Dispersal evolution in temporally variable environments: implications for plant range dynamics

Abstract

Dispersal—the movement of an individual from the site of birth to a different site for reproduction—is an ecological and evolutionary driver of species ranges that shapes patterns of colonization, connectivity, gene flow, and adaptation. In plants, the traits that influence dispersal often vary within and among species, are heritable, and evolve in response to the fitness consequences of moving through heterogeneous landscapes. Spatial and temporal variation in the quality and quantity of habitat are important sources of selection on dispersal strategies across species ranges. While recent reviews have evaluated the interactions between spatial variation in habitat and dispersal dynamics, the extent to which geographic variation in temporal variability can also shape range‐wide patterns in dispersal traits has not been synthesized. In this paper, we summarize key predictions from metapopulation models that evaluate how dispersal evolves in response to spatial and temporal habitat variability. Next, we compile empirical data that quantify temporal variability in plant demography and patterns of dispersal trait variation across species ranges to evaluate the hypothesis that higher temporal variability favors increased dispersal at plant range limits. We found some suggestive evidence supporting this hypothesis while more generally identifying a major gap in empirical work evaluating plant metapopulation dynamics across species ranges and geographic variation in dispersal traits. To address this gap, we propose several future research directions that would advance our understanding of the interplay between spatiotemporal variability and dispersal trait variation in shaping the dynamics of current and future species ranges.

Evolution of dispersal and the maintenance of fragmented metapopulations

“…While such a counterselection of dispersal was originally highlighted in theoretical models (Hastings, 1983; Travis and Dytham, 1999), empirical evidence for such effects has accumulated in recent years, for a large variety of species, from the weed Crepis sancta (Cheptou et al ., 2008), to the butterfly Proclossiana eunomia (Schtickzelle et al ., 2006) and the wolf spider Pardosa monticola (Bonte et al ., 2006). Fragmentation however also increases inbreeding, kin competition or temporal variation of the environment and all of these components usually select for higher dispersal abilities (Hamilton and May, 1977; Charlesworth and Charlesworth, 1987; Matthysen et al ., 1995; Gandon, 1999; Duputié and Massol, 2013; Cote et al ., 2017; Tung et al ., 2018; Oldfather et al ., 2021). In addition to the modulation of overall dispersal levels, fragmentation can also, under certain conditions, maintain contrasted dispersal strategies simultaneously.…”

Plant Species’ Capacity for Range Shifts at the Habitat and Geographic Scales: A Trade-Off-Based Framework

“…Colonization is so essential that programs in assisted migration are an attempt to overcome its limitations and facilitate plant species’ climate-driven range shifts [ 120 , 121 ]. Colonization also influences ecological and evolutionary dynamics within and between plant populations, and hence source–sink dynamics [ 51 , 65 , 122 ]. Aside from vicariance (i.e., fragmentation of a continuous distribution caused by dispersal barriers), rare very long-distance dispersal events [ 27 , 123 , 124 , 125 , 126 ], the spatial extent of seed rain and number of seeds dispersed far distances (the “fat tail” of the seed dispersal curve) are known to affect the rate of plant geographic range shifts and the ability to colonize new areas and habitats [ 14 , 57 , 127 , 128 ].…”

“…Aside from vicariance (i.e., fragmentation of a continuous distribution caused by dispersal barriers), rare very long-distance dispersal events [ 27 , 123 , 124 , 125 , 126 ], the spatial extent of seed rain and number of seeds dispersed far distances (the “fat tail” of the seed dispersal curve) are known to affect the rate of plant geographic range shifts and the ability to colonize new areas and habitats [ 14 , 57 , 127 , 128 ]. Plant traits influencing colonization ability also evolve in spatially and temporally variable environments, which can facilitate range shifts during climate change [ 122 ].…”

Temporal variation may have diverse impacts on range limits

“…Dispersal barriers may more likely be breached when source populations experience variability in local conditions favouring higher local dispersal. Oldfather et al [ 68 ] found empirical evidence that plants have greater dispersal at range margins when there is more temporal variability in plant demography. Sometimes, however, temporal variation favours lower dispersal [ 69 ].…”