Biology subjects

Morrison, M. L.

Publications and source records attributed to Morrison, M. L..

8 recordsLinked to original sources

bioRxiv2026

Contrasting effects of forest fragmentation on the genetics and microbiomes of an endangered arboreal primate

Landscape fragmentation, one of the leading drivers of biodiversity loss, can reshape both the genetics and microbiomes of wild populations. Although fragmentation is generally expected to limit gene flow and erode genetic diversity, and to disrupt host-associated microbial communities, these responses arise via different pathways and may therefore diverge within the same population. To understand how fragmentation simultaneously shapes population genetics and gut microbiomes, we analyzed fecal-derived host genomic and microbiome data from endangered, arboreal black howler monkeys (Alouatta pigra) across a fragmentation gradient. We then integrated these data with measures of ecological connectivity, habitat quality, and demography to identify the drivers of genetic and microbiome variation and structure. Multivariate analyses indicated that genetic patterns were shaped by both connectivity and habitat quality, whereas microbiome variation was driven mainly by habitat quality. Contrary to expectations under reduced realized connectivity with increasing isolation, monkeys showed the strongest gene flow signal in the most fragmented region, and higher genetic diversity and lower inbreeding than monkeys in continuous forest. Relatedness and isolation-by-distance patterns suggested that fragmentation has sex-specific effects on movement, disrupting the usual pattern of short-range male dispersal in the most fragmented region. Gut microbiomes, however, showed predicted negative responses to fragmentation: individuals in highly fragmented habitat had lower microbial diversity and compositional shifts consistent with lower-quality diets and increased exposure to disturbed environments. These results show contrasting biological responses to fragmentation within a single population, with genetic patterns likely resulting from compensatory behavioral flexibility and microbiome patterns reflecting local habitat degradation. Our findings underscore the need for conservation assessments that integrate multiple dimensions of population health rather than relying on any single indicator of fragmentation impact.

ecology↗

bioRxiv2026

Latitudinal dependence of stability trends in marine plankton in the Cenozoic

The temporal stability and spatial heterogeneity of global marine ecosystems under changing climates reveal how biodiversity persists or collapses. However, the deep-time evolution of these phenomena remains poorly understood. We reconstructed the stability landscape of pelagic plankton from the Cretaceous-Paleogene extinction to the present. We find that the Cenozoic was a period of punctuated volatility with high turnover post-extinction and during the Late Neogene cooling. Spatially resolved analysis revealed latitude-dependent trends: equatorial regions stabilized over time, whereas polar communities, especially in the Southern Ocean, destabilized. Equatorial regions homogenized from initially high heterogeneity, whereas polar communities showed the opposite pattern, including a latitudinal seesaw of spatial heterogeneity over the past 30 million years. These findings illuminate temporal stability and spatial heterogeneity dynamics across geologic timescales.

paleontology↗

bioRxiv2024

Oxygen is Toxic in the Cold in C. elegans.

Temperature and oxygen are two factors that profoundly affect survival limits of animals; too much or too little of either is lethal. However, both humans and animals can exhibit exceptional survival when oxygen and temperature are simultaneously low. To better understand this apparent synergistic interaction between oxygen and temperature, we assayed the survival of Caenorhabditis elegans in experimental environments at different temperatures and oxygen concentrations. While nematodes cannot survive a day in room air at 2 {degrees}C (cold shock), we found that when oxygen is low, 200-fold less than room air, they can survive this temperature for 48 hours. Consistent with this, we found that worms exposed to high oxygen concentrations, 35 times greater than room air, are more sensitive to low temperature than worms in room air. These results show that normal atmospheric levels of oxygen are toxic in the cold. Using these survival assays, we found that cold acclimatization protects worms from lethal effects of high oxygen, mutations in the cold acclimatization pathway affect oxygen tolerance, and that the naturally occurring and physiologically relevant compounds glucose, manganese (II), and ascorbate improve survival limits in both low temperature and high oxygen when supplied early in life. These results show that the interdependence of temperature and oxygen on survival in C. elegans is based in part on shared physiological mechanisms involved in response to these two environmental stressors. The evolution and natural history of stress responses in animals suggest similar phenomena may function in humans.

