Poles Apart: A Study in Contrasts


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Claire Hanson finds a seaside beach house that is much more than sedate, composed comfort. Not known for its architectural prowess, Middleton Beach is a suburb of contrasts; of post-modern mansions rising proudly, looming alongside formerly unloved seaside cottages now undergoing gentrification.

The along comes Grace with her award-winning, architect-designed home, injecting some much-needed modernist shimmy and strut to the polite, if lacklustre, beachside boulevards. Middleton Beach is an innocuous enclave, but its top end saw a plot twist recently with the addition of a seaside residence that is decidedly unpretentious and relaxed.

More than anything, the site, located within walking distance of the beach with ocean views, dictated the design. Flexibility was key, allowing for a relaxed, laid-back lifestyle. Grace says the beach house aesthetic of surrounding homes determined the design, with a modern take. This resulted in the use of black weatherboard, as well as the employment of textured materials, such as timber and recycled brick.

The house has ocean views from each of its four levels and large deck areas to the north looking over Eyre Park and the beach. Recycled brick to the garage is a feature, creating an interesting streetscape perspective at odds with its neighbours. Its seeds are efficiently dispersed by wind to a distance of several meters from the maternal plant as well as by humans along roadways and highways. The seeds of P. Most seeds therefore germinate in the following spring [44]. Seeds of this species only form a weak, persistent seed bank; 99 percent of all seedlings typically emerge within 2 years after seed dispersal [39] and references therein.

After emergence, seedlings develop a strong taproot for nutrient storage and overwintering as rosettes. Population genetic diversity of the three species, regardless of their different life history stages, has been investigated earlier. The three species strongly differed in their population genetic characteristics. The most genetically impoverished species was the annual invasive species Amaranthus retroflexus for which high inbreeding and among population differentiation was indicated Table 7.

Although both Carduus acanthoides and Pastinaca sativa exhibited low levels of inbreeding, populations of Pastinaca sativa were more structured than those of Carduus acanthoides Table 7. In the present study, we therefore compared individual life history stages of species that differ not only in their life history strategies but also in levels and patterns of genetic diversity in order to test whether there are any broad genetic differences between soil seeds and surface plants. We tested the relationship among plants derived from seeds extracted from the soil seed bank, seedlings, rosettes and mature plants over a range of localities and species.

Populations were selected on the basis of known genetic variability see above , i. These differed in habitat dynamics and population size or history see Table 8 , Fig. This minimized the risk that our data would be distorted by attributes of one particular locality. In four natural populations of our three species, we took 40 samples of each life history stage from regularly distributed permanent plots. To ensure sampling consistency, we used the same sampling strategy for all three species.

To obtain samples from different phases of the life history cycle for our genetic analysis, we sampled several consecutive life history stages: 1 the winter soil seed bank i. The number of sampled stages differed in relation to the species and its life history cycle see Table 2. In the case of the annual species Amaranthus retroflexus , we did not sample the rosette life history stage.

In the perennial Carduus acanthoides , we sampled only the rosette life history stage instead of the seedling stage because we were unable to differentiate between large seedlings and small rosettes in the field. In Pastinaca sativa , we were able to sample all stages because they strongly differed among each other. We did not succeed in obtaining the summer seed banks from four populations: Pocedelice Amaranthus , Orech Carduus , and Ostopovice and Sedlec Pastinaca.

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Soil samples of the winter seed bank were collected in February, of the summer seed bank in July. Amaranthus retroflexus was sampled in , Carduus acanthoides in and Pastinaca sativa in First, we created a 15 by 10 m grid with gridlines spaced at 5 m intervals. We then took soil samples of winter seed bank at the intersections of the gridlines by digging up soil blocks that were 20 cm long, 20 cm wide and 10 cm deep. We recorded the spatial coordinates of each sample. Emerging seedlings were harvested and transplanted into small pots. After 14 days, the soil was disturbed once again and sprayed with a gibberellic acid solution to break dormancy and speed up as well as synchronise germination of ungerminated seeds.

