I have been working as a rotating Program Director at the National Science Foundation for the last three and a half years, and I’m now a permanent Program Director in the Division of Environmental Biology‘s Evolutionary Processes Cluster. My lab at Georgia Tech is closed, and I am no longer employed there.

Anything I post here reflects only my personal views and does not necessarily represent the views of my employer or the United States.

Seyed Alireza Zamani-Dahaj, Anthony Burnetti, Thomas C. Day, Peter J. Yunker, William C. Ratcliff, and I have published a new article in the latest issue of Genes. This follows up on our previous paper on heritability with an empirical test of some of its assumptions and predictions.

Abstract:

The major transitions in evolution include events and processes that result in the emergence of new levels of biological individuality. For collectives to undergo Darwinian evolution, their traits must be heritable, but the emergence of higher-level heritability is poorly understood and has long been considered a stumbling block for nascent evolutionary transitions. Using analytical models, synthetic biology, and biologically-informed simulations, we explored the emergence of trait heritability during the evolution of multicellularity. Prior work on the evolution of multicellularity has asserted that substantial collective-level trait heritability either emerges only late in the transition or requires some evolutionary change subsequent to the formation of clonal multicellular groups. In a prior analytical model, we showed that collective-level heritability not only exists but is usually more heritable than the underlying cell-level trait upon which it is based, as soon as multicellular groups form. Here, we show that key assumptions and predictions of that model are borne out in a real engineered biological system, with important implications for the emergence of collective-level heritability.

Zamani-Dahaj, S.A., A. Burnetti, T.C. Day, P.J. Yunker, W.C. Ratcliff, and M.D. Herron. 2023. Spontaneous emergence of multicellular heritability. Genes 14: 1635. doi: 10.3390/genes14081635

Carl Simpson has authored a review of The Evolution of Multicellularity in Trends in Ecology & Evolution:

What features do all multicellular organisms share due to the common evolutionary problems and what differences are due to the constraints imposed by their unicellular ancestors? That is no easy task; not least because the answers to those questions span all biological disciplines. The new volume, The Evolution of Multicellularity edited by M.D. Herron et al., pulls together current thought on multicellularity from workers across a constellation of fields. This volume does a wonderful job covering the issues: from how to recognize multicellularity (Chapter 2), multilevel selection (Chapter 3), to multicellularity in fungi (Chapter 14), algae, and plants (Chapters 15 and 16).

Simpson, C., Coming together to understand multicellularity. Trends in Ecology & Evolution. doi https://doi.org/10.1016/j.tree.2023.01.007

A new paper by former grad student Jacob Boswell, current grad student Ross Lindsey, Emily Cook, and Frank Rosenzweig is out in Biology Methods & Protocols (open access article):

Long-term preservation of laboratory strains of Chlamydomonas reinhardtii has historically involved either liquid nitrogen cryopreservation, which is expensive and labor intensive, or storage on agar plates, which requires frequent transfer to new plates, and which may leave samples susceptible to contamination as well as genetic drift and/or selection. The emergence of C. reinhardtii as a model organism for genetic analysis and experimental evolution has produced an increasing demand for an efficient method to cryopreserve C. reinhardtii populations. The GeneArt™ Cryopreservation Kit for Algae provides the first method for algal storage at −80°C; however, little is known about how this method affects recovery of different clones, much less polyclonal populations. Here, we compare postfreeze viability of clonal and genetically mixed samples frozen at −80°C using GeneArt™ or cryopreserved using liquid nitrogen. We find that the GeneArt™ protocol yields similar percent recoveries for some but not all clonal cultures, when compared to archiving via liquid N2. We also find that relative frequency of different strains recovered from genetically mixed populations can be significantly altered by cryopreservation. Thus, while cryopreservation using GeneArt™ is an effective means for archiving certain clonal populations, it is not universally so. Strain-specific differences in freeze–thaw tolerance complicate the storage of different clones, and may also bias the recovery of different genotypes from polyclonal populations.

Boswell, J., C. R. Lindsey, E. Cook, F. Rosenzweig, & M. D. Herron. 2021. Cryopreservation of clonal and polyclonal populations of Chlamydomonas reinhardtii. Biology Methods & Protocols 6:1-6. doi: 10.1093/biomethods/bpab011

Congratulations to Charles “Ross” Lindsey for successfully defending his Master’s thesis, “Phylotranscriptomics of the volvocine algae: A model clade for the study of differentiated multicellularity,” on Friday, January 15, 2021!

EDIT April 1, 2020: updated link and slightly revised abstract to the new version

I have posted a new preprint to the PhilSci Archive:

The ‘Major Transitions in Evolution’ (MTE) framework has emerged as the dominant paradigm for understanding the origins of life’s hierarchical organization, but it has been criticized on the grounds that it lacks theoretical unity, that is, that the events that make up the category do not constitute a natural kind. I agree with this criticism, and I argue that the best response is to modify the category so that it does approximate a natural kind. Specifically, I recommend defining major transitions as all those, and only those, events and processes that result in the emergence of a new level of selection. Two sorts of changes will be required to achieve this. First, events and processes that do not meet this criterion, such as the origins of the genetic code and of human language, should be excluded. Second, events and processes that do meet the criterion, but which have generally been neglected, should be included. These changes would have the dual benefits of making MTEs a philosophically coherent category and of increasing the sample size on which we may infer trends and general principles that may apply to all MTEs.