NATURAL SELECTION AMONG HYBRIDS BETWEEN CARDUUS ACANTHOIDES AND C. NUTANS IN ONTARIO

1961 ◽  
Vol 39 (2) ◽  
pp. 269-279 ◽  
Author(s):  
Gerald A. Mulligan ◽  
Raymond J. Moore
Keyword(s):  
Natural Selection ◽  
Morphological Variation ◽  
Natural Hybridization ◽  
Hybrid Index ◽  
Local Conditions ◽  
Carduus Acanthoides ◽  
Carduus Nutans ◽  
Waste Land ◽  
Southern Half

Natural hybridization is occurring between two introduced thistles, Carduus acanthoides L. and C. nutans L., in the southern half of Grey County, Ontario. The morphological variation of plants in 37 fields, including a field near Priceville previously studied in 1952, was evaluated by means of a hybrid index in 1957. Carduus nutans was first established in the hybrid area and C. acanthoides was introduced later, probably from the region northwest of Owen Sound, into waste land near Flesherton, where hybridization first occurred. Many large hybrid populations were found in the southern portion of Grey County and most of these hybrids were very similar to C. acanthoides in morphology. It was concluded that there is a numerical supremacy of acanthoides-type hybrid segregates in the hybrid area, and that such hybrids are better adapted for survival under local conditions than C. nutans and will probably supplant the latter species.

FURTHER STUDIES ON NATURAL SELECTION AMONG HYBRIDS OF CARDUUS ACANTHOIDES AND CARDUUS NUTANS

1964 ◽  
Vol 42 (12) ◽  
pp. 1605-1613 ◽  
Author(s):  
R. J. Moore ◽  
G. A. Mulligan
Keyword(s):  
Natural Selection ◽  
Chromosome Number ◽  
Parental Species ◽  
Experimental Studies ◽  
Great Decrease ◽  
Carduus Acanthoides ◽  
Carduus Nutans ◽  
Experimental Plots ◽  
Better Than ◽  
Made In

A third 5-year survey made in 1962 of Carduus acanthoides, C. nutans, and their hybrids in Grey Co., Ontario, revealed that a great decrease in these populations had occurred. C. acanthoides and hybrids similar to this species had survived better than C. nutans but very little spread of either species seemed to have occurred in 1957–1962. In experimental plots the hybrid has been made and backcrossed to the parental species. The species differ in chromosome number (C. acanthoides, 2n = 22; C. nutans, 2n = 16) and hybrids have intermediate numbers. Evidence was found from field and experimental studies that the progeny of the F1 hybrid included a greater proportion of seedlings with the higher chromosome numbers than with the lower and intermediate numbers. It is suggested that this selection may operate through the rejection of the longer chromosomes received from C. nutans, which, in certain zygotic combinations may constitute an excess of chromatin lethal to the zygote.

Hybridization of Carduus nutans and Carduus acanthoides (Compositae): morphological variation in F1 hybrids and backcrosses

1992 ◽  
Vol 70 (11) ◽  
pp. 2303-2309 ◽  
Author(s):  
S. I. Warwick ◽  
B. K. Thompson ◽  
L. D. Black
Keyword(s):  
Morphological Variation ◽  
Morphological Traits ◽  
Parental Species ◽  
F1 Hybrids ◽  
Carduus Acanthoides ◽  
Carduus Nutans ◽  
Naturally Occurring ◽  
Morphological Criteria ◽  
Hybrid Complex ◽  
Hybrid Classes

The aim of this study was to compare patterns of morphological variation in F1 hybrids and backcrosses obtained artifically in the greenhouse relative to the parental species Carduus acanthoides (2n = 22) and Carduus nutans (2n = 16), which form a naturally occurring hybrid complex in Grey County, Ontario. The identity of parental, hybrid, and backcross genotypes was confirmed using allozyme markers. The data were used to test for hybrid (H) intermediacy in morphological traits that differentiate the two parental taxa (acronyms A and N are used for C. acanthoides and C. nutans, respectively) and to determine patterns of variation on the same traits among the four classes of backcross plants (NH, HN, AH, and HA, seed × pollen parent, respectively). Canonical multivariate analysis indicated that in general, F1 hybrids had intermediate morphologies compared with parental genotypes, although differences were observed among characters with respect to the degree of morphological intermediacy of hybrids. The backcrosses were divided into two groups, i.e., those backcrossed with C. acanthoides (AH and HA) and those with C. nutans (NH and HN). However, backcrosses also showed considerable morphological overlap with F1 hybrids. These results exemplify the utility of joint comparisons of morphology and genotypic constitution (allozymes) in the hybridization studies, and they emphasize the limitations in describing hybrid classes solely by morphological criteria. Key words: Carduus nutans, Carduus acanthoides, hybrids, backcrosses, morphological variation.