physiology↗

bioRxiv2024

Quantifying compositional variability in microbial communities with FAVA

Microbial communities vary across space, time, and individual hosts, presenting new challenges for the development of statistics measuring the variability of community composition. To understand differences across microbiome samples from different host individuals, sampling times, spatial locations, or experimental replicates, we present FAVA, a new normalized measure for characterizing compositional variability across multiple microbiome samples. FAVA quantifies variability across many samples of taxonomic or functional relative abundances in a single index ranging between 0 and 1, equaling 0 when all samples are identical and equaling 1 when each sample is entirely comprised of a single taxon. Its definition relies on the population-genetic statistic FST, with samples playing the role of "populations" and taxa playing the role of "alleles." Its convenient mathematical properties allow users to compare disparate data sets. For example, FAVA values are commensurable across different numbers of taxonomic categories and different numbers of samples considered. We introduce extensions that incorporate phylogenetic similarity among taxa and spatial or temporal distances between samples. We illustrate how FAVA can be used to describe across-individual taxonomic variability in ruminant microbiomes at different regions along the gastrointestinal tract. In a second example, a longitudinal analysis of gut microbiomes of healthy human adults taking an antibiotic, we use FAVA to quantify the increase in temporal variability of microbiomes following the antibiotic course and to measure the duration of the antibiotics influence on microbial variability. We have implemented this tool in an R package, FAVA, which can fit easily into existing pipelines for the analysis of microbial relative abundances. Significance statementStudies of microbial community composition across time, space, or biological replicates often rely on summary statistics that analyze just one or two samples at a time. Although these statistics effectively summarize the diversity of one sample or the compositional dissimilarity between two samples, they are ill-suited for measuring variability across many samples at once. Measuring compositional variability among many samples is key to understanding the temporal stability of a community across multiple time points, or the heterogeneity of microbiome composition across multiple experimental replicates or host individuals. Our proposed measure, FAVA, meets the need for a statistic summarizing compositional variability across many microbiome samples all at once.

ecology↗

bioRxiv2023

Prolonged delays in human microbiota transmission after a controlled antibiotic perturbation

Humans constantly encounter new microbes, but few become long-term residents of the adult gut microbiome. Classical theories predict that colonization is determined by the availability of open niches, but it remains unclear whether other ecological barriers limit commensal colonization in natural settings. To disentangle these effects, we used a controlled perturbation with the antibiotic ciprofloxacin to investigate the dynamics of gut microbiome transmission in 22 households of healthy, cohabiting adults. Colonization was rare in three-quarters of antibiotic-taking subjects, whose resident strains rapidly recovered in the week after antibiotics ended. In contrast, the remaining antibiotic-taking subjects exhibited lasting responses, with extensive species losses and transient expansions of potential opportunistic pathogens. These subjects experienced elevated rates of commensal colonization, but only after long delays: many new colonizers underwent sudden, correlated expansions months after the antibiotic perturbation. Furthermore, strains that had previously transmitted between cohabiting partners rarely recolonized after antibiotic disruptions, showing that colonization displays substantial historical contingency. This work demonstrates that there remain substantial ecological barriers to colonization even after major microbiome disruptions, suggesting that dispersal interactions and priority effects limit the pace of community change.

microbiology↗

bioRxiv2021

FSTruct: An Fst-based tool for measuring ancestry variation in inference of population structure

