Goel N, Keitt TH. Source-sink dynamics can maintain mismatched range and bioclimatic limits even at large spatial scales. bioRxiv [Internet]. Publisher's VersionAbstract
Bioclimatic models assume that at broad spatial scales, climate is the primary determinant of species distribution. Meanwhile, processes such as source-sink dynamics can be ignored because they are thought to manifest at length scales comparable to species mean dispersal distance. We present a reaction-diffusion model to show species can use sink patches near the bioclimatic (or niche) limit as stepping-stones to occupy sinks much further than the mean dispersal distance, thereby extending the distribution far beyond the bioclimatic envelope. This mismatch between geographical and bioclimatic limits is mediated by the shape of the bioclimatic limit and may be significant for low growth sensitivity and fast dispersal life strategy. These findings challenge one of the core assumptions of the bioclimatic models. Therefore, we advocate that biogeographers consider the role of dispersal when using bioclimatic models to generate inferences about the ecological and evolutionary processes that determine the distribution of biota.Competing Interest StatementThe authors have declared no competing interest.
Liebhold AM, Keitt TH, Goel N, Bertelsmeier C. Scale invariance in the spatial-dynamics of biological invasions. NeoBiota [Internet]. 62 :269–277. Publisher's VersionAbstract
Despite the enormous negative consequences of biological invasions, we have a limited understanding of how spatial demography during invasions creates population patterns observed at different spatial scales. Early stages of invasions, arrival and establishment, are considered distinct from the later stage of spread, but the processes of population growth and dispersal underlie all invasion phases. Here, we argue that the spread of invading species, to a first approximation, exhibits scale invariant spatial-dynamic patterns that transcend multiple spatial scales. Dispersal from a source population creates smaller satellite colonies, which in turn act as sources for secondary invasions; the scale invariant pattern of coalescing colonies can be seen at multiple scales. This self-similar pattern is referred to as “stratified diffusion” at landscape scales and the “bridgehead effect” at the global scale. The extent to which invasions exhibit such scale-invariant spatial dynamics may be limited by the form of the organisms' dispersal kernel and by the connectivity of the habitat. Recognition of this self-similar pattern suggests that certain concepts for understanding and managing invasions might be widely transferable across spatial scales.
Schank CJ, Cove MV, Arima EY, Brandt LSE, Brenes-Mora E, Carver A, Diaz-Pulido A, Estrada N, Foster RJ, God{\'ınez-Gómez O, et al. Population status, connectivity, and conservation action for the endangered Baird's tapir. Biological Conservation. 245 :108501. 1-s2.0-s0006320718317890-main.pdf
Fowler N, Keitt T, Schmidt O, Terry M, Trout K. Border wall: bad for biodiversity. Frontiers in Ecology and the Environment. 16 (3) :137-138. fowler_et_al_2018_frontiers_border_wall_letter.pdf
Salas A, Altieri AH, Wilson P, Keitt TH. Predicting the reef acoustic cuescape from the perspective of larval fishes across a habitat quality gradient. MARINE ECOLOGY PROGRESS SERIE. 605 :173-193.Abstract

ABSTRACT: The combined acoustic activity of soniferous organisms living in benthic habitats produces habitat-specific soundscapes, which are predicted to influence fish and invertebrate lar- val behavior during the settlement process. Not every sound will have the amplitude and fre- quency characteristics relative to hearing sensitivity to be used as an acoustic cue, thus the cuescape is a subset of the soundscape. These sounds vary through space and time, and little is known about how this variability could influence their role in settlement. We recorded the sound- scapes of 4 coral reefs in Caribbean Panama for 6 wk and conservatively identified the sounds most likely to compose the cuescapes used by larval fishes. While these sites represented the vari- ation in reef condition across the study area, we observed the same 4 dominant taxa groups emerge as the most likely producers of acoustic cues. These results were consistent across both time and space when compared to short-term recordings taken at these 4 reefs and at an addi- tional 11 sites 2 yr prior. Next, we used an individual-based model to test the relationship between settlement success and the natural spatiotemporal variability we observed in these potential cues. Temporal variation in the sounds resulted in variation in settlement success; however, even short- range, intermittent cues improved the likelihood of settlement. Overall, we observed similar acoustic cuescapes across reefs that varied in condition, suggesting that cuescapes can be resilient to some forms of reef degradation by retaining sounds potentially useful to larval fishes for both navigation and habitat selection.

