Allison K. Barner

Long-Term Studies Contribute Disproportionately to Ecology and Policy

Abstract As the contribution for long‐term ecological and environmental studies (LTEES) to our understanding of how species and ecosystems respond to a changing global climate becomes more urgent, the relative number and investment in LTEES are declining. To assess the value of LTEES to advancing the field of ecology, we evaluated relationships between citation rates and study duration, as well as the representation of LTEES with the impact factors of 15 ecological journals. We found that the proportionate representation of LTEES increases with journal impact factor and that the positive relationship between citation rate and study duration is stronger as journal impact factor increases. We also found that the representation of LTEES in reports written to inform policy was greater than their representation in the ecological literature and that their authors particularly valued LTEES. We conclude that the relative investment in LTEES by ecologists and funders should be seriously reconsidered for advancing ecology and its contribution to informing environmental policy.

The mixed mating system of the sea palm kelp Postelsia palmaeformis: few costs to selfing

Naturally isolated populations have conflicting selection pressures for successful reproduction and inbreeding avoidance. These species with limited seasonal reproductive opportunities may use selfing as a means of reproductive assurance. We quantified the frequency of selfing and the fitness consequences for inbred versus outcrossed progeny of an annual kelp, the sea palm (Postelsia palmaeformis). Using experimentally established populations and microsatellite markers to assess the extent of selfing in progeny from six founding parents, we found the frequency of selfing was higher than expected in every population, and few fitness costs were detected in selfed offspring. Despite a decline in heterozygosity of 30 per cent in the first generation of selfing, self-fertilization did not affect individual size or reproduction, and correlated only with a marginally significant decline in survival. Our results suggest both that purging of deleterious recessive alleles may have already occurred and that selfing may be key to reproductive assurance in this species with limited dispersal. Postelsia has an alteration of a free-living diploid and haploid stage, where the haploid stage may provide increased efficiency for purging the genetic load. This life history is shared by many seaweeds and may thus be an important component of mating system evolution in the sea.

The complex net effect of reciprocal interactions and recruitment facilitation maintains an intertidal kelp community

Summary 1. Theoretical and empirical ecology has transitioned from a focus on the role of negative interactions in species coexistence to a more pluralistic view that acknowledges that coexistence in natural communities is more complex, and depends on species interactions that vary in strength, sign, and reciprocity, and such contexts as the environment and life-history stage. 2. We used a whole-community approach to examine how species interactions contribute to the maintenance of a rocky intertidal macroalgal canopy–understorey assemblage. We determined both the types of interactions in this network, and whether interactions were sensitive to environmental gradients. 3. Focusing on a structurally dominant canopy kelp Saccharina sessilis, and its diverse co-occurring understorey assemblage, we evaluated the role of the understorey in controlling S. sessilis recruitment and quantified the reciprocal effect of the S. sessilis canopy and understorey on one another using a removal experiment replicated across 600 km of coastline. We determined the sensitivity of interactions to natural variation in light and nutrient availability (replicated among four regions on the N.E. Pacific coast), and under different wave conditions (three wave regimes). 4. Surprisingly, species interactions were similar across sites and thus not context-dependent. Unexpectedly, the understorey community had a strong positive effect on the S. sessilis canopy, whereby the adult canopy decreased dramatically following understorey removal. Additionally, S. sessilis recruitment depended on the presence of understorey coralline algal turf. In turn, the canopy had a neutral effect on the coralline understorey, but a negative effect on non-calcifying algal turfs, likely eventually generating positive indirect canopy effects on the coralline understorey. Densitydependent intraspecific competition between S. sessilis adults and recruits may moderate this positive feedback between the S. sessilis canopy and coralline understorey. 5. Synthesis. Our research highlights the importance of positive interactions for coexistence in natural communities, and the necessity of studying multiple life-history stages and reciprocal species interactions in order to elucidate the mechanisms that maintain diversity.

