Population Structure and Size-Dependent Reproductive Effort in Umbilicaria spodochroa

Mycologia ◽  
2001 ◽  
Vol 93 (3) ◽  
pp. 453 ◽  
Author(s):  
Stine Ramstad ◽  
Geir Hestmark
Keyword(s):  
Population Structure ◽  
Reproductive Effort ◽  
Size Dependent

scholarly journals Match or mismatch: the influence of phenology on size-dependent life history and divergence in population structure

2010 ◽  
Vol 79 (5) ◽  
pp. 1101-1112 ◽  
Author(s):  
Jost Borcherding ◽  
Peter Beeck ◽  
Donald L. DeAngelis ◽  
Werner R. Scharf
Keyword(s):  
Population Structure ◽  
Life History ◽  
Size Dependent

Brook Trout (Salvelinus fontinalis) Population Structure in Acidified Lac Tantaré, Quebec

1984 ◽  
Vol 41 (6) ◽  
pp. 865-877 ◽  
Author(s):  
Jean-Jacques Frenette ◽  
Julian J. Dodson
Keyword(s):  
Population Structure ◽  
Brook Trout ◽  
Sexual Maturity ◽  
Reproductive Effort ◽  
Salvelinus Fontinalis ◽  
Individual Growth ◽  
Toxic Stress ◽  
Age Classes ◽  
Recruitment Failure ◽  
Trout Population

To present evidence of acid-induced stress, we studied the population structure and distribution of brook trout (Salvelinus fontinalis) in acidified Lac Tantaré, Quebec. Trout greater than 21 cm (FL) represented only 16.2 and 10% of the population sampled in 1979 and 1980, respectively. Survival rates of trout from 1979 to 1980 indicated higher survival among individuals > 25 cm, mortality occurring primarily among fish of 13–25 cm. The marked decline in numbers of fish occurring at 21 cm coincided with the size at which 50% of the female trout population reached sexual maturity, suggesting that postspawning mortality contributes to the high mortality observed among these fish. Comparisons of population and individual growth rates revealed that smaller fish of age-classes 1 to 5 suffer higher mortality than do the larger individuals of these age-classes, implicating mortality agents other than those related to spawning. We provide evidence to support the hypothesis that the most probable cause of mortality is size-related differential exposure to toxic stress whereby small brook trout (< 25 cm) are found in lake areas (brooks) exhibiting the most potentially toxic combination of pH and aluminum, thus enhancing the exposure of the most susceptible part of the population to toxic stress. Large brook trout [Formula: see text] are found in the "safest" lake areas (springs), thus diminishing the exposure of the least susceptible part of the population to toxic stress and enhancing survival. Female trout exhibit delayed sexual maturity relative to other Quebec populations, attaining 50% maturity at age 3 and a length of 21–24 cm such that the major part of the population's reproductive effort is provided by those fish representing only 15% of the population in 1979 and 1980. During the October spawning season, 20% of potential spawners exhibited retarded oogenesis. These reductions in reproductive effort and changes in spawning site selection provide evidence in support of the hypothesis that recruitment failure may be occurring in the Tantaré brook trout population.

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.

Size-dependent reproductive effort in Amaranthus retroflexus: the influence of planting density and sowing date

2006 ◽  
Vol 84 (3) ◽  
pp. 485-492 ◽  
Author(s):  
Tianhui Wang ◽  
Daowei Zhou ◽  
Ping Wang ◽  
Hongxiang Zhang
Keyword(s):  
Reproductive Effort ◽  
Branch Length ◽  
Sowing Date ◽  
Amaranthus Retroflexus ◽  
Planting Density ◽  
Size Dependent ◽  
Sowing Dates ◽  
Wide Range ◽  
Total Branch Length ◽  
Reproductive Biomass

Size-dependent reproductive effort is an important component of plant fitness. The responses of reproductive effort to environmental factors in Amaranthus retroflexus L. were measured in two experiments. A wide range of selection pressures were generated by manipulating the sowing date (29 April, 23 May, 18 June, and 14 July) and planting density (13.4, 36, 121, and 441 plants·m–2). Allometric analysis between reproductive biomass and vegetative biomass across treatments showed that reproductive effort increased with size in response to different planting densities but decreased with size in sowing dates experiment. The allometric exponent between treatments was not influenced by planting densities but had significant variation with sowing date. Total branch length could explain most of the variation of reproductive accumulation and allocation in planting density experiments. For the plants with different sowing dates, total branch length was the main determinant of reproductive biomass, while reproductive effort mainly depended on the number of primary branches per unit stem mass. Architectural constraints with size result in size-dependent reproduction. Size-dependent reproduction in A. retroflexus was influenced by available resources and environmental conditions through the mechanisms of self-regulation of architectural traits.

Size-Dependent Effects in the Analysis of Reproductive Effort in Plants

1986 ◽  
Vol 127 (5) ◽  
pp. 667-680 ◽  
Author(s):  
Douglas A. Samson ◽  
Kenneth S. Werk
Keyword(s):  
Reproductive Effort ◽  
Size Dependent
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