About

William F. Morris studies the population ecology of plants and insects, including herbivores and pollinators. His current projects focus on the population dynamic consequences of constitutive and inducible resistance in plants, the maintenance of mutualistic interactions between flowering plants and nectar-robbing pollinators, and the use of population-level attributes to detect biotic responses to ongoing environmental changes. Additionally, he employs mathematical models to assess the viability of threatened and endangered populations. His research combines field experiments and mathematical modeling to study population dynamics in natural and managed systems. Since 2006, he has been a Professor of Biology at Duke University, affiliated with the Trinity College of Arts & Sciences. His work also involves understanding how climate-driven disturbances influence population models, the concept of demographic lability in relation to environmental variability, and the effects of climatic versus biotic drivers on plant fitness across ranges. His research is supported by multiple grants, including those from the National Science Foundation, and aims to address critical questions about how environmental changes impact biological populations.

Research topics

• Demography
• Geography
• Computer Science
• Biology
• Ecology
• Statistics
• Environmental science
• Econometrics
• Mathematics
• Algorithm

Selected publications

• Herbarium collections reveal divergent phenological and morphological responses to climate change in carnivorous plants

  SSRN Electronic Journal · 2026-01-01

  preprintOpen accessSenior author
  PublisherDOI

• data for: Climatic vs. biotic drivers effect on fitness varies with range size but not position within range in terrestrial plants

  Figshare · 2026-01-01

  datasetOpen accessSenior author

  full citation for this manuscript is: Allison M. Louthan, Aaron W. Baumgardner, Johan Ehrlén, Johan P. Dahlgren, Alexander K. Loomis, William F. Morris. Climatic vs. biotic drivers effect on fitness varies with range size but not position within range in terrestrial plants. <i>Ecological Monographs</i>all_species_for GBIF: These are data downloaded from GBIF (the Global Biodiversity Information Facility) for all species described in our manuscript. Column names are derived from GBIF records and are described on their website.demographic driver database 2021-5-6: This is a database of all demographic studies used in the paper. Column descriptions are in the excel file.

  PublisherDOI

• Diversifying With Purpose: Relative Vs. Absolute Risk

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access1st authorCorresponding
  PublisherDOI

• Local Adaptation Is Highest in Populations With Stable Long‐Term Growth

  Ecology Letters · 2025-02-01 · 2 citations

  letterOpen access

  Theory suggests that the drivers of demographic variation and local adaptation are shared and may feedback on one other. Despite some evidence for these links in controlled settings, the relationship between local adaptation and demography remains largely unexplored in natural conditions. Using 10 years of demographic data and two reciprocal transplant experiments, we tested predictions about the relationship between the magnitude of local adaptation and demographic variation (population growth rates and their elasticities to vital rates) across 10 populations of a well-studied annual plant. In both years, we found a strong unimodal relationship between mean home-away local adaptation and stochastic population growth rates. Other predicted links were either weakly or not supported by our data. Our results suggest that declining and rapidly growing populations exhibit reduced local adaptation, potentially due to maladaptation and relaxed selection, respectively.

  PublisherOA PDFDOI

• Traits Explain Canopy Tree Occurrence Along Regional Environmental Gradients: A Subset Combine to Be Useful

  Ecology and Evolution · 2025-11-28

  articleOpen access

  ABSTRACT Trait‐Species Distribution Models (trait‐SDM) help to understand the importance of plant strategies to niches, assess their generality across species and provide a path to predicting species distributions from a shortlist of traits. Yet published trait‐environment associations show considerable inconsistency. Region‐scale models may leverage more species, traits, trait ranges and climatic gradients, than at local scales, while retaining biogeographic coherence, which is lost in global compilations. Here we fit trait‐SDMs with six traits using multilevel models for over 90 eucalypt tree taxa. We model presence‐absence in 1 km 2 grid cells which contain multiple survey plots, arrayed along environmental gradients which span 120,000 km 2 , 8°C mean temperature and 900 mm annual precipitation. We found stem sapwood density, bark thickness, seed mass and maximum height were the most influential predictors in a multi‐trait model of environmental responses to temperature, water deficit, soil depth and pH. Combined, they explained 9%–19% of variance between species in environmental responses. We found less support for specific leaf area and leaf size. Species occurred unimodally along environmental gradients. Trait‐environment terms indicated species with dense stems were more likely in drier climates, thicker bark in warmer climates and that both thinner bark and larger seeds increased occurrence in shallow soils. Taller species were more common and more likely to occur towards sites that were warmer and wetter than average along the gradient. Our work has wider implications: trait‐SDMs help to test trait‐based theory about realised niches. Single trait models reflect the maximum potential explanation of niche differentiation by a trait, while multi‐trait models represent integrated phenotypes responding to multidimensional niches. For planning and management, such trait‐SDMs can provide useful predictions of where certain kinds of species occur or could be restored. But they will leave much uncertainty, especially for identifying which particular species occur where.

  PublisherDOI

• What Is Demographic Lability and When Might We Expect to See It?

