Stacy A. Krueger-Hadfield

Virginia Institute of Marine Science

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, asexual reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages si...

Life cycles with a prolonged haploid phase are thought to be correlated with greater rates of selfing and asexual reproduction. In red algae, recent population genetic studies have aimed to test this prediction but have mostly focused on marine species with separate sexes. We characterized the reproductive system of the obligately monoicous (i.e.,...

The freshwater red alga Batrachospermum gelatinosum has a well‐documented distribution spanning historically glaciated and unglaciated eastern North America. This alga has no known desiccation‐resistant propagule; thus, long‐distance dispersal events are likely rare. We predicted strong genetic structure among drainage basins and admixture among si...

The ecological, evolutionary, economic, and cultural importance of algae necessitates a continued integration of phycological research, education, outreach, and engagement. Here, we comment on several topics discussed during a networking workshop— Algae and the Environment —that brought together phycological researchers from a variety of institutio...

Temporal population genetic studies have investigated evolutionary processes, but few have characterized the temporal patterns of reproductive system variation. Yet, temporal sampling may improve our understanding of reproductive system evolution through assessing the relative rates of selfing, outcrossing, and clonality. In this study, we focus on...

Sex is a crucial process that has molecular, genetic, cellular, organismal, and population‐level consequences for eukaryotic evolution. Eukaryotic life cycles are composed of alternating haploid and diploid phases but are constrained by the need to accommodate the phenotypes of these different phases. Critical gaps in our understanding of evolution...

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, uniparental reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblage...

Chlainomonas (Chlamydomonadales, Chlorophyta) is one of the four genera of snow algae known to produce annual pink or red blooms in alpine snow. No Chlainomonas species have been successfully cultured in the laboratory, but diverse cell types have been observed from many field-collected samples, from multiple species. The diversity of morphologies...

The relative frequency of sexual versus asexual reproduction governs the distribution of genetic diversity within and among populations. Most studies on the consequences of reproductive variation focus on the mating system (i.e., selfing vs. outcrossing) of diploid‐dominant taxa (e.g., angiosperms), often ignoring asexual reproduction. Although rep...

Phenology, or seasonal variation in life cycle events, is poorly described for many macroalgal species. We describe the phenology of a non‐native population of Gracilaria vermiculophylla whose thalli are free‐living or anchored by decorating polychaetes to tube caps. At a site in South Carolina, USA, we sampled 100 thalli approximately every month...

Snow algal blooms frequently occur throughout alpine and polar environments during spring and summer months; however, our understanding of bloom dynamics is limited. We tracked a recurrent bloom of Chlainomonas sp. on Upper Bagley Lake in the North Cascade Mountains, USA, to assess the spatiotemporal dynamics in bloom color intensity, community pho...

Rhodophyta (or red algae) are a diverse and species‐rich group that forms one of three major lineages in the Archaeplastida, a eukaryotic supergroup whose plastids arose from a single primary endosymbiosis. Red algae are united by several features, such as relatively small intron‐poor genomes and a lack of cytoskeletal structures associated with mo...

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae...

The analysis of biological and ecological traits has a long history in evolutionary and ecological research. However, trait data are often scattered and standardised terminology that transcends taxonomic and biogeographical context are generally missing. As part of the development of a global trait database of marine species, we collated trait info...

Meiosis and syngamy generate an alternation between two ploidy stages, but the timing of these two processes varies widely across taxa, thereby generating life cycle diversity. One hypothesis suggests that life cycles with long-lived haploid stages are correlated with selfing, asexual reproduction, or both. Though mostly studied in angiosperms, sel...

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae...

Seaweeds are colonized by a microbial community, which can be directly linked to their performance. This community is shaped by an interplay of stochastic and deterministic processes, including mechanisms which the holobiont host deploys to manipulate its associated microbiota. The Anna Karenina principle predicts that when a holobiont is exposed t...

The genus Ludwigia L. section Jussiaea is composed of a polyploid species complex with 2x, 4x, 6x and 10x ploidy levels, suggesting possible hybrid origins. The aim of the present study is to understand the genomic relationships among diploid and polyploid species in the section Jussiaea. Morphological and cytogenetic observations, controlled cross...

