Rapid changes in seed dispersal traits may modify plant responses to global change

Abstract

When climatic or environmental conditions change, plant populations must either adapt to these new conditions, or track their niche via seed dispersal. Adaptation of plants to different abiotic environments has mostly been discussed with respect to physiological and demographic parameters that allow local persistence. However, rapid modifications in response to changing environmental conditions can also affect seed dispersal, both via plant traits and via their dispersal agents. Studying such changes empirically is challenging, due to the high variability in dispersal success, resulting from environmental heterogeneity, and substantial phenotypic variability of dispersal-related traits of seeds and their dispersers. The exact mechanisms that drive rapid changes are often not well understood, but the ecological implications of these processes are essential determinants of dispersal success, and deserve more attention from ecologists, especially in the context of adaptation to global change. We outline the evidence for rapid changes in seed dispersal traits by discussing variability due to plasticity or genetics broadly, and describe the specific traits and biological systems in which variability in dispersal is being studied, before discussing some of the potential underlying mechanisms. We then address future research needs and propose a simulation model that incorporates phenotypic plasticity in seed dispersal. We close with a call to action and encourage ecologists and biologist to embrace the challenge of better understanding rapid changes in seed dispersal and their consequences for the reaction of plant populations to global change.

Geographic variation in dispersal distance facilitates range expansion of a lake shore plant in response to climate change

“…When individuals had uniformly short dispersal distances across the species' range, or when range‐edge populations had relatively short dispersal distances, the northern limit could not keep pace with changing climatic conditions because patches that became suitable north of the range limit were not colonized. To date, remarkably few studies have rigorously quantified the extent and distribution of intraspecific variation in dispersal (Johnson et al, ; Saastamoinen et al, ). Our results highlight that the incorporation of empirical estimates of key dispersal parameters could substantially alter predictions of species' range dynamics in response to climate change.…”

“…Genetic bottlenecks during colonization events can cause reduced variation in populations that are expanding into new habitat patches (e.g., neutral genetic variation), which in turn may limit the evolutionary potential of those populations during and after establishment (Bridle & Vines, ; Gaston, ). Currently, we lack models that evaluate how pre‐existing geographic variation and evolutionary change in dispersal strategies directly influence species' range dynamics and neutral genetic variation in response to climate change (Johnson et al, ).…”

Urbanization alters plastic responses in the common dandelion Taraxacum officinale

“…The induction of defenses by spines or toxins, or the developmental of tolerance is energetically costly and is expected to trade‐off with vital traits as seed production and/or seed mass (Agrawal et al, 1999; Stearns, 1989). Escape strategies by changing growth or seed dispersal morphology (Bonte et al, 2012; Johnson et al, 2019; de la Pena & Bonte, 2014) can equally levy costs and lead to trade‐offs with other life‐history traits. These plastic responses can be expressed during ontogeny, or among generations through maternal effects, and may be subjected to selection as well (Saastamoinen et al, 2018).…”

Individual variation in dispersal and fecundity increases rates of spatial spread

“…Theoretical studies have studied the effects of non-heritable and heritable variation in dispersal rates on spatial spread. Petrovskii and Morozov [2008] and Stover et al [2014] found that non-heritable variation in dispersal rates, such as due to phenotypic plasticity in response to local environmental heterogeneity [Johnson et al, 2019], lead to fatter dispersal kernels and faster rates of spatial spread. Alternatively, theoretical studies accounting for only heritable variation found selection for increased dispersal rates on the edges of a species' range resulting in accelerating rates of spatial spread [Travis and Dytham, 2002, Hughes et al, 2007, Phillips et al, 2008, Travis et al, 2009, Phillips et al, 2010, Bouin et al, 2012, Perkins et al, 2013.…”