from the study. Hence, differences observed between populations grown in a common environment most likely represent genetic differentiation. One drawback of this method, though, is that the conditions in a greenhouse or common garden are often markedly different from field conditions, and trait functions 6 observed in the controlled environment may not be present in the field, which again might make interpretation difficult. A time-consuming, but often rewarding method is to perform reciprocal transplantations in the field. Investigating plant population responses to local vs. foreign conditions, any local adaptation should be expressed as home-site advantage of local populations. In this way, one may be able to determine whether genetic differentiation observed among populations actually represents an adaptive response to environmental selective pressure (Mazer & LeBuhn 1999). In some cases, for instance when dealing with extremely rare species, it may not be justified to perform experiments on the species, risking contributing to its extinction. There may also be other financial or practical constraints to performing reciprocal transplantations. In these cases, using experimental modeling may be a suitable method. Several models of this kind have been developed, and many are used to make predictions about future responses of plant populations to changes in their environment. When testing for local adaptation by means of reciprocal transplantation, there are two commonly used approaches. One is the ‘Local vs. foreign’ approach, according to which the home population will always perform better compared with foreign populations at the home site. The other approach is the ‘Home vs. away’ approach, where any population should always perform better at its home site than at any other site (Kawecki & Ebert 2004). According to Kawecki, the former criterion is preferred, since it deals directly with divergent natural selection acting on genetic differences in relative fitness within habitats. Thus, traits that provide an advantage under local environmental conditions should be selected for. However, these traits may perform equally well or even better in other habitat types. In the home vs. away approach, the effects of divergent selection may be difficult to separate from differences in habitat quality; A genotype that is optimally adapted to a poor-quality habitat may still perform better in a resource-rich habitat, although it is only able to outperform other genotypes in its resource-poor home-environment. Effects of soil properties Soil quality is of great importance to plant growth and persistence. It provides plants with the necessary mineral nutrients, water, and oxygen, and supports the root system that absorbs and transports these substances to the aboveground parts of the plant (Black 1957). Variation in soil properties has been reported to affect plant performance on scales of only a few centimeters (Argyres & Schmitt 1991). Examples of soil characteristics that may vary between environments are texture, nutrients, moisture and biotic content. In many cases it 7 may be difficult to separate these features, since they are strongly linked together. For example, the nitrogen content of the soil is partly determined by plants and microorganisms, which in turn are affected by temperature and water supply (Black 1957). Soil texture Soil texture can roughly be divided into three categories: Sand, silt and clay, where sand represents the coarsest soil type and clay the finest (Hansen 1926; Black 1957). Soil texture mainly imposes an indirect effect on plant performance in that it affects water availability. Which soil type is most profitable to a plant is somewhat ambiguous, in that, on the one hand, fine-textured soil has a higher water-retaining capacity, which may limit the risk of severe drought. Meanwhile, in coarse-grained soil, water is more easily accessible to the plants, but is also more rapidly lost through drainage. It is therefore difficult to determine the amount of water that is actually available to the plants judging only from soil water content (Hansen 1926; Sala et al. 1988). A model of soil water accessibility that also takes into account the climatic circumstances is the inverse-texture hypothesis, according to which plant communities growing on coarse textured soils should have higher above-ground net primary productivity (ANPP) in arid conditions, whereas in humid environments, the relationship should be reversed (Noy-Meir 1973). The effect of soil texture on plant populations has also been shown to vary with seasons. In order to study variation in Bromus tectorum performance in relation to soil type, Miller et al. (2006) manipulated water and nutrient availability across a range of soils and measured various plant traits, such as establishment and seasonal growth rates. Performance was poorer on sandy soils during the wet fall and winter season but greater during the dryer spring season, indicating a seasonal shift in the above-mentioned inverse texture hypothesis. Soil nutrients Plants depend upon a range of nutrients to perform functions such as water uptake, stomatal regulation, seed production etc. In nutrient-poor environments, plants may develop strategies to better cope with a limited supply of nutrients, or to use available nutrients more efficiently (da Silva et al. 2008). Effects of soil nutrients are often analyzed in relation to climatic factors. Among-site variation in nutrient availability has been shown to affect flowering phenology of plant populations (Black 1957; Dahlgren 2007). Investigating the effects of environmental heterogeneity on flowering phenology in