Genetic stability of Australian Phalaris (Phalaris tuberosa L.) under domestication

1971 ◽  
Vol 22 (6) ◽  
pp. 895 ◽  
Author(s):  
JR McWilliam ◽  
HE Schroeder ◽  
DR Marshall ◽  
RN Oram
Keyword(s):  
Natural Selection ◽  
Genetic Variability ◽  
Natural Regeneration ◽  
Ancestral Population ◽  
Agronomic Characters ◽  
Apparent Lack ◽  
Ecotypic Differentiation ◽  
Eastern Australia ◽  
Controlled Environments ◽  
Italian Origin

Thirty isolates of the Australian cultivar of phalaris (Phalaris tubevosa), sampled over the range of its distribution in south-eastern Australia, were evaluated as seeds and seedlings in controlled environments and as spaced plants and swards in the field. The variation found within and between the populations for a number of morphological, developmental, chemical, and agronomic characters indicates that the species has undergone little, if any, ecotypic differentiation during almost 90 years of cultivation in Australia. The results also indicate that the cultivar was derived from a single ancestral population of P. tuberosa and are consistent with the earlier claims that this population was of Italian origin. The evolutionary conservatism and the apparent lack of ecological adaptation in the cultivar are not due to a lack of genetic variability, but rather to the longevity and adaptability of individual plants, and the absence of natural regeneration in established stands, all of which have reduced the scope of natural selection.

Environmental and Genetic Control of Reproduction in Danthonia caespitosa Populations

1978 ◽  
Vol 26 (3) ◽  
pp. 351 ◽  
Author(s):  
KC Hodgkinson ◽  
JA Quinn
Keyword(s):  
Floral Induction ◽  
Flag Leaf ◽  
Day Length ◽  
Herbarium Specimens ◽  
Floral Initiation ◽  
Inflorescence Development ◽  
Southern Limit ◽  
The North ◽  
Eastern Australia ◽  
Controlled Environments

Seedlings and older plants of five populations of Danthonia caespitosa from south-eastern Australia were grown in controlled environments and in a transplant garden to determine the effect of day length, temperature, and vernalization of floral initiation and inflorescence development. The populations were selected from widely separated sites which spanned the latitudinal range (31-42°S.) for the species and extended from a hot, semiarid environment in the north to a relatively cool and moist temperature environment in the south. Examination of herbarium specimens indicated that seed set could occur as early as mid September at the northern limit for the species and not before mid January at the southern limit (Tasmania). In a uniform transplant garden located at Deniliquin (latitude 35° 23′S.) plants from the northern site reached anthesis 4 weeks earlier than plants from southern sites. Controlled environment experiments revealed that D. caespitosa is a long-day plant. Northern populations required a 9 . 5 hr day length or longer for floral induction compared with 11 hr or longer for southern populations. The number of days in inductive conditions (outside, day length 13.5 hr) required for floral initiation was 5-7 for the three most northern populations and 21-25 days for the two southern populations. Inflorescence development (initiation to flag leaf stage) was considerably slower in southern populations. All but the most northern population responded to vernalization. Flowering was earlier in temperatures that were optimal for plant growth. At high temperatures (36/31°C day/night) flowering was not significantly delayed for the three most northern populations, but was for the two southern populations, and florets contained caryopses in only the three northern populations. These results suggest that in cool and moist temperate habitats reproduction of this species is programmed by day length and temperature effects on floral initiation and development to coincide with a predictable growing season, whereas in hot semiarid habitats this control is relaxed, which permits opportunistic reproduction whenever soil moisture and temperature permit growth.

scholarly journals Long-term experimental evolution reveals purifying selection on piRNA-mediated control of transposable element expression

BMC Biology ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Ulfar Bergthorsson ◽  
Caroline J. Sheeba ◽  
Anke Konrad ◽  
Tony Belicard ◽  
Toni Beltran ◽  
...  
Keyword(s):  
Natural Selection ◽  
Transcriptional Activation ◽  
Small Rnas ◽  
Active Regions ◽  
Purifying Selection ◽  
Ancestral Population ◽  
Sequence Context ◽  
C Elegans ◽  
Population Sizes