  The American Naturalist · 2025-07-25 · 1 citations

  article1st authorCorresponding

  AbstractWhen vital rates are convex functions of environmental drivers, temporal variation in those vital rates could increase long-term stochastic fitness (so-called demographic lability). Yet no empirical cases of this phenomenon have yet been documented. We first outline three necessary steps to document lability: estimate how vital rates change with environmental drivers, quantify driver distributions, and compare the fitness effects of variation to a "no-variation" baseline driver value (typically its mean). We then review articles that presented evidence for lability and find that none fully documented it. In addition, we examine for the first time when natural selection would produce adaptive lability de novo, rather than other adaptations to stochastic environments, and we suggest that selection to better exploit the most frequent environmental states may often erode lability. Finally, we consider conditions (including life history "speed," shape of vital rate/environment relationships, and type of environmental driver) that might support lability. We argue that lability is less likely in response to abiotic than biotic drivers but question whether fast and slow life histories differ in their propensity for lability. Our principal aim is to suggest research directions that would put the intriguing idea of demographic lability on a firmer foundation.

  PublisherDOI

• Maximizing muscle deoxygenation during interval training in middle-distance runners

  European Journal of Applied Physiology · 2025-07-24 · 1 citations

  articleOpen access

  Abstract The present study aimed to investigate which of two commonly performed running interval sessions elicited the greatest magnitude of and time spent with elevated muscle deoxygenation in trained middle-distance runners. Thirteen trained middle-distance runners (22.4 ± 3.2 y; 63.1 ± 10.9 kg; n = 9 males) participated in the study. Subjects completed a field-based incremental running test and two interval sessions. The interval sessions comprised a 6 × 1 km and a 15 × 400 m interval session, both with 1 min passive recovery periods. Both sessions were implemented with the aim of achieving the maximal sustainable pace for each repetition, while mean speed, heart rate, RPE, blood lactate concentration and muscle deoxygenation responses were monitored. Mean speed during the interval repetitions was significantly higher during the 400 m intervals (~ 5.63 ± 0.35 m·s −1 vs ~ 5.30 ± 0.28 m·s −1 ; p &lt; 0.001). Both the peak magnitude of muscle deoxygenation (absolute difference ± CI 3.42 ± 2.23%; p = 0.006) and the time spent with values &gt; 60% peak muscle deoxygenation (83.5 ± 66.4 s; p = 0.02) were significantly greater during the 400 m intervals, while the time spent with a heart rate &gt; 90% peak heart rate was significantly longer during the 1 km interval session (570 ± 143, p &lt; 0.001). Despite this, there was no difference in RPE, blood lactate concentration or peak heart rate between sessions. These findings suggest that 1 km intervals may preferentially target central physiologic responses while 400 m intervals may elicit greater peripheral physiological responses in trained middle-distance runners.

  PublisherOA PDFDOI

• Author response for "Increasing Aridity May Threaten the Maintenance of a Plant Defence Polymorphism"

  2024-09-21

  peer-reviewSenior author
  PublisherDOI

• Author response for "Nonlinear life table response experiment analysis: Decomposing nonlinear and nonadditive population growth responses to changes in environmental drivers"

  2024-02-19

  peer-reviewSenior author
  PublisherDOI

• Increasing Aridity May Threaten the Maintenance of a Plant Defence Polymorphism

  Ecology Letters · 2024-12-31 · 2 citations

  articleOpen accessSenior author

  It is unclear how environmental change influences standing genetic variation in wild populations. Here, we characterised environmental conditions that protect versus erode polymorphic chemical defences in Boechera stricta (Brassicaceae), a short-lived perennial wildflower. By manipulating drought and herbivory in a 4-year field experiment, we measured the effects of driver variation on vital rates of genotypes varying in defence chemistry and then assessed interacting driver effects on total fitness (estimated as each genotype's lineage growth rate, λ) using demographic models. Drought and herbivory interacted to shape vital rates, but contrasting defence genotypes had equivalent total fitness in many environments. Defence polymorphism thus may persist under a range of conditions; however, ambient field conditions fall close to the boundary of putatively polymorphic environment space, and increasing aridity may drive populations to monomorphism. Consequently, elevated intensity and/or frequency of drought under climate change may erode genetic variation for defence chemistry in B. stricta.

  PublisherOA PDFDOI

Recent grants

• COLLABORATIVE LTREB RESEARCH: Population- and community-level mechanisms of range limitation in a variable and changing environment

  NSF · $233k · 2007–2013

• LTREB RENEWAL: Collaborative Research: Population- and community-level mechanisms of range limitation in a variable and changing environment

  NSF · $212k · 2012–2019

• Collaborative LTREB Research: How will local adaptation and environmental extremes shape continental-scale changes in species distribution and abundance?

  NSF · $233k · 2018–2025

• LTER Cross-site: Collaborative Research - Assessing the Geographic and Temporal Consistency of Life History and Demographic Patterns: A Long-term, Multi-site Comparison

  NSF · $231k · 2000–2007

• The Balance Between Benefit and Detriment in a Plant-Nectar Robber Mutualism

  NSF · $125k · 1995–1999

Frequent coauthors

• Daniel F. Doak

  University of Colorado System

  49 shared

• Allison M. Louthan

  Kansas State University

  24 shared

• Diego P. Vázquez

  Centro Científico Tecnológico - Mendoza

  22 shared

• Jeanne Altmann

  16 shared

• Brian R. Hudgens

  15 shared

• Nick M. Haddad

  Michigan State University

  15 shared

• Susan C. Alberts

  Duke University

  15 shared

• Marı́a B. Garcı́a

  15 shared

Education

• Ph.D., Zoology

  University of Washington