Actaea spicata, Dahlgren et al. 8 (2007) found that within populations, there was a variation in flowering time related to changes in microenvironment; small individuals on steep, south-facing slopes and on soils richer in potassium emerged earlier and flowered earlier. Among plots, however, flowering time was chiefly dependent on soil temperature, slope, and July canopy cover. When studying soil type and local adaptation, greenhouse experiments are sometimes used to control for surrounding environmental factors. One such experiment was carried out by Abdala-Roberts & Marquis (2007), who tested whether soil source affected reproduction in C. fasciculata, and also whether there was any local adaptation to soil abiotic conditions in the populations studied. In the greenhouse, plants from three different sites were grown on the home soil of all three sites. The results showed that soil from one site significantly increased flower production in all populations, compared to soils from the other sites. This soil had the highest percentage of organic matter and showed the highest concentrations of K, Ca, Mg and nitrates, as well as the highest pH. However, plants grown on their native soil did not outperform nonnatives, a result which suggests a plastic response to soil quality rather than local adaptation. Soil depth As mentioned above, soil water content is strongly related to soil texture. Another factor affecting soil water content is soil depth, which may influence soil water holding capacity and thereby affect reproduction, growth and survival among plant populations (Toräng et al. 2007). In a three-year study on flowering and fruit set in relation to environmental factors in Vincetoxicum hirundinaria, Ågren et al. (2008) monitored 39 populations of different size and habitat quality. Here, fruit and flower production were expected to be positively related to soil depth, particularly in dry summers. Their hypothesis was confirmed; Flower production was positively related to sun exposure and soil depth, and fruit set was indirectly affected by those variables through increase in flower number. In another field study, Kephart & Paladino (1997) aimed at identifying environmental features of two grassland microhabitats that may influence the population biology of Silene douglasii. Comparing rocky and grassy growth sites, they found both temporal and spatial variation in population growth rate. Most abiotic variables showed no significant difference between habitats or varied more seasonally within a habitat than between grassy and rocky areas. However, juvenile recruitment and adult survivorship were highest in open, rocky sites with 9 low vegetation. From these findings, it was concluded that light might be a limiting factor in deep soil areas with more vegetation, leading to life history differentiation in S. douglasii. In this case, population growth rate was indirectly affected by soil depth, in terms of increased vegetation density. Climatic variation Climatic variation has received much attention recently, much because of the issue of global warming. During the past few decades, rapid changes in flowering time in response to temperature changes have been reported. According to Fitter & Fitter (2002), there has been a major shift in first flowering date in British plant species since the 1980’s, largely due to increased temperature. In Campanula americanum, fall germinating seeds grow as annuals and spring-germinating seeds are biennials (Baskin & Baskin 1984). In this species, selection for earlier flowering by a warmer climate could result in correlated responses that alter the species life history schedule (Burgess et al. 2007). Because whole community alterations caused by global changes must begin with alterations of the population dynamics of the component species, knowledge of the demographic response of plant species to global changes is important to make predictions about future ecosystem function (Williams et al. 2007). Drought Not surprisingly, water availability plays an important role when examining adaptive responses of plant populations to climatic variation. The effect of soil properties on local adaptation in local and foreign populations of Taraxacum officinale was investigated in a common-garden experiment performed by Quiroz et al. (2009). The aim of the study was to investigate whether T. officinale populations of native and introduced origin were similarly affected by environmental conditions. Plants from native (Alpine) and introduced (Andean) populations were exposed to a drought experiment. With drought, individuals from both origins showed phenotypic plasticity in the root:shoot ratio, increasing allocation to belowground biomass. However, this plasticity was more pronounced among native individuals. Furthermore, unlike the Alpine plants, plants from the Andean populations still produced flowers when exposed to drought. Quiroz interprets this as an adaptation to the considerably dryer growing conditions in central Chile, where higher levels of drought tolerance are crucial to successful establishment. 