Abstract Background Transposable elements (TEs) are an almost universal constituent of eukaryotic genomes. In animals, Piwi-interacting small RNAs (piRNAs) and repressive chromatin often play crucial roles in preventing TE transcription and thus restricting TE activity. Nevertheless, TE content varies widely across eukaryotes and the dynamics of TE activity and TE silencing across evolutionary time is poorly understood. Results Here, we used experimentally evolved populations of C. elegans to study the dynamics of TE expression over 409 generations. The experimental populations were evolved at population sizes of 1, 10 and 100 individuals to manipulate the efficiency of natural selection versus genetic drift. We demonstrate increased TE expression relative to the ancestral population, with the largest increases occurring in the smallest populations. We show that the transcriptional activation of TEs within active regions of the genome is associated with failure of piRNA-mediated silencing, whilst desilenced TEs in repressed chromatin domains retain small RNAs. Additionally, we find that the sequence context of the surrounding region influences the propensity of TEs to lose silencing through failure of small RNA-mediated silencing. Conclusions Our results show that natural selection in C. elegans is responsible for maintaining low levels of TE expression, and provide new insights into the epigenomic features responsible.

An Experimental Field Study to Examine Whether Capillaria Hepatica (Nematoda) Can Limit House Mouse Populations in Eastern Australia.

1995 ◽  
Vol 22 (1) ◽  
pp. 31 ◽  
Author(s):  
GR Singleton ◽  
GR Singleton ◽  
LK Chambers ◽  
LK Chambers ◽  
DM Spratt ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Host Population ◽  
Rapid Decline ◽  
Low Density ◽  
Noticeable Effect ◽  
Mouse Population ◽  
Apparent Lack ◽  
Capillaria Hepatica ◽  
Experimental Field ◽  
Eastern Australia

A replicated experimental field investigation to examine the effect of the nematode parasite Capillaria hepatica on populations of Mus domesticus is described. A 2-year study was conducted at 7 sites with matching farming practices, soil types, topography and habitat heterogeneity on the Darling Downs in south-eastern Queensland, Australia, where mice cause substantial economic, social and environmental problems. A 4 km2 sampling zone was designated on each site and sites were assigned randomly to one of 3 untreated and 4 treated groups. The parasite was released successfully on 3 occasions at 3 markedly different stages of mouse population dynamics. The first release was in winter 1992 into a low-density, non-breeding population. Mice on treated sites had significantly lower survival for 6 months after the release than mice on untreated sites. The parasite had a relatively high impact on survival of young mice (<72 mm long) 2 months after its release. The greatest impact on old mice (>76 mm) occurred a month later. The most pronounced effects of C. hepatica on mouse abundance occurred during the 4 months after its release (June-September). Mice on the untreated sites, however, had poor survival in September, so by October their population abundance was at a level similar to that of the treated populations. Once breeding began in mid-October C. hepatica had no noticeable effect on mouse population dynamics. This was because the parasite (i) had no effect on breeding of mice, (ii) had minimal transmission and (iii) had a diminishing effect on survival after October. The apparent lack of transmission of C. hepatica was probably due to a combination of low population density, the transient nature of the mouse population and predominantly dry weather for 6 months after the release. A second release was made in February 1993 into a breeding, medium-density host population that was rapidly increasing in abundance. Less than 2% of the population was affected during the release so interest focused on transmission rather than the effect of the parasite on the host's demographic machinery. Transmission did occur at a low rate and the parasite persisted for 4.5 months (to June) when it was decided to boost the proportion of mice infected in order to follow its effect on the overwintering population and the demographic effects during the next breeding season. This late release was compromised by synchronous, widespread and rapid decline in mouse densities. Densities fell from greater than 500 ha to less than 1 ha in less than 6 weeks. Two messages emerge from these studies. First, C. hepatica will not limit mouse populations if it is released into a low-density population during a long dry period on the Darling Downs. Second, more information is needed about the factors that influence the survival and transmission of the parasite under field conditions.