Seaweeds are colonized by a microbial community which can be directly linked to their performance. This community is shaped by an interplay of stochastic and deterministic processes, including mechanisms which the holobiont host deploys to manipulate its associated microbiota. The Anna Karenina Principle predicts that when a holobiont is exposed to...

Abstract Invasive species can successfully and rapidly colonize new niches and expand ranges via founder effects and enhanced tolerance towards environmental stresses. However, the underpinning molecular mechanisms (i.e., gene expression changes) facilitating rapid adaptation to harsh environments are still poorly understood. The red seaweed Gracil...

The analysis of biological and ecological traits has a long history in evolutionary and ecological research. However, trait data are often scattered and standardised terminology that transcends taxonomic and biogeographical context are generally missing. As part of the development of a global trait database of marine species, we collated trait info...

Invasive species can successfully and rapidly colonize new niches and expand ranges via founder effects and enhanced tolerance towards environmental stresses. However, the underpinning molecular mechanisms (i.e., gene expression changes) facilitating rapid adaptation to harsh environments are still poorly understood. The red seaweed Gracilaria verm...

Accurate species delimitation is crucial to understanding biodiversity. In the northern Gulf of Mexico, recent genetic evidence has suggested that the tricolor Luidia lawrencei is not a species distinct from the gray Luidia clathrata. We collected Luidia specimens from Apalachee Bay, Florida, and morphologically identified 11 as L. clathrata and 16...

Many species introduced to non-native regions undergo profound phenotypic change, but conflicting evidence remains on the frequency of such trait differentiation. Here, we describe two phenotype categories—biomechanical material properties and organismal size—that differ between and within native Japanese and non-native North America and Europe sho...

Novel facultative mutualisms that develop between native and non-native ecosystem engineers can lead to the retention of the non-native partner. In some cases, behavior plays an additional, but less understood, role in the development and persistence of mutualisms. In soft-sediment marine habitats along the western Atlantic, the native decorator wo...

Whereas fungal symbionts of terrestrial plants are among the most widespread and well-studied symbioses, relatively little is known about fungi that are associated with macroalgae. To fill the gap in marine fungal taxonomy, we combined simple culture methods with amplicon sequencing to characterize the fungal communities associated with three brown...

Complex life cycles, in which discrete life stages of the same organism differ in form or function and often occupy different ecological niches, are common in nature. Because stages share the same genome, selective effects on one stage may have cascading consequences through the entire life cycle. Theoretical and empirical studies have not yet gene...

Single‐gene markers, such as the mitochondrial cox1, microsatellites, and single nucleotide polymorphisms are powerful methods to describe diversity within and among taxonomic groups and characterize phylogeographic patterns. Large repositories of publicly‐available, molecular data can be combined to generate and evaluate evolutionary hypotheses fo...

Partial clonality is known to affect the genetic composition and evolutionary trajectory of diplontic (single, free-living diploid stage) populations. However, many partially clonal eukaryotes exhibit life cycles in which somatic development occurs in both haploid and diploid individuals (haplodiplontic life cycles). Here, we studied how haplodiplo...

The genomic variation of an invasive species may be affected by complex demographic histories and evolutionary changes during the invasion. Here, we describe the relative influence of bottlenecks, clonality, and population expansion in determining genomic variability of the widespread red macroalga Agarophyton vermiculophyllum. Its introduction fro...

Partially clonality is an incredibly common reproductive mode found across all the major eukaryotic lineages. Yet, population genetic theory is based on exclusive sexuality or exclusive asexuality, and partial clonality is often ignored. This is particularly true in haplodiplontic eukaryotes, including algae, ferns, mosses, and fungi, where somatic...

Ecological and evolutionary processes differ depending on how genetic diversity is organized in space. For clonal organisms, the organization of both genetic and genotypic diversity can influence the fitness effects of competition, the mating system, and reproductive mode, which are key drivers of life cycle evolution. Understanding how individual...

Invasive species are co-introduced with microbiota from their native range and also interact with microbiota found in the novel environment to which they are introduced. Host flexibility toward microbiota, or host promiscuity , is an important trait underlying terrestrial plant invasions. To test whether host promiscuity may be important in macroal...