10 Clinal variation Many studies on local adaptation are made along clinal geographical gradients, either as reciprocal transplantations or in common-garden experiments. In one such study on Lythrum salicaria along a clinal gradient in Sweden, Olsson & Ågren (2002) found different responses in phenological and morphological traits across the country. Using a common-garden experiment, they were able to show that characters such as phenology of growth and flowering, allocation to winter buds and length of the juvenile period were correlated with latitude of origin, whereas flower morphology displayed a more mosaic pattern of variation. There was also a variation in growth pattern, with northern populations being taller early in the season, probably as a consequence of the shorter growing season. However, these plants were outgrown by plants from the southern populations at the end of the season. A replant – transplant study on a larger geographical scale was performed by Joshi et al. (2001). Here, individuals of three common plant species (Trifolium pratense, Dactylis glomerata and Plantago lanceolata) were transplanted to eight field sites across Europe and monitored for two years. Apart from testing for local adaptation, they also tested whether selection against foreign strains increased with geographical distance. In T. pratense, local adaptation was found in terms of reproduction (inflorescence diameter). In addition to higher reproductive performance, local strains of P. lanceolata and D. glomerata also showed enhanced vegetative growth (leaf length). Overall, selection was strongest against northern strains of all three species. However, climatic distance only explained 18% of the variance of distance in the analysis of selection indices, indicating that other local environmental factors may also have exerted strong selection pressures. Biotic interactions To a great extent, selection on demography and life history of plant populations is the result of biotic interactions. Biotic environments evolve, and may coevolve with plant species (Kawecki & Ebert 2004; Agrawal et al. 2006). The outcome of biotic interactions may be mutualistic, commensalistic or parasitic, sometimes altering between different modes of interaction, and has been described as the raw material for the evolution of biotic communities (Thompson 1988). 11 Pollinators There are several examples of mutualistic interactions between plants and their biotic environments. However, the most common and diverse mutualisms - at least above ground – occur between plants and their pollinators. These interactions may largely influence population persistence, and Hegland et al. (2009) suggest two ways in which plant-pollinator interactions can be disrupted: Through temporal or spatial mismatch among plants and pollinators altering the availability of mutualistic partners, which may result in rapid evolution in plant pollination and reproductive traits and in foraging and phenological traits in pollinators. Paige and Whitham (1987) studied the effects of pollinator abundance on lifehistory traits in Ipomopsis aggregata at different altitudes in Fern Mountain, Arizona. Experimental pollinator exclusions were performed, showing that at high altitudes, where pollinator abundance was fluctuating, I. aggregata could shift from its normal semelparous mode of reproduction to iteroparous reproduction in response to low levels of fruit set and pollinator abundance. In response to low fruit set, individual plants were able to reallocate resources to rosette formation, thereby shifting from semelparity to iteroparity. At lower altitudes, however, where pollinator densities normally showed little variation, only one out of 37 individuals altered its reproductive pattern in response to experimental pollinator exclusion, suggesting that flexibility in life cycle pattern may represent a local adaptation. Surrounding vegetation Apart from being affected by abiotic conditions and animal interactions, Plants are also constantly affected by the surrounding plant community, and the fitness consequences of plant - plant interactions can be positive or negative (Tuomi et al. 1999). Bischoff et al. (2006) studied the effect of competition within the local plant community on local adaptation of Holcus lanatus, Lotus corniculatus and Plantago lanceolata. Bischoff compared the performance of plants of different origin sown in weeded monocultures with the performance when sown in a local grassland community context. Local adaptation was evident in terms of seedling emergence, reproduction and survival rates of P. lanceolata, and reproductive traits such as panicle and seed number in H. lanatus. For P. lanceolata, the home vs. foreign contrast of most traits was stronger in the presence of the local plant community. For H. lanatus, on the other hand, this contrast was more pronounced when the plants were grown in a weeded monoculture. In L. corniculatus, no evidence of any home site advantage was found. According to Bischoff, these results show that local adaptation may be affected by 12 competition with the local plant community, as a result of community-specific abiotic conditions to which species are adapted. Neighboring plants may also exert chemically mediated selection pressures on plant populations. Grondahl & Ehlers (2008) performed reciprocal transplantations to investigate local adaptation to neighboring plants with aromatic compounds. Plants from environments with different terpenes were transplanted to soil containing these different terpenes and found that the transplanted plants performed better on soil containing the home-terpene, in terms of seed germination and root biomass. For Achillea millefolium, however, the aboveground biomass was lower for plants growing on home soil, which was interpreted as compensation for the increased root biomass. The results also indicated that there was a trade off between increased root biomass and reproductive investment. For both P. lanceolata and A. millefolium, reproductive investment was larger on control soil. Discussion The most common designs for studying local adaptation in plant populations are observational studies, common garden experiments and reciprocal transplant experiments. From