Natural Selection and Ecotypic Differentiation in Impatiens Pallida

1995 ◽  
Vol 65 (3) ◽  
pp. 303-324 ◽  
Author(s):  
Cynthia C. Bennington ◽  
James B. McGraw
Keyword(s):  
Natural Selection ◽  
Ecotypic Differentiation

scholarly journals Morphological and agronomical characterization and estimates of genetic parameters of sesbania Scop. (Leguminosae) accessions

1999 ◽  
Vol 22 (1) ◽  
pp. 81-93 ◽  
Author(s):  
E.A. Veasey ◽  
E.A. Schammass ◽  
R. Vencovsky ◽  
P.S. Martins ◽  
G. Bandel
Keyword(s):  
Genetic Variability ◽  
Genetic Parameters ◽  
Block Design ◽  
Soil Improvement ◽  
Morphological Characters ◽  
Wood Products ◽  
Agronomic Characters ◽  
Legume Plant ◽  
Biomass Yields ◽  
Superior Genotypes

Twenty-two accessions of seven Sesbania (Leguminosae) species: S. emerus, S. rostrata, S. tetraptera, S. exasperata (annuals), S. grandiflora, S. sesban and S. virgata (perennials), used for ruminant fodder, firewood, wood products, soil improvement, and human food, were investigated, with the aim of characterizing both inter- and intraspecific genetic variability, estimating genetic parameters for the characters evaluated and appraising the forage potential of the accessions. These were planted at the Instituto de Zootecnia, Nova Odessa, SP, Brazil, in a randomized complete block design with 22 treatments and four replications. Seventeen morphological and 17 agronomic characters were evaluated. Genetic parameters coefficient of intraspecific genetic diversity (bi) and coefficient of intraspecific genetic variation (CVgi) were obtained for the species represented by more than one accession. Highly significant differences were observed among as well as within species for most characters, showing considerable genetic variability. S. exasperata showed intraspecific genetic variability for the largest number of morphological characters. The same was observed for S. sesban for the agronomic characters. Most of the characters gave high bi values, above 0.80, indicating the possibility of selecting superior genotypes. The CVgi values, on the other hand, which indicate the magnitude of the existing genetic variability relative to the character mean, varied according to the species and character evaluated. Differences between annual and perennial species were observed, with higher biomass yields presented by the annuals at the first cut and by the perennials after the second cut, reaching the highest yield at the third cut. The annual species had higher seed production. Accession NO 934 of S. sesban gave the highest biomass yields and regrowth vigor, showing promise as a forage legume plant.

scholarly journals Evolution of genetic variance during adaptive radiation

2017 ◽  
Author(s):  
Greg M. Walter ◽  
J. David Aguirre ◽  
Mark W. Blows ◽  
Daniel Ortiz-Barrientos
Keyword(s):  
Natural Selection ◽  
Adaptive Radiation ◽  
Genetic Variance ◽  
Allelic Variation ◽  
Genetic Correlations ◽  
Leaf Traits ◽  
Adaptive Divergence ◽  
Ecotypic Differentiation ◽  
Divergent Natural Selection ◽  
Rapid Divergence

AbstractGenetic correlations between traits can bias adaptation away from optimal phenotypes and constrain the rate of evolution. If genetic correlations between traits limit adaptation to contrasting environments, rapid adaptive divergence across a heterogeneous landscape may be difficult. However, if genetic variance can evolve and align with the direction of natural selection, then abundant allelic variation can promote rapid divergence during adaptive radiation. Here, we explored adaptive divergence among ecotypes of an Australian native wildflower by quantifying divergence in multivariate phenotypes of populations that occupy four contrasting environments. We investigated differences in multivariate genetic variance underlying morphological traits and examined the alignment between divergence in phenotype and divergence in genetic variance. We found that divergence in mean multivariate phenotype has occurred along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits, and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with most of the divergence in phenotype among ecotypes associated with a change in trait combinations that had substantial levels of genetic variance in each ecotype. Overall, our results suggest that divergent natural selection acting on high levels of standing genetic variation might fuel ecotypic differentiation during the early stages of adaptive radiation.

