Cole Evo Edu Outreach (2020) 13:21 https://doi.org/10.1186/s12052-020-00135-7 Evolution: Education and Outreach BOOK REVIEW Open Access The mitochondrion as a hammer Logan W. Cole* Abstract This is a review of Mitonuclear Ecology by Geofrey E. Hill, which discusses the potential role of mitochondrial-nuclear (mitonuclear) interactions in key evolutionary processes. Keywords: Evolution, Mitochondria, Mitonuclear interactions Main text confict, and cooperation also may help molecular and In a way that is highly meta and perhaps ironic, there is cell biologists think about mitochondria in an evolution- some confict over the importance of mitonuclear inter- ary context. Te volume describes complicated concepts actions in evolutionary biology. Geofrey Hill’s Mitonu- in intuitive terms and provides an accessible overview of clear Ecology (2019) is a compelling volume that takes the diferent kinds of relevant experiments; in doing so, bold positions in these ongoing debates and will surely it provides a fairly comprehensive framework for one inspire much work in the eponymous feld. Its treatment to begin thinking about questions, and even formulat- of several topics in and around the area of mitonuclear ing ideas for potential experiments, that meaningfully interactions is accessible and carefully curated. Te vol- address the role of mitonuclear interactions in evolution. ume puts forward a coherent and intriguing worldview As someone whose doctoral dissertation work dealt with of eukaryotic evolution that centers the mitochondrion. the evolution of mitochondrial genomes, it occurred to It does, however, create some ambiguity between our me that this sort of broad treatment that bridges evolu- established understanding and the author’s fascinating- tionary and molecular considerations of mitochondria yet-debatable claims about the evolution of mitonu- would have come in handy during my qualifying exam. clear interactions and mitochondrial genomes, and their Te manner in which complicated concepts are articu- impact on eukaryotic evolution broadly considered. As lated simply and with accessible language is mirrored by the author makes very clear in the book’s preface, this is the quality of the fgures throughout the text, which col- not intended to be an unbiased summary of the subject lapse large amounts of information and arcane concepts but rather an overview of, and advocacy for, the centrality into wonderfully tidy and concise images. Early on, for of mitonuclear interactions in eukaryotic evolution. example, there is a fgure that manages to comprehen- Te bulk of this volume’s frst half provides an excellent sively explain the various trade-ofs among an array of introduction to the fundamentals of eukaryotic (nuclear approaches that assess the consequences of mitonuclear and mitochondrial) genomes, the underlying cell biology mismatches; fgures like this begin to provide an impor- of mitochondrial-nuclear interactions, the coevolution of tant foundation for meaningfully addressing real issues in the two compartments, and related areas. Tis portion is the area. Troughout the volume, there are many fgures clearly intended as a way for organismal biologists of all that contain elegant line drawings which complement the levels to begin thinking about mitochondria at molecular text in a way that erases any remaining ambiguity in the and subcellular scales, but the treatment of coevolution, basic premises and intricate hypotheses that are a part of this subject. Tat being said, there were early parts of this book *Correspondence: [email protected] where, through either curious omission or question- Department of Biology, Indiana University, Bloomington, IN, USA able exuberance, the blurring between established © The Author(s) 2020. 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The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Cole Evo Edu Outreach (2020) 13:21 Page 2 of 3 understanding and plausible but far-from-proven hammer is the mitochondrion and the nail is any of the hypotheses occurs. For example, the book’s reifca- various open questions of evolution as they pertain to tion of the mitochondrion as a pre- or co-requisite for eukaryotes. eukaryogenesis following the work of Lane et al. (2005; Ostensibly, the scope of this book is all eukaryotes but Lane and Martin 2010) ignores a still-ongoing dialogue most of the text is dedicated to metazoans with only (Lynch and Marinov 2015, 2017; Hampl et al. 2019; brief digressions to discuss other groups. It may have Chiyomaru and Takemoto 2020; Lane 2020) about better served the premise