Evaluating Temporal Consistency in Marine Biodiversity Hotspots

With the ongoing crisis of biodiversity loss and limited resources for conservation, the concept of biodiversity hotspots has been useful in determining conservation priority areas. However, there has been limited research into how temporal variability in biodiversity may influence conservation area prioritization. To address this information gap, we present an approach to evaluate the temporal consistency of biodiversity hotspots in large marine ecosystems. Using a large scale, public monitoring dataset collected over an eight year period off the US Pacific Coast, we developed a methodological approach for avoiding biases associated with hotspot delineation. We aggregated benthic fish species data from research trawls and calculated mean hotspot thresholds for fish species richness and Shannon’s diversity indices over the eight year dataset. We used a spatial frequency distribution method to assign hotspot designations to the grid cells annually. We found no areas containing consistently high biodiversity through the entire study period based on the mean thresholds, and no grid cell was designated as a hotspot for greater than 50% of the time-series. To test if our approach was sensitive to sampling effort and the geographic extent of the survey, we followed a similar routine for the northern region of the survey area. Our finding of low consistency in benthic fish biodiversity hotspots over time was upheld, regardless of biodiversity metric used, whether thresholds were calculated per year or across all years, or the spatial extent for which we calculated thresholds and identified hotspots. Our results suggest that static measures of benthic fish biodiversity off the US West Coast are insufficient for identification of hotspots and that long-term data are required to appropriately identify patterns of high temporal variability in biodiversity for these highly mobile taxa. Given that ecological communities are responding to a changing climate and other environmental perturbations, our work highlights the need for scientists and conservation managers to consider both spatial and temporal dynamics when designating biodiversity hotspots.

Patterns and Variation in Benthic Biodiversity in a Large Marine Ecosystem

While there is a persistent inverse relationship between latitude and species diversity across many taxa and ecosystems, deviations from this norm offer an opportunity to understand the conditions that contribute to large-scale diversity patterns. Marine systems, in particular, provide such an opportunity, as marine diversity does not always follow a strict latitudinal gradient, perhaps because several hypothesized drivers of the latitudinal diversity gradient are uncorrelated in marine systems. We used a large scale public monitoring dataset collected over an eight year period to examine benthic marine faunal biodiversity patterns for the continental shelf (55–183 m depth) and slope habitats (184–1280 m depth) off the US West Coast (47°20′N—32°40′N). We specifically asked whether marine biodiversity followed a strict latitudinal gradient, and if these latitudinal patterns varied across depth, in different benthic substrates, and over ecological time scales. Further, we subdivided our study area into three smaller regions to test whether coast-wide patterns of biodiversity held at regional scales, where local oceanographic processes tend to influence community structure and function. Overall, we found complex patterns of biodiversity on both the coast-wide and regional scales that differed by taxonomic group. Importantly, marine biodiversity was not always highest at low latitudes. We found that latitude, depth, substrate, and year were all important descriptors of fish and invertebrate diversity. Invertebrate richness and taxonomic diversity were highest at high latitudes and in deeper waters. Fish richness also increased with latitude, but exhibited a hump-shaped relationship with depth, increasing with depth up to the continental shelf break, ~200 m depth, and then decreasing in deeper waters. We found relationships between fish taxonomic and functional diversity and latitude, depth, substrate, and time at the regional scale, but not at the coast-wide scale, suggesting that coast-wide patterns can obscure important correlates at smaller scales. Our study provides insight into complex diversity patterns of the deep water soft substrate benthic ecosystems off the US West Coast.

Generality in multispecies responses to ocean acidification revealed through multiple hypothesis testing

Decades of research have demonstrated that many calcifying species are negatively affected by ocean acidification, a major anthropogenic threat in marine ecosystems. However, even closely related species may exhibit different responses to ocean acidification and less is known about the drivers that shape such variation in different species. Here, we examine the drivers of physiological performance under ocean acidification in a group of five species of turf-forming coralline algae. Specifically, quantitating the relative weight of evidence for each of ten hypotheses, we show that variation in coralline calcification and photosynthesis was best explained by allometric traits. Across ocean acidification conditions, larger individuals (measured as noncalcified mass) had higher net calcification and photosynthesis rates. Importantly, our approach was able to not only identify the aspect of size that drove the performance of coralline algae, but also determined that responses to ocean acidification were not dependent on species identity, evolutionary relatedness, habitat, shape, or structural composition. In fact, we found that failure to test multiple, alternative hypotheses would underestimate the generality of physiological performances, leading to the conclusion that each species had different baseline performance under ocean acidification. Testing among alternative hypotheses is an essential step toward determining the generalizability of experiments across taxa and identifying common drivers of species responses to global change.

Back Page Photo Series: Intertidal After Dark

How did you find yourself studying intertidal zones? I find myself as an intertidal ecologist due to a surprising combination of happenstance and interest. Growing up in coastal Connecticut, I always felt an affinity for marine ecology. But when I decided to attend the University of Chicago, I figured I would have few chances to study ocean ecosystems while based in the Midwest. Luckily, in my third year, I took a course taught by Catherine Pfister, who I soon discovered worked in the rocky intertidal ecosystem of Washington’s Olympic Peninsula. When I approached Catherine about working in her lab, she happened to have a languishing project perfect for an undergraduate. We worked together for two years, eventually publishing the project (Barner et al. 2011). After I graduated, I knew that I wasn’t done with the intertidal, or with the Pacific Northwest. I was offered the opportunity to pursue a Ph.D. in ecology at Oregon State University, and I have spent five very happy field seasons in Oregon’s rocky intertidal.