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Genetic Consideration in Ecological Restoration Bibliography

Topic Chosen:
   Examples of genetic and environmental interactions;

 
Antonovics, J.; Primack, R.B. 1982. Experimental ecological genetics in Plantago VI. The demography of seedling transplants of P. lanceolata. Journal of Ecology. 70: 55-75.  
 
(1) The relative importance of genotype and of environment in determining differences in life-history characters such as mortality, growth rate, and fecundity among populations of Plantago lanceolata was assessed by reciprocal transplanting of seedlings among six field-sites (2) In most cases environmental differences were much more important than genotypic ones. Different environments imposed different life-histories (3) Reciprocal transplants between field sites make operational such concepts as environmental heterogeneity and stress, and allow natural selection to be studied. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient; Examples of phenotypic plasticity;   
 

 
Bischoff, A.; Vonlanthen, B.; Steinger, T.; Muller-Scharer, H. 2006. Seed provenance matters - Effects on germination of four plant species used for ecological restoration. Basic and Applied Ecology. 7, 4: 347-359.  
 
The use of local seed provenances is often recommended in restoration and habitat creation because they are thought to be better adapted to local habitat conditions. However, spatial scales and the degree of population differentiation are not well known and germination is often not included in comparisons between provenances. We analysed germination as a key trait of plant development in five provenances of four species used for ecological restoration on arable land (wildflower strips). Germination was tested under different conditions in growth chambers (early vs. late spring) and in the field (non-com petition vs. competition). We also examined the contribution of non-genetic (maternal) effects to population differentiation. Large differences in germination traits were found between the provenances in growth chambers and in the field. The ranking was species - specific, but largely consistent across all tested environments. Local provenances did not generally exhibit higher germination percentages in the field relative to non-local provenances. Due to the high stability of germination traits across various environments, growth chamber tests provided a reliable prediction for provenance differences in the field. The differences among provenances seemed to be largely genetically determined as the inclusion of seed mass in the analysis to control for maternal. effects did not decrease the degree differences between-provenance differences. In one species, however, non-genetic contributions to population differentiation were found by comparing F1 seeds grown under homogeneous conditions and original seed material. We conclude that potentially large between -provenance differences in germination traits need to be considered in ecological. restoration projects, particularly in non-permanent systems where they may determine vegetation devetopment. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of a relationship between seed source and restoration success; Discussion of important genetic considerations in ecological restoration;   
 

 
Booy, G.; Hendriks, R.J.J.; Smulders, M.J.M.; Van Groenendael, J.M.; Vosman, B. 2000. Genetic Diversity and the Survival of Populations. Plant Biology. 2, 4: 379-395.  
 
In this comprehensive review, a range of factors is considered that may influence the significance of genetic diversity for the survival of a population. Genetic variation is essential for the adaptability of a population in which quantitatively inherited, fitness-related traits are crucial. Therefore, the relationship between genetic diversity and fitness should be studied in order to make predictions on the importance of genetic diversity for a specific population. The level of genetic diversity found in a population highly depends on the mating system, the evolutionary history of a species and the population history (the latter is usually unknown), and on the level of environmental heterogeneity. An accurate estimation of fitness remains complex, despite the availability of a range of direct and indirect fitness parameters. There is no general relationship between genetic diversity and various fitness components. However, if a lower level of heterozygosity represents an increased level of inbreeding, a reduction in fitness can be expected. Molecular markers can be used to study adaptability or fitness, provided that they represent a quantitative trait locus (QTL) or are themselves functional genes involved in these processes. Next to a genetic response of a population to environmental change, phenotypic plasticity in a genotype can affect fitness. The relative importance of plasticity to genetic diversity depends on the species and population under study and on the environmental conditions. The possibilities for application of current knowledge on genetic diversity and population survival for the management of natural populations are discussed. 
 
Included in Topics:  Examples of how species characteristics (life history, mating system, distribution, seed banking) may affect patterns of genetic variation; Examples of genetic and environmental interactions; Discussion of important genetic considerations in ecological restoration;   
 

 
Bourdeau, P.F. 1963. Photosynthesis and Respiration of Pinus strobus L. Seedlings in Relation to Provenance and Treatment. Ecology. 44, 4: 710-716.  
 
Photosynthesis and respiration were measured under various conditions of temperature and illumination in seedlings of Pinus strobus from several geographic origins kept over winter outdoors and in a heated greenhouse...seed provenance had no significant effect on respiration, although at high temperature there seemed to be a tendency for plants of southern origin kept indoors to have somewhat higher rates. Plants of southern origins were more efficient in weak light and had lower light compensation points than those of northern origins but they were less efficient at low temperature. It is concluded that genetic variability in photosynthetic and respiratory response exists in Pinus strobes although its effects appear only under certain combinations of treatment and environmental conditions. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Cheplick, G.P.; White, T.P. 2002. Saltwater spray as an agent of natural selection: no evidence of local adaptation within a coastal population of Triplasis purpurea (Poaceae) 1. American Journal of Botany. 89, 4: 623-631.  
 
