Biology subjects

Searcy, C. A.

Publications and source records attributed to Searcy, C. A..

6 recordsLinked to original sources

bioRxiv2026

Do microbial effects on hosts vary across life stage and vitalrate?

Interactions with microbial symbionts are widespread and can influence host fitness through effects on survival, growth, and reproduction. Demographic and evolutionary theory suggests that symbiont effects on components of host fitness should often vary in strength and even in direction as host and symbiont allocate limited resources. Through a meta-analysis of 1,736 host-symbiont effect size measurements, we evaluated how commonly the direction of symbiont effects varies across host life history stages and vital rates, and whether these effects across stages and vital rates differ across taxa. Contrary to our prediction, we found that, compared to a null expectation, published effects on host vital rates more often occurred consistently in the same direction, rather than in opposition. This finding suggests that symbiosis often provides benefits to host performance that manifest across vital rates. While the direction of symbiotic effect was often consistent, the magnitude of effects differed across fitness components and across host taxonomic groups, highlighting diverse demographic mechanisms by which symbiosis can influence host fitness. For hosts in the Poaceae family, we also found that effects of symbiosis varied across symbiont type: vertically-transmitted Epichloe fungi most strongly benefited seed germination, while the benefits of mycorrhizal fungi and bacterial endophytes were stronger for adult growth and reproduction. Importantly, this literature survey also highlights gaps in the current literature on host-microbe symbiosis. Most studies measure growth during juvenile stages for taxa from iconic, well-studied symbioses. Meta-analytic estimates of symbiotic effects on host life history provide a path towards quantitatively modeling host-symbiont demography across the tree of life.

ecology↗

bioRxiv2026

Mutualistic microbes drive niche expansion yet constrain diversification

Mutualistic interactions are widely hypothesized to expand ecological niches and promote diversification, yet evidence for this relationship at macroevolutionary scales remains limited. Here, we investigate how fungal seed endophytes (Epichloe) influence niche breadth and diversification across over 100 species of the globally-distributed grass genus Poa. Combining global-scale climate, environmental, phylogenetic, and symbiosis data, we constructed species distribution models for suites of symbiotic and non-symbiotic plant species, then used a range of phylogenetic comparative methods to assess the influence of these symbionts on niche breadth, niche breadth evolution, and diversification. Endophyte-positive species had [~]1.4 times broader primary niche axes (most often associated with temperature tolerances), [~]2.5 times larger geographic ranges, and >30 times faster rates of niche breadth evolution than non-symbiotic species. Endophytic plants also had significantly drier climate centroids, consistent with endophyte-mediated drought tolerance, while simultaneously showing constraints along specific niche dimensions. Despite pronounced niche expansion, hidden state speciation and extinction models revealed two modes of diversification: endophytes decrease diversification rates in young lineages, and have a neutral effect in older lineages. Together, our results demonstrate that mutualists can enhance ecological flexibility while simultaneously constraining macroevolutionary outcomes, revealing a decoupling of niche expansion and diversification, and highlighting the complex role of symbiosis in shaping host evolutionary trajectories.

evolutionary biology↗

bioRxiv2025

The microbial landscape: soil microbiome properties predict plant species distributions

Plant species distributions are shaped by interactions with the abiotic and biotic environment. Despite the known importance of soil microbiomes in shaping plant diversity and function, no study has explicitly determined the ability of the soil microbiome to predict plant species distributions at large scales. We employed paired above- and belowground surveys of plant occurrence and soil microbial taxa and functions across habitat patches (n = 676), applying machine-learning-based distribution modeling to identify the relative influence of the soil microbiome and environmental attributes in predicting plant species (n = 50) distributions across the landscape. We discovered that while abiotic gradients of known importance in this ecosystem were the strongest predictors of many plant species distributions, microbial predictors could have similar or greater influence. Microbiome predictors were collectively more important than abiotic environmental variables for 38% of plant species in this study and explained >70% of the predicted distribution for one species. We identified four microbiome attributes of landscape-scale importance for predicting plant species distributions including prokaryotic richness, fungal richness, the abundance of fungal pathogens, and the abundance of prokaryotic phosphate transport genes in soil. Our findings reveal a previously underappreciated role of the soil microbiome in shaping plant species distributions at a landscape scale, with implications for plant community structure in the context of both ecosystem restoration and future global change.

