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Paul, J.R., and S.J. Tonsor (2008) Explaining geographic range size by species age: a test using Neotropical Piper species. Pp 46-62 in Tropical Forest Community Ecology, Carson, W.P., and S. Schnitzer, Ed. Blackwell Publishing, Oxford Tonsor, S.J., C. Scott, I. Boumaza, T.R. Liss, J.L. Brodsky, and E. Vierling (2008) Heat shock protein 101 effects in A. thaliana: genetic variation, fitness and pleiotropy in controlled temperature conditions. Mol. Ecol. 17:1614-1626 The Hsp100/ClpB heat shock protein family is ancient and required for high temperature survival, but natural variation in expression and its phenotypic effects is unexplored in plants. In controlled environment experiments, we examined the effects of variation in the Arabidopsis cytosolic AtHsp101 (hereafter Hsp101). Ten wild-collected ecotypes differed in Hsp101 expression responses across a 22 to 40 degrees C gradient. Genotypes from low latitudes expressed the least Hsp101. We tested fitness and pleiotropic consequences of varying Hsp101 expression in 'control' vs. mild thermal stress treatments (15/25 degrees C D/N vs. 15/25 degrees D/N plus 3 h at 35 degrees C 3 days/week). Comparing wild type and null mutants, wt Columbia (Col) produced approximately 33% more fruits compared to its Hsp101 homozygous null mutant. There was no difference between Landsberg erecta null mutant NIL (Ler) and wt Ler; wt Ler showed very low Hsp101 expression. In an assay of six genotypes, fecundity was a saturating function of Hsp101 content, in both experimental treatments. Thus, in addition to its essential role in acquired thermal tolerance, Hsp101 provides a substantial fitness benefit under normal growth conditions. Knocking out Hsp101 decreased fruit production, days to germination and days to bolting, total dry mass, and number of inflorescences; it increased transpiration rate and allocation to root mass. Root : total mass ratio decayed exponentially with Hsp101 content. This study shows that Hsp101 expression is evolvable in natural populations. Our results further suggest that Hsp101 is primarily an emergency high-temperature tolerance mechanism, since expression levels are lower in low-latitude populations from warmer climates. Hsp101 expression appears to carry an important trade-off in reduced root growth. This trade-off may select for suppressed expression under chronically high temperatures.
Majetic, C.J., R.A. Raguso, S.J. Tonsor, and T.-L. Ashman (2007) Flower color-flower scent associations in polymorphic Hesperis matronalis (Brassicaceae). Phytochemistry 68:865-874 Floral scent emission rate and composition of purple and white flower color morphs of Hesperis matronalis (Brassicaceae) were determined for two populations and, for each, at two times of day using dynamic headspace collection and GC-MS. The floral volatile compounds identified for this species fell into two main categories, terpenoids and aromatics. Principal component analysis of 30 compounds demonstrated that both color morphs emitted more scent at dusk than at dawn. Color morphs varied in chemical composition of scent, but this differed between populations. The white morphs exhibited significant differences between populations, while the purple morphs did not. In the white morphs, one population contains color-scent associations that match expectations from classical pollination syndrome theory, where the flowers have aromatic scents, which are expected to maximize night-flying moth pollinator attraction; in the second population, white morphs were strongly associated with terpenoid compounds. The potential impact that pollinators, conserved biosynthetic pathways, and the genetics of small colonizing populations may have in determining population-specific associations between floral color and floral scent are discussed. Tonsor, S.J., and S.M. Scheiner (2007) Plastic trait integration across a CO2 gradient in Arabidopsis thaliana. Am. Nat. 169:E119-E140 Shifts across environments in patterns of trait integration may govern or alter adaptive responses. Changes in resource supply rates may be an especially important cause of plasticity of trait integration since they can lead to shifts in co-limitation and co-regulation of traits. Traditional evolutionary genetic characterization of trait integration relies on covariance analyses. Structural equation modeling (SEM) can complement such analyses. SEM provides insights into causal structure not possible with a covariance analysis, thereby providing mechanistic understanding of shifts in integration and suggesting likely foci of selection in changing environments. We tested for changes in trait integration by growing 35 genotypes of Arabidopsis thaliana (Brassicaceae; mouse-eared cress), from throughout the species' range in four atmospheric CO2 concentrations, 250 (past), 355(~recent CO2), 530, and 710 (future) µIM-1. SEM revealed significant shifts in the integration of N, C, and H2O use and their effects on reproductive dry mass across the CO2 gradient. The low CO2 stress of 