An ability to tolerate airborne saltwater spray is critical for plant populations in coastal environments. The opportunity for continued microevolution for improved salt tolerance can exist if there is variation in the response of genetic families to saltwater spray. Our objective was to determine whether or not there was differentiation among subpopulations near (15 m) and far (80 m) from shore and among families within subpopulations in relation to the effects of salt spray on life history traits in a population of the dunegrass Triplasis purpurea. In this annual, most seeds are matured in cleistogamous spikelets on axillary, leaf-sheath enclosed panicles and show poor dispersal capacity. Plants were reared in the greenhouse from seeds of 13 and 11 families from the near and far subpopulations, respectively. Fifty percent of plants in a family were subjected to 6 seawater sprays/wk, resulting in weekly salt deposition of 213 mg/cm2; the others were sprayed with distilled water. Data were recorded on life span, tiller numbers, root and shoot dry mass, and seed production. There was no effect of subpopulation on any measured trait and, hence, no evidence for local adaptation to salt spray. Final tiller numbers, but not dry mass or seed production, were reduced by salt spray. However, for most traits there were significant family (within subpopulation) effects, indicating genetic substructuring. Life span and mean seed mass showed a significant family by treatment interaction, indicating genetic variation in phenotypic responses to salt spray. Life span and mean seed mass were reduced by salt spray in some, but not all, families. Path analysis revealed that an increase in life span or tiller number indirectly increased seed production via direct effects on vegetative mass. For this relatively salt-tolerant T. purpurea population on the south shore of Staten Island, New York, USA, salt sprays may not be a significant agent of natural selection. However, there are pronounced phenotypic differences among inbred family groups and opportunity for genetic substructuring within these subpopulations. Variable effects of salt spray among families could result in microevolutionary changes in life span and mean seed mass, both of which impact annual fitness in this dunegrass. 
 
Included in Topics:  Examples of among and within-population genetic diversity; Examples of genetic and environmental interactions;   
 

 
Daws, M.I.; Lydall, E.; Chmielarz, P.; Leprince, O.; Matthews, S.; Thanos, C.A.; Pritchard, H.W. 2004. Developmental heat sum influences recalcitrant seed traits in Aesculus hippocastanum across Europe. New Phytologist. 162, 1: 157-166.  
 
An analysis was made of seed traits along a north-south gradient spanning 19deg of latitude in Europe using Aesculus hippocastanum, which originates from Greece and the Balkans and has been introduced throughout Europe. Because summer temperatures decrease with increasing latitude in Europe, we tested the hypothesis that the heat sum during seed development influences physical, physiological and biochemical seed traits. Seeds from Greece (within the natural range) had a fresh mass five times higher than those from Scotland (most northerly seed lot), and a lower axis moisture content and solute potential. In addition, Greek seeds germinated at cooler temperatures, and were more desiccation tolerant. Principal component analysis (PCA) showed that the observed patterns in seed characteristics were consistent and predictable: a single PCA axis explained 86.6% of the variation in the dataset. This axis correlated strongly with the heat sum accumulated by the seeds during development. The results support the notion that seeds from further north were shed less developed as a consequence of cooler temperatures during development, and provide a quantitative explanation for intraspecies variability in recalcitrant seed traits for this and, possibly, other species. *NOTE that this paper is relevant to questions regarding whether seed can be grown up in an area with a climate that is dissimilar to the source and potential use site. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of ways to maintain desired genetic composition and diversity;   
 

 
El-Keblawy, A.; Al-Ansari, F. 2000. Effects of site of origin, time of seed maturation, and seed age on germination behavior of Portulaca oleracea from the Old and New Worlds. Canadian Journal of Botany. 78, 3: 279-287.  
 
The effects of site of origin, time of seed maturation, and seed age on germination behavior, in terms of final percentage of germination and time for 50% of final germination were investigated in the widespread weed Portulaca oleracea L. Seeds were collected in August from one population at each of three geographical regions of the Old and New Worlds representing temperate (Southern Ontario, Canada), Mediterranean (Tanta, Egypt), and subtropical (Al-Ain, United Arab Emirates (U.A.E.)) climates. The freshly harvested seeds were incubated in both light and dark at 15, 25, and 40 C. Seeds of the U.A.E. site showed little dormancy and germinated faster under a wider range of incubation conditions than did seeds from the Canadian site. To assess the effect of time of seed maturation on germination behavior, seeds were collected during the different seasons (November, February, May, and August) of the U.A.E. population. The percentage of germination was significantly higher for seeds collected in May and November and germination was significantly faster for those collected in May and August. Response of germination to light and temperature varied according to site of origin and time of seed maturation. Seeds from the Canadian site and those that matured during winter from the U.A.E. site required light and high temperature for optimal germination. The effect of seed age on percentage of germination and rate was significant at the Canadian site but not at the Egyptian and U.A.E. sites. Seed stored for 5 months at room temperature germinated significantly faster and to a higher percentage than freshly harvested seeds. Results are discussed in light of the adaptation of seed dormancy and time of germination to the prevailing environmental conditions. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Fitzpatrick, B.M.; Shaffer, H.B. 2004. Environment-dependent admixture dynamics in a tiger salamander hybrid zone. Evolution. 58, 6 
 
