Biographical sketch

David Graham Lloyd was born on June 20,1937 at Manaia, Taranaki on the North Island of New Zealand, with his identical twin brother Peter Lloyd (Fig. 1.1a). Apparently, the twins were so similar that only their mother could tell them apart reliably. Unfortunately, she died of cancer when they were eight leaving their father, a dairy farmer at Taranaki, to raise the twins, their brother Trevor and sister Judith. We are particularly indebted to Peter and Trevor Lloyd for providing many of the details for this biographical sketch of David Lloyd.

David had a fairly happy childhood at Manaia with the farm routine of twice daily milking of cows and visits to his grandfather's farm next door to see the poultry and bees. David later worked during holidays in the local cheese factory, which his father supplied with milk, and in the ''gut room'' of the slaughter house stripping by hand the contents of animal intestines before they were processed into sausage casings. According to Trevor, this was one of the worst jobs locally ''and regarded as the bottom of the heap socially and work-wise.'' However, swimming in local rivers, the town swimming pool and a nearby beach were great childhood pleasures, although their mother's death cast a large shadow over the children's early lives.

By all accounts, David excelled at school, attending Manaia primary school where he and Peter skipped a grade because they were brighter than most students in their cohort. From 1950 to 1954, David attended New Plymouth Boys High School along with brother Peter. New Plymouth was a boarding school known mostly for rugby, rather than academic excellence: a "boarding school for country kids, no more.'' However, David was taught by several exceptional teachers, fostering an early interest in the sciences. While at New Plymouth, David was also head prefect of Pridham House and, despite being small in stature, was an outstanding athlete (sprinting and long jump) and Rugby football player. After completing high school, he and Peter both obtained Taranaki scholarships to assist in their subsequent university education.

David's family upbringing and school experiences provide no obvious indication that he was destined to become one of New Zealand's most influential biologists. David was the only member of his family to choose biology as a profession and, although at school he was strongly attracted to the sciences, especially physics, he was not an especially outdoors type, rarely went camping, and had no particular affinity for plants and animals. According to Peter, ''both brothers were attracted by theory and abstract reasoning, rather than a childhood fascination with frogs.'' From Peter's perspective it is ''uncertain why David chose botany at university,'' although according to the molecular evolutionist David Penny, who also attended New Plymouth and went on to Canterbury, the enlightened analytical botanical teaching of W. R. Philipson at Canterbury, rather than the traditional descriptive approach, was probably formative. The interests of the Lloyd twins

Figure 1.1 Images of David G. Lloyd from throughout his life. (a) The twins Peter (P) and David (D) at an early age. (b) As a young man prior to departure to the United States to start doctoral studies at Harvard. (c) At the start of his academic career in the glasshouse at the University of Canterbury with his Cotula (Leptinella) collection. (d) Conducting field studies of Narcissus in Andalucia, Spain, during March 1990. (e) In his office at Canterbury at the time of his election in 1992 to the fellowship of the Royal Society of London.

Figure 1.1 Images of David G. Lloyd from throughout his life. (a) The twins Peter (P) and David (D) at an early age. (b) As a young man prior to departure to the United States to start doctoral studies at Harvard. (c) At the start of his academic career in the glasshouse at the University of Canterbury with his Cotula (Leptinella) collection. (d) Conducting field studies of Narcissus in Andalucia, Spain, during March 1990. (e) In his office at Canterbury at the time of his election in 1992 to the fellowship of the Royal Society of London.

diverged during high school, as Peter was attracted to the humanities and David to the sciences.

With scholarships in hand, the Lloyd twins went off to university in 1955, with David entering Canterbury College (now University of Canterbury) at Christchurch and Peter going to Victoria University College, Wellington (now Victoria University). According to Peter, despite this divergence the two ''remained very similar in intellect'' over the years. At Canterbury, David was the first person to complete the new 4-year B.Sc. honours degree, finishing with first-class honours (1959). Peter was also awarded first-class honours in a Master of Arts degree, and the brothers then both applied for the prestigious Frank Knox Memorial Scholarship and were ranked first (David) and second (Peter), apparently causing some confusion in the application process. As for many young and ambitious students, it was time to leave the academic isolation of New Zealand and obtain ''OE'' (overseas experience). Both brothers chose to conduct their doctoral studies in the United States, with David going to Harvard University and Peter to Duke University. Today, Peter Lloyd is Emeritus Professor of Economics at the University of Melbourne, Australia, having specialized in international trade. He has some regrets that ''I did not collaborate as much as I would have liked with David during our careers, despite the similarities between economic and evolutionary theories.'' Although they did not publish together, it is probably no coincidence that some of David Lloyd's most interesting theoretical contributions were based on ideas from economic theory, for which he has acknowledged Peter (see Lloyd and Venable 1992).

