Comparison of size-dependent reproductive effort in two dandelion (Taraxacum officinale) populations

1998 ◽  
Vol 76 (1) ◽  
pp. 166-173 ◽  
Author(s):  
Clive VJ Welham ◽  
Robert A Setter
Keyword(s):  
Life History ◽  
Reproductive Effort ◽  
Seed Mass ◽  
Taraxacum Officinale ◽  
Reproductive Morphology ◽  
Size Dependent ◽  
Alfalfa Field ◽  
History Approach ◽  
Total Seed ◽  
Lower Ratio

Reproductive effort in dandelions (Taraxacum officinale Weber) from two different habitats was compared. One dandelion population occupied a 5-year-old alfalfa (Medicago spp.) field, an environment subject to regular disturbance but with a relatively low density of neighbours. Individuals from the second population were derived from a number of undisturbed sites where the density of neighbouring grasses was high. Three hypotheses were evaluated with respect to the observed patterns of reproductive effort. One hypothesis, that reproductive effort was a function of differences between habitats in resource availability, did not provide an explanation for our results. A second hypothesis considered patterns of reproductive effort when mortality rates varied with degree of disturbance and neighbour density, which was a consequence of each habitat representing a different successional environment. A third hypothesis used a life-history approach to predict reproductive effort when mortality schedules were size dependent. Both of these hypotheses received support for their predictions. There was more than a sixfold variation in reproductive effort among individuals from the alfalfa field and a fourfold variation on the undisturbed sites. Much of this variation, however, was attributable to a size-dependent relationship between reproductive effort and vegetative mass. Total reproductive effort (total seed plus scape mass) in both populations increased linearly with vegetative mass, but the slope for the population from the alfalfa field was significantly higher. In contrast, proportional reproductive effort (total seed plus scape mass per vegetative mass) showed a curvilinear increase for the alfalfa field population but was linear and negative for the undisturbed population. There were also important differences between the populations in reproductive morphology. Larger plants on the alfalfa field had longer average scape lengths, produced more flower heads (capitula) per plant, had greater seed production, and had a lower ratio of seed mass per pappus area; only mean scape and mean seed mass did not differ significantly. We suggest that dandelions on the alfalfa field have a different reproductive morphology to facilitate colonization of open areas on the field.Key words: Taraxacum, dandelion, reproductive effort, biomass, life history, neighbour density, agriculture, weed.

Within and among plant variation in seed mass and pappus size in Tragopogon dubious

1989 ◽  
Vol 67 (5) ◽  
pp. 1298-1304 ◽  
Author(s):  
Mark A. McGinley
Keyword(s):  
Salt Lake ◽  
Salt Lake City ◽  
Seed Mass ◽  
Developmental Constraints ◽  
Position Effects ◽  
Plant Variation ◽  
Selection For ◽  
Lake City ◽  
Total Seed ◽  
Stalk Length

Individual seed mass of two seed morphs of Tragopogon dubious (L.) varied among plants and within and among flowering heads within individual plants growing near Salt Lake City, UT. Seeds of the light morph from the center of a receptacle were smaller than outer seeds, suggesting that variation in seed mass within heads was due to position effects. The total seed mass per head, seed number per head, and mean seed mass per head of both morphs declined in most plants over the season. Heads with larger total seed mass contained larger seeds both within and between plants so seasonal patterns in seed mass may be influenced by seasonal variation in the amount of resources available for investment in seeds. Seeds of the light colored morph had a greater dispersal potential than seeds from the dark colored morph because their disk loading was lower. Pappus size (both pappus radius and stalk length) increased with the number of seeds per head which may increase the efficiency of packaging fruits on the receptacle. Heads with a larger total seed mass allocated a smaller proportion of their resources to the dark seed morph which may serve to decrease the level of sibling competition experienced by the less dispersing seed morph. Thus, variation in investment in offspring may arise as a combination of developmental constraints and selection for variable investment.