After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger salamander (A. californiense). Hybridization and backcrossing have been occurring in central California for 50-60 years, or an estimated 15-30 generations. We studied genetic and ecological factors influencing admixture of these two divergent gene pools by analyzing frequencies of hybrid genotypes in three kinds of breeding habitats: natural vernal pools, ephemeral man-made cattle ponds, and perennial man-made ponds. Perennial ponds tended to have higher frequencies of nonnative alleles than either type of seasonal pond, even in cases where perennial and seasonal ponds are within a few hundred meters. Thus, the hybrid zone has a mosaic structure that depends on pond hydrology or ecology. The presence of some broadly acting constraints on admixture is suggested by linkage disequilibria between physically unlinked molecular markers within ponds. In addition, we found several marker-specific deviations from Hardy-Weinberg equilibrium. One marker showed a consistent deficit of heterozygotes across pond types. Another showed heterozygote deficits only in vernal pools. A third was more likely to have heterozygote excess in ephemeral cattle ponds. These patterns indicate that admixture is influenced by complex genotype-by-environment interactions. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of gene flow between introduced and native populations; Examples from animals;   
 

 
Fornoni, J.; Valverde, P.L.; Nunez-Farfan, J. 2003. Quantitative genetics of plant tolerance and resistance against natural enemies of two natural populations of Datura stramonium. Evolutionary Ecology Research. 5, 7: 1049-1065.  
 
Plants can respond to damage from natural enemies through resistance and/or tolerance. Evolution of these traits among natural plant populations can be constrained by (1) the absence of genetic variation or (2) because of the presence of a trade-off between resistance and tolerance. This last hypothesis remains one of the main assumptions of evolutionary theory of plant-natural enemy interactions. Such a trade-off could represent a constraint for adaptive evolution because high levels of resistance or tolerance could be attained but not both. In this study. we examined the presence of genetic variation in tolerance and resistance, the existence of a negative genetic correlation between tolerance and resistance, and the extent of genetic differentiation in plant defensive strategies between two natural populations of Datura stramonium of Central Mexico. A reciprocal transplant experiment using paternal half-sib families was performed. The results of this experiment showed: (1) the presence of additive genetic variation for tolerance and resistance (h(N)(2) = 0.41-0.49) in both populations at their native site: (2) genetic differentiation in tolerance and resistance between populations and (3) an environment-dependent genetic correlation between tolerance and resistance. The results support the hypothesis that a negative genetic correlation between tolerance and resistance can potentially constrain the simultaneous evolution of both traits within populations. Furthermore, genetic differentiation between populations supports the expectation that tolerance and resistance represent redundant alternatives against natural enemies. Thus. G x E interactions may represent an important causal factor promoting geographic variation in the outcome of the interaction between plants and their natural enemies. 
 
Included in Topics:  Examples of genetic and environmental interactions; Genetic considerations in multi-species interactions; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Fornoni, J.; Valverde, P.L.; Nunez-Farfan, J. 2004. Population variation in the cost and benefit of tolerance and resistance against herbivory in Datura stramonium. Evolution. 58, 8: 1696-1704.  
 
In this study we examine the hypothesis that divergent natural selection produces genetic differentiation among populations in plant defensive strategies (tolerance and resistance) generating adaptive variation in defensive traits against herbivory. Controlled genetic material (paternal half-sib families) from two populations of the annual Datura stramonium genetically differentiated in tolerance and resistance to herbivory were used. This set of paternal half-sib families was planted at both sites of origin and the pattern of genotypic selection acting on tolerance and resistance was determined, as well as the presence and variation in the magnitude of allocational costs of tolerance. Selection analyses support the adaptive differentiation hypothesis. Tolerance was favored at the site with higher average level of tolerance, and resistance was favored at the site with higher average level of resistance. The presence of significant environmentally dependent costs of tolerance was in agreement with site variation in the adaptive value of tolerance. Our results support the expectation that environmentally dependent costs of plant defensive strategies can generate differences among populations in the evolutionary trajectory of defensive traits and promote the existence of a selection mosaic. The pattern of contrasting selection on tolerance suggests that, in some populations of D. stramonium, tolerance may alter the strength of reciprocal coevolution between plant resistance and natural enemies. 
 
Included in Topics:  Examples of genetic and environmental interactions; Genetic considerations in multi-species interactions; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Gauthier, P.; Lumaret, R.; Bedecarrats, A. 1998. Ecotype differentiation and coexistence of two parapatric tetraploid subspecies of cocksfoot (Dactylis glomerata) in the Alps. New Phytologist. 139, 4: 741-750.  
 
