Prey responses to disturbance cues: Effects of familiarity, kinship, and past experience with risk

Prey can acquire information about predators by eavesdropping on conspecific cues, but these cues are not always reliable. In aquatic systems, disturbance cues are pulses of urea or ammonia that are often released by prey while fleeing a predator; nearby individuals typically display antipredator responses after detecting these cues. Despite the importance of disturbance cues to aquatic prey survival, they remain largely understudied in terms of their function and evolution. Here, I sought to test whether disturbance cues might function as an antipredator signal. Using a series of experiments, I assessed how familiarity and relatedness with individuals releasing the cues affects the antipredator response of the receiver, and whether background risk levels for the cue releaser and receiver play a role in the response exhibited by the receiver. If prey rely more on disturbance cues from familiar, related, or high predation risk background conspecifics, then I expect to see a heightened fright response to these cues. To test this, I raised wood frog (Lithobates sylvaticus) egg clutches and obtained disturbance cues from groups of tadpoles by simulating a predator chase. Counter to expectation, tadpoles exposed to disturbance cues from unfamiliar individuals displayed a fright response, whereas disturbance cues from familiar individuals were ignored, possibly because these cues became unreliable after being detected repeatedly in the absence of a true threat. Tadpoles responded similarly to the disturbance cues of related and unrelated individuals, suggesting that related individuals did not provide more reliable information. When manipulating background predation risk, high-risk receivers but not low-risk receivers responded to disturbance cues from low-risk donors, suggesting a lower response threshold in high risk prey. Disturbance cues from high-risk donors also elicited more of a fright response in both high- and low-risk receivers. This suggests that high risk prey release more, or more potent disturbance cues. Taken together, these experiments provide strong evidence that tadpoles detect variation in disturbance cues and may be capable of modulating their disturbance cues as antipredator signals. These findings are of important consideration for conservationists studying how Allee effects manifest in threatened aquatic species such as anuran tadpoles

Demographic and evolutionary responses of reef-building corals to climate change

Kevin Bairos-Novak studied coral responses to climate change across the Great Barrier Reef. He modelled coral evolution across future climates and found that coral evolution may keep pace with climate change if carbon emissions are substantially reduced and if healthy corals continue to produce enough new coral recruits

Coral adaptation to climate change: meta-analysis reveals high heritability across multiple traits

Anthropogenic climate change is a rapidly intensifying selection pressure on biodiversity across the globe and, particularly, on the world's coral reefs. The rate of adaptation to climate change is proportional to the amount of phenotypic variation that can be inherited by subsequent generations (i.e., narrow-sense heritability, h2). Thus, traits that have higher heritability (e.g., h2 > 0.5) are likely to adapt to future conditions faster than traits with lower heritability (e.g., h2 0.50) for metrics related to survival and immune responses. Some of these values are higher than typically observed in other taxa, such as survival and growth, while others were more comparable, such as gene expression and photochemistry. There was no detectable effect of temperature on heritability, but narrow-sense heritability estimates were generally lower than broad-sense estimates, indicative of significant non-additive genetic variation across traits. Trait heritability also varied depending on coral life stage, with bleaching and growth in juveniles generally having lower heritability compared to bleaching and growth in larvae and adults. These differences may be the result of previous stabilizing selection on juveniles or may be due to constrained evolution resulting from genetic trade-offs or genetic correlations between growth and thermotolerance. While we find no evidence that heritability decreases under temperature stress, explicit tests of the heritability of thermal tolerance itself—such as coral thermal reaction norm shape—are lacking. Nevertheless, our findings overall reveal high trait heritability for the majority of coral traits, suggesting corals may have a greater potential to adapt to climate change than has been assumed in recent evolutionary models

Impacts of ocean warming on echinoderms: A meta‐analysis

Rising ocean temperatures are threatening marine species and populations worldwide, and ectothermic taxa are particularly vulnerable. Echinoderms are an ecologically important phylum of marine ectotherms and shifts in their population dynamics can have profound impacts on the marine environment. The effects of warming on echinoderms are highly variable across controlled laboratory-based studies. Accordingly, synthesis of these studies will facilitate the better understanding of broad patterns in responses of echinoderms to ocean warming. Herein, a meta-analysis incorporating the results of 85 studies (710 individual responses) is presented, exploring the effects of warming on various performance predictors. The mean responses of echinoderms to all magnitudes of warming were compared across multiple biological responses, ontogenetic life stages, taxonomic classes, and regions, facilitated by multivariate linear mixed effects models. Further models were conducted, which only incorporated responses to warming greater than the projected end-of-century mean annual temperatures at the collection sites. This meta-analysis provides evidence that ocean warming will generally accelerate metabolic rate (+32%) and reduce survival (−35%) in echinoderms, and echinoderms from subtropical (−9%) and tropical (−8%) regions will be the most vulnerable. The relatively high vulnerability of echinoderm larvae to warming (−20%) indicates that this life stage may be a significant developmental bottleneck in the near-future, likely reducing successful recruitment into populations. Furthermore, asteroids appear to be the class of echinoderms that are most negatively affected by elevated temperature (−30%). When considering only responses to magnitudes of warming representative of end-of-century climate change projections, the negative impacts on asteroids, tropical species and juveniles were exacerbated (−51%, −34% and −40% respectively). The results of these analyses enable better predictions of how keystone and invasive echinoderm species may perform in a warmer ocean, and the possible consequences for populations, communities and ecosystems

RawData_for_Bairos-Novak_et_al

The raw data in an Excel spreadsheet used in the R analysis. See the 'metadata' tab of the spreadsheet for more information

R Script for Data Analysis

An R script file with comments to obtain the test statistics and values observed in the manuscript

script_Bairos-Novak_et_al_2019_JAE

R script used in the analysis of the publication "A Novel Alarm Signal in Aquatic Prey: Familiar Minnows Coordinate Group Defenses Against Predators Through Chemical Disturbance Cues" (see comments throughout code for more information)

data_Bairos-Novak_et_al_2019_JAE

Microsoft Excel spreadsheet of data used in the analysis of the publication "A Novel Alarm Signal in Aquatic Prey: Familiar Minnows Coordinate Group Defenses Against Predators Through Chemical Disturbance Cues" (see 'metadata' sheet inside .xlsx workbook)

Data for fear recovery in minnows

There are three datasheets. The first is all data on observers across treatments. The second contains data on models across treatments on day 9 of the experiment. The third contains data on replacement models at different time periods

Data from 'Chemical disturbance cues in aquatic systems: a review and prospectus'

In the natural environment, animals can face potentially dangerous and often regular exposure to major environmental fluctuations like flash flooding and drought, or the approach of a predator. For many aquatic species, exposure to these ecological disturbances triggers the release of ‘disturbance cues’ – generally characterized as chemicals released when animals are startled but not injured. While the chemistry of such cues remains largely unexplored, they appear to provide early warning information to nearby individuals, potentially leading behavioural decisions that increase overall fitness, particularly for social species that may coordinate group defence. In the literature, disturbance cues have received little attention relative to other chemical cues, such as damage-released alarm cues. However, recent advances in the study of disturbance cue communication have led an uptick in research on the subject. Here, we review the existing literature on responses to disturbance cues in aquatic systems. Although the majority of studies involve behavioural responses to a simulated predator approach, we describe various disturbance types across a broad range of taxa. We discuss the ecological implications of disturbance cues, including their role in risk assessment, signalling, learning, and species specificity. We also address several methodological challenges for this developing field of study, as well as the ethical and conservation implications of this research going forward. Future research on disturbance cues should address a number of key unknowns, including questions regarding disturbance cue chemistry, function, and generality