Rapid phenotypic differentiation and local adaptation in Japanese knotweed s.l. (Reynoutria japonicaandR. ×bohemica, Polygonaceae) invading novel habitats

Abstract

PREMISE: Many plant invaders like the Japanese knotweeds are thought to colonize new habitats with low genetic diversity. Such species provide an opportunity to study rapid adaptation to complex environmental conditions. METHODS: Using replicate reciprocal transplants of clones across three habitats, we described patterns of phenotypic response and assessed degree of local adaptation. KEY RESULTS: We found plants from beach habitats had decreased height, number of leaves, leaf area, and biomass allocation to roots and shoots compared to plants from marsh and roadside habitats when grown in their home habitat. In the marsh habitat, marsh plants were generally larger than beach plants, but not different from roadside plants. There were no differences among plants from different habitats grown in the roadside habitat. Despite this evidence of differentiation in beach and marsh habitats, we found mixed evidence for local adaptation. In their "home site" plants from the marsh habitat had greater biomass than plants from the beaches but not compared to plants from roadsides. Biomass comparisons in other habitats were either maladaptive or not significant. However, plants from the roadside had greater survival in their "home site" compared to foreign plants. There were no differences in survival in the other habitats. CONCLUSIONS: We found phenotypic differentiation associated with habitats despite the low reported genetic diversity for these populations. Our results partially support the hypothesis of local adaptation in marsh and roadside habitats. Identifying whether these patterns of differentiation result from genetic or heritable non-genetic mechanisms will require further work.

Attenuated total reflection Fourier- transformed infrared spectroscopy reveals environment specific phenotypes in clonal Japanese knotweed

“…Physiological variation of Japanese knotweed grown in different habitats has been recorded in previous studies, including differences in height, number of leaves, leaf surface area and biomass allocation (Walls, 2010;Yuan et al, 2022). All the rhizomes used for these controlled growth experiments were extracted from the same source, but recent research indicates that the environmental adaptations observed here may be in uenced by the original source of the rhizomes and could have differed if these were collected from another habitat type (Yuan et al, 2022). The growth environment plays a signi cant role in phenotypic presentation, and this study has explored the in uence of speci c environmental variables.…”

“…Although IAS generally display greater plasticity, this is not always correlated with a tness bene t (Davidson et al, 2011). Physiological variation of Japanese knotweed grown in different habitats has been recorded in previous studies, including differences in height, number of leaves, leaf surface area and biomass allocation (Walls, 2010;Yuan et al, 2022). All the rhizomes used for these controlled growth experiments were extracted from the same source, but recent research indicates that the environmental adaptations observed here may be in uenced by the original source of the rhizomes and could have differed if these were collected from another habitat type (Yuan et al, 2022).…”