Jack pine cone quality and cache sizes of red squirrels in southern New Brunswick, Canada

1997 ◽  
Vol 75 (2) ◽  
pp. 332-335 ◽  
Author(s):  
Michael A. Setterington ◽  
Daniel M. Keppie
Keyword(s):  
New Brunswick ◽  
Pinus Banksiana ◽  
Seed Mass ◽  
Dry Mass ◽  
Jack Pine ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrels ◽  
Length Width ◽  
Total Seed ◽  
Number Of Seeds

Relationships between external cone characteristics (length, width, wet and dry mass), cone quality (total seed mass as a proportion of cone mass, total number of seeds per cone, total seed mass per cone), and number of cones in caches were evaluated for caches of jack pine (Pinus banksiana) cones belonging to red squirrels (Tamiasciurus hudsonicus) in two plantations in southern New Brunswick. Cone length and mass were good predictors of the total number of seeds per cone and total seed mass per cone. Length accounted for a small proportion of the variance of total seed mass as a proportion of cone mass. There was no relationship between the number of seeds or total seed mass per cone and the number of cones per cache.

Meristem allocation and life-history evolution in herbaceous plants

2006 ◽  
Vol 84 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Stephen P. Bonser ◽  
Lonnie W. Aarssen
Keyword(s):  
Life History ◽  
Apical Dominance ◽  
Reproductive Effort ◽  
Life History Evolution ◽  
Meristem Development ◽  
Vegetative Traits ◽  
History Evolution ◽  
Meristem Allocation ◽  
Branching Intensity ◽  
Iteroparous Species

Generalisations of life histories in plants are often framed in terms of allocation to reproduction. For example, relative allocation to reproduction is commonly found to be higher in semelparous than in iteroparous plant species. However, the association between vegetative traits and life history has been largely unexplored. In higher plants, reproductive and vegetative function can be measured in terms of meristem allocation. Under this approach, two vegetative traits (apical dominance (the suppression of axillary meristem development) and branching intensity (the commitment of axillary meristems to branches)) can be measured as well as one reproductive trait (reproductive effort). We used phylogenetically independent contrasts to compare reproductive and vegetative function in annual semelparous and perennial iteroparous species. Twenty congeneric species pairs (each species pair represented by one semelparous and one iteroparous species) across nine families were selected based on availability of herbarium specimens. Semelparous life-history evolution was associated with higher reproductive effort. Conversely, iteroparous life-history evolution was associated with higher apical dominance. Branching intensity was not associated with life history. An evolutionary association between life history and apical dominance but not branching intensity suggests a complex relationship between allocation to vegetative traits and the evolution of plant strategies across environments.

A Primer of Life Histories

2021 ◽  
Author(s):  
Jeffrey A. Hutchings
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Theory ◽  
Life History Traits ◽  
Reproductive Effort ◽  
Effective Means ◽  
Academic Experience ◽  
Sustainable Exploitation ◽  
Evolution Of Life ◽  
Opportune Time

Life histories describe how genotypes schedule their reproductive effort throughout life in response to factors that affect their survival and fecundity. Life histories are solutions that selection has produced to solve the problem of how to persist in a given environment. These solutions differ tremendously within and among species. Some organisms mature within months of attaining life, others within decades; some produce few, large offspring as opposed to numerous, small offspring; some reproduce many times throughout their lives while others die after reproducing just once. The exponential pace of life-history research provides an opportune time to engage and re-engage new generations of students and researchers on the fundamentals and applications of life-history theory. Chapters 1 through 4 describe the fundamentals of life-history theory. Chapters 5 through 8 focus on the evolution of life-history traits. Chapters 9 and 10 summarize how life-history theory and prediction has been applied within the contexts of conservation and sustainable exploitation. This primer offers an effective means of rendering the topic accessible to readers from a broad range of academic experience and research expertise.

