Modelling compensatory regrowth with bud dormancy and gradual activation of buds

Lehtila, K

K. Lehtila, Modelling compensatory regrowth with bud dormancy and gradual activation of buds, EVOL ECOL, 14(4-6), 2000, pp. 315-330

47

INGLESE

Article

Environment/Ecology

EVOLUTIONARY ECOLOGY

0269-7653 → ACNP

14

4-6

2000

315 - 330

ISI

0269-7653(2000)14:4-6<315:MCRWBD>2.0.ZU;2-J

Many plants show compensatory regrowth after herbivory and dormant buds oft en have an important role in compensatory responses. Theoretical models hav e shown that herbivore damage may select for a bud bank, i.e., a pool of do rmant buds that are protected from herbivory and that are activated after h erbivore damage. Earlier models assumed that undamaged plants cannot activa te their dormant buds without damage, although they apparently have suffici ent resources for successful seed production through the additional shoots dormant buds could produce. However, many plants are able to gradually acti vate buds over an extended period of time without any cue from damage. The aim of this study was to analyze how herbivory imposes selection for gradua l mobilization of the bud bank. I assume that selection pressures that affe ct the fraction of buds active at each time point include damage by herbivo res, time left to the end of season, and the opportunity costs of dormant b uds. I modelled bud dynamics with gradual activation when there is a single damage event and (i) when the seed set of a shoot is not dependent on the time it is active, or (ii) when the seed set of a shoot diminishes with lat er activation. In addition, I analyzed how (iii) risk of repeated herbivory affects selection for gradual activation. Under these models, gradual acti vation is optimal over a wide range of herbivory pressures. Selection appea rs to favour activation of all buds at the beginning of the season only whe n herbivore pressure is weak and when early shoots have a higher seed set t han late shoots. Alternatively, strong herbivore pressure and late damage m ay select for a large bud bank throughout the growing season, without gradu al activation; the bud bank is only mobilized after damage. In this case, d amaged plants can overcompensate, i.e. they have a higher seed set than und amaged plants with the same bud activation pattern. Selection for overcompe nsation demands a stronger herbivore pressure in this current model than in earlier bud bank models. The model never predicts selection for overcompen sation when there is a risk of repeated herbivory.