KEY WORDS: Coral reef · Soundscape · Larval fish · Larval settlement · Acoustics · Modeling · Cues · Fish behavior

Keitt T. Border wall would kill natural treasures and change the environment. The Hill [Internet]. Publisher's Version
Keitt T. thk686/kdtools: cran_0.1.0. [Internet]. Publisher's Version
Dietze MC, Fox A, Beck-Johnson LM, Betancourt JL, Hooten MB, Jarnevich CS, Keitt TH, Kenney MA, Laney CM, Larsen LG, et al. Iterative near-term ecological forecasting: Needs, opportunities, and challenges. Proceedings of the National Academy of Sciences [Internet]. Publisher's VersionAbstract
Two foundational questions about sustainability are “How are ecosystems and the services they provide going to change in the future?” and “How do human decisions affect these trajectories?” Answering these questions requires an ability to forecast ecological processes. Unfortunately, most ecological forecasts focus on centennial-scale climate responses, therefore neither meeting the needs of near-term (daily to decadal) environmental decision-making nor allowing comparison of specific, quantitative predictions to new observational data, one of the strongest tests of scientific theory. Near-term forecasts provide the opportunity to iteratively cycle between performing analyses and updating predictions in light of new evidence. This iterative process of gaining feedback, building experience, and correcting models and methods is critical for improving forecasts. Iterative, near-term forecasting will accelerate ecological research, make it more relevant to society, and inform sustainable decision-making under high uncertainty and adaptive management. Here, we identify the immediate scientific and societal needs, opportunities, and challenges for iterative near-term ecological forecasting. Over the past decade, data volume, variety, and accessibility have greatly increased, but challenges remain in interoperability, latency, and uncertainty quantification. Similarly, ecologists have made considerable advances in applying computational, informatic, and statistical methods, but opportunities exist for improving forecast-specific theory, methods, and cyberinfrastructure. Effective forecasting will also require changes in scientific training, culture, and institutions. The need to start forecasting is now; the time for making ecology more predictive is here, and learning by doing is the fastest route to drive the science forward.
Pen˜a TS, Watson JR, Gonza´lez-Guzma´n LI, Keitt TH. Step-wise drops in modularity and the fragmentationof exploited marine metapopulations. Landscape Ecology [Internet]. Publisher's Version pena-et-al-2017.pdf
Lasky JR, Keitt TH, Weeks BC, Economo EP. A hierarchical model of whole assemblage island biogeography. Ecography [Internet]. :n/a–n/a. Publisher's VersionAbstract

Island systems have long played a central role in the development of ecology and evolutionary biology. However, while many empirical studies suggest species differ in vital biogeographic rates, such as dispersal abilities, quantitative methods have had difficulty incorporating such differences into analyses of whole-assemblages. In particular, differences in dispersal abilities among species can cause variation in the spatial clustering and localization of species distributions. Here, we develop a single, hierarchical Bayes, assemblage-wide model of 252 bird species distributions on the islands of Northern Melanesia and use it to investigate a) whether dispersal limitation structures bird assemblages across the archipelago, b) whether species differ in dispersal ability, and c) test the hypothesis that wing aspect ratio, a trait linked to flight efficiency, predicts differences inferred by the model. Consistent with island biogeographic theory, we found that individual species were more likely to occur on islands with greater area, and on islands near to other islands where the species also occurred. However, species showed wide variation in the importance and spatial scale of these clustering effects. The importance of clustering in distributions was greater for species with low wing aspect ratios, and the spatial scale of clustering was also smaller for low aspect ratio species. These findings suggest that the spatial configuration of islands interacts with species dispersal ability to affect contemporary distributions, and that these species differences are detectable in occurrence patterns. More generally, our study demonstrates a quantitative, hierarchical approach that can be used to model the influence of dispersal heterogeneity in diverse assemblages and test hypotheses for how traits drive dispersal differences, providing a framework for deconstructing ecological assemblages and their drivers.This article is protected by copyright. All rights reserved.