In 1959 David left New Zealand for the first time (Fig. 1.1b), travelling by boat through the Panama Canal to New York and then on to Boston. At Harvard he initially intended to work on maize genetics with Paul Mangelsdorf, but soon became more attracted to studies of variation and evolution in wild plant populations. For his doctoral dissertation David chose to work with the sys-tematist Reed Rollins on Leavenworthia, a genus of annual crucifers rich in floral and mating system diversity. His Ph.D. thesis is a classic study of the causes and consequences of the evolution of selfing from outcrossing and was published in 1965 as a massive, 131-page article in the Contributions from the Gray Herbarium of Harvard University. This article is widely cited and contains many of Lloyd's early ideas on selective mechanisms. After completing his thesis in 1964, David returned to New Zealand, taking up a research fellowship at the University of Canterbury. In 1967, David became employed as a lecturer in botany at the University of Canterbury, where he remained for the rest of his career, eventually becoming Professor of Plant Science in 1986. During David's time at Canterbury a generation of researchers in plant ecology and evolution made the long trek to New Zealand to work with him as graduate students, post-doctoral fellows or visiting professors. International visitors enabled Lloyd to keep abreast of the latest developments in the burgeoning field of plant reproductive biology, particularly during the 1970s and 1980s.

David Lloyd's publications during his tenure at the University of Canterbury reveal several features of his character and intellectual development. Lloyd's career was based on ideas, and he believed strongly that the originators of ideas should be acknowledged. Consequently, Lloyd's papers are characterized by reviews of relevant intellectual precedent and he viewed papers by others who ignored this precedent to be disrespectful. Lloyd's publications during the first decade of his career describe his functional interpretations of plant reproduction based on direct observation. These descriptions are largely unsupported by statistical analysis and indeed Lloyd used such approaches sparingly throughout his career. However, Lloyd's conceptual approach to biology eventually led him to formulate his ideas mathematically, allowing him to manipulate concepts in a formal manner that often revealed unexpected conclusions. Although theoretical approaches had dominated population genetics since its inception during the 1930s and were being applied increasingly by animal ecologists led by R. H. MacArthur, ecological and evolutionary botany had remained largely immune to mathematical analysis (but see Lewis 1941; Crosby 1949). Consequently, Lloyd's initial theoretical publications in 1974 (Lloyd 1974a, b, c) were among the first to apply the power of mathematics to the conceptual analysis of plant reproduction. Lloyd was particularly attracted to the optimality approaches being applied in the developing field of evolutionary ecology and used the analogy between constrained optimization and natural selection to great effect in his analysis of reproductive strategies. After convincing himself that simpler pheno-typic models often identified the same optima as more complex genetic models (Lloyd 1977), Lloyd focused on phenotypic traits in his mathematical analysis of the evolution of plant reproduction. Interestingly, although Lloyd continued publishing descriptive papers on plant adaptations, he tended to present such observations separately from his theoretical papers. Nevertheless, Lloyd's theory was always motivated biologically and incorporated his intimate knowledge of reproductive mechanisms. The extensive body of concepts that Lloyd developed through keen observation, incisive intellect and realistic theory established him as the founder of the theory of plant reproduction and comprise his enduring legacy.

David Lloyd received many awards and distinctions during his career. He was elected to the Royal Society of New Zealand in 1984 and in 1993 he was made a foreign honorary member of the American Academy of Arts and Sciences. In 1992 he became only the seventh scientist resident in New Zealand to be elected to the Royal Society of London (Fig 1.1e). Signing the charter book in London and seeing Charles Darwin's signature also in the book was of special significance for Lloyd. Darwin had been a major influence on his work, particularly Darwin's pioneering work on plant sexual systems (Darwin 1877). Lloyd's citation from his election certificate to the Royal Society succinctly summarizes his main contributions:

Distinguished for his elegant experimental and theoretical studies of sexuality in flowering plants and of its costs and benefits. He has analyzed the ways in which natural selection may influence the allocation of resources between the sexes and the conflict of interest between maternal investment in the numbers and size of progeny. He has also made major contributions to understanding the special features of the flora of New Zealand and outlying islands.

Tragically, soon after this highpoint of his scientific career, Lloyd's life changed forever. On December 17,1992 he was admitted to hospital with a mysterious ailment and soon lost his vision and went into a coma. Although David revived from the coma, paralysis effectively ended his career. When illness struck, the hand-written manuscript of Lloyd's magnum opus, a volume on evolutionary strategies, was only partially complete and the scientific community was deprived of a major synthesis of his theories on evolution and selection. As discussed below, several papers from this planned book (Lloyd 2000a, b, c) have been published subsequently owing to the efforts of several of Lloyd's closest colleagues, Lynda Delph, Curtis Lively, and Colin Webb. After a long and heroic struggle, David Lloyd died peacefully on May 30, 2006 at his home in Christchurch, with his wife Linda Newstrom-Lloyd, also a reproductive biologist, and several family members by his side.

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