observational studies, local differences have been reported in features such as rate of survival, germination of seedlings, growth rate and flowering phenology. However, there is no knowing whether these findings represent local adaptation of phenotypic plasticity. To rule out phenotypic plasticity, many studies have been performed using common garden experiments. Here, variation in vegetative growth, reproduction, survival, seedling germination and phenology has been reported as local adaptations in plant populations. However, using common garden experiments may still not answer the question whether the observed genotypic variation is actually the result of selection pressure imposed by the environment or whether it is merely the result of factors such as isolation or genetic drift. I found two examples of reciprocal transplantation studies on local adaptation in plant life history traits. In one of these studies, where local adaptation to climatic factors was studied on a European scale, local adaptation was mainly expressed in reproductive features, although to some extent also in vegetative growth. In the other, which focused on the effects of neighboring plants with aromatic compounds, local plants performed better in terms of seed germination and below-ground biomass. There were also examples where common garden studies were combined with experimental manipulations. Using this type of design, it is possible to expose plants of different origins to simulated field conditions of varying quality, 13 while still working in a controlled environment. These experiments may provide more valid information about local adaptation than regular common garden experiments. Judging from these studies, it would seem that observational studies should be combined with, or followed by, experimental studies, when studying local adaptation in plant populations. The environmental factors discussed in this paper affected different aspects of life history of the studied populations. On small spatial scales, under similar climatic and geographic conditions, plant population responses were expressed in terms of flowering phenology, flower production and seedling recruitment. On larger spatial scales, where the plant populations studied were often exposed to different latitudinal or altitudinal conditions, evidence of local adaptation was mainly found in traits such as phenology of growth and flowering, growth pattern and reproductive effort. Regarding soil properties, most of the studies were observational, which makes it difficult to draw conclusions about local adaptation. Moreover, soil properties seemed to act on rather local scales, and were often closely linked to other environmental factors, such as vegetation structure and humidity. However, whether adaptive or plastic, the traits affected by heterogeneous soil conditions were vegetative, demographic and phenological. Responses to climatic variation included variation in reproductive characters and flowering phenology. In addition, differences in drought-resistance between populations of different origin were found, indicating local adaptation. Finally, in the studies on adaptation of plants to their biotic environment, effects on reproductive pattern, demography and vegetative growth were observed. Many articles on local adaptation highlight the difficulty to distinguish possible driving forces behind the observed patterns of differentiation (Kephart & Paladino 1997; Crémieux et al. 2008). One reason for this is that many environmental factors often act together on the demography and life history of plant populations, such as soil texture and humidity or soil depth combined with sun exposure and vegetation density. Due to the unstable nature of the biotic environment itself, plants tend to respond to biotic selective agents in a mosaic pattern and it is often difficult to disentangle selection pressures exerted by single agents. Plant population size has frequently been reported to affect pollinator abundance and activity. Moreover, plants themselves may exert considerable selective pressure on neighboring plant species. Furthermore, the selective impact of certain environmental conditions may vary between years or even between seasons; different combinations of soil characteristics and climatic condition may render different selective pressures, governed by factors such as soil 14 water retaining capacity. Despite these difficulties, though, the effort of conducting research on environmentally induced life history differentiation in plant populations is still worthwhile, since it provides valuable information about evolutionary mechanisms, and demographic responses to changing environmental conditions. Furthermore, in terms of conservation, increased knowledge of life history responses to environmental heterogeneity on different temporal and spatial scales is of great importance. By combining observational and experimental methods for detecting local adaptation, a greater understanding of the processes governing life history responses to environmental variation may be obtained. Acknowledgements Thanks to my supervisor Johan Ehrlén for reading and providing comments on this paper. References Abdala-Roberts, L. & Marquis, R. J. (2007) Test of local adaptation to biotic interactions and soil abiotic conditions in the ant-tended Chamaecrista fasciculata (Fabaceae). – Oecologica 154: 315-326. Agrawal, A. A., Lau, J. A. & Hambäck, P. (2006) Community heterogeneity and the evolution of interactions between plants and insect herbivores. – The Quarterly Review of Biology 81: 349-376. Ågren, J., Ehrlén, J. & Solbreck, C. (2008) Spatio-temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size. – Journal