From each population, forty seedlings were randomly harvested, grown to maturity and subjected to allozyme electrophoresis. We believe that we were able to establish plants from most seeds stored in the seed banks. Using a gibberellic acid solution, we broke dormancy of a majority of ungerminated dormant seeds because only a minimal portion of the seeds remained in the soil. We have to admit, however, that our results could be influenced by a bias in the differential establishment rates of seeds from different seed banks collected from different populations and different species.

They pointed out that this possibility is to some extent a technical issue because seedlings must grow large enough before they can be used for allozyme analysis, and many plants experience some degree of early mortality. On the other hand, the use of small seedlings is impossible because of the low enzyme activity in this life stage as found in Atriplex tatarica. We then collected subsequent life history stages within the grid established during the winter seed bank soil sample collection.

We randomly collected 4 seedlings, 4 rosettes and 4 fruiting plants around each of ten intersections of the gridlines but no further than 5 m away. Seedlings and rosettes were transported to the Experimental garden where they were grown to maturity and subjected to allozyme electrophoresis. From each fruiting plant, a single young expanded leaf was collected in the field, kept in a cool box and transported to the laboratory for subsequent analysis.

Soil samples of summer seed banks were taken and processed in the same way as in the winter seed bank. In total, samples were analysed, i. All samples were analysed by gel electrophoresis using selected enzymes for methodological details of analysing Carduus acanthoides , see [46] , for Amaranthus retroflexus, see [45]. Data for Pastinaca sativa have not yet been published.

For a summary of the enzymatic systems used, see Table 3. To estimate genetic diversity and genetic structure, a locus was considered polymorphic if the frequency of the most common allele did not exceed 0. Genetic diversity parameters, i. This method allowed us to test whether these F statistics were significantly different from zero determined by bootstrap replicates.

Probability values for differences between various life history stages are given for two-sided t-tests after 10 permutations. To test for differences in allelic composition among stages and populations, we ran an exact test of population differentiation [50] with the programme TFPGA [51] , using dememorization steps, 20 batches and permutations per batch.

Genetic variation at the level of populations and stages was investigated with a nested analysis of molecular variance stages nested within populations; AMOVA [52]. Levels of genetic differentiation were measured by F CT , F SC , and F ST , referring to the differentiation among populations, among stages within populations and within stages, respectively.

Levels of significance were determined by computing random permutation replicates. No specific permits were required for the described field studies, which took place on localities with public right-of-way and did not involve endangered or protected species. Allele frequencies of Amaranthus retroflexus. Allele frequencies at six loci in four populations and four life history stages of Amaranthus retroflexus are given.

Allele frequencies of Carduus acanthoides. Allele frequencies at eight loci in four populations and life history stages of Carduus acanthoides are given. Allele frequencies of Pastinaca sativa. Allele frequencies at eight loci in four populations and five life history stages of Pastinaca sativa are given. Conceived and designed the experiments: BM. Analyzed the data: BM. Wrote the paper: BM VM.

Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing aboveground plants represent a nonrandom sample of the seed bank. Download: PPT. Table 1. Analysis of molecular variance in Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa. Table 2. Population genetic characteristics for individual life history stages of Amaranthus retroflexus , Carduus acanthoides and Pastinaca sativa.

Results Hierarchical Analysis of Molecular Variance Hierarchical analyses of molecular variance AMOVA computed separately for Amaranthus retroflexus , Carduus acanthoides and Pastinaca sativa revealed that most of the genetic diversity was partitioned within life history stages; the analysis accounted for Figure 1.

Population genetic characteristics of Amaranthus retroflexus. Figure 2. Population genetic characteristics of Carduus acanthoides. Figure 3. Population genetic characteristics of Pastinaca sativa. Table 3. Tests for differences in allele frequencies of individual loci and over all loci. Comparison of Life History Stages within Populations When we tested differences among life history stages separately for individual populations of the three species, we obtained inconsistent results concerning individual parameters, populations and species Figs.

