Biogenic structural complexity is a key driver of biodiversity and ecosystem functioning, yet its ecological and environmental determinants remain poorly understood across broad biogeographic scales. Here, we conducted standardized 90‐day field experiments at 16 coastal sites, spanning a 41‐degree latitudinal gradient, using naturally assembled marine fouling communities on settlement panels. We measured rugosity as our metric...

Seagrass wasting disease, caused by parasitic slime nets in the genus Labyrinthula , affects seagrasses globally with outbreaks occurring at local to regional scales. Though prior research showed variation in pathogenicity across strains, little is known about the broad-scale diversity and biogeography of Labyrinthula species. We used targeted amplicon-based high throughput sequencing (HTS) to examine the phylogeography of Lab...

Disease is a key driver of community and ecosystem structure, especially when it strikes foundation species. In the widespread marine foundation species eelgrass ( Zostera marina ), outbreaks of wasting disease have caused large‐scale meadow collapse in the past, and the causative pathogen, Labyrinthula zosterae , is commonly found in meadows globally. Research to date has mainly focused on abiotic environmental drivers of sea...

Aim Biogenic structural complexity increases mobile animal richness and abundance at local, regional and global scales, yet animal taxa vary in their response to complexity. When these taxa also vary functionally, habitat structures favouring certain taxa may have consequences for ecosystem function. We characterised global patterns of epifaunal invertebrates in eelgrass ( Zostera marina ) beds that varied in structural and ge...

The extent of parallel genomic responses to similar selective pressures depends on a complex array of environmental, demographic, and evolutionary forces. Laboratory experiments with replicated selective pressures yield mixed outcomes under controlled conditions and our understanding of genomic parallelism in the wild is limited to a few well‐established systems. Here, we examine genomic signals of selection in the eelgrass Zo...

Ocean warming endangers coastal ecosystems through increased risk of infectious disease, yet detection, surveillance, and forecasting of marine diseases remain limited. Eelgrass ( Zostera marina ) meadows provide essential coastal habitat and are vulnerable to a temperature‐sensitive wasting disease caused by the protist Labyrinthula zosterae . We assessed wasting disease sensitivity to warming temperatures across a 3500 km st...

One objective of eco‐evolutionary dynamics is to understand how the interplay between ecology and evolution on contemporary timescales contributes to the maintenance of biodiversity. Disturbance is an ecological process that can alter species diversity through both ecological and evolutionary effects on colonization and extinction dynamics. While analogous mechanisms likely operate among genotypes within a population, empirica...

Human activities degrade and fragment coastal marine habitats, reducing their structural complexity and making habitat edges a prevalent seascape feature. Though habitat edges frequently are implicated in reduced faunal survival and biodiversity, results of experiments on edge effects have been inconsistent, calling for a mechanistic approach to the study of edges that explicitly includes indirect and interactive effects of ha...

Susan Lynn Williams (1951–2018) was an exceptional marine ecologist whose research focused broadly on the ecology of benthic nearshore environments dominated by seagrasses, seaweeds, and coral reefs. She took an empirical approach founded in techniques of physiological ecology. Susan was committed to applying her research results to ocean management through outreach to decision-makers and resource managers. Susan’s career incl...

Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass ( Zostera marina ) at 48 sites across its Northern Hemisphere range, encompassin...

Genetic diversity within key species can play an important role in the functioning of entire communities. However, the extent to which different dimensions of diversity (e.g., the number of genotypes vs. the extent of genetic differentiation among those genotypes) best predicts functioning is unknown and may yield clues into the different mechanisms underlying diversity effects. We explicitly test the relative influence of gen...

Environmental heterogeneity contributes to coexistence by allowing species with different traits to persist when different species perform best at different times or places. This interaction between niche differences and environmental variability may also help explain relationships between biodiversity and ecosystem functioning, but few data are available to rigorously evaluate this hypothesis. We assessed how a biologically r...

Functional trait differences and genetic distance are increasingly used as metrics to predict the outcome of species interactions and the maintenance of diversity. We apply these ideas to intraspecific diversity for the seagrass Zostera marina (eelgrass), by explicitly testing the influence of trait distance and genetic relatedness on the outcome of pairwise interactions among eelgrass genotypes. Increasing trait distance (but...

The importance of herbivores and of plant diversity for community succession and recovery from disturbance is well documented. However, few studies have assessed the relative magnitude of, or potential interactions between, these factors. To determine the combined effect of herbivory and surrounding algal species richness on the recovery of a rocky intertidal community, we conducted a 27‐month field experiment assessing algal...

Ecology Letters (2010) 13: 194–201 Abstract A rapidly accumulating body of research has shown that species diversity consistently affects the functioning of ecosystems. The incorporation of trophic complexity and the extension of this research to larger scales and natural ranges in species diversity remain as important challenges for understanding the true magnitude of these effects in natural systems. Here, we test whether th...

Although human‐mediated extinctions disproportionately affect higher trophic levels, the ecosystem consequences of declining diversity are best known for plants and herbivores. We combined field surveys and experimental manipulations to examine the consequences of changing predator diversity for trophic cascades in kelp forests. In field surveys we found that predator diversity was negatively correlated with herbivore abundanc...