scholarly journals Nitrogen Fertilizer Management Practices to Enhance Seed Production by `Anaheim Chili' Peppers

1990 ◽  
Vol 115 (2) ◽  
pp. 245-251 ◽  
Author(s):  
J.O. Payero ◽  
M.S. Bhangoo ◽  
J.J. Steiner
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Management Practices ◽  
Irrigation System ◽  
Seed Mass ◽  
Fruit Production ◽  
Trickle Irrigation ◽  
Total N ◽  
Leaf Petiole ◽  
Total Seed

The effects of six applied N treatments differing by rates and frequencies of application on the yield and quality of pepper (Capsicum annuum var. annuum L. `Anaheim Chili') grown for seed was studied. The timing of N applications was based on crop phenology, leaf petiole nitrate-nitrogen concentrations (NO3-N) minimum thresholds, and scheduled calendar applications of fixed amounts of N. Solubilized NH4NO3 was applied through a trickle-irrigation system to ensure uniform and timely applications of N. Rate of mature (green and red) fruit production was unaffected by any treatment except weekly applications of 28 kg·ha-1 of N, which stopped production of mature fruit before all other treatments. Early season floral bud and flower production increased with increasing amounts of N. The two highest total N treatments produced more floral buds and flowers late in the season than the other treatments. Total fruit production was maximized at 240 kg N/ha. Differences in total fruit production due to frequency of N application resulted at the highest total N level. Red fruit production tended to be maximized with total seasonal applied N levels of 240 kg·ha-1 and below, although weekly applications of N reduced production. Total seed yield was a function of red fruit production. Pure-1ive seed (PLS) production was a function of total seed production. Nitrogen use efficiency (NUE) for red fruit production also decreased with N rates >240 kg·ha-1, but PLS yield and NUE decreased in a near-linear fashion as the amount of total seasonal applied N increased, regardless of application frequency. Season average NO3-N (AVE NO3-N) values >4500 mg·kg-1 had total seed and PLS yields less than those treatments <4000 mg·kg-1. Six-day germination percentage was reduced with weekly N applications of 14 kg·ha-1. Seed mass was reduced with weekly N applications of 28 kg·ha-1. Final germination percent, seedling root length and weight, and field emergence were unaffected by any of the N treatments. These findings indicate that different N management strategies are needed to maximize seed yield compared to fruit yield and, therefore, there may be an advantage to growing `Anaheim Chili' pepper specifically for seed.

Serotiny and life history of Pinus contorta var. latifolia

1985 ◽  
Vol 63 (5) ◽  
pp. 938-945 ◽  
Author(s):  
Patricia S. Muir ◽  
James E. Lotan
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Pinus Contorta ◽  
Reproductive Effort ◽  
Basal Area ◽  
Western Montana ◽  
Tree Age ◽  
Selective Pressures ◽  
Area Growth ◽  
History Of

Mature serotinous and nonserotinous trees of Pinus contorta Dougl. var. latifolia Engelm. in the Bitterroot Watershed of western Montana do not differ in most life-history characteristics (reproductive or vegetative). No differences between trees of the two cone types were found in height, basal area, basal area growth rates over the lives of the trees, or crown ratio. Cone number, weights of individual cones and seeds, and estimates of reproductive effort were similar in serotinous and non-serotinous trees. Reproductive characteristics were either independent of tree age, or related similarly in trees of the two cone types. Nonserotinous trees may, however, have more seeds per cone than serotinous trees. This difference in seed numbers may be adaptive if serotinous trees invest relatively heavily in cone materials to protect seeds (which are retained in cones for many years), while nonserotinous trees (which shed seeds each year) invest relatively heavily in seeds. Trees of the two cone types differ mainly in the particular types of disturbance favoring their regeneration, but they often grow in the same stands where there are similar selective pressures on most aspects of their biology. Gene flow between them probably homogenizes all but those differences maintained by strong selective pressures.

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