Oculomotor system can differentially process red and green colors during saccade programming in the presence of a competing distractor

Selective attention filters irrelevant information entering our brain to allow for fine-tuning of the relevant information processing. In the visual domain, shifts of attention are most often followed by a saccadic eye movement to objects and places of high relevance. Recent studies have shown that the stimulus color can affect saccade target selection and saccade trajectories. While those saccade modulations are based on perceptual color space, the level in the visual processing hierarchy at which color selection biases saccade programming remains unclear. As color has also been shown to influence manual response inhibition which is a key function of the prefrontal cortex, we hypothesized that the effects of color on executive functions would also inherently affect saccade programming. To test this hypothesis, we measured behavioral performance and saccade metrics during a modified saccadic Stroop task which reflects competition between color words ("RED" and "GREEN") and their color at the level of the prefrontal cortex. Our results revealed that the oculomotor system can differentially process red and green colors when planning a saccade in the presence of a competing distractor.

Consumptive effects and mismatch in predator-prey turnover rates cause inversion of biomass pyramids

The mismatch between the turnover rates of predators and prey is one of the oldest explanations for the existence of inverted trophic pyramids. To date, the hypotheses regarding trophic pyramids have all been based on consumptive trophic links between predators and prey, and the relative contribution of non-consumptive effects is still unknown. In this study, we investigated if the inversion of pyramids in bromeliad ecosystems is driven by (i) a rapid colonization of organisms having short cohort interval production (CPI), and (ii) the prevalence of consumptive or non-consumptive effects of top predators. We used a manipulative experiment to investigate the patterns of prey colonization and to partition the net effects of the dominant predator (damselfly larvae) on biomass pyramids into consumptive (uncaged damselfly larvae) and non-consumptive effects (caged damselfly larvae). Consumptive effects of damselflies strengthened the inversion of trophic pyramids. Non-consumptive effects, however, did not affect the shape of biomass pyramids. Instead, the rapid colonization of organisms with predominantly short CPI sustained the large biomass of top predators found in natural bromeliad ecosystems. Prey colonized bromeliads rapidly, but this high production was never visible as standing stock because damselflies reduce prey densities by more than a magnitude through direct consumption. Our study adds to the growing evidence that there are a variety of possible ways that biomass can be trophically structured. Moreover, we suggest that the strength of biomass pyramids inversion may change with the time of ecological succession as prey communities become more equitable.

From the predictable to the unexpected: kelp forest and benthic invertebrate community dynamics following decades of sea otter expansion

The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One iconic example of this is keystone predation by sea otters in the Northeast Pacific. Here, we combine spatial time series of sea otter abundance, canopy kelp area, and benthic invertebrate abundance from Washington State, USA, to examine the shifting consequences of sea otter reintroduction for kelp and kelp forest communities. We leverage the spatial variation in sea otter recovery to understand connections between sea otters and the kelp forest community. Sea otter increases created a pronounced decline in sea otter prey-particularly kelp-grazing sea urchins-and led to an expansion of canopy kelps from the late 1980s until roughly 2000. However, while sea otter and kelp population growth rates were positively correlated prior to 2002, this association disappeared over the last two decades. This disconnect occurred despite surveys showing that sea otter prey have continued to decline. Kelp area trends are decoupled from both sea otter and benthic invertebrate abundance at current densities. Variability in kelp abundance has declined in the most recent 15 years, as it has the synchrony in kelp abundance among sites. Together, these findings suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now, other factors may be as or more important in influencing community dynamics. Thus, the utility of sea otter predation in ecosystem restoration must be considered within the context of complex and shifting environmental conditions.