• 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.
  • Selected Publications

    Academic Article

    Year Title Altmetric
    2023 Genome-scale signatures of adaptive gene expression changes in an invasive seaweed Gracilaria vermiculophyllaMolecular Ecology.  32:613-627. 2023
    2023 Non-native hosts of an invasive seaweed holobiont have more stable microbial communities compared to native hosts in response to thermal stressEcology and Evolution.  13. 2023
    2022 Genetic Evidence Supports Species Delimitation of Luidia in the Northern Gulf of MexicoBiological Bulletin.  243:28-37. 2022
    2022 Individuals from non-native populations are stronger and bigger than individuals from native populations of a widespread seaweedBiological Invasions.  24:2169-2180. 2022
    2022 Fungal endophytes vary by species, tissue type, and life cycle stage in intertidal macroalgae 2022
    2022 Native tube-building polychaete prefers to anchor non-native alga over other macrophytesOecologia.  198:967-980. 2022
    2021 Intraspecific diversity and genetic structure in the widespread macroalga Agarophyton vermiculophyllum 2021
    2021 The role of host promiscuity in the invasion process of a seaweed holobiont 2021
    2021 A Subtropical Nudibranch, Polycera hummi (Abbott 1952), Described for the First Time from VirginiaNortheastern Naturalist.  28:N15-N23. 2021
    2021 Founder effects shape linkage disequilibrium and genomic diversity of a partially clonal invaderMolecular Ecology.  30:1962-1978. 2021
    2021 Revisiting the ‘bank of microscopic forms’ in macroalgal-dominated ecosystems 2021
    2021 Using RAD-seq to develop sex-linked markers in a haplodiplontic alga 2021
    2021 Does a complex life cycle affect adaptation to environmental change? Genome-informed insights for characterizing selection across complex life cycleProceedings of the Royal Society B: Biological Sciences.  288. 2021
    2021 Exploring the Genetic Consequences of Clonality in Haplodiplontic TaxaJournal of Heredity.  112:92-107. 2021
    2021 Sex and Asex: A Clonal LexiconJournal of Heredity.  112:1-8. 2021
    2021 The Combined Effect of Haplodiplonty and Partial Clonality on Genotypic and Genetic Diversity in a Finite Mutating PopulationJournal of Heredity.  112:78-91. 2021
    2021 The Contribution of Clonality to Population Genetic Structure in the Sea Anemone, Diadumene lineataJournal of Heredity.  112:122-139. 2021
    2020 Evolutionary Phycology: Toward a Macroalgal Species Conceptual Framework 2020
    2020 To gel or not to gel: differential expression of carrageenan-related genes between the gametophyte and tetasporophyte life cycle stages of the red alga Chondrus crispusScientific Reports.  10. 2020
    2020 Influence of nutrients on ploidy-specific performance in an invasive, haplodiplontic red macroalga 2020
    2020 Genetic diversity of a marine foundation species, Laminaria hyperborea (Gunnerus) Foslie, along the coast of IrelandEuropean Journal of Phycology.  55:310-326. 2020
    2020 A review of subtidal kelp forests in Ireland: From first descriptions to new habitat monitoring techniquesEcology and Evolution.  10:6819-6832. 2020
    2020 How do microbiota associated with an invasive seaweed vary across scales?Molecular Ecology.  29:2094-2108. 2020
    2020 Inbreeding shapes the evolution of marine invertebratesEvolution.  74:871-882. 2020
    2020 What’s ploidy got to do with it? Understanding the evolutionary ecology of macroalgal invasions necessitates incorporating life cycle complexity 2020
    2019 Environmental regulation of individual body size contributes to geographic variation in clonal life cycle expression 2019
    2019 Incorporating Ploidy Diversity into Ecological and Community Genetics 2019
    2019 The Use of Photographic Color Information for High-Throughput Phenotyping of Pigment Composition in Agarophyton vermiculophyllum (Ohmi) Gurgel, J.N.Norris & Fredericq 2019
    2019 Genera of phytopathogenic fungi: GOPHY 3Studies in Mycology.  94:1-124. 2019
    2019 First record of Laminaria ochroleuca Bachelot de la Pylaie in Ireland in Béal an Mhuirthead, county Mayo 2019
    2018 Everywhere you look, everywhere you go, there’s an estuary invaded by the red seaweed Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967BioInvasions Records.  7:343-355. 2018
    2018 Nonnative Gracilaria vermiculophylla tetrasporophytes are more difficult to debranch and are less nutritious than gametophytes 2018
    2018 Combining niche shift and population genetic analyses predicts rapid phenotypic evolution during invasion 2018
    2018 Palatability of an introduced seaweed does not differ between native and non-native populations 2018
    2017 When Invaders Go Unnoticed: The Case of Gracilaria vermiculophylla in the British Isles 2017
    2017 In situ common garden assays demonstrate increased defense against natural fouling in non-native populations of the red seaweed Gracilaria vermiculophylla 2017
    2017 Genetic identification of source and likely vector of a widespread marine invaderEcology and Evolution.  7:4432-4447. 2017
    2016 New record of the non-native seaweed gracilaria parvispora in Baja California - A Note on Vergara-Rodarte et al. (2016) 2016
    2016 Invasion of novel habitats uncouples haplo-diplontic life cyclesMolecular Ecology.  25:3801-3816. 2016
    2016 Editorial 2016
    2016 The importance of effective sampling for exploring the population dynamics of haploid-diploid seaweeds 2016
    2016 Genotypic diversity in a non-native ecosystem engineer has variable impacts on productivity 2016
    2015 O father where art thou" Paternity analyses in a natural population of the haploid-diploid seaweed Chondrus crispusHeredity.  114:185-194. 2015
    2015 Development and characterization of microsatellite loci for the haploid-diploid red seaweed Gracilaria vermiculophyllaPeerJ.  2015. 2015
    2014 Genotyping an Emiliania huxleyi (prymnesiophyceae) bloom event in the North Sea reveals evidence of asexual reproductionBiogeosciences.  11:5215-5234. 2014
    2014 Chondrus crispus - A present and historical model organism for red seaweedsAdvances in Botanical Research.  71:53-89. 2014
    2013 Intergametophytic selfing and microgeographic genetic structure shape populations of the intertidal red seaweed Chondrus crispusMolecular Ecology.  22:3242-3260. 2013
    2013 Reproductive Effort of Mastocarpus papillatus (Rhodophyta) Along the California Coast1 2013
    2011 Genetic population structure and mating system in Chondrus crispus (Rhodophyta) 2011
    2009 On the use of experimental diets for physiological studies of hydrozoans 2009