250 µIM-1 had the most divergent integration structures. Standardized total effects of C-assimilation, water loss, and early N mass changed in sign across the C-supply gradient and the total effect of quantum yield decreased from significant to non-significant values across the gradient. Transpiration exhibited significant genetic variation and is thus a candidate target for selection and adaptation under novel growth CO2 concentrations. The strength of the correlation between C-assimilation and transpiration declined by 19% from 250 to 710 µIM-1, indicating a partial decoupling of their current mutual evolutionary constraint in the atmosphere of the future. Structural equation analysis of functional integration provides unique insights into the mechanisms through which changes in limiting resources can alter the nature of trait integration. Tonsor, S.J., C. Alonso-Blanco, and M. Koornneef (2005) Gene function beyond the single trait: natural variation, gene effects, and evolutionary ecology in Arabidopsis thaliana. Plant Cell Environ. 28:2-20 The purpose of plant functional genomics is to describe the patterns of gene expression and internal plant function underlying the ecological functions that sustain plant growth and reproduction. Plants function as integrated systems in which metabolic and developmental pathways draw on common resource pools and respond to a relatively small number of signal/response systems. Plants are also integrated with their environment, exchanging energy and matter with their surroundings and are consequently sensitive to changes in energy and resource fluxes. These two levels of integration complicate the description of gene function. Internal integration results in single genes often affecting multiple characteristics (pleiotropy) and interacting with multiple other genes (epistasis). Integration with the external environment leads to gene expression and the genes' phenotypic effects varying across environmental backgrounds (gene-environment interaction). An accurate description of the function of all genes requires an augmentation, already underway, of the study of isolated developmental and metabolic pathways to a more integrated approach involving the study of genetic effects across scales of variation usually regarded as the purview of ecological and evolutionary research. Since the evolution of gene function also depends on this complex of gene effects, progress in evolutionary genetics will also require understanding the nature of gene interactions and pleiotropy and the constraints and patterns they impose on adaptive evolution. Studying gene function in the context of the integrated organism is a major challenge, best met by developing co-ordinated research efforts in model systems. This review highlights natural variation in A. thaliana as a system for understanding integrated gene function in an ecological and evolutionary context. The current state of this research integration in A. thaliana is described by summarizing relevant approaches, current knowledge, and some potentially fruitful future studies. By introducing some of the fundamental questions of ecological and evolutionary research, experimental approaches and systems that can reveal new facets of gene function and gene effect are also described. A glossary is included in the Appendix.
Jenkins-Klus, D., S. Kalisz, P.S. Curtis, J.A. Teeri, and S.J. Tonsor (2001) Family- and population-level responses to atmospheric CO2 concentration: gas exchange and the allocation of C, N, and biomass in Plantago lanceolata (Plantaginaceae). Am. J. Bot. 88:1080-1087 To ascertain the potential for evolutionary responses to changing atmospheric CO2 content, we partitioned response to elevated CO2 in Plantago lanceolata between families and populations in 18 families in two populations. Plants were grown in 35 Pa and 71 Pa partial pressure of CO2 (pCO2) in open-top chambers. We measured above- and below ground mass, carbon (C), nitrogen (N), hexose sugar, and gas exchange properties in both CO2 treatments. Families within populations differed in mass, mass allocation, root:shoot ratios, above ground %N, C:N ratio, and gas exchange properties. The CO2Xfamily interaction is the main indicator of potential evolutionary responses to changing CO2. Significant CO2 X family interactions were observed for N content, C:N ratio, and photosynthetic rate (A: instantaneous light-saturated carbon assimilation capacity), but not for stomatal conductance. Families differed significantly in acclimation across time. The ratio of A (elevated /ambient growth CO2) when measured at a common internal CO2 partial pressure was 0.79, indicating down-regulation of A under CO2 enrichment. Mass, C:N ratio, %C, and soluble sugar all increased significantly but overall %N did not change. Increases in %C and sugar were significant and were coincident with redistribution of N aboveground. The observed variation among populations and families in response to CO2 is evidence of the potential for novel evolutionary trajectories with rising atmospheric CO2.