NATURAL HYBRIDIZATION BETWEEN CARDUUS ACANTHOIDES AND CARDUUS NUTANS IN ONTARIO

1956 ◽  
Vol 34 (1) ◽  
pp. 71-85 ◽  
Author(s):  
R. J. Moore ◽  
G. A. Mulligan
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
First Generation ◽  
Natural Hybridization ◽  
Clear Correlation ◽  
Hybrid Index ◽  
Carduus Acanthoides ◽  
Hybrid Plants ◽  
Gametic Selection ◽  
Generation Hybrid

A survey was made of the occurrence of natural hybrids between two species of introduced thistles, Carduus acanthoides L. var. acanthoides and C. nutans L. var. nutans, in Grey County, Ontario. The population of one field was studied in detail. Specimens were taken and their morphological variation was evaluated by means of a hybrid index. These species have different chromosome numbers: C. acanthoidcs L., 2n = 22; C. nutans L., 2n = 16. All the intervening numbers were found in the hybrids. There is a clear correlation between chromosome number and hybrid index: plants with the chromosome number of a first generation hybrid have an index intermediate between those of the parental species. The chromosome numbers of seedlings raised from seed collected from hybrid plants were determined. It was found that seedlings with the number 2n = 22 were much more frequent than those with other numbers. It is suggested that both ecological and gametic selection are acting in this area to favor production and survival of plants with the chromosome number and morphology of C. acanthoides.

THE BIOLOGY OF CANADIAN WEEDS.: 89. Carduus nutans L. and Carduus acanthoides L.

1988 ◽  
Vol 68 (4) ◽  
pp. 1053-1068 ◽  
Author(s):  
A. M. DESROCHERS ◽  
J. F. BAIN ◽  
S. I. WARWICK
Keyword(s):  
Biological Control ◽  
Seed Production ◽  
Germination Rate ◽  
Effective Means ◽  
Western Canada ◽  
Control Methods ◽  
Carduus Acanthoides ◽  
Carduus Nutans ◽  
Introduced Weeds

Carduus nutans L. and C. acanthoides L. are introduced weeds, primarily of roadsides, fields and pasturelands. Both species occur in eastern and western Canada with C. nutans more common than C. acanthoides in western Canada. High seed production and germination rate on open soil contribute to the success of the species as weeds, as do the spiny leaves and stems which deter grazing by animals. Mowing or the application of hormone-like herbicides are both effective means of control. Biological control methods have also been used for both species, but have been most successful in the control of C. nutans.Key words: Musk thistle, nodding thistle, plumeless thistle, Carduus spp.

scholarly journals Towards a new history and geography of human genes informed by ancient DNA

2014 ◽  
Author(s):  
Joseph Pickrell ◽  
David Reich
Keyword(s):  
Natural Selection ◽  
Ancient Dna ◽  
Population Replacement ◽  
Local Conditions ◽  
Geographic Locations ◽  
Technological Advances ◽  
Genome Wide ◽  
Human Genes ◽  
Genome Wide Data ◽  
History Of

Genetic information contains a record of the history of our species, and technological advances have transformed our ability to access this record. Many studies have used genome-wide data from populations today to learn about the peopling of the globe and subsequent adaptation to local conditions. Implicit in this research is the assumption that the geographic locations of people today are informative about the geographic locations of their ancestors in the distant past. However, it is now clear that long-range migration, admixture and population replacement have been the rule rather than the exception in human history. In light of this, we argue that it is time to critically re-evaluate current views of the peopling of the globe and the importance of natural selection in determining the geographic distribution of phenotypes. We specifically highlight the transformative potential of ancient DNA. By accessing the genetic make-up of populations living at archaeologically-known times and places, ancient DNA makes it possible to directly track migrations and responses to natural selection.

scholarly journals Why call it developmental bias when it is just development?

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Isaac Salazar-Ciudad
Keyword(s):  
Natural Selection ◽  
Morphological Variation ◽  
Morphological Evolution ◽  
Developmental Constraints ◽  
Evolution And Development ◽  
Different Types ◽  
Change Of Perspective ◽  
Opinion Article ◽  
Main Factor

