Nowak, C. M. | Search bioRxiv

bioRxiv2023

Flood-irrigated agriculture mediates climate-induced wetland scarcity for summering sandhill cranes in western North America

Documenting a species extent is often the first step in understanding its ecology and is critical to informing conservation planning. Basic information about species distributions is lacking in many regions of the world, forcing natural resource managers to answer complex ecological questions with incomplete data. Information gaps are compounded by climate change, driving resource bottlenecks that can act as new and powerful demographic constraints on fauna. Here, we reconstructed greater sandhill crane (Antigone canadensis tabida) summering range in western North America using movement data from 120 GPS-tagged individuals to determine how landscape composition shaped their distributions. Landscape variables developed from remotely sensed data were combined with bird locations using cloud computing and machine learning to model distribution probabilities. Additionally, land-use practices and land ownership were summarized within summer range as a measure of use dependence. Wetland variables identified as important predictors of bird distributions were also evaluated in a post hoc analysis using satellite imagery to measure the long-term (1984-2022) effects of climate-driven surface water drying. Wetlands and associated agricultural practices accounted for 1.2% of the summer range but were key predictors of greater sandhill crane occurrence. Bird distributions were patterned primarily by riparian floodplains that concentrated water, wetlands, and flood-irrigated agriculture in otherwise arid and semi-arid landscapes. Findings highlighted the critical role of private lands in greater sandhill crane ecology as they accounted for 78% of predicted distributions. Wetland drying observed in portions of the range from 1984 to 2022 represented an emerging ecological bottleneck that could limit future greater sandhill crane summer range. Study outcomes provide novel insight into the significance of ecosystem services provided by flood-irrigated agriculture that supported nearly 60% of the wetland resources used by birds. Findings suggest greater sandhill cranes function as an umbrella species for agroecology and climate change adaptation strategies seeking to reduce agricultural water use through improved efficiency while also maintaining distinct flood-irrigation practices supporting greater sandhill cranes and other wetland-dependent wildlife. To inform conservation design, we make our wetland and sandhill crane summering distributions publicly available as interactive web-based mapping tools.

systems biology↗

bioRxiv2021

Impact of Variability in Cell Cycle Periodicity on Cell Population Dynamics

The cell cycle consists of a series of orchestrated events controlled by molecular sensing and feedback networks that ultimately drive the duplication of total DNA and the subsequent division of a single parent cell into two daughter cells. The ability to block the cell cycle and synchronize cells within the same phase has helped understand factors that control cell cycle and the properties of each individual phase. Intriguingly, when cells are released from a synchronized state, they do not maintain synchronized cell division and rapidly become asynchronous. The rate and factors that control cellular desynchronization remain largely unknown. In this study, using a combination of experiments and simulations, we investigate the desynchronization properties in cervical cancer cells (HeLa) starting from the G1/S boundary following double-thymidine block. Propidium iodide (PI) DNA staining was used to perform flow cytometry cell cycle analysis at regular intervals of 8 hours, and a custom auto-similarity function to assess the desynchronization and quantify the convergence to asynchronous state. In parallel, we developed a single-cell phenomenological model the returns the DNA concentration across the cell cycle stages and fitted the parameters using experimental data. Simulations of population of cells reveal that the cell cycle desynchronization rate is primarily sensitive to the variability of cell cycle duration within a population. To validate the model prediction, we introduced lipopolysaccharide (LPS) to increase cell cycle noise. Indeed, we observed an increase in cell cycle variability under LPS stimulation in HeLa cells, accompanied with an enhanced rate of cell cycle desynchronization. Our results show that the desynchronization rate of artificially synchronized in-phase cell populations can be used a proxy of the degree of variance in cell cycle periodicity, an underexplored axis in cell cycle research.

systems biology↗