Aphids and Mycorrhizal Fungi Shape Maternal Effects in Senecio vulgaris

Abstract

Plant performance in any one generation is affected not only by the prevailing environmental conditions, but also by the conditions experienced by the parental generation of those plants. These maternal effects have been recorded in a many plant species, but the influence of external biotic (as opposed to abiotic) factors on shaping maternal effects have been rarely examined. Furthermore, almost all previous studies have taken place over one plant generation, rather than across multiple generations. Here, we studied the influence of insect herbivory and arbuscular mycorrhizal (AM) fungal colonisation on the shaping of maternal effects in the annual forb Senecio vulgaris. We grew plants with and without aphids (Myzus persicae) and AM fungi (hereafter termed 'induction events') over four successive generations, wherein seeds from plants in any one treatment were used to grow plants of the same treatment in the next generation, all in identical environmental conditions. We found strong evidence of maternal effects in the second plant generation, i.e., after one induction event. These plants took longer to germinate, flowered in a shorter time, produced lighter seeds and were shorter and of lower biomass than their parents. Aphid attack tended to enhance these effects, whereas AM fungi had little influence. However, thereafter there was a gradual recovery in these parameters, so that plants experiencing three inductions showed similar life history parameters to those in the original generation. We conclude that experiments investigating maternal effects need to be performed over multiple plant generations and that biotic factors such as insects and mycorrhizas must also be taken into account, along with abiotic factors, such as nutrient and water availability.

Keywords: Myzus persicae; Senecio vulgaris; arbuscular mycorrhiza; herbivory; insect; maternal effects.

Figure 1

(A) Mean seed germination time of S. vulgaris grown with or without arbuscular mycorrhizal fungi and aphids for four successive generations. Vertical lines represent ± one standard error. (B) Mean seed germination time of S. vulgaris grown without AM fungi, aphids or both, from parents that experienced these treatments (2A, B and C; 3A, B and C and 4A, B and C plants in Figure S1).

Figure 2

(A) Mean time to first flowering of S. vulgaris grown with or without arbuscular mycorrhizal fungi and aphids for four successive generations. Vertical lines represent ± one standard error. (B) Mean time to first flowering of S. vulgaris grown without AM fungi, aphids or both, from parents that experienced these treatments (2A, B and C; 3A, B and C and 4A, B and C plants in Figure S1).

Figure 3

(A) Mean seed weight of S. vulgaris grown with or without arbuscular mycorrhizal fungi and aphids for four successive generations. Vertical lines represent ± one standard error. (B) Mean seed weight of S. vulgaris grown without AM fungi, aphids or both, from parents that experienced these treatments (2A, B and C; 3A, B and C and 4A, B and C plants in Figure S1).

Figure 4

(A) Mean final plant height of S. vulgaris grown with or without arbuscular mycorrhizal fungi and aphids for four successive generations. Vertical lines represent ± one standard error. (B) Mean final plant height of S. vulgaris grown without AM fungi, aphids or both, from parents that experienced these treatments (2A, B and C; 3A, B and C and 4A, B and C plants in Figure S1).

Figure 5

(A) Mean total dry biomass of S. vulgaris grown with or without arbuscular mycorrhizal fungi and aphids for four successive generations. Vertical lines represent ± one standard error. (B) Mean total dry biomass of S. vulgaris grown without AM fungi, aphids or both, from parents that experienced these treatments (2A, B and C; 3A, B and C and 4A, B and C plants in Figure S1).