    Research Overview

  • 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.

    Marine Evolutionary Ecology, Population Genetics, Molecular Ecology, Phycology, Scientific Communication
  • Principal Investigator On

  • CAREER: At the Convergence of Life Cycles and Reproductive Systems: Insights into the Evolutionary Ecology of Sex  awarded by NSF - National Science Foundation
  • Characterizing The Reproductive System in Two Invasive Avrainvillea Populations  awarded by ALABAMA ACADEMY OF SCIENCE - NEW
  • Characterizing the Reproductive System in Two Invasive Avrainvillea Populations  awarded by Phycological Society of America
  • EAGER: Collaborative Research: Developing Tools to Assess the Evolutionary Implications of Partial Clonality in Alpine Snow Algae  awarded by NSF - National Science Foundation
  • Engaging Communities in Biodiversity Monitoring and Evolutionary Ecology of Alabama’s Freshwater Red Macroalgae  awarded by ALABAMA ACADEMY OF SCIENCE - NEW
  • Engaging Community Scientists in Monitoring Freshwater Red Macroalgae  awarded by British Phycological Society
  • Establishing Critical Reproductive System Data for Hypnea Cervicornis Throughout the Hawaiian Archipelago  awarded by Phycological Society of America
  • Exposing Subtle Niche Differentiation Between the Isomorphic Ploidy Stages of Gracilaria Vermiculophylla from Non-Native Fixed and Free-Floating Populations  awarded by THE INTERNATIONAL PHYCOLOGICAL SOCIETY
  • Fungalbase: Combining a Culture Dependent and Independent Approach to Assess the Endophytic Diversity in Different Algal Life History Phases  awarded by Marine Biological Association
  • Incorporating the Ecology and Evolution of Haploid-Diploid Life Cycles into Biodiversity Surveys of Freshwater Red Algae  awarded by HURON MOUNTAIN WILDLIFE FOUNDATION (HMWF)
  • Investigating the Eco-Evolutionary Maintenance of Complex Life Cycles Using Freshwater Red Algae  awarded by Sigma Xi
  • Investigating the Eco-Evolutionary Maintenance of Complex Life Cycles in Freshwater Red Algae  awarded by THE INTERNATIONAL PHYCOLOGICAL SOCIETY
  • Investigating the Eco-Evolutionary Maintenance of Complex Life Cycles in Freshwater Red Macroalgae  awarded by Phycological Society of America
  • Management Solutions to Mitigate the Spread of Chondria tumulosa in Papahanaumokuakea  awarded by COLLEGE OF CHARLESTON
  • RII-Track 1. Ridge to Reef Processes and Interdependent Drivers of Small Island Resilience  awarded by UNIVERSITY OF THE VIRGIN ISLANDS
  • Reproductive System Variation in Fixed and Free-Floating Gracilaria Vermiculophylla Populations  awarded by THE INTERNATIONAL PHYCOLOGICAL SOCIETY
  • Spatiotemporal Adaptation in The Rocky Intertidal: Evolutionary Responses of Intertidal Chondrus Crispus Populations to Climate Change  awarded by Phycological Society of America
  • The Impacts of Climate Change on Mating Systems and Life Cycle Evolution in the Sea. A Case Study of Macroalgae at the Warm Edge of a Fast-Warming Sea  awarded by United States - Israel Binational Science Foundation
  • The Role OF Herbivory In Haploid-Diploid Life Cycle Maintenance  awarded by ALABAMA ACADEMY OF SCIENCE - NEW
  • Ulva Diversity Along the Eastern Shore of Virginia  awarded by THE LINNEAN SOCIETY OF LONDON
  • Understanding the Impacts of the Invasive Alga Chondria to Support Management of Papahanaumokuakea  awarded by COLLEGE OF CHARLESTON
  • Teaching Activities

