Stacy A. Krueger-Hadfield headshot.

Stacy A. Krueger-Hadfield

Assistant Professor
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Campbell Hall 244A
(205) 934-6034

Research and Teaching Interests: Marine Evolutionary Ecology, Population Genetics, Molecular Ecology, Phycology, Scientific Communication

Office Hours: By appointment


  • B.S., California State University Northridge, Environmental Biology
  • M.S., California State University Northridge, Marine Biology
  • Ph.D., Pontificia Universidad Católica de Chile, Marine Ecology
  • Ph.D., Université de Pierre et Marie Curie Sorbonne Universités, Molecular Ecology/Phycology

I grew up in the San Fernando Valley in southern California. Regular trips to the seaside and tide pools along the central coast and Monterey Bay engendered a lifelong interest in marine biology. As an undergraduate I developed a keen interest in marine macroalgae, particularly mating system variation. Mating systems (i.e., which individuals exchange gametes) exert strong influence on the evolutionary ecology of a species. Though they have been extensively studied in plants and animals, we know very little about these patterns in organisms with more complex life cycles, such as marine macroalgae.

I was fortunate to be able to hone my algal affinities further as a Sally Casanova Pre-Doctoral Fellow at the Station Biologique de Roscoff. I had the opportunity to work with the laboratory led by Myriam Valero, one of the world leaders investigating mating systems in the marine environment with an emphasis on ecologically and economically important seaweeds. After my fellowship, I was the recipient of a French PhD fellowship and embarked on a co-tutelle dissertation where I was able to conduct research along the coasts of Brittany and in Juan Correa’s laboratory in Santiago, Chile. My years as Ph.D. student enabled me to work at one of the best marine stations in the world, but also fulfill a childhood dream of traveling and living in Europe and South America.

After completing my Ph.D., I embarked upon two post-doctoral appointments. The first was just across the English Channel in Plymouth at the Marine Biological Association of the United Kingdom. I became interested in the impacts of the biological invasions on mating system patterns using ascidians (or sea squirts) as models. At the same time I began working on microalgal population structure and adapting the tools and techniques that work readily in macroscopic organisms to these teeny tiny algae in the open ocean. In 2013, I moved back to the United States where I was one of the leaders of a large, collaborative project with colleagues at the College of Charleston, GEOMAR (Kiel, Germany), Station Biologique de Roscoff (France), and several Japanese universities (Kagoshima University, Tohoku University, Hokkaido University, and Fukui Prefectural University) investigating genetic adaptation during biological invasions.

In 2014, I became a regular contributor to the blog The Molecular Ecologist (TME) in which I write weekly shorts (and sometimes longer posts — see this post on my journey to becoming a marine biologist) on the latest in molecular ecology. As I began working with my fellow contributors, I became more interested in scientific communication, both among other scientists in different disciplines and with the general public. In addition to my role as a blogger at TME, I have also gotten involved in other outreach for the classroom to bridging the gap between science and art. I am looking forward to continuing and expanding these programs at UAB and in Birmingham.

Research Interests

I am excited to build my laboratory and expand the hypotheses and models with which I have had the privilege to investigate. I am a marine evolutionary ecologist with an international reputation for improving our understanding of the impacts of seascapes and complex life cycle on marine population dynamics. In a broader context, the majority of my work utilizes organisms integral to global processes, such as primary production. I draw on my experience as both a field and molecular ecologist using natural history, manipulative field experiments and population genetic and genomic approaches to study a suite of marine biodiversity (e.g., invertebrates, ascidians, algae) and habitats (e.g., temperate rocky shores, mudflats, open ocean). I am looking forward to delving into adapting new molecular tools for organisms with complex life cycles to enable the study of genetic and phenotypic patterns in natural populations.

My research can be broadly defined by three, interwoven themes:

  • Connectivity: What are the patterns of gene flow across habitats and species? Population connectivity is central to marine ecosystem resilience. Unlike terrestrial ecosystems in which the subfield of landscape genetics is more advanced, there are severe knowledge gaps in the understanding of marine genetic structure. In the past few years, seascape genetics (the marine equivalent to landscape genetics) has made great strides in describing gene flow in the sea hitherto considered to be stochastic due to non-linear relationships between geographic distances and genetic differentiation. Comparatively little research has focused on the seascape genetics of organisms with more complex life cycles in which there are two free-living stages differing in ploidy levels. One of the major hallmarks of my research is the study of haploid-diploid algal population structure and gene flow. Marine algae are fundamental components of the global ecosystem through diverse processes, such as primary production, carbon transport, and the formation of three-dimensional structure and complexity in near-shore marine communities.
  • Life History Evolution: What factors underlie the maintenance of haploid-diploidy? My research provides evidence of metapopulation dynamics within the intertidal shorescape with core and marginal population dynamics, highlighting the role of marginal, high shore populations in the adaptive potential of these species to increasing environmental stress scenarios. For example, though sexual reproduction connects the haploid and diploid phases regardless of tidal height in the red seaweed Chondrus crispus, the pathogenic, endophytic alga Ulvella operculata may underlie the maintenance of haploid-diploidy. My dissertation was the first to demonstrate increased infection rates in male versus female gametophytes (with potential implications for the reproductive mode and mating system) as well as the correlation of infection rates with haploid-diploid ratios. Recently, I led a study in which the haploid-diploid life cycle was completely uncoupled during the invasion of novel habitats in the ubiquitous marine invader Gracilaria vermiculophylla. During the invasion of the Northern Hemisphere, this seaweed was primarily introduced to soft-bottomed habitats in which hard substratum is rare. Therefore, spores cannot easily recruit to the population. As a consequence, introduced populations have lost the free-living haploid stage.
  • Impact of Global Change on Marine Populations: How do populations respond to environmental perturbations? Over the course of the 20th century, sea levels rose in elevation, became warmer and more acidic, and biological invasions increased. These physical changes will continue to accelerate, significantly altering both near-shore and open-ocean ecosystems. It is difficult to ascertain whether marine populations will decline, experience range changes (e.g., shift poleward), or adapt in response to changing environmental conditions. I explore the impacts of environmental perturbations on marine populations using several approaches: (i) microevolutionary responses to climate change, (ii) macroecology, and (iii) biological invasions. I use models ranging from single-celled microalgae to ascidians (or sea squirts) to explore how global change will impact population dynamics in the marine environment.

Recent Courses

  • BY 695/BY 795: Scientific Communication

Select Publications

Academic Distinctions and Professional Societies

  • British Phycological Society
  • Phycological Society of America
  • Society for the Study of Evolution