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Ambulatory dispersal in Tetranychus urticae: an artificial selection experiment on propensity to disperse yields no response.

Tien NS, Sabelis MW, Egas M - Exp. Appl. Acarol. (2011)

Bottom Line: Upward and downward selection on propensity to leave the colony was performed for seven generations in four replicate artificial selection experiments and the results were compared to control lines.No consistent responses to selection were found and no significant effect on life-history traits (oviposition rate, juvenile survival, development rate and number of adult offspring) or sex ratio was present across the replicates.The data suggest that our base population of spider mites harbours at best a low amount of additive genetic variation for this behaviour.

View Article: PubMed Central - PubMed

Affiliation: Institute For Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94248, 1090GE Amsterdam, The Netherlands. N.S.H.Tien@uva.nl

ABSTRACT
Dispersal to new hosts is an important process for an invasive herbivore, such as the two-spotted spider mite. A recent study, using artificial selection experiments, has suggested that genetic variation and genetic trade-offs are present for propensity to disperse in this species. However, due to the experimental setup alternative explanations for the response to selection could not be ruled out. Using an altered setup, we investigated whether the propensity for ambulatory dispersal differs genetically between individuals and whether genetic correlations with life-history traits exist. Upward and downward selection on propensity to leave the colony was performed for seven generations in four replicate artificial selection experiments and the results were compared to control lines. No consistent responses to selection were found and no significant effect on life-history traits (oviposition rate, juvenile survival, development rate and number of adult offspring) or sex ratio was present across the replicates. The data suggest that our base population of spider mites harbours at best a low amount of additive genetic variation for this behaviour.

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Fraction dispersing females over time (group dispersal index). Upward selected (black circles and straight black line) and downward selected (white circles and dashed line) lines and the control lines (grey circles and grey line) of the four replicates (1–4). Dispersal was measured as fraction females that migrated away from the leaf disc, out of an initial colony of ten females. Error bars are standard errors of the mean
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Fig1: Fraction dispersing females over time (group dispersal index). Upward selected (black circles and straight black line) and downward selected (white circles and dashed line) lines and the control lines (grey circles and grey line) of the four replicates (1–4). Dispersal was measured as fraction females that migrated away from the leaf disc, out of an initial colony of ten females. Error bars are standard errors of the mean

Mentions: When placing ten females on a small leaf disc, within 3 days on average 34% of the females dispersed to a new leaf disc. The fraction dispersers over time is shown in Fig. 1. The dispersal over time of the high and low lines showed no consistent patterns compared to that of their control line. In replicate 1 (χ2 = 14.6, P < 0.001), the low line had a higher dispersal rate than the control line (z = 2.9, P < 0.01), while the high line was not significantly different from the control line (z = −0.8, P = 0.4). In replicate 2, there was no significant difference in either treatment (χ2 = 1.6, P = 0.4). In replicate 3 (χ2 = 34.8, P < 0.001) both treatments had lower dispersal rates than the control line (high line: z = −5.0, P < 0.001, low line: z = −5.0, P < 0.001). Only in replicate 4 (χ2 = 81.8, P < 0.001) did the lines behave as expected: the high line showed a higher dispersal rate (z = 4.4, P < 0.001), while the low line exhibited a lower dispersal rate (z = 4.7, P < 0.001). When focussing on the ultimate fraction of dispersers in this experiment, the dispersal rate of the selection lines was not significantly different from that of their control lines in three of the replicates (Table 1). Only in replicate 4 were differences found: The low line had less dispersers than the control line (Table 1). Together, these results show that the differences in dispersal behaviour between the lines were small and not related to selection treatment.Fig. 1


Ambulatory dispersal in Tetranychus urticae: an artificial selection experiment on propensity to disperse yields no response.

Tien NS, Sabelis MW, Egas M - Exp. Appl. Acarol. (2011)

Fraction dispersing females over time (group dispersal index). Upward selected (black circles and straight black line) and downward selected (white circles and dashed line) lines and the control lines (grey circles and grey line) of the four replicates (1–4). Dispersal was measured as fraction females that migrated away from the leaf disc, out of an initial colony of ten females. Error bars are standard errors of the mean
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040828&req=5

Fig1: Fraction dispersing females over time (group dispersal index). Upward selected (black circles and straight black line) and downward selected (white circles and dashed line) lines and the control lines (grey circles and grey line) of the four replicates (1–4). Dispersal was measured as fraction females that migrated away from the leaf disc, out of an initial colony of ten females. Error bars are standard errors of the mean
Mentions: When placing ten females on a small leaf disc, within 3 days on average 34% of the females dispersed to a new leaf disc. The fraction dispersers over time is shown in Fig. 1. The dispersal over time of the high and low lines showed no consistent patterns compared to that of their control line. In replicate 1 (χ2 = 14.6, P < 0.001), the low line had a higher dispersal rate than the control line (z = 2.9, P < 0.01), while the high line was not significantly different from the control line (z = −0.8, P = 0.4). In replicate 2, there was no significant difference in either treatment (χ2 = 1.6, P = 0.4). In replicate 3 (χ2 = 34.8, P < 0.001) both treatments had lower dispersal rates than the control line (high line: z = −5.0, P < 0.001, low line: z = −5.0, P < 0.001). Only in replicate 4 (χ2 = 81.8, P < 0.001) did the lines behave as expected: the high line showed a higher dispersal rate (z = 4.4, P < 0.001), while the low line exhibited a lower dispersal rate (z = 4.7, P < 0.001). When focussing on the ultimate fraction of dispersers in this experiment, the dispersal rate of the selection lines was not significantly different from that of their control lines in three of the replicates (Table 1). Only in replicate 4 were differences found: The low line had less dispersers than the control line (Table 1). Together, these results show that the differences in dispersal behaviour between the lines were small and not related to selection treatment.Fig. 1

Bottom Line: Upward and downward selection on propensity to leave the colony was performed for seven generations in four replicate artificial selection experiments and the results were compared to control lines.No consistent responses to selection were found and no significant effect on life-history traits (oviposition rate, juvenile survival, development rate and number of adult offspring) or sex ratio was present across the replicates.The data suggest that our base population of spider mites harbours at best a low amount of additive genetic variation for this behaviour.

View Article: PubMed Central - PubMed

Affiliation: Institute For Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94248, 1090GE Amsterdam, The Netherlands. N.S.H.Tien@uva.nl

ABSTRACT
Dispersal to new hosts is an important process for an invasive herbivore, such as the two-spotted spider mite. A recent study, using artificial selection experiments, has suggested that genetic variation and genetic trade-offs are present for propensity to disperse in this species. However, due to the experimental setup alternative explanations for the response to selection could not be ruled out. Using an altered setup, we investigated whether the propensity for ambulatory dispersal differs genetically between individuals and whether genetic correlations with life-history traits exist. Upward and downward selection on propensity to leave the colony was performed for seven generations in four replicate artificial selection experiments and the results were compared to control lines. No consistent responses to selection were found and no significant effect on life-history traits (oviposition rate, juvenile survival, development rate and number of adult offspring) or sex ratio was present across the replicates. The data suggest that our base population of spider mites harbours at best a low amount of additive genetic variation for this behaviour.

Show MeSH