  • BY245 - Biol Data Interpret & Analysis (Spring Term 2023)
  • BY245 - Fundamental Scientific Invest. (Fall Term 2020)
  • BY245 - Fundamental Scientific Invest. (Summer Term 2020)
  • BY398 - Undergrad Research - RES (Fall Term 2018)
  • BY398 - Undergrad Research - RES (Spring Term 2017)
  • BY398 - Undergrad Research - RES (Spring Term 2018)
  • BY398 - Undergrad Research - RES (Spring Term 2019)
  • BY398 - Undergrad Research - RES (Spring Term 2023)
  • BY429 - Intro to Evolutionary Process (Fall Term 2017)
  • BY429 - Intro to Evolutionary Process (Fall Term 2019)
  • BY429 - Intro to Evolutionary Process (Spring Term 2021)
  • BY468 - Conservation Genetics (Spring Term 2019)
  • BY468 - Conservation Genetics (Spring Term 2020)
  • BY468 - Ecological Genetics (Fall Term 2022)
  • BY491 - Biology Capstone - Evolution (Fall Term 2017)
  • BY491 - Biology Capstone - Evolution (Fall Term 2019)
  • BY491 - Biology Capstone - Evolution (Spring Term 2018)
  • BY491 - Biology Capstone - Evolution (Spring Term 2021)
  • BY495 - Special Topics in Biology (Spring Term 2018)
  • BY555 - Biol Data Interpret & Analysis (Spring Term 2023)
  • BY555 - Prin of Scientific Investig (Fall Term 2020)
  • BY555 - Prin of Scientific Investig (Summer Term 2020)
  • BY595 - Special Topics in Biology I (Summer Term 2020)
  • BY629 - Evolutionary Biology (Fall Term 2017)
  • BY629 - Evolutionary Biology (Fall Term 2019)
  • BY629 - Evolutionary Biology (Spring Term 2021)
  • BY655 - Biometry (Spring Term 2019)
  • BY668 - Conservation Genetics (Spring Term 2019)
  • BY668 - Conservation Genetics (Spring Term 2020)
  • BY668 - Ecological Genetics (Fall Term 2022)
  • BY670 - Scientific Communication (Fall Term 2019)
  • BY678 - Biology Graduate Seminar (Spring Term 2023)
  • BY695 - Special Topics in Biology I (Fall Term 2016)
  • BY695 - Special Topics in Biology I (Fall Term 2022)
  • BY695 - Special Topics in Biology I (Spring Term 2018)
  • BY696 - Special Topics in Biology II (Fall Term 2019)
  • BY696 - Special Topics in Biology II (Spring Term 2023)
  • BY698 - Nonthesis Research (Fall Term 2019)
  • BY698 - Nonthesis Research (Fall Term 2021)
  • BY698 - Nonthesis Research (Fall Term 2022)
  • BY698 - Nonthesis Research (Spring Term 2020)
  • BY698 - Nonthesis Research (Spring Term 2022)
  • BY698 - Nonthesis Research (Spring Term 2023)
  • BY698 - Nonthesis Research (Summer Term 2019)
  • BY698 - Nonthesis Research (Summer Term 2021)
  • BY698 - Nonthesis Research (Summer Term 2022)
  • BY755 - Biometry (Spring Term 2019)
  • BY768 - Conservation Genetics (Fall Term 2018)
  • BY768 - Conservation Genetics (Spring Term 2019)
  • BY770 - Scientific Communication (Fall Term 2019)
  • BY770 - Scientific Communication (Spring Term 2022)
  • BY795 - Special Topics in Biology I (Fall Term 2016)
  • BY795 - Special Topics in Biology I (Spring Term 2018)
  • BY795 - Special Topics in Biology I (Spring Term 2018)
  • BY796 - Special Topics in Biology II (Fall Term 2019)
  • BY798 - Nondissertation Research (Fall Term 2022)
  • BY798 - Nondissertation Research (Spring Term 2019)
  • BY798 - Nondissertation Research (Spring Term 2021)
  • BY798 - Nondissertation Research (Spring Term 2022)
  • BY798 - Nondissertation Research (Spring Term 2023)
  • BY798 - Nondissertation Research (Summer Term 2020)
  • BY798 - Nondissertation Research (Summer Term 2021)
  • BY798 - Nondissertation Research (Summer Term 2022)
  • BY799 - Dissertation Research (Spring Term 2023)
  • Education And Training

  • Doctor of Philosophy in Ecology, Catholic University of Chile 2011
  • Doctor of Philosophy in Ecology, Pierre and Marie Curie University (Paris 6) 2011
  • Master of Sciences or Mathematics in Marine Biology and Biological Oceanography, California State University System : Northridge 2008
  • Bachelor of Science or Mathematics in Environmental Biology, California State University System : Northridge 2006
  • Full Name

  • Stacy Krueger-Hadfield