of Ecology 96: 334-345. Argyres, A. Z. & Schmitt, J. (1991) Microgeographic genetic structure of morphological and life history traits in a natural population of Impatiens capensis. – Evolution 45: 178-189. Baskin, J. M. & Baskin, C. C. (1984) The ecological life cycle of Campanula americana in northcentral Kentucky. – Bulletin of the Torrey Botanical Club 111: 329-337. Bischoff, A., Crémieux, L., Smilauerova, M., Lawson, C. S., Mortimer, S. R., Dolezal, J., Lanta, V., Edwards, A. R., Brook, A. J., Macel, M., Leps, J., Steinger, T. & Müller-Schärer, H. (2006) Detecting local adaptation in windspread grassland species – the importance of scale and local plant community. – Journal of Ecology 94: 1130-1142. Black, C. A. (1957) Soil-plant relationships. John Wiley & sons, Iowa. Burgess 2007, K. S., Etterson, J. R. & Galloway, L. F. (2007) Artificial selection shifts flowering phenology and other correlated traits in an autotetraploid herb. – Heredity 99: 641-648. 15 Crémieux, L., Bischoff, A., Šmilauernová, M., Lawson, C. S., Mortimer, S. R., Doležal, J., Lanta, V., Edwards, A. R., Brook, A. J., Tscheulin, T., Macel, M., Lepš, J., Müller-Schärer, H. & Steinger, T. (2008) Potential contribution of natural enemies to patterns of local adaptation in plants. – New Phytologist 180: 524-533. Dahlgren, J. P., von Zeipel, H. & Ehrlén, J. (2007) Variation in vegetative and flowering phenology in a forest herb caused by environmental heterogeneity. – American Journal of Botany 94(9): 1570-1576. Davis, M. B., Shaw, R. G. & Etterson, J. R. (2005) Evolutionary responses to changing climate. – Ecology 86(7): 1704-1714. Fitter, A. H. & Fitter, R. S. R. (2002) Rapid changes in flowering time in British plants. – Science 296: 1689-1691. Grøndahl, E. & Ehlers, B. K. (2008) Local adaptation to biotic factors: Reciprocal transplants of four species associated with aromatic Thymus pulegioides and T. serpyllum. – Journal of Ecology 96: 981-992. Hansen, H. C. (1926) The water-retaining power of the soil. – The Journal of Ecology 14: 111-119. Hegland, S. J., Nielsen, A., Lázaro, A., Bjerknes, A. & Totland, Ø. (2009) How does climate warming affect plant-pollinator interactions? – Ecology Letters 12: 184-195. Joshi, J., Schmid, B., Caldeira, M. C., Dimitrakopoulus, P. G., Good, J., Harris, R., Hector, A., Huss-Danell, K., Jumpponen, A., Minns, A., Mulder, C. P. H., Pereira, J. S., Prinz, A., Scherer-Lorenzen, M., Siamantziouras, A. S. D., Terry, A. C., Troumbis, A. Y. & Lawton, J. H. (2001) Local adaptation enhances performance of common plant species. Ecology Letters 4: 536-544. Kalisz, S. & Wardle, G. M. (1994) Life history variation in Campanula americana (Campanulaceae): Population differentiation. – American Journal of Botany 81(5): 521-527. Kawecki, T. J. & Ebert, D. (2004) Conceptual issues in local adaptation. – Ecology Letters 7: 1225-1241. Kephart, S. R. & Paladino, C. (1997) Demographic change and microhabitat variability in a grassland endemic, Silene douglasii var. oraria (Caryophyllaceae). – American Journal of Botany 84(2): 179-189. Macel, M., Lawson, C. S., Mortimer, S. R., Šmilauernová, M., Bischoff, A., Crémieux, L., Doležal, J., Edwards, A. R., Lanta, V., Bezemer, T. M., van der Putten, W. H., Igual, J. M., Rodriguez-Barrueco, C., Müller-Schärer, H. & Steinger, T. (2007) Climate vs. soil factors in local adaptation of two common plant species. – Ecology 88(2): 424-433. Mazer, S. J. & LeBuhn, G. (1999) Genetic variation in life-history traits: heritability estimates within and genetic differentiation among populations. In Vuorisalo, T. O. & Mutikainen, P. 16 K. (Eds.) Life History Evolution in Plants. Kluwer Academic Publishers, Norwell, MA, pp 85-148. Miller, M. E., Belnap, J., Beatty, S. B. & Reynolds, R. L. (2006) Performance of Bromus tectorum L. in relation to soil properties, water additions, and chemical amendments in calcareous soils of southeastern Utah, USA. – Plant Soil 288: 1-18. Niklas, K. J. (1997) The Evolutionary Biology of Plants. The University of Chicago Press, London. Noy-Meir, I. (1973) Desert ecosystems: environment and producers. – Annual Reviews of Ecology and Systematics 4: 25-51. Olsson, K., Ågren, J. (2002) Latitudinal population differentiation in phenology, life history and flower morphology in the perennial herb Lythrum salicaria. – Journal of Evolutionary Biology 15: 983-996. Paige, K. N. & Whitham, T. G. (1987) Flexible life history traits: shifts by scarlet gilia in response to pollinator abundance. – Ecology 68(6): 1691-1695. Quiroz, C. L., Choler, P., Baptist, F., González-Teuber, M., Molina-Montenegro, M. A. & Cavieres, L. A. (2009) Alpine dandelions originated in the native and introduced range differ in their response to environmental constraints. – Ecological research 24: 175-183. Roff, D. A. (2002) Life History Evolution. Sinauer Associates, Sunderland, MA. Sala, O. E., Parton, W. J., Joyce, L. A. & Lauenroth, W. K. (1988) Primary production of the central grassland region of the United States. – Ecology 69(1): 40-45. da Silva, C. E. M., de Carvalho Goncalves, J. F. & Feldpausch, T. R. (2008) Water-use efficiency of tree species following calcium and phosphorous application on an abandoned pasture, central Amazonia, Brazil. – Environmental and Experimental Botany 64: 189-195. Stearns, S. C. (1992) The Evolution of Life Histories. Oxford University Press, USA. Thompson, J. N. (1988) Variation in interspecific interactions. – Annual Review of Ecology and Systematics 19: 65-87. Toräng, P. (2007) Pollinators, enemies, drought, and the evolution of reproductive traits in Primula farinosa. Uppsala University. Tuomi, J., Augner, M. & Leimar, O. (1999) Fitness interactions among plants: optimal defence and evolutionary game theory. In Vuorisalo, T. O. & Mutikainen, P. K. (Eds.) Life History Evolution in Plants. Kluwer Academic Publishers, Norwell, MA, pp 63-81. White, T. C. R. (1984) The abundance of invertebrate herbivores in relation to the availability of nitrogen in stressed food plants. – Oecologia 63: 90-105. 