Table 4. Tests for differences in allele frequencies among individual life history stages of Carduus acanthoides. Table 5. Tests for differences in allele frequencies among individual life history stages of Amaranthus retroflexus. Table 6. Tests for differences in allele frequencies among individual life history stages of Pastinaca sativa. Table 7. Genetic diversity of Amaranthus retroflexus , Carduus acanthoides and Pastinaca sativa from other studies. Discussion The potential role of soil seed banks in evolutionary dynamics of plant populations has evoked many theoretical [20] , [24] — [31] as well as empirical studies [9] , [11] — [17] , [32] — [35].

Figure 4. Location of Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa populations. Conclusions We have demonstrated for the first time the extent to which the summer soil seed bank differs from other life history stages. Study Sites We tested the relationship among plants derived from seeds extracted from the soil seed bank, seedlings, rosettes and mature plants over a range of localities and species.

Sample Collection and Allozyme Analysis In four natural populations of our three species, we took 40 samples of each life history stage from regularly distributed permanent plots. Statistical Analysis To estimate genetic diversity and genetic structure, a locus was considered polymorphic if the frequency of the most common allele did not exceed 0. Permissions No specific permits were required for the described field studies, which took place on localities with public right-of-way and did not involve endangered or protected species. Supporting Information.

Table S1. Table S2. Table S3. Author Contributions Conceived and designed the experiments: BM. References 1. Roberts HA Seed banks in soils. Adv Appl Biol 6: 1— View Article Google Scholar 2. Am J Bot — View Article Google Scholar 3. Cambridge: Cambridge University Press. San Diego: Academic Press. Thompson K, Grime JP Seasonal variation in the seed banks of herbaceous species in ten contrasting habitats. J Ecol — View Article Google Scholar 6. Fenner M Seed Ecology.

6. #Trumputin: A study in contrasts - Times of India

Am Nat — View Article Google Scholar 9. Am J Bot 29— View Article Google Scholar Nature — Cabin RJ Genetic comparison of seed bank and seedling populations of the desert mustard Lesquerella fendleri. Evolution — A multipopulation study of the desert mustard Lesquerella fendleri Brassicaceae. Am J Bot 30— A study of Atriplex tatarica Chenopodiaceae.

Mol Ecol — Heredity — Brassicaceae in dynamic habitats: Genetic composition and diversity of seed bank and established populations. Basic Appl Ecol 4: — Kalisz S Fitness consequences of mating system, seed weight, and emergence date in a winter annual, Collinsia verna. Cohen D Optimizing reproduction in a randomly varying environment. J Theor Biol — Cohen D Optimizing reproduction in a randomly varying environment when a correlation may exist between the conditions at the time a choice has to be made and the sibsequent outcome. J Theor Biol 1— Venable DL, Brown JS The selective interactions of dispersal, dormancy and seed size as adaptations for reducing risk in variable environments.

Venable DL Modeling the evolutionary ecology of seed banks.

Poles Apart- Pink Floyd Lyrics

Ecology of Soil Seed Banks. Nunney L The effective size of annual plant populations: The interaction of seed bank with fluctuating population size in maintaining genetic variation. Pacala SW Neighborhood models of plant populations dynamics.

A study in contrasts

Multi-species models of annuals. Theor Popul Biol — Rees M Evolutionary ecology of seed dormancy and seed size. Caswell H, Hastings A Fecundity, developmental time, and population growth rate: an analytical solution. Theor Popul Biol 71— Genetic structure and genetic diversity of surface populations and diaspore bank in the liverwort Mannia fragrans Aytoniaceae.


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Oikos 1—5. An experimental seed bank study of Atriplex tatarica Chenopodiaceae. Flora — Amaranthus retroflexus L. Watson and A. Can J Plant Sci —

Poles Apart: A Study in Contrasts Poles Apart: A Study in Contrasts
Poles Apart: A Study in Contrasts Poles Apart: A Study in Contrasts
Poles Apart: A Study in Contrasts Poles Apart: A Study in Contrasts
Poles Apart: A Study in Contrasts Poles Apart: A Study in Contrasts
Poles Apart: A Study in Contrasts Poles Apart: A Study in Contrasts
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