Two tetraploid subspecies of Dactylis glomerata L., subsp. reichenbachii (Hausm.) Stebbins et Zohary and subsp. glomerata, occur in the French Alps. The former is confined to dolomitic, south-facing, alpine lawns above 2000 m, whereas the latter occurs in non-dolomitic habitats in subalpine meadows mainly below 1900 m. Previous studies of allozyme variation have shown that genetic introgression between the two subspecies occurs over large areas. By contrast, morphologically intermediate individuals only occur in an extremely narrow area, suggesting that the morphological and physiological differences between the two subspecies is of adaptive significance. A reciprocal clone transplant experiment was set up to examine (1) any genetic differences between subspecies indicative of ecotypic differentiation in relation to habitat characteristics and (2) the level of phenotypic plasticity in the two subspecies. Genetic differentiation was confirmed by a statistically significant taxon x site interaction effect in anova for all traits studied. The glomerata populations produced more tillers, longer leaves and higher culms in all sites, especially in their home environment. However, reichenbachii populations produced more seeds than the glomerata populations in the original reichenbachii environment, suggesting ecotypic differentiation between the two subspecies. This result might also explain why the glomerata subspecies is unable to colonize dolomitic habitats occupied by the reichenbachii subspecies. The reichenbachii populations showed less plasticity than the glomerata populations for leaf length and floriferous tiller number, a result which is discussed in the context of the response of plants from productive and non-productive habitats to environmental variation. 
 
Included in Topics:  Examples of differences in subspecies and in populations with different ploidy levels; Examples of genetic and environmental interactions; Examples of ecotypes; Examples of local adaptation across a biotic or abiotic gradient; Examples of phenotypic plasticity;   
 

 
Gordon, D.R.; Rice, K.J. 1998. Patterns of differentiation in wiregrass (Aristida beyrichiana): implications for restoration efforts. Restoration Ecology. 6: 166-174.  
 
Aristida beyrichiana (wiregrass) is increasingly being planted in restoration projects across the southeastern coastal plain, with little focus on genetic differences among populations across the region. Local and regional population differentiation for establishment and growth traits were examined in common garden and reciprocal transplant experiments. Seeds from up to 20 plants from each of seven populations were collected in northern and central Florida sites that encompassed gradients of soils, hydrology, and temperature. Reciprocal seed transplants using three of the common garden populations were conducted in two consecutive years. In the common garden, significant population differences were seen in seed weight, seedling emergence and survival, tiller height, number of tillers, the relationship between tiller number and tiller height, and flowering. Variation among maternal families was seen in tiller number and in the relationship between tiller number and tiller height. The reciprocal transplant study did not detect either local adaptation to sites of origin or consistent superiority of one source population or planting site in seedling establishment. These results suggest that the probability of seedling establishment is primarily dependent on environmental conditions rather than genetic differences. Genetic variation for traits related to fitness (e.g., tiller number) may be retained within populations because phenotypically plastic growth responses of seedlings to environmental variation buffer genetic variation against the action of selection. But despite the lack of evidence for genetic influences on initial establishment in wiregrass, our common garden study suggests genetic differences among populations. This result, when combined with previous results indicating local adaptation in later life stages of wiregrass, suggests that restoration efforts involving this species should use local seed sources from sites with similar soil and hydrological conditions. 
 
Included in Topics:  Examples of among and within-population genetic diversity; Examples of genetic and environmental interactions; Examples of phenotypic plasticity; Discussion of important genetic considerations in ecological restoration;   
 

 
Gray, A. 1996. Genetic Diversity and Its Conservation in Natural Populations of Plants. Biodiversity Letters. 3, 3: 71-80.  
 
This paper reviews patterns of genetic diversity in natural populations of plants: patterns which have emerged from more than 70 years of genecological investigation and 30 years of allozyme analysis. The compelling conclusion to be drawn from these empirical studies is that genetic diversity in most plant species lies along the axis of environmental, and specifically habitat, variability. This predominance of genotype-environment correlations, a testimony to the power and ubiquity of natural selection, demands that strategies for the conservation of genetic diversity involve sampling or protection schemes which are stratified across environments or habitat-types. The genetic response of species' populations to their environment is affected, or constrained, by a range of intrinsic biological properties such as the breeding system and external processes such as those which cause fluctuations in population size. Insight into the impact of such forces on the genetic diversity and structure of natural populations has been the major gain from studies of allozyme variation. However, there is some doubt about the neutrality of allozyme loci, and often no correlation can be found between levels of allozyme variation and those in quantitative trait loci. Furthermore, variation in intrinsic properties and external forces accounts for relatively small amounts of the between-species variation in genetic diversity (but rather more of the variation in their population genetic structure). Coupled with the remarkable, and largely unpredictable, range of diversity patterns found in rare and endangered species, this has led to the view that there are no useful generalizations on which to base conservation strategies. Each and every species must be investigated. Here I suggest that this view has been based on an inappropriate group of species (the rare and endangered) and that a habitat-based conservation strategy has generic utility. Because of the remarkably small numbers of plants needed to capture most of a species' genetic diversity, sampling, or conserving, across habitats can be adjusted to account for the expected levels of between-population differentiation. Prediction of these levels may be improved by taking a phylogenetic approach. 
 
Included in Topics:  Examples of among and within-population genetic diversity; Examples of how species characteristics (life history, mating system, distribution, seed banking) may affect patterns of genetic variation; Examples of genetic and environmental interactions;   
 

 
Gray, A.J. 1974. The genecology of salt marsh plants. Aquatic Ecology. 8, 1: 152-165.  
 
