Metapopulations and metacommunities: combining spatial and temporal perspectives in plant ecology

Abstract

Summary1. Metapopulation and metacommunity theories occupy a central role in ecology, but can be difficult to apply to plants. Challenges include whether seed dispersal is sufficient for population connectivity, the role of seed banks and problems with studying colonization and extinction in long-lived and clonal plants. Further, populations often do not occupy discrete habitat patches. Despite these difficulties, we present case studies to illustrate explicit integration of spatial and temporal data in plant ecology. 2. First, on the population level, we focused on two early successional species that lack discrete habitat patches. Multi-year data sets taken with a grid approach and simple models permit the analysis of landscape dynamics that reflect regional as well as local processes. Using Silene latifolia, we examined colonization. We found evidence for seed dispersal and connectivity among populations across a large landscape. With Helianthus annuus, a species with seed banks, we determined the degree to which landscape-level patterns of abundance were predicted by local processes (previous year recruitment at a site plus seed banks) vs. seed dispersal. Local processes dominated dynamics. 3. Second, at the community level, we utilized a landscape-level experiment to examine the influence of environmental gradients and spatial processes (dispersal limitation) on community composition during 18 years of succession. Throughout succession, environmental and spatial factors both contributed significantly to spatial variation in species composition (beta diversity). When connectivity was disrupted, space was the dominant factor underlying beta diversity, and this did not change over time. Across more connected communities, spatial effects diminished over succession as the importance of environmental factors increased, consistent with species-sorting metacommunity models. 4. Synthesis. Metapopulation ⁄ metacommunity concepts emphasize the interaction between space and time in ecological processes. Spatial processes, such as long-distance dispersal, play a crucial role in creating new populations. Temporal processes, including seed banks, may dominate dynamics at both local and regional scales. The relative importance of spatial vs. temporal processes changes as populations persist and communities assemble over time; these patterns may only emerge after many years. Integrating long-term data with spatial data is thus essential for understanding spatio-temporal patterns inherent in metapopulation and metacommunity theories.

Habitat fragmentation and biodiversity conservation: key findings and future challenges

“…For instance, priority effects (Fukami 2015) and a combination of deterministic and stochastic processes may influence the trajectory of community assembly in fragmented systems (Norden et al 2015). Patterns of beta diversity can be altered by fragmentation overlaying successional dynamics (Alexander et al 2012). While the processes of assembly and relaxation do share some generalizable effects (Haddad et al 2015, discussed above), we do not fully understand the ways in which these systems converge and diverge from each other, creating a primary source of confusion within the study of fragmentation.…”

Roles of maternal effects and nuclear genetic composition change across the life cycle of crop–wild hybrids

“…By contrast, wild-produced hybrid progeny are more likely to remain in the seed bank and thus facilitate persistence of crop alleles, even without recurrent gene fl ow. This is notable given the importance of seed banks for wild sunfl ower population dynamics ( Alexander et al, 2009 ;Alexander et al, 2012 ). For example, 10-23% of seedlings in a wild population had their origin in seed banks ( Alexander and Schrag, 2003 ).…”

“…Future researchers could quantify the covariance between genetic maternal effects expressed by the mother (e.g., pericarp characteristics, seed size) and those expressed by the offspring (e.g., dormancy, seedling size) ( Kirkpatrick and Lande, 1989 ;Räsänen and Kruuk, 2007 ). Another promising direction is demographic modeling, with the goal of linking models of crop-wild hybridization/genetic assimilation (e.g., Wolf et al, 2001 ) with models of seed bank dynamics ( Alexander et al, 2012 ). Genetic maternal effects on dormancy should be included in such models to help clarify whether such transgenerational effects are simply "noise" or have population level consequences ( Räsänen and Kruuk, 2007 ;Donohue, 2009 ).…”

Dormancy in metacommunities

“…Despite its potential importance for local-and regional-scale processes, dormancy has yet 66 to be adequately incorporated into metacommunity ecology (Leibold and Norberg 2004;Alexander et al 2012). Here, we explore the role of dormancy in metacommunities 68 from both ecological and evolutionary perspectives.…”