Craig W. Osenberg

Understanding how variation in key abiotic and biotic factors interact at ecologically relevant spatial scales is crucial for predicting population dynamics, distributions, and abundances. This is especially true for vectors that transmit human pathogens. However, studies investigating the effects of environmental variation on vectors have typically investigated environmental factors in isolation or in laboratory experiments that examine constant environmental conditions that often do not occur in the field. To address these limitations, we conducted a semi‐field experiment in Athens, Georgia, using the invasive Asian tiger mosquito ( Aedes albopictus ). We selected nine sites that varied in impervious surface and vegetation cover to explore effects of natural variation in microclimate (specifically, temperature, and relative humidity) on mosquitoes. We manipulated conspecific larval density at each site and repeated the experiment in summer and fall to further increase the variability in temperature and relative humidity. We then evaluated the original design features (land cover, larval density, and season), and their interactions, on the mean proportion of females emerging, juvenile development time, size upon emergence, and estimated per capita population growth (i.e., fitness). We found significant effects of larval density, land cover, and season on all response variables, including a non‐intuitive decrease in development time with increasing larval density in fall. We repeated these analyses using the hypothesized microclimate drivers of these effects: temperature and relative humidity. In general, the model using the microclimate variables outperformed the model using land use and season, highlighting the roles of temperature and relative humidity and their interactions with density on mosquito traits and dynamics. Our study demonstrates that ignoring the interaction between variation in biotic (e.g., intraspecific competition) and abiotic (e.g., temperature and relative humidity) variables could reduce the accuracy and precision of models used to predict mosquito population and pathogen transmission dynamics, especially those inferring dynamics at finer spatial scales across which transmission and control occur.

Although corals are highly regenerative, some colonies in reef ecosystems completely recover from sublethal damage while other colonies exhibit partial mortality to similar injuries. To understand factors that might naturally curtail regenerative ability, we experimentally wounded small colonies in three coral genera ( Acropora , Pocillopora , Porites ) by mimicking natural corallivory using scraping (tissue and skeletal damage) or airbrushing (deep tissue removal with no skeletal injury). We found all scraped wounds regenerated rapidly in Acropora and Porites , while Pocillopora fragments frequently retained open lesions. In stark contrast, airbrushing resulted in algal colonization and delayed tissue healing and regeneration across all corals. Detailed cellular analysis of Porites wounds revealed two general phases comprising tissue regeneration: a healing phase defined by rapid coverage of bare skeleton with coenosarc, pigment cells and gastrodermal reformation, and then a second phase lasting one week ending in polyp regeneration. Red fluorescence appeared transiently in scrape wounds but persisted in tissue at the wound margin surrounding algae in airbrush wounds, suggesting that algal occupation of the wound bed inhibits coenosarc healing. Lastly, histological cross-sections of healing airbrush wounds in Porites revealed progressive loss of deep tissue leading to skeletal breakdown beneath the wound. Together, our results demonstrate the biphasic nature of tissue regeneration in colonial corals and provide a framework for understanding how biotic factors impact tissue repair and regeneration in nature.

Coral resilience is increasingly recognized as the product of complex interactions between corals, their endosymbiotic algae and external symbionts such as fishes and invertebrates. While previous studies have documented how coral-associated fishes influence coral growth and thermal tolerance, their role in supporting tissue repair and regeneration following physical injury remains poorly understood. Here, we experimentally test whether coral-associated fishes facilitate wound healing in the coral Pocillopora spp. We imposed small and large wounds and monitored healing in the presence and absence of coral-dwelling damselfishes (Dascyllus flavicaudus). Corals exposed to fishes exhibited faster wound closure and higher photosynthetic efficiency in recently regenerated tissue, particularly for larger wounds. These findings suggest that coral-associated fishes promote the energetic and microenvironmental conditions necessary for tissue repair. Our results extend the emerging understanding of coral holobiont resilience, highlighting the importance of external symbionts in sustaining coral recovery from physical disturbances.

Herbivores play key roles on reefs by consuming algae that compete with corals. Cleaning mutualisms can alter the distribution and feeding behavior of herbivorous fishes and may indirectly affect benthic communities. These dynamics were examined on patch reefs with and naturally without the bluestreak cleaner wrasse, Labroides dimidiatus , in July 2021 in Moorea, French Polynesia (17°28’35.52"S, 149°48’58.35"W) using herbivory assays, fish and benthic community surveys, and behavioral observations of cleaners and the client Ctenochaetus striatus . Herbivory rates on two macroalgae ( Asparagopsis and Sargassum ) were similar between reefs with cleaners present versus absent. Benthic communities were also similar, although turf algae associated with Stegastes damselfish was more abundant on reefs with cleaners. Smaller reefs with cleaners had greater fish abundances than smaller reefs lacking cleaners, though fish community trophic composition was similar between the two reef types. Bite rates for Ctenochaetus striatus were unaffected by cleaner presence, suggesting no foraging tradeoffs associated with cleaning. Rates of different cleaner behaviors (cleaning, cheating, chasing) varied among client trophic groups, with most interactions involving herbivores/detritivores. Moreover, the relative positiveness of cleaner behaviors (i.e., ratio of cleaning to cheating and chasing) was correlated with the difference in the densities of client species between reefs with cleaners present versus absent: i.e., clients with more positive cleaning interactions were more abundant on reefs with cleaners. These results suggest that cleaners did not affect herbivory, and that the hypothesized indirect effects were weak, because cleaner-client interactions were dominated by negative cleaner behaviors, which impeded strong responses of clients.