1. Salt marshes lie on the interface zone between totally marine and totally terrestrial environments and are characterised by both linear variation patterns (gradients) and point-to-point variation patterns (mosaics). The variability in some examples of flowering plant species commonly found on salt marshes suggests that disruptive selective in this heterogeneous environment has led to wide adaptive divergence. 2. In particular populations of those species with high ecological amplitudes are likely to exhibit wide variability. 3. Studies on such a species, Aster tripolium L., using mainly collateral cultivation techniques, have revealed habitat-correlated variation in life cycle, fruit size and number, and germination requirements--all characters of fundamental biological significance. 4. The response to salt marsh environments included both genetic change and phenotypic plasticity. The importance in future work of identifying to which selective aspects of the environments particular characters are responding is emphasized, together with the need to evaluate, especially in perennial species, the respective roles of genetic and plastic responses. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient; Examples of phenotypic plasticity;   
 

 
Gregor, J.W.; Watson, P.J. 1961. Ecotypic Differentiation: Observations and Reflections. Evolution. 15, 2: 166-173.  
 
1. Observations on leaf length responses of Plantago lanceolata gamodemes to a range of habitat conditions indicate that it requires a considerable difference in phytosocial environment before exogenous adaptation becomes associated with detectable ecotypic differentiation. 2. Since ecotypic discontinuities are rarer than had initially been imagined, it would seem that a better understanding of ecotypic patterns could be achieved through the accumulation of records in which the emphasis has been transferred from the discrete ecotype to the trends of ecotypic differentiation. Such a change in emphasis would in no way invalidate Turesson's original concept. What does detract from its significance is the wrongful use of the term ecotype. 3. To facilitate the accumulation of information relating to ecotypic as well as to other micro-evolutionary patterns, it is suggested that the investigator should record in terms of demes whatever entities he is able to detect by the techniques he chooses to employ. 4. A merit of the deme terminology from the genecological point of view is that the categories are in no sense mutually exclusive, since the same population may be referable to several different categories according to which of its properties is taken into account, and the categories may be coincident or overlapping. Moreover, by avoiding absolute standards the flexibility of this terminology makes it useful over a wide range of genecological techniques. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples from 'classic' ecotype research; Issues of scale in determining ecotypes;   
 

 
Hoffmann, A.A.; Merila, J. 1999. Heritable variation and evolution under favourable and unfavourable conditions. TRENDS in Ecology & Evolution. 14: 96-101.  
 
Genetic variability in quantitative traits can change as a direct response to the environmental conditions in which they are expressed. Consequently, similar selection in different environments might not be equally effective in leading to adaptation. Several hypotheses, including recent ones that focus on the historical impact of selection on populations, predict that the expression of genetic variation will increase in unfavourable conditions. However, other hypotheses lead to the opposite prediction. Although a consensus is unlikely, recent Drosophila and bird studies suggest consistent trends for morphological traits under particular conditions. 
 
Included in Topics:  Theoretical discussion of the distribution of genetic diversity within and among species; Examples of changes in genetic diversity and local adaptation over time; Examples of genetic and environmental interactions; Theoretical discussion of local adaptation;   
 

 
Jana, S.; Zhang, Q.; Saghai-Maroof, M.A. 1989. Influence of environments on the development of multivariate structures in a barley composite cross at three locations. Genome. 32: 40-45.  
 
No abstract. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of ways to maintain desired genetic composition and diversity; Examples of genetic shifts in cultivation; Examples from agriculture;   
 

 
Knight, T.M.; Miller, T.E. 2004. Local adaptation within a population of Hydrocotyle bonariensis. Evolutionary Ecology Research. 6, 1: 103-114.  
 
Local adaptation may occur when selection for heritable traits differs from environment to environment and gene flow among environments is restricted. In this study, we used reciprocal transplants to explore both the existence and possible causes of local adaptation in the clonal plant Hydrocotyle bonariensis at high and low elevations of sand dunes on St. George Island, Florida. Individuals found in high dune areas had substantially longer and more internodes and produced larger leaves than those from low dune areas. Reciprocal transplants used 10 genets from high dunes and 10 from low dunes. Greenhouse-grown, replicate plants from each genet were transplanted to high and low dune sites in the field, with and without the natural vegetation removed. The resulting plant growth was consistent with patterns of local adaptation: plants from high sites grew better in high sites than did plants from low sites and vice versa. A significant source x site interaction was found for final below-ground, but not above-ground, biomass. In plots with surrounding vegetation removed, plants from high and low dunes performed similarly in both environments, suggesting that local adaptation was related to interactions with other plants at each dune height. Small-scale local adaptation may be more likely in clonal plants undergoing little gene flow in spatially heterogeneous environments. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Li, C.; Wu, N.; Liu, S. 2005. Development of freezing tolerance in different altitudinal ecotypes of Salix paraplesia. Biologia Plantarum. 49, 1: 65-71.  
 