Kalisz, S., J. Nason, F.M. Hanzawa, and S.J. Tonsor (2001) Spatial population genetic structure in Trillium grandiflorum: the roles of dispersal, mating, history and selection. Evolution 55:1560-1568 The roles of the various potential ecological and evolutionary causes of spatial population genetic structure (SPGS) cannot in general be inferred from the extant structure alone. However, a stage-specific analysis can provide clues as to the causes of SPGS. We conducted a stage-specific SPGS analysis of a mapped population of ~2,000 Trillium grandiflorum (Liliaceae), a long-lived perennial herb. We compared SPGS for juvenile (J), non-reproductive (NR), and reproductive (R) stages. Fisher's exact test showed that genotypes had Hardy-Weinberg frequencies at all loci and stage classes. Allele frequencies did not differ between stages. Bootstrapped 99% confidence intervals (99%CI) indicate that F statistic values are indistinguishable from zero, (except for a slightly negative Fit for the R stage). Spatial autocorrelation was used to calculate f, the average kinship coefficient between individuals within distance intervals. Null hypothesis 99%CIs for f were constructed by repeatedly randomizing genotypic locations. Significant positive fine-scale genetic structure was detected in the R and NR stages, but not in the J stage. This structure was most pronounced in the R stage, and declined by about half in each remaining stage: near-neighbor f = 0.122, 0.065, 0.027, for R, NR, and J, respectively. For R and NR, the near-neighbor f lies outside the null hypothesis 99%CI, indicating kinship at approximately the level of half-sibs and first cousins, respectively. We also simulated the expected SPGS of juveniles post dispersal, based on measured R-stage SPGS, the mating system, and measured pollen and seed dispersal properties. This provides a null hypothesis expectation (as a 99%CI) for the J-stage correlogram, against which to test the likelihood that post-dispersal events have influenced J-stage SPGS. The actual J correlogram lies within the null hypothesis 99%CI for the shortest distance interval and nearly all other distance intervals indicating that the observed low recruitment, random mating and seed dispersal patterns are sufficient to account for the disappearance of SPSG between the R and the J stages. The observed increase in SPGS between J and R stages has two potential explanations: history and local selection. The observed low total allelic diversity is consistent with a past bottleneck: a possible historical explanation. Only a longitudinal stage-specific study of SPGS structure can distinguish between historical events and local selection as causes of increased structure with increasing life history stage.
Kalisz, S., F.M. Hanzawa, S.J. Tonsor, D.A. Thiede, and S. Voigt (1999) Ant-mediated seed dispersal affects distance, density and spatial pattern of seed relatedness in Trillium grandiflorum. Ecology 80:2620-2634 Seed dispersal creates the initial spatial distribution of individuals in a population and in conjunction with the mating system influences spatial patterns of relatedness. This spatial template of related individuals sets the stage for all subsequent density-dependent and frequency-dependent interactions. In this study we document how ant-mediated seed dispersal affects the number and relatedness of seeds in both dispersed and undispersed aggregations and how these patterns influence seedling emergence in the long-lived perennial, Trillium grandiflorum. Experimental hand-pollinations in two years demonstrated that selfing is extremely rare and suggested that self-incompatibility (SI) is a likely explanation. Our multi-locus outcrossing estimate ( tm=1.05 ± 0.056) confirmed this result and also suggests that seeds within a fruit are likely to have the same pollen parent. Thus a highly outcrossing mating system is the initial determinant of relatedness among seeds within a fruit. We tracked uniquely coded, radiolabeled seeds from 30 and 40 fruits in 1991 and 1992, respectively to determine how dispersal alters this initial relatedness of seeds. Of the 335 and 876 seeds labeled in these two years, we recovered 63% and 76% of the seeds post-dispersal, and found that 19% and 23% of the recovered seeds were dispersed more than 10 cm from the maternal parent in the first and second years, respectively. In both years ant-mediated dispersal reduced the number of seeds near the maternal parent. However, the effect of seed dispersal on the number of seeds in aggregations varied among years. Ant-mediated dispersal increased the number of seeds in dispersed aggregations in the first year and decreased the number in the second year. The average seed dispersal distance also differed between years, 2.41 m (± 0.33) vs. 0.53 m (± 0.06) in years 1 and 2, respectively. Ant-mediated seed dispersal decreased the probability of a seed having a sibling as its nearest neighbor post-dispersal between one third to one half. In contrast, seedling emergence was related to neither dispersal nor seed aggregation size in our study. However, the fitness effects of dispersal may be important later in the life cycle of this long lived species and as such was undetected. One scenario is that plants derived from seeds dispersed out of their sibling relatedness group may gain minority advantage both in terms of mating success (if the population is SI) and other frequency dependent processes like disease resistance.