ecology↗

bioRxiv2025

Climate variability disrupts mutualism-driven increases in population persistence

Understanding how species interactions impact population dynamics and long-term persistence over broad temporal and spatial scales is crucial for predicting species distributions and responses to global change. Here, we integrate range-wide field surveys of [~]90 grass host populations spanning 13 years with demographic modeling based on six-year common garden experiments conducted across the host range to demonstrate that mutualistic fungal endophytes promote population-level persistence and growth of their native host grass across its distribution, with non-mutualistic populations four times more likely to go locally extinct. Despite providing population-level benefits, endophyte prevalence declined eight-fold more in historically mutualistic populations that experienced high climate variability. Thus, mutualisms can underpin population persistence and buffer hosts against environmental stress, but may themselves be vulnerable to global change, with concerning implications for long-term population viability and, ultimately, species distributions under an increasingly uncertain climate.

ecology↗

bioRxiv2024

50-year fire legacy regulates soil microbial carbon and nutrient cycling responses to new fire

Fire disturbances are becoming more common, more intense, and further-reaching across the globe, with consequences for ecosystem functioning. Importantly, fire can have strong effects on the soil microbiome, including community and functional changes after fire, but surprisingly little is known regarding the role of soil fire legacy in shaping responses to recent fire. To address this gap, we conducted a manipulative field experiment administering fire across 32 soils with varying fire legacies, including combinations of 1-7 historic fires and 1-33 years since most recent fire. We analyzed soil metatranscriptomes, determining for the first time how fire and fire legacy interactively affect metabolically-active soil taxa, the microbial regulation of important carbon (C), nitrogen (N) and phosphorus (P) cycling, expression of carbohydrate-cycling enzyme pathways, and functional gene co-expression networks. Experimental fire strongly downregulated fungal activity while upregulating many bacterial and archaeal phyla. Further, fire decreased soil capacity for microbial C and N cycling and P transport, and drastically rewired functional gene co-expression. Perhaps most importantly, we highlight a novel role of soil fire legacy in regulation of microbial C, N, and P responses to recent fire. We observed a greater number of functional genes responsive to the interactive effects of fire and fire legacy than those affected solely by recent fire, indicating that many functional genes respond to fire only under certain fire legacy contexts. Therefore, without incorporating fire legacy of soils, studies will miss important ways that fire shapes microbial roles in ecosystem functioning. Finally, we showed that fire caused significant downregulation of carbon metabolism and nutrient cycling genes in microbiomes under abnormal soil fire histories, producing a novel warning for the future: human manipulation of fire legacies, either indirectly through global change-induced fire intensification or directly through fire suppression, can negatively impact soil microbiome functional responses to new fires.

ecology↗

bioRxiv2024

Linear infrastructure drives biotic homogenization among bird species of a tropical dry forest

Linear infrastructures (LIs) such as roads, railroads, and powerlines are expanding rapidly around the globe. While most future developments are projected to take place in tropical regions, available information on impacts of LIs is biased towards single species studies of solely road impacts in temperate regions. Therefore, we investigated impacts of three types of LIs (road, railroad, and powerline) on the bird community of a tropical dry forest. Point-count surveys to record avian richness and abundance were conducted at 80 plots that were spatially stratified to include sites proximate to all possible LI combinations. Five measures of vegetation structure were collected at each plot as well. We then assessed the relationship between the bird community (i.e., richness, abundance, composition) and distance to each LI type while accounting for variation in vegetation structure. Species richness and abundance both declined significantly (25% and 20%, respectively) from edge habitat next to railroad to interior forest plots, while community composition was significantly altered by the distance to all three LIs. Road and railroad (both forms of dynamic infrastructure with moving vehicles) had similar effects on the bird community that contrasted with those of powerline (a type of static infrastructure). The resulting ordination reveled that Sri Lankan endemics are significantly disfavored by LI proximity, while the three species most often found proximal to LIs all have naturalized populations across the world. Our results emphasize that LI drive biotic homogenization by favoring generalist species at the expense of unique elements of the biota.

ecology↗