Salix paraplesia was used as an experimental model to investigate the effect of short day photoperiod (SD) and low temperature (LT) on development of freezing tolerance and on endogenous abscisic acid (ABA) contents. We characterized differences in SD and LT-induced cold acclimation in three ecotypes from different altitudes. The results demonstrated that cold acclimation could be triggered by exposing the plants to SD or LT alone, and that a combination of the different treatments had an additive effect on freezing tolerance in all ecotypes studied. However, the high altitudinal ecotype was more responsive to SD and LT than the low altitudinal ecotype. Development of freezing tolerance induced by SD and LT was accompanied by changes in ABA contents which were ecotype-dependent. Although the stem had higher initial freezing tolerance, the leaves developed freezing tolerance more quickly than the stem and thus leaves may provide an interesting experimental system for physiological and molecular studies of cold acclimation in woody plants. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of ecotypes; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Lofflin, D.L.; Kephart, S.R. 2005. Outbreeding, seedling establishment, and maladaptation in natural and reintroduced populations of rare and common Silene douglasii (Caryophyllaceae). American Journal of Botany. 92, 10: 1691-1700.  
 
Reintroductions are increasingly used to enhance declining populations, yet comparative data for critical germination and establishment phases are seldom available for both rare and common herbaceous perennials. After introducing a total of > 1800 seeds, we compared experimentally manipulated and natural populations of widespread Silene douglasii var. douglasii relative to rare S. douglasii var. oraria, known in only three coastal headlands. Despite equivalent ex situ germination, oraria field plots produced significantly fewer juveniles than douglasii plots indicating that seedling survival limits plant establishment. We also evaluated transplant vs. seed reintroductions as restoration tools, the effect of inbreeding on fitness, and the potential importance of buried seed pools. Germination declined rapidly for seeds over 1-2 years old, and only 2.2% of newly collected seeds of oraria survived as seedlings. Transplant survival over 5 years was greatest for outbred progeny; furthermore, 75% of the new seedlings emerged near outbred progeny from the original reintroduction. Despite similar ovule numbers and pollinator visitation, transplants exhibited 49-179% maladaptation in the formerly grazed site, with significantly lower fruit and seed set than adults in more diverse natural populations. This study experimentally identifies several key factors affecting plant reintroductions, facilitating effective development of large-scale reintroduction strategies for native perennials. 
 
Included in Topics:  Examples of the importance of genetic diversity; Examples of genetic and environmental interactions; Examples of the negative effects of inbreeding depression;   
 

 
Sharif-Zadeh, F.; Murdoch, A.J. 2000. The effects of different maturation conditions on seed dormancy and germination of Cenchrus ciliaris. Seed Science Research. 10: 447-457.  
 
Seeds of Cenchrus ciliaris L. were produced under different hydro-photo-thermal environments with and without fertilizer. Dormancy loss of spikelets and extracted caryopses was tested during dry after-ripening at 40C and 43% equilibrium relative humidity. Caryopses had higher initial germination and lost their dormancy faster than spikelets. Dormancy of both caryopses and spikelets generally decreased with an increase of maturation temperature and fertility, whereas dormancy increased if water stress was imposed during maturation. The latter effect was smaller when the mother plants were exposed to water stress after caryopses were fully formed than when water stress cycles were applied throughout maturation. Daylength extension (to 14 or 18 h d-1) by artificial light increased dormancy of both caryopses and spikelets. The effect of long days declined when plants were exposed to natural daylight for more than 10 h d-1. The after-ripening curves were consistent with the hypothesis that dormancy periods of individual seeds are normally distributed within each seed lot. Rates of loss of dormancy were quantified by the slopes of these curves. In a given experiment, these rates were identical for caryopses but not always for spikelets that matured in diverse environments. Even for caryopses, however, the slopes varied between experiments. Therefore, the results do not support the hypothesis that a dormancy model can be applied universally to all seed lots of Cenchrus ciliaris. Methods of predicting the period of after-ripening required to achieve desired levels of dormancy for reseeding degraded rangelands are discussed. Note: Demonstrates why growing seeds in distant location for bulking purposes may not be a good idea. 
 
Included in Topics:  Examples of genetic and environmental interactions; Use of natives and techniques in ecological restoration;   
 

 
Stanton, M.L.; Galen, C. 1997. Life on the edge: Adaptation versus environmentally mediated gene flow in the snow buttercup, Ranunculus adoneus. The American Naturalist. 150, 2: 143-178.  
 
We used experimental transplant studies to understand how dispersal and habitat-specific selection interact to influence plant populations occupying heterogeneous environments. The snow buttercup (Ranunculus adoneus) occupies a steep ecological and flowering time gradient caused by persistent snowmelt differences within its snow bed habitat. We transplanted seeds, seedlings, and adults to learn about the potential interactions between dispersal and selection. We found that adaptive differentiation is not occurring along the snowmelt gradient, despite striking differences in microhabitat conditions and reproductive phenology between early- and late-melting sites. Instead, our results imply that environmentally based differences in seed quality are contributing to directional gene flow from early-melting locations toward late-melting locations. Emergence and early survival of seedlings is greater in late-melting sites in some years, but the larger seeds produced by maternal plants in early-melting locations consistently have a fitness advantage in all parts of the snow bed. Larger seeds survive longer in the soil and have a second peak of seedling emergence in their third year, but these late-emerging seedlings are successful only if dispersed to less vegetated, late-melting destinations. The longer growing season in early melting sites enhances vegetative growth at all life-history stages and increases fecundity of seedling transplants but also limits the opportunity for establishment from seed. Our demographic analysis suggests that maternal environmental effects on propagule quality can lead to directional gene flow from benign to marginal sites in populations occupying heterogeneous habitats. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of broad adaptation;   
 

 
Verhoeven, K.J.F.; Vanhala, T.K.; Biere, A.; Nevo, E.; Van Damme, J.M.M. 2004. The genetic basis of adaptive population differentiation: A quantitative trait locus analysis of fitness traits in two wild barley populations from contrasting habitats. Evolution. 58, 2: 270-283.  
 