Tonsor, S.J., and C.J. Goodnight (1997) Evolutionary predictability in natural populations: Do mating system and non-additive genetic variance interact to affect heritabilities in Plantago lanceolata? Evolution 51:1771-1782 Quantitative genetics has been an immensely powerful tool in manipulating the phenotypes of domesticated plants and animals. Its application to natural populations is not so facile as might at first seem. Much of the predictive power of quantitative genetics depends on the breeder's control over the context in which phenotype and mating are being expressed. In the natural world, these contexts are often difficult to describe, let alone control. We are left, therefore, with a poor understanding of the limits of quantitative genetics in natural populations. The major contextual factors of importance have been outlined by Barker and Thomas (1987). One of the crucial contextual elements for assessing breeding value is the genetic background in which an individual's genes are being assessed. When interacting genes are polymorphic within a population, the degree of mating among relatives can influence the correlations among mates and the predictions of a response to selection. Population structure can strongly influence the degree to which dominance and epistasis influences additive genetic variance and heritability (Goodnight 1988; Willis and Orr 1993). The extent of inbreeding can also influence heritabilities through its effect on the environmental component of phenotypic variance (Falconer, 1981). The applicability of standard quantitative genetic breeding designs to the measurement of heritabilities in natural populations therefore depends in part on: 1) the mating system of the population, and 2) the importance of gene interactions in determining phenotypic variation. We tested for an effect of mating structure on the partitioning of phenotypic variance and heritability by comparing two breeding designs in a common environment. Both breeding designs used 139 pollen parents taken from mapped locations in a population of Plantago lanceolata L., and crossed to 280 seed parents from the same population. One design was random-mating, the second was biased towards near-neighbor matings to an extent determined by field-measure of pollen-mediated gene flow distances (Tonsor, 1985). The offspring were grown randomly mixed in a common garden. Nine traits were measured: central corm diameter, number of leaves, density of hairs (cm-2) on the leaves, dry weight per unit leaf area, photosynthetic capacity, transpiration rates, water use efficiency and reproductive dry weight. Heritabilities and variance components from the two designs were compared using randomization tests. None of the variance components or the heritabilities differed significantly between breeding designs at the 0.05 level. The test could distinguish differences between the heritabilities measured in the two breeding designs as small as 0.11, on average. Thus, for the degree of inbreeding normally exhibited in P. lanceolata, there is insufficient gene interaction present within populations to influence the partitioning of variance between additive and non-additive components, or to influence heritability estimates to a meaningful extent, practically speaking. We suggest that for Plantago other sources of variation in heritability estimates, such as maternal effects and G X E interactions, are more important influences than the interaction between inbreeding and gene interactions, and standard heritability estimate based on random breeding is as accurate as one taking the natural mating structure into account.
Curtis, P.S., D.K. Klus, S. Kalisz, and S.J. Tonsor (1996) Intraspecific variation in CO2 responses in Raphanus raphanistrum and Plantago lanceolata: assessing the potential for evolutionary change with rising CO2. Pp 13-28 in Carbon Dioxide, Populations and Communities, Bazzaz, F., and C. Korner, Ed. Academic Press, New York Elevated atmospheric CO2 has well-documented effects on plant physiology and growth that may alter important ecosystem processes, particularly carbon storage and nutrient cycling. Differential sensitivity among species to elevated CO2 may also alter interspecific interactions, resulting in changes in community structure. Predictions of the ecological consequences of elevated atmospheric CO2 have almost always been based on mean physiological and growth responses from a small, and often arbitrary subsample of the species being considered. However, mean responses estimated from a small number of individuals are probably not representative of the range of responses found among distinct populations or genotypes of a species. This range of responses determines the evolutionary potential of a species. Thus the question of potential evolutionary responses to elevated atmospheric CO2 has yet to be addressed. To improve our understanding of the evolutionary potential in CO2 responses, we characterized 12 paternal families in Raphanus raphanistrum and 18 maternal families of Plantago lanceolata. In both experiments, siblings from each family were maintained in each of two CO2 atmospheres: 35 ppm and 700 ppm. R. raphanistrum was grown in open-top chambers at the University of Michigan Biological Station, P. lanceolata in open-top chambers at Kellogg Biological Station. R. raphanistrum exhibited significant genetic variation in life history and reproductive characteristics among families, with significant differences in responses between the two years of the study. P. lanceolata also showed significant among-family variation in responses of photosynthetic rate to elevated CO2, with 11 families showing no response, and seven families with up to 75% greater rates in the 700 ppm atmosphere. Most P. lanceolata families showed no increased biomass gain at 700ppm CO2, while a few showed significant increases, and one family decreased its mass significantly. Thus, our studies showed substantial among family intraspecific variation in response