Landscape Genetics of Plants: Challenges and Opportunities

Abstract

Dispersal is one of the most important but least understood processes in plant ecology and evolutionary biology. Dispersal of seeds maintains and establishes populations, and pollen and seed dispersal are responsible for gene flow within and among populations. Traditional views of dispersal and gene flow assume models that are governed solely by geographic distance and do not account for variation in dispersal vector behavior in response to heterogenous landscapes. Landscape genetics integrates population genetics with Geographic Information Systems (GIS) to evaluate the effects of landscape features on gene flow patterns (effective dispersal). Surprisingly, relatively few landscape genetic studies have been conducted on plants. Plants present advantages because their populations are stationary, allowing more reliable estimates of the effects of landscape features on effective dispersal rates. On the other hand, plant dispersal is intrinsically complex because it depends on the habitat preferences of the plant and its pollen and seed dispersal vectors. We discuss strategies to assess the separate contributions of pollen and seed movement to effective dispersal and to delineate the effects of plant habitat quality from those of landscape features that affect vector behavior. Preliminary analyses of seed dispersal for three species indicate that isolation by landscape resistance is a better predictor of the rates and patterns of dispersal than geographic distance. Rates of effective dispersal are lower in areas of high plant habitat quality, which may be due to the effects of the shape of the dispersal kernel or to movement behaviors of biotic vectors. Landscape genetic studies in plants have the potential to provide novel insights into the process of gene flow among populations and to improve our understanding of the behavior of biotic and abiotic dispersal vectors in response to heterogeneous landscapes.

Life in the desert: The impact of geographic and environmental gradients on genetic diversity and population structure of Ivesia webberi

“…Due to the spatial configuration of these populations, we also (d) tested the central-marginal hypothesis (CMH), which predicts decreased gene flow and increased pairwise genetic differentiation among populations towards the edge of the species range (Micheletti & Storfer, 2015). Despite the challenges associated with modeling plant landscape genetics due to their sedentary life, and passive seed and pollen dispersal, plant species offer an excellent opportunity to explore species' interactions with the landscape (Alvarado-Serrano et al, 2019;Cruzan & Hendrickson, 2020). Furthermore, plants like I. webberi with short generation times are expected to respond quicker to environmental and landscape changes; these effects can be observed in the distribution of genetic variation within the species (Aguilar et al, 2008).…”

Drivers of genetic differentiation and recent evolutionary history of an Eurasian wild pea

“…IBR takes this effect into account in addition to the geographic distance and can therefore be considered an extension of the simple IBD model. IBR is particularly important for plants because they cannot easily move through inhabitable areas like cities, cropland or large water bodies and was found to be a better predictor of plants dispersal capabilities than IBD (Cruzan & Hendrikson, 2020, Grasty et al, 2020). Besides those processes that directly affect geneflow patterns among populations, the demographic history of a species can indirectly influence the genetic differentiation between populations.…”

Strong gene flow explains lack of mating system variation in the perennial herb, Vincetoxicum hirundinaria, in a fragmented landscape

“…Gene flow depends on the landscape structure, mating system, pollination vectors and the adaptations of seeds for dispersal (Schmidt et al 2009, Buehler et al 2012, Sork et al 1999, Cruzan and Hendrickson 2020). The naturally fragmented structure of our study area, where large bodies of water separate islands only some of which have suitable habitats for V. hirundinaria , suggests that there are obstacles for successful gene flow.…”