We used a quantitative trait locus (QTL) approach to study the genetic basis of population differentiation in wild barley, Hordeum spontaneum. Several ecotypes are recognized in this model species, and population genetic studies and reciprocal transplant experiments have indicated the role of local adaptation in shaping population differences. We derived a mapping population from a cross between a coastal Mediterranean population and a steppe inland population from Israel and assessed F-3 Progeny fitness in the natural growing environments of the two parental populations. Dilution of the local gene pool, estimated as the proportion of native alleles at 96 marker loci in the recombinant lines, negatively affected fitness traits at both sites. QTLs for fitness traits tended to differ in the magnitude but not in the direction of their effects across sites, with beneficial alleles generally conferring a greater fitness advantage at their native site. Several QTLs showed fitness effects at one site only, but no opposite selection on individual QTLs was observed across the sites. In a common-garden experiment, we explored the hypothesis that the two populations have adapted to divergent nutrient availabilities. In the different nutrient environments of this experiment, but not under field conditions, fitness of the F-3 progeny lines increased with the number of heterozygous marker loci. Comparison of QTL-effects that underlie genotype X nutrient interaction in the common-garden experiment and genotype X site interaction in the field suggested that population differentiation at the field sites may have been driven by divergent nutrient availabilities to a limited extent. Also in this experiment no QTLs were observed with opposite fitness effects in contrasting environments. Our data are consistent with the view that adaptive differentiation can be based on selection on multiple traits changing gradually along ecological gradients. This can occur without QTLs showing opposite fitness effects in the different environments, that is, in the absence of genetic trade-offs in performance between environments. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient; Examples of hybrid vigor (heterosis); Examples of outbreeding depression (hybrid breakdown);   
 

 
Via, S.; Lande, R. 1985. Genotype-Environment Interaction and the Evolution of Phenotypic Plasticity. Evolution. 39, 3: 505-522.  
 
Studies of spatial variation in the environment have primarily focused on how genetic variation can be maintained. Many one-locus genetic models have addressed this issue, but, for several reasons, these models are not directly applicable to quantitative (polygenic) traits. One reason is that for continuously varying characters, the evolution of the mean phenotype expressed in different environments (the norm of reaction) is also of interest. Our quantitative genetic models describe the evolution of phenotypic response to the environment, also known as phenotypic plasticity (Gause, 1947), and illustrate how the norm of reaction (Schmalhausen, 1949) can be shaped by selection. These models utilize the statistical relationship which exists between genotype-environment interaction and genetic correlation to describe evolution of the mean phenotype under soft and hard selection in coarse-grained environments. Just as genetic correlations among characters within a single environment can constrain the response to simultaneous selection, so can a genetic correlation between states of a character which are expressed in two environments. Unless the genetic correlation across environments is +1, polygenic variation is exhausted, or there is a cost to plasticity, panmictic populations under a bivariate fitness function will eventually attain the optimum mean phenotype for a given character in each environment. However, very high positive or negative correlations can substantially slow the rate of evolution and may produce temporary maladaptation in one environment before the optimum joint phenotype is finally attained. Evolutionary trajectories under hard and soft selection can differ: in hard selection, the environments with the highest initial mean fitness contribute most individuals to the mating pool. In both hard and soft selection, evolution toward the optimum in a rare environment is much slower than it is in a common one. A subdivided population model reveals that migration restriction can facilitate local adaptation. However, unless there is no migration or one of the special cases discussed for panmictic populations holds, no geographical variation in the norm of reaction will be maintained at equilibrium. Implications of these results for the interpretation of spatial patterns of phenotypic variation in natural populations are discussed. 
 
Included in Topics:  Examples of genetic and environmental interactions; Theoretical discussion of local adaptation; Theoretical discussion of phenotypic plasticity;   
 

 
Volis, S.; Mendlinger, S.; Ward, D. 2002. Differentiation in populations of Hordeum spontaneum along a gradient of environmental productivity and predictability: life history and local adaptation. Biological Journal of the Linnean Society. 77, 4: 479-490.  
 
