About

Alexandra Bely is a professor in the Department of Biology at the University of Maryland and serves as the Director of the Biology Honors Program. Her research interests focus on the evolution of regeneration and asexual reproduction, invertebrate biology, and freshwater biology. She has a background in general biology from the University of Maryland, College Park, and earned her Ph.D. in Ecology and Evolution from the State University of New York-Stony Brook, where she was advised by Gregory Wray. Following her doctoral studies, she completed a postdoctoral fellowship at the University of California–Berkeley in the Department of Molecular and Cell Biology under the supervision of David A. Weisblat. Her work involves studying the biology of invertebrates, particularly annelids, with an emphasis on regeneration, agametic reproduction, and cellular diversity. Bely has contributed to understanding the physiology of regeneration in invertebrates, the evolutionary pathways to carnivory in meiofaunal annelids, and the cellular origins of adult cell types in annelids. Her research integrates aspects of ecology, evolution, and developmental biology, and she is actively involved in advancing knowledge in these fields through her publications and academic leadership.

Research topics

• Evolutionary biology
• Biology
• Genetics
• Computer Science
• Cell biology
• Ecology
• Anatomy
• Computational biology
• Zoology

Selected publications

• Regeneration physiology of invertebrates

  Journal of Experimental Biology · 2025-11-15

  articleSenior author

  One of the great puzzles in biology is to understand the mechanisms underlying animal regeneration. Most recent efforts have used developmental and informatics approaches to understand how regenerated structures are formed, framing regeneration as a developmental outcome. However, regeneration is a complex process that also involves dynamic physiological mechanisms that support and fuel the rebuilding of lost structures. To develop a full understanding of regeneration, including how it relates to the ecology and evolution of organisms, it is essential to understand regeneration physiology. Despite the importance of physiological processes for regeneration, studies of regeneration focused on energetics, metabolism and environmental effects are scarce and have not been synthesized. This Review discusses the current understanding of regeneration physiology, focusing specifically on data from invertebrate animals where such information is especially dispersed and in need of synthesis. Considering data from diverse animal phyla, we review evidence for the consumption of different nutritional substrates during regeneration, summarize how aerobic and anaerobic metabolism appear to be broadly important to regeneration across animal phyla, and discuss how environmental and biotic factors can affect regeneration outcomes. We also introduce the concept of the 'physiological regeneration niche', describing the abiotic and biotic parameters where regeneration is possible, to expand consideration of regeneration in an ecological context. Significant gaps remain in understanding the physiological processes that underlie invertebrate regeneration, and we highlight some of these, including the need for broader taxonomic sampling, assessments of anaerobic metabolism during regeneration, investigations of multiple stressor effects on regeneration and comparisons between regenerators and non-regenerators.

  PublisherDOI

• From Mud to Meat: Comparative Metabarcoding Reveals Two Different Evolutionary Paths to Carnivory in a Group of Meiofaunal Annelids

  Molecular Ecology · 2025-10-28

  articleOpen accessSenior authorCorresponding

  Evolutionary transitions to carnivory represent profound shifts in feeding mode that are often accompanied by widespread changes in organismal function, behaviour and ecology. Such transitions have evolved numerous times among animals, and predator-prey interactions have been major drivers of animal evolution. Despite the ecological and evolutionary importance of carnivory, the evolutionary steps leading to this feeding mode are poorly understood. Although relatively rare, lineages that have recently adopted predatory lifestyles are particularly valuable for understanding the evolution of carnivory. The annelid genus Chaetogaster, composed of small freshwater oligochaetes, is unusual in having recently evolved carnivory not just once but twice, making it an excellent model to infer evolutionary steps from detritivory to carnivory. We performed a gut-content analysis of eight Chaetogaster species and a detritivorous outgroup, using 18S rDNA metabarcoding complemented by visual gut content assessment to infer diets. We found that species within the lineages presumed to be carnivorous had large fractions of animal metabarcoding reads, as predicted. Their closest relatives, however, differed in dietary profiles. We infer that the closest relatives of one carnivorous lineage, which are generalist predators, primarily feed on ciliates, while the closest relatives of the second carnivorous lineage, which are mollusc symbionts, are detritivores. Our data suggest that carnivory evolved two ways in Chaetogaster, with one transition mediated by ciliate feeding and a second mediated by symbiosis. Overall, this study suggests that carnivory can evolve from noncarnivorous ancestors through distinct evolutionary pathways, even among closely related lineages.