The bacteria found on and inside animals can play important roles in the health and function of the host individual. However, the factors that control which species colonize a host are complex. In this study, we investigated the effect of environmental stress on the composition of the bacterial community associated with the sea anemone Diadumene li...

Organisms across the tree of life have complex life cycles that include both sexual and asexual reproduction or that are obligately asexual. These organisms include ecologically dominant species that structure many terrestrial and marine ecosystems, as well as many pathogens, pests, and invasive species. We must consider both the evolution and main...

Theoretical ecological models, such as succession and facilitation, were defined in terrestrial habitats, and subsequently applied to marine and freshwater habitats in intertidal and then subtidal realms. One such model is the soil seed bank, defined as all viable seeds (or fruits) found near the soil surface that facilitate community restoration/r...

For many taxa, including isomorphic haplodiplontic macroalgae, determining sex and ploidy is challenging, thereby limiting the scope of some population demographic and genetic studies. Here, we used double digest restriction site‐associated DNA sequencing (ddRAD‐seq) to identify sex‐linked molecular markers in the widespread red alga Agarophyton ve...

The AdjustaDepth TechnoEconomic Analysis was prepared by Mark E. Capron PE, Co-PI, under the direction of Kelly Lucas, PhD, PI and submitted April 3, 2019 to U.S. Department of Energy ARPA-E under Phase 1 Contract DE-AR0000916. Its 33 tabs present the cost and yield projections for growing Gracilaria tikvahiae in the Gulf of Mexico. It can be adapt...

Species concepts formalize evolutionary and ecological processes, but often conflict with one another when considering the mechanisms that ultimately lead to species delimitation. Evolutionary biologists are, however, recognizing that the conceptualization of a species is separate and distinct from the delimitation of species. Indeed, if species ar...

Chondrus crispus is a marine red alga with sulfated galactans, called carrageenans, in its extracellular matrix. Chondrus has a complex haplodiplontic life cycle, alternating between male and female gametophytes (n) and tetrasporophytes (2n). The Chondrus life cycle stages are isomorphic; however, a major phenotypic difference is that carrageenan c...

Aim Kelp forests worldwide are important marine ecosystems that foster high primary to secondary productivity and multiple ecosystem services. These ecosystems are increasingly under threat from extreme storms, changing ocean temperatures, harvesting, and greater herbivore pressure at regional and global scales, necessitating urgent documentation o...

Communities are shaped by scale dependent processes. To study the diversity and variation of microbial communities across scales, the invasive and widespread seaweed Agarophyton vermiculophyllum presents a unique opportunity. We characterized pro‐ and eukaryotic communities associated with this holobiont across its known distribution range, which s...

Worldwide, kelp populations are stressed by warming, increased storms and other anthropogenic disturbances. Marine population distributions are projected to retreat poleward with climate change if they cannot adapt to changing conditions, which would potentially lead to a regime shift in subtidal habitats. In Northern Europe, Laminaria hyperborea i...

Worldwide, macroalgae have invaded near‐shore marine ecosystems. However, their haplodiplontic life cycles have complicated efforts to predict patterns of growth and spread, particularly since most theoretical predictions are derived from diplontic taxa (i.e., animals). To complete one revolution of the life cycle, two separate ploidy stages, often...

Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of non‐random mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focu...

Abstract Background During a biodiversity survey of Béal an Mhuirthead, Co. Mayo, a small population of Laminaria ochroleuca Bachelot de Pylaie was discovered in a semi-protected cove on the northwest part of the headland among a mixed macroalgal assemblage including the kelps Laminaria digitata and Saccharina latissima. This is the first record of...

Clonal behavior has been hypothesized to provide an escape from allometric metabolic scaling that limits the maximum mass achieved by a single individual. Here, we demonstrate the capacity of a wide-spread, non-native sea anemone to buffer its colony biomass accumulation rate across environments by modulating ramet body size through environmentally...

Pigment variation within and among algal species may have important ecological consequences because small changes in the concentration and composition of pigments can influence the photosynthetic efficiency and rate as well as the spectra of light utilized. Toward the goal of developing a rapid method for comparing pigment composition among algal t...

