Integrative Paleobotany: Affirming the Role of Fossils in Modern Plant Biology—Introduction and Dedication
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Int. J. Plant Sci. 180(6):459–463. 2019. SPECIAL ISSUE—ROTHWELL CELEBRATION q 2019 by The University of Chicago. All rights reserved. 1058-5893/2019/18006-0001$15.00 DOI: 10.1086/704242 INTEGRATIVE PALEOBOTANY: AFFIRMING THE ROLE OF FOSSILS IN MODERN PLANT BIOLOGY—INTRODUCTION AND DEDICATION Ignacio H. Escapa,* Alexandru M.F. Tomescu,1,† Michael T. Dunn,‡ and Ruth A. Stockey§ *Consejo Nacional de Investigaciones Científicas y Técnicas, Museo Paleontológico Egidio Feruglio, Trelew, Chubut 9100, Argentina; †Department of Biological Sciences, Humboldt State University, Arcata, California 95521, USA; ‡Department of Agriculture, Biology, and Health Sciences, Cameron University, Lawton, Oklahoma 73505, USA; and §Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA Gar Rothwell was named Distinguished Professor at Ohio University in 2004. Photo courtesy of Fred C. Tom of Lamborn’s Studio, Athens, Ohio. If you are interested in plant evolution, try this quick exercise: have evolved as a result of a long process in which failed attempts take a phylogenetic tree of the plant kingdom, close your eyes, are the rule, and as a result, the diversity of extinct forms accu- and point your finger randomly to a node of the phylogeny. Irre- mulated in the fossil record far exceeds that recorded in the ex- spective of the clade to which you are pointing, there is one thing tant flora. From this simple concept, Gar W. Rothwell made his you should know about it: the living representatives of that clade career. Because of that, here is a second thing you should know about the plant clade to which you pointed at random: Gar has, 1 Author for correspondence; email: [email protected]. more likely than not, contributed information about evolution 459 This content downloaded from 201.250.027.037 on June 07, 2020 15:47:03 PM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c). 460 INTERNATIONAL JOURNAL OF PLANT SCIENCES in that clade at some point in his career. Gar was one of the prin- karyotes, fungi, liverworts, mosses, lycopsids, sphenopsids, ferns cipal contributors to the revival of paleobotany from a largely of a wide variety of lineages, pteridosperms, conifers and conif- descriptive discipline to a vibrant field of investigation at the erophytes, cycads, ginkgophytes, bennettitaleans, and angio- forefront of modern evolutionary sciences that contributes cru- sperms—nothing has escaped Gar’s inquisitive eye. These de- cial insights into plant evolution, equal in importance to those scriptions of fossil taxa, which led to the development of several provided by genetics and molecular biology. Because of this, now-classic whole-plant concepts, have always represented for the impact of Gar’s scientific contributions reaches far beyond Gar only the first step in understanding broader and deeper pro- the field of paleobotany, with important implications for wide cesses in plant evolution and development. Gar has also used areas of plant biology, including anatomy and morphology, de- these fossils to develop innovative ideas and approaches for doc- velopment, systematics, phylogeny, and evolution. umenting the natural history of species long extinct and to in- Gar earned a master’s degree in the laboratory of Thomas N. form some of the most vexing unanswered questions in plant Taylor (University of Illinois at Chicago, 1966) studying Paleo- evolution and phylogeny. Over the past few decades, no scientist zoic seeds in the genus Conostoma (Rothwell and Eggert 1970; has been more influential in affirming and expanding the poten- Rothwell 1971a). He subsequently earned his PhD degree in the tial of paleobotany as an integral contributor to evolutionary laboratory of Wilson N. Stewart (University of Alberta, 1973), plant biology than Gar. In terms of organismal biology and nat- where he reconstructed the plants in the seed fern genus Calli- ural history, in landmark studies Gar documented several as- stophyton (Rothwell 1972b, 1975, 1980, 1981). His work was pects of reproductive biology of the early seed plants, including instrumental in ushering in studies of fossil plants as whole liv- the hydrasperman reproductive syndrome (Rothwell 1971a, ingorganisms,lookingatbothstructureanddevelopment.These 1971b, 1986; Rothwell and Scheckler 1988; Serbet and Roth- early experiences launched Gar on a career in plant evolution- well 1995), pollination drops (Rothwell 1977) and pollen tubes ary biology that stretched over a half century, during which he (Rothwell 1972a) of Carboniferous seed ferns (pteridosperms), occupied positions at the University of Alberta, University of and seed dormancy in Paleozoic