  PublisherOA PDFDOI

• Annelid adult cell type diversity and their pluripotent cellular origins

  Nature Communications · 2024 · 39 citations

  • Biology
  • Evolutionary biology
  • Cell biology

  Many annelids can regenerate missing body parts or reproduce asexually, generating all cell types in adult stages. However, the putative adult stem cell populations involved in these processes, and the diversity of cell types generated by them, are still unknown. To address this, we recover 75,218 single cell transcriptomes of the highly regenerative and asexually-reproducing annelid Pristina leidyi. Our results uncover a rich cell type diversity including annelid specific types as well as novel types. Moreover, we characterise transcription factors and gene networks that are expressed specifically in these populations. Finally, we uncover a broadly abundant cluster of putative stem cells with a pluripotent signature. This population expresses well-known stem cell markers such as vasa, piwi and nanos homologues, but also shows heterogeneous expression of differentiated cell markers and their transcription factors. We find conserved expression of pluripotency regulators, including multiple chromatin remodelling and epigenetic factors, in piwi+ cells. Finally, lineage reconstruction analyses reveal computational differentiation trajectories from piwi+ cells to diverse adult types. Our data reveal the cell type diversity of adult annelids by single cell transcriptomics and suggest that a piwi+ cell population with a pluripotent stem cell signature is associated with adult cell type differentiation.

  PublisherOA PDFDOI

• Investment in regeneration versus asexual reproduction is resource‐dependent in a freshwater annelid

  Functional Ecology · 2024-02-13 · 3 citations

  articleOpen accessSenior author

  Abstract The post‐embryonic developmental processes of regeneration and asexual agametic reproduction are widespread and often co‐occur in animals. These traits are of great ecological significance, but their physiological dynamics within species are not well understood. In naid annelids, regeneration and asexual reproduction via fission are evolutionarily related and mechanistically similar yet distinct, making these animals useful systems in which to study resource allocation strategies between the two processes. How asexual reproductive investment varies as a function of somatic investment demands was tested in the naid Pristina leidyi by repeatedly amputating the heads of individual worms, allowing regeneration to proceed, and measuring reproductive output over time. Treatments were replicated under high and low food levels to determine to what extent the investment dynamic between regeneration and fission is affected by the resource pool. Reproductive output was affected by injury and regeneration frequency in a resource‐dependent manner, such that only worms with less food availability exhibited reproductive deficits; injury and regeneration did not affect reproductive output of worms under the high food condition. When reproductive output was decreased, this occurred not through a reduction in offspring quantity but a reduction in offspring quality. In the offspring of experimental animals, body size and fission speed were dependent on parental feeding level and to a lesser and inconsistent extent on parental injury history, but regeneration speed was unaffected by parental treatment. These findings suggest that, in a species capable of both regeneration and asexual reproduction: (1) the resource pool is a key factor mediating the resource investment pattern between regeneration and fission; (2) sacrificing per‐offspring investment rather than fecundity may be an optimal strategy if resources are limiting; (3) regeneration and fission have evolved distinct resource allocation pathways. This work prompts further questions about the physiological dynamics between regeneration and asexual reproduction in animals, such as whether and to what extent these have evolved adaptively, including in response to injury and resource pressures. Read the free Plain Language Summary for this article on the Journal blog.

  PublisherOA PDFDOI

• Cryptic carnivores: Intercontinental sampling reveals extensive novel diversity in a genus of freshwater annelids

  Molecular Phylogenetics and Evolution · 2023-02-27 · 5 citations

  articleSenior author
  PublisherDOI

• Annelid adult cell type diversity and their pluripotent cellular origins

  bioRxiv (Cold Spring Harbor Laboratory) · 2023 · 15 citations

  • Biology
  • Cell biology
  • Evolutionary biology

  + cell population with a pluripotent stem cell signature will serve as a platform for the study of annelid stem cells and their role in regeneration.

  PublisherOA PDFDOI

• Integrative biology of injury in animals

  Biological reviews/Biological reviews of the Cambridge Philosophical Society · 2022 · 47 citations

  Senior authorCorresponding
  • Computer Science
  • Biology
  • Ecology

  Mechanical injury is a prevalent challenge in the lives of animals with myriad potential consequences for organisms, including reduced fitness and death. Research on animal injury has focused on many aspects, including the frequency and severity of wounding in wild populations, the short- and long-term consequences of injury at different biological scales, and the variation in the response to injury within or among individuals, species, ontogenies, and environmental contexts. However, relevant research is scattered across diverse biological subdisciplines, and the study of the effects of injury has lacked synthesis and coherence. Furthermore, the depth of knowledge across injury biology is highly uneven in terms of scope and taxonomic coverage: much injury research is biomedical in focus, using mammalian model systems and investigating cellular and molecular processes, while research at organismal and higher scales, research that is explicitly comparative, and research on invertebrate and non-mammalian vertebrate species is less common and often less well integrated into the core body of knowledge about injury. The current state of injury research presents an opportunity to unify conceptually work focusing on a range of relevant questions, to synthesize progress to date, and to identify fruitful avenues for future research. The central aim of this review is to synthesize research concerning the broad range of effects of mechanical injury in animals. We organize reviewed work by four broad and loosely defined levels of biological organization: molecular and cellular effects, physiological and organismal effects, behavioural effects, and ecological and evolutionary effects of injury. Throughout, we highlight the diversity of injury consequences within and among taxonomic groups while emphasizing the gaps in taxonomic coverage, causal understanding, and biological endpoints considered. We additionally discuss the importance of integrating knowledge within and across biological levels, including how initial, localized responses to injury can lead to long-term consequences at the scale of the individual animal and beyond. We also suggest important avenues for future injury biology research, including distinguishing better between related yet distinct injury phenomena, expanding the subjects of injury research to include a greater variety of species, and testing how intrinsic and extrinsic conditions affect the scope and sensitivity of injury responses. It is our hope that this review will not only strengthen understanding of animal injury but will contribute to building a foundation for a more cohesive field of 'injury biology'.