to elevated CO2. This variation is a necessary precondition to any evolutionary response to rising CO2 and could lead to large shifts in average population-level responses under elevated CO2 conditions. Evolutionary changes could thus alter both ecosystem-level and community level interactions among species. Whitlock, M.C., P.C. Phillips, F.B.G. Moore, and S.J. Tonsor (1995) Multiple fitness peaks and epistasis. Annu. Rev. Ecol. Syst. 26:601-629 The importance of genetic interactions in the evolutionary process has been debated for more than half a century. Genetic interactions such as underdominance and epistasis (the interaction among genetic loci in their effects on phenotypes or fitness) can play a special role in the evolutionary process because they can create multiple fitness optima (adaptive peaks) separated by fitness minima (adaptive valleys). The valleys prevent deterministic evolution from one peak to another. We review the evidence that genetic interaction is a common phenomenon in natural populations. Some studies give strong circumstantial evidence for multiple fitness peaks, although the mapping of epistatic interactions onto fitness surfaces remains incompletely explored and absolute proof that multiple peaks exist can be shown to be empirically impossible. We show that there are many reasons that epistatic polymorphism is very difficult to find, even when interactions are an extremely important part of the genetic system. When polymorphism results in the presence of multiple fitness peaks within a group of interbreeding populations, one fitness peak will quickly be nearly fixed within all interbreeding populations, but when epistatic or underdominant loci are nearly fixed, there will be no direct evidence of genetic interaction. Thus when complex landscapes are evolutionarily most important, evidence for alternative high fitness genetic combinations will be most ephemeral. Genetic interactions have been most clearly demonstrated in wide crosses within species and among closely related species. This evidence suggests that genetic interactions may play an important role in taxonomic diversification and species-level constraints. Population genetic analyses linked with new approaches in metabolic and molecular genetic research are likely to provide exciting new insights into the role of gene interactions in the evolutionary process.
Moore, F.B.G., and S.J. Tonsor (1994) A simulation of Wright's shifting balance process: migration and the three phases. Evolution 48:69-80 Wright partitioned the shifting-balance process into three phases. Phase one is the shift of a deme within a population to the domain of a higher adaptive peak from that of the historical peak. Phase two is mass selection within a deme towards that higher peak. Phase three is the conversion of additional demes to the higher peak. The migration rate between demes is critical for the existence of phases one and three. Phase one requires small effective population sizes, hence low migration rates. Phase three is optimal under high migration rates that spread the most-fit genotype from deme to deme. Thus, a population-wide peak shift requires intermediate levels of migration. By altering the rates of phases one and three, migration affects the predominant direction of mass selection within a population. This study examines the degree to which migration, through its effects on phases one and three, determines the probability of a simulated population arriving at its genotypic optimum after 12,000 generations. These simulations reveal that there is a range of migration rates for which an entire population might be expected to shift to a higher peak. Below m = 0.001 peak shifts occur frequently (phases I and II) but are not successfully exported out of subpopulations (phase III), and above 0.01 peak shifts within demes (phase I and II), required to initiate phase III, become increasingly uncommon. Because it is unlikely that real populations will have uniform migration rates from generation to generation, the probable effects of varying migration rates on broadening the range of conditions producing peak shifts are discussed.
Tonsor, S.J., S. Kalisz, J. Fisher, and T.P. Holtsford (1993) A life history-based view of population genetic structure in Plantago lanceolata. Evolution 47:833-843 We explored the extent to which the soil seed bank differed genetically and spatially in comparison to two actively growing stages in a natural population of Plantago lanceolata. All seed-bank seeds, seedlings, and adults of P. lanceolata within eight subunits in a larger population were mapped, subjected to starch gel electrophoresis, and allozyme analysis in 1988. Gel electrophoresis was also used to estimate the mating system in two years, 1986 and 1988. The spatial distributions of seeds, seedlings, and adults were highly coincident. Allele frequencies of the dormant seeds differed significantly from those of the adults for four of the five polymorphic loci. In addition, a comparison of the genotype frequencies of the three life-history stages indicated that the seed bank had an excess of homozygotes. Homozygosity, relative to Hardy-Weinberg expectations, decreased during the life cycle (for seed bank, seedlings, and adults respectively: F(it) = 0.19, 0.09, 0.01; F(is) = 0.14, 0.04, -0.12). Spatial genetic differentiation increased sixfold during the life cycle: (for seed bank, seedling and adults: F(st) = 0.02, 0.05, 0.12). The apparent selfing rate was 0.01 in 1986 and 0.09 in 1988. These selfing rates are not large enough to account for the elevated homozygosity of the seed bank. Inbreeding depression, overdominance for fitness, and a ''temporal Wahlund's effect'' are discussed as possible mechanisms that could generate high homozygosity in the seed bank, relative to later life-history stages. In Plantago lanceolata, the influence of the mating system and the ''genetic memory'' of the seed bank are obscured by the time plants reach the reproductive stage.