Levy O, Buckley LB, Keitt TH, Angilletta MJ. A dynamically downscaled projection of past and future microclimates. Ecology [Internet]. :n/a–n/a. Publisher's VersionAbstract
Ecological forecasting requires information about the climatic conditions experienced by organisms. Despite impressive methodological and computational advances, ecological forecasting still suffers from poor resolutions of environmental data. Published data comprise relatively few layers of surface climate and suffer from coarse temporal resolution. Hence, models using these data might underestimate heterogeneity of microclimates and miss biological consequences of climatic extremes. Moreover, we currently lack predictions about vegetation cover in future environments, a key factor for estimating the spatial heterogeneity of microclimates and hence the capacity for behavioral thermoregulation. Here, we describe microclimates and vegetation for the past and the future at spatial and temporal resolutions of 36 km (approximately 0.3°) and 1 h, respectively. We used the Weather Research and Forecasting model to downscale published, bias-corrected predictions of a global-circulation model from a resolution of 0.9° latitude and 1.25° (approximately 100 km in latitude and 130 km in longitude). Output from this model was used as input for a microclimate model, which generated temperatures and wind speeds for 1980–1999 and 2080–2099 at various heights, as well as soil temperatures at various depths and shade intensities. We also predicted the percentage of green vegetation and the percentage of shade given the angle of the sun. These data were evaluated using several criteria, each of which shed light on a different aspect of value to researchers. The metadata describe the modeling protocol, microclimate calculations, computer programs, and the evaluation process.This article is protected by copyright. All rights reserved.
Levy O, Buckley LB, Keitt TH, Angilletta MJ. Ontogeny constrains phenology: opportunities for activity and reproduction interact to dictate potential phenologies in a changing climate. Ecology Letters [Internet]. :n/a–n/a. Publisher's VersionAbstract

As global warming has lengthened the active seasons of many species, we need a framework for predicting how advances in phenology shape the life history and the resulting fitness of organisms. Using an individual-based model, we show how warming differently affects annual cycles of development, growth, reproduction and activity in a group of North American lizards. Populations in cold regions can grow and reproduce more when warming lengthens their active season. However, future warming of currently warm regions advances the reproductive season but reduces the survival of embryos and juveniles. Hence, stressful temperatures during summer can offset predicted gains from extended growth seasons and select for lizards that reproduce after the warm summer months. Understanding these cascading effects of climate change may be crucial to predict shifts in the life history and demography of species.

Keitt TH, Addis C, Mitchell D, Salas A, Hawkes CV. Climate change, microbes, and soil carbon cycling. In: Marxsen J, Liebig J Climate Change and Microbial Ecology: Current and Future Trends. Norwich, UK: Caister Academic Press ; pp. 220.Abstract

Microbial responses to climate change will partly control the balance of soil carbon storage and loss under future temperature and precipitation conditions. We propose four classes of response mechanisms that can allow for a more general understanding of microbial climate responses. We further explore how a subset of these mechanisms results in microbial responses to climate change using simulation modeling. Specifically, we incorporate soil moisture sensitivity into two current enzyme-driven models of soil carbon cycling and find that moisture has large effects on predictions for soil carbon and microbial pools. Empirical efforts to distinguish among response mechanisms will facilitate our ability to further develop models with improved accuracy.