17 Williams, A. L., Wills, K. E., Janes, J. K., Vander Schoor, J. K., Newton, P. C. D. & Hovenden, M. J. (2007) Warming and free-air CO2 enrichment alter demographics in four co-occurring grassland species. – New Phytologist 176: 365-374. Serien Plants & Ecology (ISSN 1651-9248) har tidigare haft namnen "Meddelanden från Växtekologiska avdelningen, Botaniska institutionen, Stockholms Universitet" nummer 1978:1 – 1993:1 samt "Växtekologi". (ISSN 1400-9501) nummer 1994:1 – 2003:3. Följande publikationer ingår i utgivningen: 1978:1 1978:2 1978:3 1978:4: 1978:5 1979:1 1979:2 1979:3 1979:4 1979:5 1980:1 1980:2 1980:3 1981:1 1983:1 1984:1 1986:1 1986:2 1987:1 1987:2 1988:1 1988:2 1988:3 1989:1 Liljelund, Lars-Erik: Kompendium i matematik för ekologer. Carlsson, Lars: Vegetationen på Littejåkkadeltat vid Sitasjaure, Lule Lappmark. Tapper, Per-Göran: Den maritima lövskogen i Stockholms skärgård. Forsse, Erik: Vegetationskartans användbarhet vid detaljplanering av fritidsbebyggelse. Bråvander, Lars-Gunnar och Engelmark, Thorbjörn: Botaniska studier vid Porjusselets och St. Lulevattens stränder i samband med regleringen 1974. Engström, Peter: Tillväxt, sulfatupptag och omsättning av cellmaterial hos pelagiska saltvattensbakterier. Eriksson, Sonja: Vegetationsutvecklingen i Husby-Långhundra de senaste tvåhundra åren. Bråvander, Lars-Gunnar: Vegetation och flora i övre Teusadalen och vid Autaoch Sitjasjaure; Norra Lule Lappmark. En översiktlig inventering med anledning av områdets exploatering för vattenkraftsändamål i Ritsemprojektet. Liljelund, Lars-Erik, Emanuelsson, Urban, Florgård, C. och Hofman-Bang, Vilhelm: Kunskapsöversikt och forskningsbehov rörande mekanisk påverkan på mark och vegetation. Reinhard, Ylva: Avloppsinfiltration - ett försök till konsekvensbeskrivning. Telenius, Anders och Torstensson, Peter: Populationsstudie på Spergularia marina och Spergularia media. I Frödimorfism och reproduktion. Hilding, Tuija: Populationsstudier på Spergularia marina och Spergularia media. II Resursallokering och mortalitet. Eriksson, Ove: Reproduktion och vegetativ spridning hos Potentilla anserina L. Eriksson, Torsten: Aspekter på färgvariation hos Dactylorhiza sambucina. Blom, Göran: Undersökningar av lertäkter i Färentuna, Ekerö kommun. Jerling, Ingemar: Kalkning som motåtgärd till försurningen och dess effekter på blåbär, Vaccinium myrtillus. Svanberg, Kerstin: En studie av grusbräckans (Saxifraga tridactylites) demografi. Nyberg, Hans: Förändringar i träd- och buskskiktets sammansättning i ädellövskogen på Tullgarnsnäset 1960-1983. Edenholm, Krister: Undersökningar av vegetationspåverkan av vildsvinsbök i Tullgarnsområdet. Nilsson, Thomas: Variation i fröstorlek och tillväxthastighet inom släktet Veronica. Ehrlén, Johan: Fröproduktion hos vårärt (Lathyrus vernus L.). - Begränsningar och reglering. Dinnétz, Patrik: Local variation in degree of gynodioecy and protogyny in Plantago maritima. Blom, Göran och Wincent, Helena: Effekter of kalkning på ängsvegetation. Eriksson, Pia: Täthetsreglering i Littoralvegetation. 18 1989:2 Kalvas, Arja: Jämförande studier av Fucus-populationer från Östersjön och västkusten. 1990:1 Kiviniemi, Katariina: Groddplantsetablering och spridning hos smultron, Fragaria vesca. 1990:2 Idestam-Almquist, Jerker: Transplantationsförsök med Borstnate. 1992:1 Malm, Torleif: Allokemisk påverkan från mucus hos åtta bruna makroalger på epifytiska alger. 1992:2 Pontis, Cristina: Om groddknoppar och tandrötter. Funderingar kring en klonal växt: Dentaria bulbifera. 1992:3 Agartz, Susanne: Optimal utkorsning hos Primula farinosa. 1992:4 Berglund, Anita: Ekologiska effekter av en parasitsvamp - Uromyces lineolatus på Glaux maritima (Strandkrypa). 1992:5 Ehn, Maria: Distribution and tetrasporophytes in populations of Chondrus crispus Stackhouse (Gigartinaceae, Rhodophyta) on the west coast of Sweden. 1992:6 Peterson, Torbjörn: Mollusc herbivory. 1993:1 Klásterská-Hedenberg, Martina: The influence of pH, N:P ratio and zooplankton on the phytoplanctic composition in hypertrophic ponds in the Trebon-region, Czech Republic. 1994:1 Fröborg, Heléne: Pollination and seed set in Vaccinium and Andromeda. 1994:2 Eriksson, Åsa: Makrofossilanalys av förekomst och populationsdynamik hos Najas flexilis i Sörmland. 1994:3 Klee, Irene: Effekter av kvävetillförsel på 6 vanliga arter i gran- och tallskog. 1995:1 Holm, Martin: Beståndshistorik - vad 492 träd på Fagerön i Uppland kan berätta. 1995:2 Löfgren, Anders: Distribution patterns and population structure of an economically important Amazon palm, Jessenia bataua (Mart.) Burret ssp. bataua in Bolivia. 1995:3 Norberg, Ylva: Morphological variation in the reduced, free floating Fucus vesiculosus, in the Baltic Proper. 1995:4 Hylander, Kristoffer & Hylander, Eva: Mount Zuquala - an upland forest of Ethiopia. Floristic inventory and analysis of the state of conservation. 1996:1 Eriksson, Åsa: Plant species composition and diversity in semi-natural grasslands with special emphasis on effects of mycorrhiza. 1996:2 Kalvas, Arja: Morphological variation and reproduction in Fucus vesiculosus L. populations. 1996:3 Andersson, Regina: Fågelspridda frukter kemiska och morfologiska egenskaper i relation till fåglarnas val av frukter. 