Meagher, W.L., and S.J. Tonsor (1992) Checklist of the flora of the Augusta Floodplain preserve. A life history-based view of population genetic structure in Plantago lanceolata. Michigan Botanist 31:83-98 Tonsor, S., and S. Kalisz (1991) Ecological genetics, microevolution and changes in atmospheric chemistry: Population-level techniques. Pp 00-00 in Genetics and Air Pollution, Taylor, G.E., M.T Claegg, and L.F. Pitelka, Ed. Springer-Verlag, Berlin Tonsor, S. (1990) Spatial patterns of differentiation for gene flow in Plantago lanceolata. Evolution 44:1373-1378
Tonsor, S.J. (1989) Relatedness and intraspecific competition in Plantago lanceolata. Am. Nat. 134:897-906 This experiment looked for an effect of relatedness on plant performance under competitive conditions in the perennial weed Plantago lanceolata L. (Plantaginaceae). Seeds from a diallel breeding design were used to establish green-house pots containing three competing individuals. Three groups of pots were set up: those with full-sib, half-sib, and unrelated plants. Plants were not given nutrients after the first 5 wk and were watered only when wilting. At the end of the growing season, all plants were harvested and their parts counted, dried, and weighed. Relatedness among competitors did not affect aboveground dry weight. There was, however, a significant decrease in the within-pot variance of vegetative and total dry weights. There was also an increase in the number of plants flowering per pot with an increase in relatedness. The differences in within-pot dry-weight variances and the propensity for reproduction among relatedness treatments are at least partially explained by the differences among relatedness treatments in the contribution of maternally inherited variation in performance to the within-pot variances of performance. The contribution of inherited variation in performance to the fitness effects of local relatedness can strongly reflect environmental variation. Inherited variation is likely to be a major determinant of the differences in the fitness effects of relatedness seen in existing empirical studies.
Tonsor, S.J. (1985) Leptokurtic pollen flow, non-leptokurtic gene flow in a wind-pollinated herb, Plantago lanceolata L. Oecologia 67:442-446 Tonsor, S.J. (1985) Intrapopulational variation in pollen-mediated gene flow in Plantago lanceolata L. Evolution 39:775-782 The extent of genetic variation in pollen-mediated gene flow distance was measured for a population of the wind-pollinated herb, Plantago lanceolata. Twenty-nine genotypes were collected from a natural population, clonally replicated, and grown to reproductive maturity in a greenhouse. Relative gene flow distances were measured for each replicate and genotype in a wind tunnel. Approximately five percent of the total variation in gene flow distance was attributable to variation among genotypes. Most of the remaining variation was attributable to differences between the early part of the growing season, when most of the flowering occurs, and the remainder of the season, when flowering is sparse. The rankings of the genotypes' gene flow distances showed significant concordance between the early-season measures and measures from later in the summer. There was no correlation between the average inflorescence height for a plant and the average gene flow distance for that plant. For analysis of pollen characteristics suspected as causal factors of variation in gene flow distance, the variation in gene flow distance was divided into two components: that due to environmental (seasonal) differences, and that due to the differences among genotypes within runs. Variation in both the buoyant properties of the pollen grains and their adhesiveness was significantly partially correlated with environmental variation in gene flow distance, while only the buoyant properties of the pollen grains were significantly partially correlated with among-genotype variation in gene flow distances.
Clough, J.M., J.A. Teeri, and S.J. Tonsor (1983) Photosynthetic adaptation of Solanum dulcamera L. to sun and shade environments. V. A physiological characterization of Gauhl's sun and shade ecotypes. Oecologia 60:348-352 Teeri, J.A., S.J. Tonsor, and M. Turner (1981) Leaf thickness and carbon isotope composition in the Crassulaceae. Oecologia 50:367-369 Teeri, J.A., and S.J. Tonsor (1981) Variability in photoperiod and the inhibition of flowering in a high latitude population of Saxifraga rivularis. Can. J. Bot. 59:388-391 |
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