Reciprocal introduction of seeds and seedlings of wild barley, Hordeum spontaneum, originating in four different environments of Israel was used to: (1) test for local adaptation, (2) make inferences about environmental effects on life-history and reproductive traits, and (3) identify trait combinations with recognizable 'strategies'. The four populations examined represented the following environments: (1) desert - low productivity and predictability, drought stress; (2) semi-steppe batha - moderate productivity and predictability; (3) grassland - high productivity and predictability; and (4) mountain - high productivity and predictability but with severe frost stress. Significant genotype-by-environment interactions were observed for yield and reproductive biomass, seedling biomass and percentage germinated and survived seeds, suggesting local ecotype adaptation. Increasing productivity and predictability of environment in respect to rainfall, without concomitant frost stress, was found to select for high reproductive biomass and large seeds, a high fraction of germinating seeds and high vigour of seedlings. The optimal strategy changes with increasing productivity and predictability and involves a trade-off between seed size and number, with reduced yield but increased seed mass, consistent with competition selection (or K-selection sensu MacArthur & Wilson (1967)) type. No specific life-history adaptations to predictable frost stress were detected for the mountain ecotype, but there was higher survival of seedlings in their indigenous (mountain) environment compared with other ecotypes. The latter appears to be a physiological adaptation to frost, which is consistent with selection for stress tolerance (or S-selection sensu Grime (1977)) type. The other stress factor, drought, which is very unpredictable in deserts, was associated with high seed dormancy, small seed size and low vigour of seedlings, but relatively high yield, which is consistent with a stress-escape bet-hedging strategy. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of ecotypes; Examples of local adaptation across a biotic or abiotic gradient;   
 

 
Wang, H.; McArthur, E.D.; Sanderson, S.C.; Graham, J.H.; Freeman, D.C. 1997. Narrow Hybrid Zone Between Two Subspecies of Big Sagebrush (Artemisia tridentata: Asteraceae). IV. Reciprocal Transplant Experiments. Evolution. 51, 1: 95-102.  
 
Does endogenous (disruption of coadapted gene complexes) or exogenous (Genetic x Environment interactions) selection stabilize the big sagebrush (Artemisia tridentata) hybrid zone? After two years of study, our reciprocal transplant experiments showed significant genotype by environment interactions for a number of fitness components, including germination, growth, and reproduction. Hybrids were the most fit within the hybrid garden. In the parental gardens, the native parental taxon was more fit than either the alien parental or hybrids. These results are consistent with the bounded hybrid superiority model, which assumes exogenous selection, but are clearly at odds with the dynamic equilibrium model, which assumes endogenous selection and universal hybrid unfitness. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of local adaptation across a biotic or abiotic gradient; Theoretical discussion of hybridization; Theoretical discussion of outbreeding depression;   
 

 
Warwick, S.I.; Briggs, D. 1979. The Genecology of Lawn Weeds. III. Cultivation Experiments with Achillea millefolium L., Bellis perennis L., Plantago lanceolata L., Plantago major L. and Prunella vulgaris L. Collected from Lawns and Contrasting Grassland Habitats. New Phytologist. 83, 2: 509-536.  
 
An investigation of the nature of adaptive variation was conducted on five common lawn weeds (Achillea millefolium, Bellis perennis, Plantago lanceolata, Plantago major and Prunella vulgaris) collected from lawns, heavily grazed turf, seasonally mown or grazed grasslands and grassy areas not seasonally reduced in height by grazing and/or mowing. As expected, marked size differences in the 'wild' phenotype of individuals from contrasting man-managed grassland communities were found. All five taxa exhibited a continuous pattern of variation, with plants from lawns and heavily grazed habitats being significantly smaller in size than plants from areas seasonally mown and/or grazed and grassland habitats not seasonally reduced by grazing or mowing. Cultivation experiments were conducted over a 2 year period on populations from each of the habitat types. Habitat-correlated differences in size and erectness observed in the field collections of Plantago major persisted in cultivation. In the other taxa, the overall pattern of distinct phenotypic differences associated with the different habitat types was not maintained in cultivation. However, in all five species statistically significant differences between and within populations were maintained in almost all characters investigated. Of particular interest was the evidence for genetically fixed dwarf/prostrate plants cultivated from samples collected from many of the lawn and heavily grazed grassland populations. While populations of Plantago major were homogeneous in cultivation, in the other taxa, plants phenotypically dwarf/prostrate in the field either remained dwarf/prostrate or grew into tall plants. This suggests the importance of both genotypic differentiation and phenotypic plasticity as adaptive strategies in short turf habitats. Populations of the five taxa from grasslands not regularly grazed or mown did not yield particularly tall variants, although they were consistent in their lack of dwarf/prostrate plants. Erect early-flowering variants of Prunella vulgaris and Plantago lanceolata were found in samples cultivated from the ancient hay meadows of Oxford. Close study of our experiments in both 1975 and 1976 revealed year to year differences in morphology and behaviour. Population x year interactions were investigated in Plantago major. Sampling procedures for genecological studies, the problems of inherent within-habitat heterogeneity, and difficulties in the design and interpretation of cultivation experiments are discussed. The notion of 'persistent difference' is examined in the light of our studies of year to year differences. The patterns and processes of population differentiation in lawns and other grassland types (with special reference to selection and gene flow) are considered in relation to breeding systems and population structure. The adaptive significance of phenotypic plasticity and ecotypic differentation are discussed. 
 
Included in Topics:  Examples of genetic and environmental interactions; Examples of ecotypes; Examples of phenotypic plasticity; Characteristics of cultivars;   
 

 

 

 

 

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