1996:4 Lindgren, Åsa: Restpopulationer, nykolonisation och diversitet hos växter i naturbetesmarker i sörmländsk skogsbygd. 1996:5 Kiviniemi, Katariina: The ecological and evolutionary significance of the early life cycle stages in plants, with special emphasis on seed dispersal. 1996:7 Franzén, Daniel: Fältskiktsförändringar i ädellövskog på Fagerön, Uppland, beroende på igenväxning av gran och skogsavverkning. 1997:1 Wicksell, Maria: Flowering synchronization in the Ericaceae and the Empetraceae. 1997:2 Bolmgren, Kjell: A study of asynchrony in phenology - with a little help from Frangula alnus. 1997:3 Kiviniemi, Katariina: A study of seed dispersal and recruitment of plants in a fragmented habitat. 1997:4 Jakobsson, Anna: Fecundity and abundance - a comparative study of grassland species. 1997:5 Löfgren, Per: Population dynamics and the influence of disturbance in the Carline Thistle, Carlina vulgaris. 19 1998:1 Mattsson, Birgitta: The stress concept, exemplified by low salinity and other stress factors in aquatic systems. 1998:2 Forsslund, Annika & Koffman, Anna: Species diversity of lichens on decaying wood - A comparison between old-growth and managed forest. 1998:3 Eriksson, Åsa: Recruitment processes, site history and abundance patterns of plants in semi-natural grasslands. 1998:4 Fröborg, Heléne: Biotic interactions in the recruitment phase of forest field layer plants. 1998:5 Löfgren, Anders: Spatial and temporal structure of genetic variation in plants. 1998:6 Holmén Bränn, Kristina: Limitations of recruitment in Trifolium repens. 1999:1 Mattsson, Birgitta: Salinity effects on different life cycle stages in Baltic and North Sea Fucus vesiculosus L. 1999:2 Johannessen, Åse: Factors influencing vascular epiphyte composition in a lower montane rain forest in Ecuador. An inventory with aspects of altitudinal distribution, moisture, dispersal and pollination. 1999:3 Fröborg, Heléne: Seedling recruitment in forest field layer plants: seed production, herbivory and local species dynamics. 1999:4 Franzén, Daniel: Processes determining plant species richness at different scales examplified by grassland studies. 1999:5 Malm, Torleif: Factors regulating distribution patterns of fucoid seaweeds. A comparison between marine tidal and brackish atidal environments. 1999:6 Iversen, Therese: Flowering dynamics of the tropical tree Jacquinia nervosa. 1999:7 Isæus, Martin: Structuring factors for Fucus vesiculosus L. in Stockholm south archipelago - a GIS application. 1999:8 Lannek, Joakim: Förändringar i vegetation och flora på öar i Norrtälje skärgård. 2000:1 Jakobsson, Anna: Explaining differences in geographic range size, with focus on dispersal and speciation. 2000:2 Jakobsson, Anna: Comparative studies of colonisation ability and abundance in semi-natural grassland and deciduous forest. 2000:3 Franzén, Daniel: Aspects of pattern, process and function of species richness in Swedish seminatural grasslands. 2000:4 Öster, Mathias: The effects of habitat fragmentation on reproduction and population structure in Ranunculus bulbosus. 2001:1 Lindborg, Regina: Projecting extinction risks in plants in a conservation context. 2001:2 Lindgren, Åsa: Herbivory effects at different levels of plant organisation; the individual and the community. 2001:3 Lindborg, Regina: Forecasting the fate of plant species exposed to land use change. 2001:4 Bertilsson, Maria: Effects of habitat fragmentation on fitness components. 2001:5 Ryberg, Britta: Sustainability aspects on Oleoresin extraction from Dipterocarpus alatus. 2001:6 Dahlgren, Stefan: Undersökning av fem havsvikar i Bergkvara skärgård, östra egentliga Östersjön. 2001:7 Moen, Jon; Angerbjörn, Anders; Dinnetz, Patrik & Eriksson Ove: Biodiversitet i fjällen ovan trädgränsen: Bakgrund och kunskapsläge. 2001:8 Vanhoenacker, Didrik: To be short or long. Floral and inflorescence traits of Bird`s eye primrose Primula farinose, and interactions with pollinators and a seed predator. 2001:9 Wikström, Sofia: Plant invasions: are they possible to predict? 2001:10 von Zeipel, Hugo: Metapopulations and plant fitness in a titrophic system – seed predation and population structure in Actaea spicata L. vary with population size. 20 2001:11 Forsén, Britt: Survival of Hordelymus europaéus and Bromus benekenii in a deciduous forest under influence of forest management. 2001:12 Hedin, Elisabeth: Bedömningsgrunder för restaurering av lövängsrester i Norrtälje kommun. 2002:1 Dahlgren, Stefan & Kautsky, Lena: Distribution and recent changes in benthic macrovegetation in the Baltic Sea basins. – A literature review. 2002:2 Wikström, Sofia: Invasion history of Fucus evanescens C. Ag. in the Baltic Sea region and effects on the native biota. 2002:3 Janson, Emma: The effect of fragment size and isolation on the abundance of Viola tricolor in semi-natural grasslands. 2002:4 Bertilsson, Maria: Population persistance and individual fitness in Vicia pisiformis: the effects of habitat quality, population size and isolation. 2002:5 Hedman, Irja: Hävdhistorik och artrikedom av kärlväxter i ängs- och hagmarker på Singö, Fogdö och norra Väddö. 2002:6 Karlsson, Ann: Analys av florans förändring under de senaste hundra åren, ett successionsförlopp i Norrtälje kommuns skärgård. 2002:7 Isæus, Martin: Factors affecting the large and small scale distribution of fucoids in the Baltic Sea. 2003:1 Anagrius, Malin: Plant distribution patterns in an urban environment, Södermalm, Stockholm. 2003:2 Persson, Christin: Artantal och abundans av lavar på askstammar – jämförelse mellan betade och igenvuxna lövängsrester. 2003:3 Isæus, Martin: Wave impact on macroalgal communities. 2003:4 Jansson-Ask, Kristina: Betydelsen av pollen, resurser och ljustillgång för reproduktiv framgång hos Storrams, Polygonatum multiflorum. 