conifers (Mapes et al. 1989). London–Chelsea College, Ohio University, and Oregon State Together with collaborators, Gar described what is still the old- University. Throughout his career, Gar’s scholarly work and est seed plant reconstructed as a whole plant, the pteridosperm contributions have been recognized by numerous awards and Elkinsia (Rothwell et al. 1989; Rothwell and Serbet 1992; Ser- honors: theIsabel Cookson Award, the EdgarT. WherryAward, bet and Rothwell 1992). His studies of the apical organization the Michael A. Cichan Award, the Merit Award of the Botani- of lepidodendralean rooting structures (rhizomorphs; Rothwell cal Society of America, and honorary membership in the Inter- 1984; Rothwell and Pryor 1991), the lepidodendralean embryo national Organization of Palaeobotany, where he served for anatomy (Stubblefield and Rothwell 1981; Pigg and Rothwell 12 years as secretary-treasurer and president. 1983b), and the body plan of the Chaloneriaceae (Pigg and Gar is the author, with Wilson Stewart, of one of the most Rothwell 1979, 1983a) led to a paradigm shift in our under- impactful and widely used textbooks in the field of paleobotany standing of the structure and evolution of the body plan of iso- and plant evolution—Paleobotany and the Evolution of Plants. etalean lycopsids (Rothwell and Erwin 1985). Gar’s continued Published in 1993, this textbook explains in direct and engaging exploration of coal ball floras put on firm footing the idea that prose the crucial role of fossils, and of their anatomy and mor- the rise and the first major radiation of leptosporangiate ferns phology, in understanding the origin and evolution of all major occurred in the Carboniferous (Rothwell 1978, 1987a, 1996, plant groups. For more than a quarter century it has provided 1999; Trivett and Rothwell 1988; Rothwell and Good 2000; inspiration to numerous paleobotanists and structural botanists Tomescu et al. 2006; Rothwell and Stockey 2008). His studies worldwide. spanningseveraldecadesalsopainstakinglydocumentedtheevo- The results of the research program that Gar has led are re- lution of conifer reproductive structures, from the early conifers flected in the more than 250 peer-reviewed journal articles and of the Paleozoic (Rothwell 1982; Mapes and Rothwell 1984, book chapters published in more than 30 scientific journals that 1991, 1998; Rothwell et al. 1997, 2005, 2007; Hernandez- cover the fields of botany and paleobotany (e.g., International Castillo et al. 2001, 2009; Rothwell and Mapes 2001) to the Journal of Plant Sciences, American Journal of Botany, and Re- origins of modern conifer families (Falder et al. 1998; Ratzel view of Palaeobotany and Palynology) and the broader area of et al. 2001; Klymiuk et al. 2011; Rothwell et al. 2011, 2012; the natural sciences (e.g., Science and Nature). However, Gar’s Serbet et al. 2013; Atkinson et al. 2014a, 2014b; Rothwell and influence in the field of plant biology cannot be reduced to a num- Ohana 2016). In studies of broader scope, Gar surveyed the di- ber of publications—it is best reflected in the quality, relevance, versity of fossil and extant plants, contributing novel perspec- and impact of these contributions, which combine a classic per- tives on the evolution of sporophyte body plans and branching spective derived from detailed anatomical and morphological patterns across the entire embryophyte clade (Rothwell 1995; descriptions of fossil species with innovative methodologies and Tomescu et al. 2014) and on the diversity and evolution of stelar approaches. Gar conducted most of these studies in collabora- architecture across the tracheophyte clade (Rothwell 1976; Beck tion with his students and other fellow paleobotanists and plant et al. 1982). biologists. The inclusion of fossil plants in phylogenetic analyses ranks Gar is a time traveler: the species he has described belong to a among Gar’s most important contributions to evolutionary bi- time slice that spans more than 400 million years. His studies ology. Extinct species exhibiting novel combinations of charac- have investigated plants and other organisms from the Paleozoic ters refashion our understanding of evolutionary relationships to the present and have addressed an incredibly large number of and are key to studies of deep phylogeny. Gar’s work has been lineages, many of them described as new species, genera, fami- at the forefront of the integration of fossils in studies of system- lies, and even classes. He has made detailed descriptions of pro- atics and phylogeny. He was one of the pioneering paleobota- This content downloaded from 201.250.027.037 on June 07, 2020 15:47:03 PM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c). ESCAPA ET AL.—INTEGRATIVE PALEOBOTANY 461 nists to empirically address