Biological invasions represent grave threats to terrestrial, aquatic, and marine ecosystems, but our understanding of the role of evolution during invasions remains rudimentary. In marine environments, macroalgae account for a large percentage of invaders, but their complicated life cycles render it difficult to move methodologies and predictions w...

Studies in ecological and community genetics have advanced our understanding of the role of intraspecific diversity in structuring communities and ecosystems. However, in near‐shore marine communities, these studies have mostly been restricted to seagrasses, marsh plants, and oysters. Yet, macroalgae are critically important ecosystem engineers in...

p>This paper represents the third contribution in the Genera of Phytopathogenic Fungi (GOPHY) series. The series provides morphological descriptions, information about the pathology, distribution, hosts and disease symptoms for the treated genera, as well as primary and secondary DNA barcodes for the currently accepted species included in these. Th...

AdjustaDepth Project was funded by the U.S. Department of Energy Advanced Research Projects Agency - Energy to design an artificial reef system for growing and harvesting seaweed for advanced sustainable biofuels. The team discovered that the system grows more seaweed per hectare when it is part of a complete ecosystem with shellfish, finfish, and...

Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967 is a red alga native to the northwest Pacific, but over the last 100 years, this ecosystem engineer has invaded estuaries throughout the Northern Hemisphere. Despite previous studies documenting populations in estuarine habitats in British Columbia, California, and Baja California, our knowledge of...

The US Department of Energy Advanced Research Projects Agency-Energy (ARPA-E) MacroAlgae Research Inspiring Novel Energy Research (MARINER) program is encouraging technologies for the sustainable harvest of large funding research of macroalgae for biofuels at less than $80 per dry metric ton (DMT). The Ocean Forests team, led by the University of S...

Theory predicts that the maintenance of haplodiplontic life cycles requires ecological differences between the haploid gametophytes and diploid sporophytes, yet evidence of such differences remain scarce. The haplodiplontic red seaweed Gracilaria vermiculophylla has invaded the temperate estuaries of the Northern Hemisphere, where it commonly modif...

Flora marina Antarctica: patrimonio de biodiversidad Iván Gómez Ocampo Ediciones Kultrún, Valdivia, Chile, 2015. ISBN: 978-956-344-058-4, 243 pp. [To purchase, contact Dr Humberto E. Gonzalez at hgonzale@uach.cl] - Stacy A. Krueger-Hadfield

Generalist consumers potentially limit introduced prey populations when they are willing and able to consume those prey, but because generalist consumers vary in feeding preference, they are not equally effective in resisting invasions. Previous work suggested that during the introduction of the red seaweed Gracilaria vermiculophylla to North Ameri...

Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967 is a red alga native to the northwest Pacific, but over the last 100 years, this ecosystem engineer has invaded estuaries throughout the Northern Hemisphere. Despite previous studies documenting populations in estuarine habitats in British Columbia, California, and Baja California, our knowledge of...

Our knowledge of non-native algae in benthic estuarine habitats is relatively poor, especially compared to algal introductions along open shores or on floating structures. Gracilaria vermiculophylla is a widespread macroalgal invader in the temperate estuaries of the Northern Hemisphere, and, here, we expand its documented range within northeastern...

The susceptibility of native and non-native populations of the red alga Gracilaria vermiculophylla to fouling was compared in common garden experiments. Native and non-native algae were enclosed into dialysis membrane tubes, and the tubes were exposed to natural fouling. Fouling on the outside of the tubes was mediated by chemical compounds excrete...

The identification of native sources and vectors of introduced species informs their ecological and evolutionary history and may guide policies that seek to prevent future introductions. Population genetics provides a powerful set of tools to identify origins and vectors. However, these tools can mislead when the native range is poorly sampled or f...

Genetic sequence data allows for the identification of previously imperceptible cryptic species. Cryptic species are common in algae that have few morphologically distinguishable features. Identifying cryptic species with asexual life cycles requires consideration of whether the biology of the algae meets the assumptions of the analysis used to del...

The delimitation of species in the Gracilariales is often difficult due to the lack of diagnostic morphologicalcharacters. As aresult, non-native species are often misidentified without the use of moleculartools. Recently, studies have investigated the agar quality of the dominant gracilarioids pecies in the Laguna San Ignacio in Baja Califronia Su...

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