Meta‐analysis (MA), a powerful tool for synthesizing reported results, is influential in ecology. While ecologists have long been well‐informed on the potential problems associated with nonindependence in experimental work (e.g., pseudoreplication), they have, until recently, largely neglected this issue in MA. However, results used in MAs are likely much more similar when they come from the same locality, system, or laboratory. A simple and common form of nonindependence in MA arises when multiple data points, that is, observed effect sizes, come from the same paper. We obtained original data from 20 published MAs, reconstructed the published analyses, and then, for 14 that had not accounted for a paper effect, used three approaches to evaluate whether within‐paper nonindependence was a problem. First, we found that “nonsense” explanatory variables added to the original analyses were statistically significant ( p < 0.05) far more often than the expected 5% (25%–50% for four nonsense variables). For example, the number of vowels in the first author's name had a significant effect 50% of the time. Second, we found that an added dummy variable, which was randomly assigned at one of two levels, was statistically significant an average of 38% of the time, far exceeding the expected 5%. Even after including a random paper effect in the analyses, there was still an excess of significant results, suggesting that the within‐paper nonindependence was more complex than modeled with the random paper effect. Third, we repeated the original MAs that did not include random paper effects ( n = 14 MAs) but added a random paper effect to each revised analysis. In 12 out of the 14 MAs, an added random effect was statistically significant (indicating group nonindependence that was not accounted for in the original analyses), and often the original inferences were substantially altered. Further, incorporating random paper effects was not a sufficient solution to nonindependence. Thus, problems resulting from nonindependence are often substantial, and accounting for the problem will likely require careful consideration of the details of the potential dependence among observed effect sizes. MAs that do not properly account for this problem may reach unwarranted conclusions.

Debates over whether and how populations are regulated have recently shifted away from detecting and instead towards quantifying the strength of density dependence and its variation among systems. Yet, the degree of variation in density‐dependent mortality and the factors driving this variation remain poorly understood. Here, we conducted a meta‐analysis of 38 reef fish species across 56 studies, which yielded 147 estimates of intraspecific density‐dependent mortality, primarily during early or small life stages. The magnitude of density‐dependent mortality (the increase in the per capita mortality rate due to one fish per unit area of habitat) was surprisingly inconsistent both within and among species. Several factors emerged as drivers of variation. Predators amplified the negative effects of density, and density‐dependent mortality was greater for species that typically colonize at low densities or achieve larger maximum sizes. However, even within a single species, the strength of density‐dependent mortality varied dramatically—often by several orders of magnitude—and sometimes changed sign. This heterogeneity likely reflects multiple processes acting together, including environmental context (e.g., predator density or refuge availability), traits of the focal organism (e.g., size) and methodological differences (e.g., study design) among studies. Our results underscore the need for future efforts to quantify and report ancillary variables and strive to identify how much these factors contribute to population regulation.

Debates over whether and how populations are regulated have recently shifted away from detecting and instead towards quantifying the strength of density-dependence and its variation among systems. Yet, the degree of variation in density-dependent mortality and the factors driving this variation remain poorly understood. Here, we conducted a meta-analysis of 38 reef fish species across 56 studies, which yielded 147 estimates of intraspecific density-dependent mortality, primarily during early or small life stages. The magnitude of density-dependent mortality (the increase in the per capita mortality rate due to one fish per unit area of habitat) was surprisingly inconsistent both within and among species. Several factors emerged as drivers of variation. Predators amplified the negative effects of density, and density-dependent mortality was greater for species that typically colonize at low densities or achieve larger maximum size. However, even within a single species, the strength of density-dependent mortality varied dramatically — often by several orders of magnitude — and sometimes changed sign. This remarkable heterogeneity suggests that environmental variation might overshadow species-specific traits or that methodological variation among studies constrains our ability to perceive drivers. Our results underscore the need for future efforts to identify the factors that drive this variability in population regulation.

Rapid warming could drastically alter host–parasite relationships, which is especially important for fisheries crucial to human nutrition and economic livelihoods, yet we lack a synthetic understanding of how warming influences parasite‐induced mortality in these systems. We conducted a meta‐analysis using 266 effect sizes from 52 empirical papers on harvested aquatic species and determined the relationship between parasite‐induced host mortality and temperature and how this relationship was altered by host, parasite, and study design traits. Overall, higher temperatures increased parasite‐induced host mortality; however, the magnitude of this relationship varied. Hosts from the order Salmoniformes experienced a greater increase in parasite‐induced mortality with temperature than the average response to temperature across fish orders. Opportunistic parasites were associated with a greater increase in infected host mortality with temperature than the average across parasite strategies, while bacterial parasites were associated with lower infected host mortality as temperature increased than the average across parasite types. Thus, parasites will generally increase host mortality as the environment warms; however, this effect will vary among systems.