Abstract
Inbreeding and enemy infestation are common in plants and can synergistically reduce their performance. This inbreeding ×environment (I × E) interaction may be of particular importance for the success of plant invasions if introduced populations experience a release from attack by natural enemies relative to their native conspecifics. Here, we investigate whether inbreeding affects plant infestation damage, whether inbreeding depression in growth and reproduction is mitigated by enemy release, and whether this effect is more pronounced in invasive than native plant populations. We used the invader Silene latifolia and its natural enemies as a study system. We performed two generations of experimental out‐ and inbreeding within eight native (European) and eight invasive (North American) populations under controlled conditions using field‐collected seeds. Subsequently, we exposed the offspring to an enemy exclusion and inclusion treatment in a common garden in the species’ native range to assess the interactive effects of population origin (range), breeding treatment, and enemy treatment on infestation damage, growth, and reproduction. Inbreeding increased flower and leaf infestation damage in plants from both ranges, but had opposing effects on fruit damage in native versus invasive plants. Inbreeding significantly reduced plant fitness; whereby, inbreeding depression in fruit number was higher in enemy inclusions than exclusions. This effect was equally pronounced in populations from both distribution ranges. Moreover, the magnitude of inbreeding depression in fruit number was lower in invasive than native populations. These results support that inbreeding has the potential to reduce plant defenses in S. latifolia, which magnifies inbreeding depression in the presence of enemies. However, future studies are necessary to further explore whether enemy release in the invaded habitat has actually decreased inbreeding depression and thus facilitated the persistence of inbred founder populations and invasion success.
Highlights
Understanding the forces that promote or prevent species range expansions remains a challenging goal in ecology (Barrett, 2015)
Numerous invasions were accompanied by repeated population bottlenecks during initial introduction and/or colonization at the leading edge of expansion, which resulted in successive genetic depletion and severe inbreeding in phases most crucial for invasion success
Our study provides support that inbreeding × environment (I×E) interactions can contribute to successful plant invasion and that these interactions are shaped by the evolutionary histories of plant populations
Summary
Understanding the forces that promote or prevent species range expansions remains a challenging goal in ecology (Barrett, 2015). 2002) and colonization abilities (Hufbauer, Rutschmann, Serrate, Vermeil de Conchard, & Facon, 2013). Such inbreeding × environment (I×E) interactions are increasingly perceived as potential determinants of species ranges and their dynamics under global change (Colautti, Alexander, Dlugosch, Keller, & Sultan, 2017; Leimu, Vergeer, Angeloni, & Ouborg, 2010; Reed, Fox, Enders, & Kristensen, 2012; Schrieber & Lachmuth, 2017). Numerous invasions were accompanied by repeated population bottlenecks during initial introduction and/or colonization at the leading edge of expansion, which resulted in successive genetic depletion and severe inbreeding in phases most crucial for invasion success (reviewed in Schrieber & Lachmuth, 2017)
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