In model-based inference of population structure from individual-level genetic data, individuals are assigned membership coefficients in a series of statistical clusters generated by clustering algorithms. Distinct patterns of variability in membership coefficients can be produced for different groups of individuals, for example, representing different predefined populations, sampling sites, or time periods. Such variability can be difficult to capture in a single numerical value; membership coefficient vectors are multivariate and potentially incommensurable across groups, as the number of clusters over which individuals are distributed can vary among groups of interest. Further, two groups might share few clusters in common, so that membership coefficient vectors are concentrated on different clusters. We introduce a method for measuring the variability of membership coefficients of individuals in a predefined group, making use of an analogy between variability across individuals in membership coefficient vectors and variation across populations in allele frequency vectors. We show that in a model in which membership coefficient vectors in a population follow a Dirichlet distribution, the measure increases linearly with a parameter describing the variance of a specified component of the membership vector. We apply the approach, which makes use of a normalized FST statistic, to data on inferred population structure in three example scenarios. We also introduce a bootstrap test for equivalence of two or more groups in their level of membership coefficient variability. Our methods are implemented in the R package FSTruct.

evolutionary biology↗

bioRxiv2020

Ten-year projection of white-nose syndrome disease dynamics at the southern leading-edge of infection in North America

Predicting the emergence and spread of infectious diseases is critical for effective conservation of biodiversity. White-nose syndrome (WNS), an emerging infectious disease of bats, has resulted in high mortality in eastern North America. Because the fungal causative agent Pseudogymnoascus destructans is constrained by temperature and humidity, spread dynamics may vary greatly by geography. Environmental conditions in the southern part of the continent, where disease dynamics are typically studied, making it difficult to predict how the disease will manifest. Herein, we modeled the spread of WNS in Texas based on available cave densities and average dispersal distances of species occupying these sites, and projected these results out to 10 years. We parameterized a predictive model of WNS epidemiology and its effects on hibernatory bat populations with observed environmental data from bat hibernation sites in Texas. Our model suggests that bat populations in northern Texas will be more affected by WNS mortality than southern Texas. As such, we recommend prioritizing the preservation of large overwintering colonies of bats in north Texas through management actions. Our model further illustrates that infectious disease spread and infectious disease severity can become uncoupled over a gradient of environmental variation. Finally, our results highlight the importance of understanding host, pathogen and environmental conditions in various settings to elucidate what may happen across a breadth of environments.

ecology↗

bioRxiv2020

Secondhand homes: Woodpecker cavity location and structure influences secondary nester's success.

O_LIUnderstanding how ecosystem engineers influence other organisms has long been a goal of ecologists. Woodpeckers select nesting sites with high food availability and will excavate and then abandon multiple cavities through their lifetime. These cavities are crucial to secondary cavity nesting birds (SCB) that are otherwise limited by the availability of naturally occurring cavities. C_LIO_LIOur study examined the role food resources have on the nest site location and home range size of woodpeckers, and the respective influence woodpeckers and the construction of cavities have on the nesting success of SCB. C_LIO_LIUsing five years of avian point count data to locate golden-fronted woodpeckers (GFWO: Melanerpes aurifrons), we correlated insect availability with GFWO home range size and determined differences in insect availability between GFWO occupied and unoccupied sites, while recording nesting success (success: [≥] 1 fledgling) for the GFWO and common SCB in south Texas: Black-crested Titmouse (Baeolophus atricristatus), Ash-throated Flycatcher (Myiarchus cinerascens), Brown-crested Flycatcher (Myiarchus tyrannulus), and Bewicks Wren (Thryomanes bewickii). We used model averaging to fit species-specific logistic regression models to predict nest success based on cavity metrics across all species. C_LIO_LISites occupied by GFWO had a higher biomass of insects in orders Coleoptera, Hymenoptera, and Orthoptera than unoccupied sites, and there was a negative correlation between the availability of these insect orders and home-range size. GFWO had increased nest success in trees with increased vegetation cover and lower levels of decay, while SCB had higher levels of nesting success in abandoned GFWO cavities opposed to naturally occurring ones, and in trees with low decay. C_LIO_LIOur results suggest that SCB may be drawn to nest in abandoned woodpecker cavities where they have higher rates of nest success compared to natural cavities. Additionally, the prevalence for GFWO to excavate cavities in trees with lower levels of decay contradicts previous literature and may indicate a novel temperature trade-off, with live trees requiring more energy to excavate, but providing more protection from high breeding season temperatures in arid and semi-arid areas. C_LI

ecology↗