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A study on the dispersal, morphological responses, reproductive performance, and survival in …


Biology Articles » Protistology » Evolution of dispersal and life history strategies – Tetrahymena ciliates » Figures

Figures
- Evolution of dispersal and life history strategies – Tetrahymena ciliates

 

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Figure 1   Principal component plots expressing correlations between cell morphology and growth variables in presence of nutrients for the ten T. thermophila strains studied. See text for details. PC1G expressed the opposition between strains with big round versus small elongated cells at carrying capacity. PC2G illustrated the r versus K strategy of growth, while PC3G represented overall growth performance.

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Figure 2  Principal component plot representing correlations between cell morphology and survival variables under starvation for the ten T. thermophila strains. PC1S is linked to overall survival and elongation capabilities. PC2S represented the cell elongation strategy, opposing strains where all cells elongates similarly for a long time to strains where some cells elongate more than others, up to becoming dispersal morphs. 

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Figure 3   Correlation of dispersal rate and cell elongation in the dispersal experiment in presence of nutrients for the ten T. thermophila strains studied.

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Figure 4  Correlation of life-history traits for the ten T. thermophila strains we studied. A) In the experiment on dispersal in presence of nutrients, a higher dispersal rate was associated with larger cell elongation. B) Strains with a high dispersal rate also had a greater probability of successfully colonizing a new patch as single cells. Strains adept at dispersing (C) and colonizing (D) grew faster and reached a higher final cell density in the presence of nutrients (PC3G). Elongation strategy (PC2S) was also associated to cell morphology and performance: strains producing more dispersal morphs and presenting a greater variance in elongation were characterized by small elongated cells (versus big round) at carrying capacity (E) and an overall inferior performance of growth in nutrient-rich medium (F). Strains presenting a K strategy of growth in nutrient-rich medium presented superior abilities to survive and elongate under starvation conditions (G). Note: because the variables whose correlation we studied do not come from the same experiment, each inset indicates the mean Spearman's correlation coefficient computed over 1000 random associations of replicates (r), the proportion of these associations where correlation was significant (s) and the probability to obtain this proportion by chance (P). See text for detail. Graphs, however, display means of five random associations to illustrate within strain variation. 

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Figure 5   Summary principal component plot representing the correlations between the seven variables summarizing the four experiments. Graph displays means of five random associations to illustrate within strain variation; see text for detail.

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Figure 6  A) Typical digital picture of Tetrahymena thermophila cells used to extract quantitative variables. B) Cells (D2 strain) in normal growth condition (with nutrients) showing large size and a largely rounded shape. C) Cells (20 strain) eight hours after nutrient removal, showing reduced size and (middle cell) the typical elongated shape of the fast-swimming dispersal morph described by Nelsen and Debault [69]. 

 


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