Tape Grass Life History Metrics Associated with Environmental Variables in a Controlled Estuary

In migratory species, the timing of arrival at the breeding grounds is a life-history trait with major fitness consequences. The optimal arrival date varies from year-to-year, and animals use cues to adjust their arrival dates to match this annual variation. However, which cues they use to time their arrival and whether these cues actually predict the annual optimal arrival date is largely unknown. Here, we integrate causal and evolutionary analysis by identifying the environmental variables used by a migratory songbird to time its arrival dates and testing whether these environmental variables also predicted the optimal time to arrive. We used 11 years of male arrival data of a pied flycatcher population. Specifically, we tested whether temperature and normalized difference vegetation index (NDVI) values from their breeding grounds in the Netherlands and from their wintering grounds in Ivory Coast explained the variation in arrival date, and whether these variables correlated with the position of the annual fitness peak at the breeding grounds. We found that temperature and NDVI, both from the wintering and the breeding grounds, explained the annual variation in arrival date, but did not correlate with the optimal arrival date. We explore three alternative explanations for this lack of correlation. Firstly, the date of the fitness peak may have been incorrectly estimated because a potentially important component of fitness (i.e., migration date dependent mortality en route or directly upon arrival) could not be measured. Secondly, we focused on male timing but the fitness landscape is also likely to be shaped by female timing. Finally, the correlation has recently disappeared because climate change disrupted the predictive value of the cues that the birds use to time their migration. In the latter case, birds may adapt by altering their sensitivity to temperature and NDVI.

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Environmental heterogeneity and life history variability in the freshwater clams, Pisidium variabile (Prime) and Pisidium compressum (Prime) (Bivalvia: Pisidiidae)

Canadian Journal of Zoology ◽

10.1139/z82-363 ◽

1982 ◽

Vol 60 (11) ◽

pp. 2841-2851 ◽

Cited By ~ 14

Author(s):

Carl M. Way ◽

Thomas E. Wissing

Keyword(s):

Life History ◽

Environmental Variables ◽

Environmental Heterogeneity ◽

Reproductive Rate ◽

Bet Hedging ◽

Net Reproductive Rate ◽

Age At First Reproduction ◽

Physiological Limits ◽

Life History Characteristics ◽

Freshwater Clams

The pisidiid clams, Pisidium variabile (Prime) and Pisidium compressum (Prime), from permanent ponds in southwestern Ohio are iteroparous, bivoltine, and have approximate longevities of 1 year. Intrapopulation differences in life history characteristics are discussed in relation to environmental heterogeneity. For the P. variabile population, only age at first reproduction (110 and 226 days for the spring and fall generations, respectively) is different for both annual generations. This is due to differences in environmental variables (temperature, dissolved oxygen levels, food availability) which set physiological limits on growth, reproduction, and maintenance functions. The spring and fall generations of P. compressum show differences in several life history characteristics: age at first reproductive (122 and 270 days, respectively), net reproductive rate (8.7 and 3.7, respectively), r (0.005 and 0.003, respectively), and the number of broods per year (2 and 1, respectively). The results of this study tend to question the validity of using current theories (e.g, r- and K-selection, bet-hedging) which attempt to predict the set of demographic characteristics that should be found in populations under varying environmental circumstances.

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Lichen fecundity on the Precambrian Shield: an alternative life history strategy approach

Botany ◽

10.1139/cjb-2014-0086 ◽

2014 ◽

Vol 92 (10) ◽

pp. 723-735 ◽

Cited By ~ 3

Author(s):

C. Deduke ◽

T. Booth ◽

M.D. Piercey-Normore

Keyword(s):

Life History ◽

Species Richness ◽

Environmental Variables ◽

Life History Strategy ◽

Ground Cover ◽

Life History Strategies ◽

Habitat Specificity ◽

Significant Difference ◽

Species Similarity ◽

Saxicolous Lichens

Symbiotic interactions are widespread in nature, but the relationship between life history, fecundity, and habitat specificity has been underexplored. This study investigated the life history strategies of foliose saxicolous lichens relative to their surrounding communities. Macrolichens were collected from 39 transects in Manitoba and Ontario. Frequency and percentage of ground cover of macrolichens, environmental variables, and numbers of apothecia and ascospores were recorded. Lichen assemblages were characterized using species similarity in a cluster analysis and ordination methods and were defined into communities using analysis of variance of the biotic variables among assemblages. Lichen life history strategies were inferred from community features, lichen fecundity, and morphological features. The general linear model determined which environmental variables may have influenced fecundity. The 81 species of macrolichens present in three lichen communities differed in species richness, with low species richness in the open mossy rock community, moderate in the grassy rock community, and high in the treed rock community. Three foliose saxicolous lichens dominated particular communities, and the life history strategy was characterized as competitive for Arctoparmelia centrifuga (L.) Hale, stress tolerant for Xanthoparmelia viriduloumbrina (Gyel.) Lendemer, and ruderal generalist for Xanthoparmelia cumberlandia (Gyel.) Hale. The proportion of sexual and asexual reproductive propagules for macrolichens showed uniformity between communities despite a significant difference in species richness. The study provides insights into the ecology of saxicolous lichens growing in the boreal forest and a characterization of lichen communities, and it shows how morphologically similar lichens can exhibit different life history strategies.

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Sensitivity of terrestrial isopod populations (Armadillidium) to food quality differences

Canadian Journal of Zoology ◽

10.1139/z71-105 ◽

1971 ◽

Vol 49 (5) ◽

pp. 667-674 ◽

Cited By ~ 21

Author(s):

H. Gray Merriam

Keyword(s):

Life History ◽

Environmental Factors ◽

Food Quality ◽

Environmental Variables ◽

Structured Populations ◽

Individual Growth ◽

Rate Functions ◽

Systems Modelling ◽

Control Patterns ◽

Population Sensitivity

Effects of food quality on individual growth and life history features are measured from large single-age cultures, and consequences of these effects are demonstrated on large structured populations in optimized environments.Food quality, and other environmental variables, can dictate irregular rate functions which may control patterns of population performance. Analysis of population sensitivity to changes in such environmental factors, and resulting feedback, is necessary for adequate systems modelling.

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