Speciation is responsible for the vast diversity of life, and hybrid inviability, by reducing gene flow between populations, is a major contributor to this process. In the parasitoid wasp genus Nasonia, F 2 hybrid males of Nasonia vitripennis and Nasonia giraulti experience an increased larval mortality rate relative to the parental species. Previous studies indicated that this increase of mortality is a consequence of incompatibilities between multiple nuclear loci and cytoplasmic factors of the parental species, but could only explain ∼40% of the mortality rate in hybrids with N. giraulti cytoplasm. Here we report a locus on chromosome 5 that can explain the remaining mortality in this cross. We show that hybrid larvae that carry the incompatible allele on chromosome 5 halt growth early in their development and that ∼98% die before they reach adulthood. On the basis of these new findings, we identified a nuclear-encoded OXPHOS gene as a strong candidate for being causally involved in the observed hybrid breakdown, suggesting that the incompatible mitochondrial locus is one of the six mitochondrial-encoded NADH genes. By identifying both genetic and physiological mechanisms that reduce gene flow between species, our results provide valuable and novel insights into the evolutionary dynamics of speciation. K E Y W O R D S :Cytonuclear incompatibility, mitochondria, oxidative phosphorylation, speciation.

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Contrary to concerns of some critics, we present evidence that biomedical research is not dominated by a small handful of model organisms. An exhaustive analysis of research literature suggests that the diversity of experimental organisms in biomedical research has increased substantially since 1975. There has been a longstanding worry that organism-centric funding policies can lead to biases in experimental organism choice, and thus negatively impact the direction of research and the interpretation of results. Critics have argued that a focus on model organisms has unduly constrained the diversity of experimental organisms. The availability of large electronic databases of scientific literature, combined with interest in quantitative methods among philosophers of science, presents new opportunities for data-driven investigations into organism choice in biomedical research. The diversity of organisms used in NIH-funded research may be considerably lower than in the broader biomedical sciences, and may be subject to greater constraints on organism choice.

Abstract. Journal of the History of Biology provides a fifty-year long record for examining the evolution of the history of biology as a scholarly discipline. In this paper, we present a new dataset and preliminary quantitative analysis of the thematic content of JHB from the perspectives of geography, organisms, and thematic fields. The geographic diversity of authors whose work appears in JHB has increased steadily since 1968, but the geographic coverage of the content of JHB articles remains strongly lopsided toward the United States, United Kingdom, and western Europe and has diversified much less dramatically over time. The taxonomic diversity of organisms discussed in JHB increased steadily between 1968 and the late 1990s but declined in later years, mirroring broader patterns of diversification previously reported in the biomedical research literature. Finally, we used a combination of topic modeling and nonlinear dimensionality reduction techniques to develop a model of multi-article fields within JHB. We found evidence for directional changes in the representation of fields on multiple scales. The diversity of JHB with regard to the representation of thematic fields has increased overall, with most of that diversification occurring in recent years. Drawing on the dataset generated in the course of this analysis, as well as web services in the emerging digital history and philosophy of science ecosystem, we have developed an interactive web platform for exploring the content of JHB, and we provide a brief overview of the platform in this article. As a whole, the data and analyses presented here provide a starting-place for further critical reflection on the evolution of the history of biology over the past half-century. IntroductionIn a scathing 1990 review, the late historian of science John Farley complained that, "from its first twoissue volume in 1968, through its increase to three issues per year in 1982, until today, Journal of the History of Biology has provided an outlet for the self-perpetuating oligarchy of Darwin scholars" (Farley, 1990). "Is this healthy, I wonder?" Farley went on, "Has the profession now reached such a size that the members can afford to speak only to each other?". Farley enumerated a variety of themes and fields that, in his view, had been chronically underserved in the pages of JHB, including oceanography, ethology, botany, anatomy, physiology, biochemistry, bacteriology, and others. Worse, Farley seemed to suggest that JHB had nearly missed the social turn in the history of science, remaining fixated on "the history of biological concepts."It is worth considering the most charitable subtext of his assertions: that as the flagship periodical of the field, the contents of JHB are a window onto the diversity and the development of the history of biology. Indeed, early reviewers (e.g. Brown, 1968) hailed JHB as a signpost for the maturation of the history of biology as a distinct specialization within the history of science. The approaching quinquagenary of that first issue i...