PROFESSOR ROSSITER H. CROZIER 1943-2009

Photo: Alex Wild Ross H. Crozier died 12 November while working from his laboratory at James Cook University in Townsville, Australia, after suffering a heart attack. He was 66. Professor Crozier was a major contributor to our understanding, both empirical and theoretical, of the evolutionary genetics of social breeding systems, particularly those of social insects. He was an Australian Research Council Professorial Fellow, a member of the Australian Academy, and a fellow of the American Association for the Advancement of Science. In 2006, he received the inaugural Hamilton Award from the International Union for the Study of Social Insects in recognition of outstanding achievements in the area of social insect research. It is fitting that Ross would have won this award because he so well exposed the significance of William D. Hamilton's theory of kin selection and its associated concept of inclusive fitness—even correcting some of Hamilton's key calculations from his seminal 1964 papers. A proponent of selfish gene thinking throughout his career, and ever the enthusiast for the molecular approach, Crozier bridged the gap between kin theory and empirical genetics like none before him, and his pioneering efforts paved the way toward the now burgeoning field of sociogenomics. Ross was born in India during World War II, and spent parts of his youth living abroad. But by age 9, he was enrolled as a boarder at Geelong Grammar in his native Australia. After pondering a career in journalism, Ross began a zoology major at nearby Melbourne University. There, he met Malaysian science student Yuen Ching Kok, his future wife and research partner of more than 40 years. Together, they would move to the United States, and in 1969 Ross would earn his Ph.D. from Cornell University. Soon after, Ross began as assistant professor at the University of Georgia, and in 1975 repatriated to begin a 15-year career at the University of New South Wales in Sydney. Crozier began in ant cytogenetics, but soon took a leading role in the theoretical and empirical study of relatedness: he advocated its utility in evolutionary studies as a measure of reproductive worth, and was the first to derive the correct pedigree-based estimates of relatedness for male-haploidy and X-linked genes. His insight was significant for it enabled the empirical genetic study of Hymenopteran societies (ants, bees and wasps), around which Hamilton's theory was rapidly developing. He would later help formulate more widely applicable, statistical estimators of relatedness that proved a major advance for studying genetic structure of whole populations, social or otherwise; an approach that opened a new field highlighting the presence and significance of such structure using molecular markers such as mtDNA and microsatellites. From his base Down Under, Ross’s reputation as an international leader in the fields of molecular biology and social behavior began to grow. In 1990, Crozier moved to LaTrobe University in Melbourne as professor of genetics and head of department. Despite this extra responsibility, Ross remained ever involved in the day to day activities of his large and diversified research group, which, in 2000, he relocated to James Cook, in tropical Australia. There, Ross was appointed professor of evolutionary genetics and awarded a personal chair. Over the years, Ross and Ching's laboratory gained renown for its nurturing and intellectually rich atmosphere. They attracted students, research fellows, and visiting faculty from all corners of Australia, as well as from the U.S., Denmark, China, France, Switzerland, Canada, U.K., Finland, Japan, Indonesia, Germany, and beyond. Ross welcomed all into his laboratory and into his life. Many will have experienced Ross’s generosity and his liking for people at Christmas dinners that he and Ching held, to which lonesome students and academics a long way from home were invited, as well as family members. Ross was never more comfortable than when surrounded by his students, postdocs, and colleagues, talking research or politics, and sharing anecdotes from the field or from the laboratory. Many will remember the weekly laboratory meetings, which Ross held in his office—buttressed, as it was, with books floor to ceiling, overflowing with stacks of journals, and, on these occasions, stocked with wine and cheese. Ever supportive of his students, but not one to give away too much, Ross had a knack for subtle comment; either, just enough to embolden a student with confidence or encourage them to rethink their stance. Ross was a great mentor. He spoke softly, but when he did, people listened. Though always an ant-man, Ross’s work would come to embrace the entire social spectrum, from termites to bees to birds, and much else besides. In 1993, Ross and Ching published the complete sequence of the honey bee mitochondrial genome. Recognized as “a milestone in molecular entomology” (MA Hoy. 1995. Insect Molecular Genetics), it represented the first complete insect sequence outside of the flies. Their accomplishment is all the more impressive when one considers such an undertaking was a decade ahead of expectation for even a busy molecular ecology laboratory. Its painstaking assembly showed that mitochondrial gene order changes could be extensive, and highlighted how directional mutation pressure can yield problems in phylogeny reconstruction. Moreover, it showed something of Ross’s own character—a careful, consistent man of high intellect, driven by dogged determination. Ever humble, he once joked that he should not have been listed as an author on this “Crozier and Crozier” classic (1993. Genetics 133: 97–117). But, with a wink, he quips how he “Gave into Ching's insistence.” Ross’s success was not based on a single achievement, discovery, paper, or even topic. Rather, it was his style to chip away at dozens of questions he found interesting. He was at the forefront of genetic studies on caste determination, wrote authoritatively on the evolution of reproductive altruism, and once codiscovered an ant with the lowest possible number of chromosomes (1!). A careful writer, he clarified how selection should act on kin recognition and sex-determining loci, and showed how the evolution and expression of immune genes is affected by group living. He was a vocal proponent for statistical approaches to phylogenetic tree reconstruction, and applied phylogeny to many questions of social evolution and conservation biology. Throughout his career, Crozier revisited certain curiosities, including the question of multiple mating in social insects—a paradoxical situation that significantly reduces intracolonial relatedness, and therefore promotes conflict over cooperation. As exemplified here, it was Crozier's way to first develop the ideas that potentially resolved outstanding questions, then return to test them as analytical or DNA technologies advanced sufficiently to yield new insights. This style of addressing thought-provoking questions with new ideas and new tools made the “Crozier Lab” fertile training ground for many aspiring biologists. To them—to many—Ross not only studied social insects, he validated them as model systems in the study of how natural selection works. In 1996, he published, with Pekka Pamilo, an exposition of this ability in Evolution of Social Insect Colonies: Sex Allocation and Kin-Selection (Oxford University Press). Although Ross’s entire career was spent on the front lines of science, he was as active behind them, upholding a vast tapestry of personal correspondence. To ask Ross a question over e-mail was surely to prompt a fast and informative response, if not two or three as he strived to be as helpful as possible. This made him naturally effective to the many societies that he served, including a former role as vice President for the Society for the Study of Evolution, and associate editor for Evolution. It is sobering to think that Ross is gone, but his memory and influence will live on through the many students and colleagues that he taught, coached, and befriended. Ross went at the height of his powers, doing what he did so well, with Ching by his side. He will be sadly missed for his enthusiasm, profound knowledge, and gentle mentorship.

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