scholarly journals Phylogeography of the Common New Zealand Wrasse Species, Notolabrus Celidotus, and the Phylogenetics of the Pseudolabrine Tribe

2021 ◽  
Author(s):  
◽  
Surrey Lisa Scott
Keyword(s):  
New Zealand ◽  
Genetic Variability ◽  
Mitochondrial Dna Control Region ◽  
North West ◽  
16S Gene ◽  
Local Setting ◽  
Eastern Australia ◽  
Population Structuring ◽  
High Gene ◽  
Temperate Fish

<p>The New Zealand coastline and marine environment is a diverse place and presents plenty of dispersal obstacles to many of the organisms that live there. This thesis investigates the phylogeography of one of the most common fish species around the coast of New Zealand, the endemic wrasse Notolabrus celidotus, using the mitochondrial DNA control region and compares genetic variability to another common New Zealand wrasse, Notolabrus fucicola in a local setting. These species are part of a tribe of temperate fish, the pseudolabrines, which can be found throughout the South and North-West Pacific. The phylogeny of this tribe was also analysed using the mitochondrial 16S gene to investigate the relationships among the New Zealand pseudolabrines and to those species elsewhere. The results suggest that pseudolabrines from mainland New Zealand are closely related and are likely to have originated from southern Australia while species from the Kermadec Islands and other northern islands are more closely related to the species of eastern Australia. The Notolabrus and Pseudolabrus genera should be reviewed to remedy paraphyly of Pseudolabrus. Furthermore, N. celidotus shows no population structuring throughout its range and appears to be rapidly expanding. Genetic variability was similar for both N. celidotus and N. fucicola. The results suggest that the pseudolabrine tribe has made multiple migrations to New Zealand where Notolabrus celidotus was able to spread around the three main islands and, likely facilitated by a long planktonic larval duration, was able to maintain high gene flow among populations.</p>

scholarly journals Genetic Variability, Heritability, and Genotypic Correlation of Soybean Agronomic Characters

2021 ◽  
Vol 19 (2) ◽  
pp. 117
Author(s):  
Heru Kuswantoro ◽  
Moch Muchlish Adie ◽  
Pratanti Haksiwi Putri
Keyword(s):  
Genetic Variability ◽  
Plant Height ◽  
Seed Yield ◽  
Seed Weight ◽  
Genetic Parameters ◽  
Genotypic Correlation ◽  
Agronomic Characters ◽  
Days To Maturity ◽  
100 Seed Weight ◽  
Number Of Branches

<p>Genetic parameters are important in genetic improvement and variety development. This study aimed to determine the effective characters that can be applied as selection criterion in soybean breeding using genetic parameters. About 100 soybean genotypes were grown in the Muneng Agricultural Technology Research and Assessment Installation from April to July 2020. The trial was conducted using a randomized complete block design. The results showed that high genetic variability was found on days to maturity, number of branches per plant, number of productive nodes per plant, 100-seed weight, and seed yield. The high heritability was shown by days to maturity, plant height, number of branches per plant, and 100-seed weight. All phenotypic correlations were significant, except for the correlation between seed yield and days to maturity, plant height, number of branches, and number of productive nodes. The seed yield had no genotypic correlation with all agronomic characters observed. The genotypic correlation was only significant for plant height and number of productive nodes, number of branches and number of filled pods, as well as number of productive nodes and 100-seed weight. Therefore, the improvement of seed yield can be conducted through direct selection using the seed yield parameter or indirectly using the 100-seed weight.<br /><br /></p>

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