Enemy release mitigates inbreeding depression in native and invasive Silene latifolia populations: experimental insight into the role of inbreeding × environment interactions in invasion success

Abstract

37Inbreeding and enemy infestation are common in plants and can synergistically reduce their 38 performance. This inbreeding × environment (I×E) interaction may be of particular 39 importance for the success of plant invasions if introduced populations experience a release 40 from attack by natural enemies relative to their native conspecifics. Using native and invasive 41 plant populations, we investigate whether inbreeding affects infestation damage, whether 42 inbreeding depression in performance is mitigated by enemy release and whether genetic 43 differentiation among native and invasive plants modifies these I×E interactions. We used the 44 plant invader Silene latifolia and its natural enemies as a study system. We performed two 45 generations of experimental out-and inbreeding within eight native (European) and eight 46 invasive (North American) S. latifolia populations under controlled conditions using field-47 collected seeds. Subsequently, we exposed the offspring to an enemy exclusion and 48 inclusion treatment in a common garden in the species' native range to assess the interactive 49 effects of population origin (range), breeding treatment and enemy treatment on infestation 50 damage as well as plant performance. Inbreeding increased flower and leaf infestation 51 damage in plants from both ranges, but had opposing effects on fruit damage in native 52 versus invasive plants. Both inbreeding and enemy infestation had negative effects on plant 53 performance, whereby inbreeding depression in fruit number was higher in enemy inclusions 54 than exclusions in plants from both ranges. Moreover, the magnitude of inbreeding 55 depression in fruit number was lower in invasive than native populations. Our results support 56 that inbreeding increases enemy susceptibility of S. latifolia, which magnifies inbreeding 57 depression in the presence of enemies. Enemy release in the invaded habitat may thus 58 increase the persistence of inbred founder populations and thereby contribute to successful 59 invasion. Moreover, our findings emphasize that genetic differentiation among native and 60 invasive plants can shape the magnitude and even the direction of inbreeding effects. 61 4 Keywords 62 biological invasion, genetic differentiation, genetic paradox, herbivory, purging, white 63 campion 64Understanding the forces that promote or prevent species range expansions remains a 66 challenging goal in ecology (Barrett, 2015). During invasion of a new range, populations can 67

Inbreeding diminishes herbivore‐induced metabolic responses in native and invasive plant populations

“…The more the genetic pathways required in a specific environment, the higher the exposure of loci negatively affected by inbreeding to selection and the higher the probability for I × E interactions (Sandner & Matthies, ). Using the same inbred and outbred families of S. latifolia as in the present study, Schrieber et al () quantified inbreeding depression in native and invasive populations under attack by multiple herbivores. The latter study yields additional information about whether diminished metabolic responses to herbivores in inbred plants have the potential to magnify inbreeding depression in S. latifolia .…”