of the book to place complete the energetic requirements of various eukaryotic fea- focus on metazoans and to set aside these digressions, tures. Also, some framing of methods suggests that the as they can be somewhat misleading or incomplete. feld is better poised to address Hill’s focal questions For example, the book discusses a plausible and cogent than it may be. When the volume discusses the mer- hypothesis that connects low mutation rates in plant its of cybrid cell lines, it cites studies with cybrid pairs mitochondrial DNA (mtDNA) to a lower degree of tis- that are comparatively distantly related (e.g. Barrien- sue specialization and a lesser need for a sequestered tos et al. 1998; Enoki et al. 1994) while the evolution- germline. Tis hypothesis, however, rests on the prem- ary questions dealt with in later chapters are those of ise that we have signifcant knowledge of plant mtDNA population-level processes or at the precipice of specia- mutation rates, which we do not. As such, intentionally tion. Notably, the role of mitonuclear confict is largely or not, this volume’s treatment of the issue confates dismissed despite it being a potentially fruitful line of our measures of synonymous substitution rates in plant inquiry (Ågren 2013; Havird et al. 2019). mtDNA (Drouin et al. 2008; Richardson et al. 2013) Te latter portion of the book takes on a more polemic with mutation rates. Tese sorts of nuances are glazed character, but, as such, deals with those controversial over in these digressions but are central to addressing questions most interesting to evolutionary geneticists and defning these questions. and presents thoughtful hypotheses, supported by vary- A seminar or discussion course with this volume as a ing degrees of evidence. Tough one may disagree as to guide could be enlightening. Such a course could serve the relative importance of mitonuclear interactions in a variety of participants including graduate students, the evolution of sex, speciation, mate choice, senescence, postdoctoral researchers, faculty, or even upper-division and adaptive radiation, expounding upon these bold undergraduate students. Te organization of this book hypotheses is quite welcome here, as the goal of this part would be useful in bringing a variety of participants from of book is clearly to advocate for preeminence of mito- backgrounds across organismal and molecular biology to nuclear interactions in eukaryotic evolution. In some this discussion, even if they are entirely new to the sub- parts, however, this veers into an unfounded assured- ject. Te frst half of the book would give participants a ness of the importance of mitonuclear interactions. For foundation in understanding mitonuclear interactions example, the author refers to mitonuclear coadaptation while, later in the course, the controversial ideas in the as “a precise and universal explanation for the evolution second half, supplemented by recent papers including of genetic incompatibilities between populations,” which those highlighted by the text, may serve as points of lively is an incredibly bold claim that is nigh impossible to debate and discussion. demonstrate. Whether you agree with its assertions or its char- On occasion the volume treats certain unproven or acterization of the subfeld, this book is a must-read ungeneralizable hypotheses, including the aforemen- for anyone interested in how mitonuclear interactions tioned energetic necessity of mitochondria for com- impact evolution. Te author expounds on many com- plexity and mitonuclear species concept, mitonuclear pelling ideas, some of which may eventually provide mate choice, and the role of mitochondrial introgres- wide-ranging explanations for evolutionary phenomena, sion in adaptation, as canonical parts of our knowledge and these ideas deserve consideration and scrutiny. Te or widely-applicable solutions to longstanding evolu- reader should heed the author’s own warning and treat tionary problems. Te author states that Nick Lane’s the volume as the point-of-view and impetus for further 2005 book, Power, Sex, Suicide: Mitochondria and the research that it claims to be, rather than any sort of defn- Meaning of Life, prompted him to consider a greater itive or even-handed treatment of the subject. Tis book role for the mitochondrion’s subcellular processes in has the capacity to inspire, or at the very least reorient, evolution. Clearly, this mitochondrion-centric frame- anyone working, or who wants to work, at the intersec- work is that in which the stances expressed in the lat- tion of mitochondria and evolution.