2003:5 Sundblad, Göran: Using GIS to simulate and examine effects of wave exposure on submerged macrophyte vegetation. 2004:1 Strindell, Magnus: Abundansförändringar hos kärlväxter i ädellövskog – en jämförelse av skötselåtgärder. 2004:2 Dahlgren, Johan P: Are metapopulation dynamics important for aquatic plants? 2004:3 Wahlstrand, Anna: Predicting the occurrence of Zostera marina in bays in the Stockholm archipelago,northern Baltic proper. 2004:4 Råberg, Sonja: Competition from filamentous algae on Fucus vesiculosus – negative effects and the implications on biodiversity of associated flora and fauna. 2004:5 Smaaland, John: Effects of phosphorous load by water run-off on submersed plant communities in shallow bays in the Stockholm archipelago. 2004:6 Ramula Satu: Covariation among life history traits: implications for plant population dynamics. 2004:7 Ramula, Satu: Population viability analysis for plants: Optimizing work effort and the precision of estimates. 2004:8 Niklasson, Camilla: Effects of nutrient content and polybrominated phenols on the reproduction of Idotea baltica and Gammarus ssp. 2004:9 Lönnberg, Karin: Flowering phenology and distribution in fleshy fruited plants. 2004:10 Almlöf, Anette: Miljöfaktorers inverkan på bladmossor i Fagersjöskogen, Farsta, Stockholm. 2005:1 Hult, Anna: Factors affecting plant species composition on shores - A study made in the Stockholm archipelago, Sweden. 2005:2 Vanhoenacker, Didrik: The evolutionary pollination ecology of Primula farinosa. 2005:3 von Zeipel, Hugo: The plant-animal interactions of Actea spicata in relation to spatial context. 21 2005:4 Arvanitis, Leena T.: Butterfly seed predation. 2005:5 Öster, Mathias: Landscape effects on plant species diversity – a case study of Antennaria dioica. 2005:6 Boalt, Elin: Ecosystem effects of large grazing herbivores: the role of nitrogen. 2005:7 Ohlson, Helena: The influence of landscape history, connectivity and area on species diversity in semi-natural grasslands. 2005:8 Schmalholz, Martin: Patterns of variation in abundance and fecundity in the endangered grassland annual Euphrasia rostkovia ssp. Fennica. 2005:9 Knutsson, Linda: Do ants select for larger seeds in Melampyrum nemorosum? 2006:1 Forslund, Helena: A comparison of resistance to herbivory between one exotic and one native population of the brown alga Fucus evanescens. 2006:2 Nordqvist, Johanna: Effects of Ceratophyllum demersum L. on lake phytoplankton composition. 2006:3 Lönnberg, Karin: Recruitment patterns, community assembly, and the evolution of seed size. 2006:4 Mellbrand, Kajsa: Food webs across the waterline - Effects of marine subsidies on coastal predators and ecosystems. 2006:5 Enskog, Maria: Effects of eutrophication and marine subsidies on terrestrial invertebrates and plants. 2006:6 Dahlgren, Johan: Responses of forest herbs to the environment. 2006:7 Aggemyr, Elsa: The influence of landscape, field size and shape on plant species diversity in grazed former arable fields. 2006:8 Hedlund, Kristina: Flodkräftor (Astacus astacus) i Bornsjön, en omnivors påverkan på växter och snäckor. 2007:1 Eriksson, Ove: Naturbetesmarkernas växter- ekologi, artrikedom och bevarandebiologi. 2007:2 Schmalholz, Martin: The occurrence and ecological role of refugia at different spatial scales in a dynamic world. 2007:3 Vikström, Lina: Effects of local and regional variables on the flora in the former semi-natural grasslands on Wäsby Golf club’s course. 2007:4 Hansen, Joakim: The role of submersed angiosperms and charophytes for aquatic fauna communities. 2007:5 Johansson, Lena: Population dynamics of Gentianella campestris, effects of grassland management, soil conditions and the history of the landscape 2007:6 von Euler, Tove: Sex related colour polymorphism in Antennaria dioica. 2007:7 Mellbrand, Kajsa: Bechcombers, landlubbers and able seemen: Effects of marine subsidies on the roles of arthropod predators in coastal food webs. 2007:8 Hansen, Joakim: Distribution patterns of macroinvertebrates in vegetated, shallow, soft-bottom bays of the Baltic Sea. 2007:9 Axemar, Hanna: An experimental study of plant habitat choices by macroinvertebrates in brackish soft-bottom bays. 2007:10 Johnson, Samuel: The response of bryophytes to wildfire- to what extent do they survive in-situ? 2007:11 Kolb, Gundula: The effects of cormorants on population dynamics and food web structure on their nesting islands. 2007:12 Honkakangas, Jessica: Spring succession on shallow rocky shores in northern Baltic proper. 2008:1 Gunnarsson, Karl: Påverkas Fucus radicans utbredning av Idotea baltica? 2008:2 Fjäder, Mathilda: Anlagda våtmarker i odlingslandskap- Hur påverkas kärlväxternas diversitet? 22 2008:3 Schmalholz, Martin: Succession in boreal bryophyte communities – the role of microtopography and post-harvest bottlenecks. 2008:4 Jokinen, Kirsi: Recolonization patterns of boreal forest vegetation following a severe flash flood. 2008:5 Sagerman, Josefin: Effects of macrophyte morphology on the invertebrate fauna in the Baltic Sea. 2009:1 Andersson, Petter: Quantitative aspects of plant-insect interaction in fragmented landscapes – the role of insect search behaviour. 2009:2 Kolb, Gundula: The effects of cormorants on the plant-arthropod food web on their nesting islands. 2009:3 Johansson, Veronika: Functional traits and remnant populations in abandoned semi-natural grasslands. 2009: 4 König, Malin: Phenotypic selection on flowering phenology and herbivory in Cardamine amara. 2009:5 Forslund, Helena: Grazing and the geographical range of seaweeds – The introduced Fucus evanescens and the newly described Fucus radicans. 23