  PublisherOA PDFDOI

• Journey beyond the embryo: The beauty of Pristina and naidine annelids for studying regeneration and agametic reproduction

  Current topics in developmental biology/Current Topics in Developmental Biology · 2022-01-01 · 4 citations

  article1st authorCorresponding
  PublisherDOI

• A phylum-wide survey reveals multiple independent gains of head regeneration in Nemertea

  Proceedings of the Royal Society B Biological Sciences · 2019-03-06 · 54 citations

  articleOpen access

  Animals vary widely in their ability to regenerate, suggesting that regenerative ability has a rich evolutionary history. However, our understanding of this history remains limited because regenerative ability has only been evaluated in a tiny fraction of species. Available comparative regeneration studies have identified losses of regenerative ability, yet clear documentation of gains is lacking. We assessed ability to regenerate heads and tails either through our own experiments or from literature reports for 35 species of Nemertea spanning the diversity of the phylum, including representatives of 10 families and all three orders. We generated a phylogenetic framework using sequence data to reconstruct the evolutionary history of head and tail regenerative ability across the phylum and found that all evaluated species can remake a posterior end but surprisingly few could regenerate a complete head. Our analysis reconstructs a nemertean ancestor unable to regenerate a head and indicates independent gains of head regenerative ability in at least four separate lineages, with one of these gains taking place as recently as the last 10-15 Myr. Our study highlights nemerteans as a valuable group for studying evolution of regeneration and identifying mechanisms associated with repeated gains of regenerative ability.

  PublisherOA PDFDOI

• A phylum-wide survey reveals multiple independent gains of head regeneration ability in Nemertea

  bioRxiv (Cold Spring Harbor Laboratory) · 2018-10-11 · 1 citations

  preprintOpen access

  Abstract Animals vary widely in their ability to regenerate, suggesting that regenerative abilities have a rich evolutionary history. However, our understanding of this history remains limited because regeneration ability has only been evaluated in a tiny fraction of species. Available comparative regeneration studies have identified losses of regenerative ability, yet clear documentation of gains is lacking. We surveyed regenerative ability in 34 species spanning the phylum Nemertea, assessing the ability to regenerate heads and tails either through our own experiments or from literature reports. Our sampling included representatives of the 10 most diverse families and all three orders comprising this phylum. We generated a phylogenetic framework using sequence data to reconstruct the evolutionary history of head and tail regeneration ability across the phylum and found that while all evaluated species can remake a posterior end, surprisingly few could regenerate a complete head. Our analysis reconstructs a nemertean ancestor unable to regenerate a head and indicates at least four separate lineages have independently gained head regeneration ability, one such gains reconstructed as taking place within the last 10-15 mya. Our study highlights nemerteans as a valuable group for studying evolution of regeneration and identifying mechanisms associated with repeated gains of regenerative ability.

  PublisherDOI

Recent grants

• Evolution of regeneration: a comparative study in annelids

  NSF · $390k · 2005–2009

• Loss and rescue of regeneration in naidine annelids

  NSF · $450k · 2009–2013

• EDGE CT: Catalyzing regeneration research by developing functional tools for post-embryonic stages

  NSF · $935k · 2019–2024

Frequent coauthors

• Eduardo E. Zattara

  National University of Comahue

  22 shared

• Gregory A. Wray

  Duke University

  17 shared

• Allen G. Collins

  Smithsonian Institution

  11 shared

• B. Duygu Özpolat

  Washington University in St. Louis

  10 shared

• Cheryl Lewis Ames

  Tohoku University

  9 shared

• Joseph F. Ryan

  Whitney Museum of American Art

  8 shared

• Paulyn Cartwright

  University of Kansas

  7 shared

• Fernando Ángel Fernández‐Álvarez

  Institut Català de Ciències del Clima

  5 shared

Labs

• BELY LABPI

  Current Lab Members