AbstractThe concept of developmental constraints has been central to understand the role of development in morphological evolution. Developmental constraints are classically defined as biases imposed by development on the distribution of morphological variation.This opinion article argues that the concepts of developmental constraints and developmental biases do not accurately represent the role of development in evolution. The concept of developmental constraints was coined to oppose the view that natural selection is all-capable and to highlight the importance of development for understanding evolution. In the modern synthesis, natural selection was seen as the main factor determining the direction of morphological evolution. For that to be the case, morphological variation needs to be isotropic (i.e. equally possible in all directions). The proponents of the developmental constraint concept argued that development makes that some morphological variation is more likely than other (i.e. variation is not isotropic), and that, thus, development constraints evolution by precluding natural selection from being all-capable.This article adds to the idea that development is not compatible with the isotropic expectation by arguing that, in fact, it could not be otherwise: there is no actual reason to expect that development could lead to isotropic morphological variation. It is then argued that, since the isotropic expectation is untenable, the role of development in evolution should not be understood as a departure from such an expectation. The role of development in evolution should be described in an exclusively positive way, as the process determining which directions of morphological variation are possible, instead of negatively, as a process precluding the existence of morphological variation we have no actual reason to expect.This article discusses that this change of perspective is not a mere question of semantics: it leads to a different interpretation of the studies on developmental constraints and to a different research program in evolution and development. This program does not ask whether development constrains evolution. Instead it asks questions such as, for example, how different types of development lead to different types of morphological variation and, together with natural selection, determine the directions in which different lineages evolve.

scholarly journals Natural hybridization between immigrant narrow–barred Spanish mackerel Scomberomorus commerson (Lacepède, 1800) and endemic West African Spanish mackerel Scomberomorus tritor (Cuvier, 1832) in the Egyptian Mediterranean coast

2021 ◽  
pp. 219-227
Author(s):  
S. A. Bakhoum
Keyword(s):  
Function Analysis ◽  
Mediterranean Coast ◽  
West African ◽  
Natural Hybridization ◽  
Hybrid Index ◽  
Mahalanobis Distances ◽  
Mean Values ◽  
Spanish Mackerel ◽  
Scomberomorus Commerson ◽  
Abu Qir Bay

Immigrant narrow–barred Spanish mackerel, West African Spanish mackerel and specimens with an external appearance somewhere between these putative parents were collected from Abu Qir Bay, East Alexandria, Egypt. The hybrid index results and univariate and multivariate analysis indicated a natural hybridization between these two species. The discriminant function analysis successfully classified individual fish in the data to one of the three fish groups. Squared Mahalanobis distances extracted from the groups indicated the three groups were clearly distinct from each other. Moreover, distances between the hybrid and Scomberomorus tritor were longer than those of the hybrid and S. commerson. The mean values of the condition factor for the hybri were significantly higher than those of S. commerson. Natural mortality of the hybrid was significantly lower than that of the exotic parent (S. commerson), indicating that the environmental conditions in the examined region are more suitable for the hybrid type species than for the invasive parental species.

scholarly journals Environmental variability and the initiation of dispersal: turbulence strongly increases seed release

2005 ◽  
Vol 273 (1587) ◽  
pp. 751-756 ◽  
Author(s):  
Olav Skarpaas ◽  
Richard Auhl ◽  
Katriona Shea
Keyword(s):  
Turbulent Flows ◽  
Environmental Variability ◽  
Metapopulation Dynamics ◽  
Carduus Acanthoides ◽  
Carduus Nutans ◽  
Wind Speeds ◽  
Quantitative Studies ◽  
Spatial Pattern Formation ◽  
Critical Process ◽  
Laminar And Turbulent Flows

Dispersal is a critical process in ecology. It is an important biological driver of, for example, invasions, metapopulation dynamics, spatial pattern formation and pathogen movement. Much is known about the effect of environmental variability, including turbulence, on dispersal of diaspores. Here, we document experimentally the strong but under-explored influence of turbulence on the initiation of dispersal. Flower heads of two thistle species ( Carduus nutans and Carduus acanthoides ) with ripe seeds were exposed to series of laminar and turbulent air flows of increasing velocity in a wind tunnel. Seed release increased with wind speeds for both laminar and turbulent flows for both species. However, far more seeds were released, at significantly lower wind speeds, during turbulent flows. These results strongly suggest a need for more quantitative studies of abscission in the field, as well as dispersal models that incorporate variability in the diaspore release phase.

A Conceptual Roadmap to Homology

2014 ◽  
Author(s):  
Günter P. Wagner
Keyword(s):  
Natural Selection ◽  
Morphological Variation ◽  
Research Program ◽  
Phenotypic Diversity ◽  
Evolutionary Explanation ◽  
Body Parts ◽  
Developmental Evolution ◽  
Homologous Genes ◽  
Character Identity ◽  
The Difference

This chapter proposes a conceptual roadmap to homology, with the goal of supporting the research program of developmental evolution that seeks to explain the patterns of phenotypic diversity. It offers a mechanistic developmental and evolutionary explanation of the evolution of body plans and the origin of character identities. It also examines the difference between the origin of homologs (that is, novelties) and their modification by natural selection (that is, adaptation); the limits of homology, focusing on the lack of individuality of body parts; homologous genes; characters and character states; variational modalities; character identity and repeated body parts; and character swarms. Finally, it considers alternative conceptualizations of homology, conceptual liberalism, and how to sort patterns of morphological variation.

Sign in / Sign up

Export Citation Format

Share Document