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Seasonal Plasticity in Two Satyrine Butterflies: State-Dependent Decision Making in Relation to Daylength
Karl Gotthard, Sören Nylin and Christer Wiklund
Vol. 84, No. 3 (Mar., 1999), pp. 453-462
Stable URL: http://www.jstor.org/stable/3546424
Page Count: 10
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In this study we investigate how the need for seasonal timing of diapause and sexual maturation have selected for plasticity in life history traits in two butterfly species, Lasiommata maera and Lopinga achine. We test the general hypothesis that insects living in temperate areas should have shorter development times at progressively later dates of the growth season, and that they use daylength as a cue to determine the date. Both species have two different larval growth periods, the first in autumn and the second after termination of diapause in spring. Due to the difference in photoperiodic change in autumn and spring, we expected larvae to interpret daylengths qualitatively differently in the two growth periods. In other words, developmental decisions in response to daylength should depend on the seasonal state (autumn or spring) of larvae. In laboratory experiments we investigated the reaction norms relating larval development times to daylength. In both species the slopes of these reaction norms were different in autumn and in spring. The results of the experiment on L. maera supported specific predictions both in autumn and in spring. The same was true in autumn for L. achine but development time in spring seemed to be insensitive to daylength. In all cases, short development times were associated with high larval growth rates rather than with small final body sizes. Growth and development in these species can be described as state-dependent decision processes, where information about the external and internal environment is used at several points in development.
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