Rapid evolution of dispersal‐related traits during range expansion of an invasive vine Mikania micrantha

Abstract

Rapid range expansion of invasive plants provides a unique opportunity to explore evolutionary changes of dispersal-related traits during the invasion process. Increasing evidence now suggests that a higher dispersal rate is favored at the invasion front. However, little is known about the role of genetic diff erentiation and phenotypic plasticity on patterns of dispersal ability during the invasion process. In this study, we combined a fi eld survey and a common garden transplant experiment to test for evidence of genetically based dispersal ability in Mikania micrantha , a highly invasive vine, across its invaded range in southern China. Th ree dispersal-related traits, plume loading, seed mass and pappus radius, were measured in both natural and common garden populations. We found that in natural conditions, plume loading and seed mass signifi cantly decreased with expanding distance from the source population, but in controlled conditions, these two traits exhibited a signifi cant humped trend against percent fi eld cover, indicating that dispersal ability of M. micrantha was selected for during range expansion and that the related traits were likely to be under genetic control. Furthermore, rebounding dispersal ability was detected in highly competitive sites in the range core, which suggested that this evolutionary process was likely partially driven by intraspecifi c competition. Because more and more plant species are under spatial nonequilibirum due to climate change, this study can serve to provide hints at the fate of spatially fl uctuant populations.

Spatial Selection and Local Adaptation Jointly Shape Life-History Evolution during Range Expansion

“…The empirically observed increased dispersal at the range front is in line with several studies on postglacial range expansion (Cwynar and Macdonald 1987), invasions (Travis and Dytham 2002;Phillips et al 2006;Huang et al 2015), and climate change (Thomas et al 2001;Travis et al 2013). Because this pattern matched best with our range expansion scenarios, this indicates that dispersal ability is positively selected at the expansion front through the process of spatial selection and most likely not by adaptation to local environmental conditions (i.e., local temperature and growing season length in our model).…”

“…First, since the most dispersive phenotypes accumulate at the expansion front, assortative mating takes place Shine et al 2011). This results in increased dispersal abilities at the range front, as has been illustrated theoretically (e.g., Travis and Dytham 2002;Burton et al 2010;Perkins et al 2013) as well as empirically through field and common garden studies (e.g., Phillips et al 2006;Mitikka and Hanski 2010;Hill et al 2011;Huang et al 2015) and experimental evolution (Fronhofer and Altermatt 2015). Dispersal evolution thus affects (Kubisch et al 2014) and is affected by range expansion (reviewed in Hill et al 2011).…”

Expanding population edges: theories, traits, and trade‐offs

“…Plume and wing loading refer to the ratio of the seed mass to its area (Vogel & Vogel, ), where decreased plume and wing loading is correlated to greater dispersal potential (Andersen, ). Consistent with patterns of greater dispersal ability at range margins, seeds measured from the edge tend to have decreased mass, plume loading (Huang et al ., ), and wing loading (Cwynar & MacDonald, ) (Table ). Feathery structures like the pappus in diaspores are also larger (Monty & Mahy, ), which increases air drag and prolongs the period of descent, resulting in further displacement.…”

Dispersal: a central and independent trait in life history

“…Dispersal and traits related to growth can be selected during range expansion and eventually affect species range limits (Phillips et al , Kubisch et al , Therry et al , , Fronhofer and Altermatt , Huang et al ). This process of spatial sorting is expected to theoretically accelerate range expansion and invasions (Shine et al , Bénichou et al ).…”