Smithsonian Botanical Symposium 2008 Archive Page
The seventh annual Smithsonian Botanical Symposium "Partners in Evolution: Interactions, Adaptations, and Speciation" was held 26 April 2008 at the Smithsonian Institution's National Museum of Natural History, Washington, DC. This Symposium, hosted by the Departments of Botany and Entomology, addressed the various ecological interactions, evolutionary adaptations, and co-radiations of plants and animals in habitats across the planet and explore the processes of coevolution.
Plants and animals have ecologically interacted for hundreds of millions of years. These interactions have resulted in adaptations and specializations in both the plants and the animals. In some cases these adaptations have resulted from the coevolution of the two lineages. This Symposium, hosted by the Departments of Botany and Entomology, will address the various ecological interactions, evolutionary adaptations, and co-radiations of plants and animals in habitats across the planet and explore the processes of coevolution. The Symposium highlights the new hall of coevolution, entitled "Partners in Evolution — Butterflies and Plants," which opened at the National Museum of Natural History in February of 2008.
Saturday April 26, Morning Session
NMNH Baird Auditorium
8:30 a.m. Registration and Coffee, Evans Gallery (enter through Constitution Avenue Lobby)
9:00 a.m. Welcome, Warren L. Wagner, Chair of Botany, Smithsonian Institution. Presentation of the José Cuatrecasas Medal for Excellence in Tropical Botany, Laurence Dorr, Department of Botany, Smithsonian Institution.
9:30 a.m. Judith L. Bronstein, The University of Arizona, U.S.A. "Mutualism, Diversity, and Diversification"
10:15 a.m. Coffee Break, Upper Level of the Museum Rotunda
10:45 a.m. Conrad Labandeira, Department of Paleobiology, Smithsonian Institution, U.S.A. "What Can We Learn from the Fossil Record of Plant-Insect Associations?"
11:30 a.m. Olle Pellmyr, University of Idaho. U.S.A. "Coevolution and Obligate Mutualism: What We are Learning from Yuccas and Yucca Moths"
12:15 p.m. Boxed Lunch, Upper Level of Museum Rotunda
NMNH Baird Auditorium
2:00 p.m. W. John Kress, Department of Botany, Smithsonian Institution, U.S.A.; Ethan J. Temeles, Amherst College, U.S.A.; and, Vinita Gowda, The George Washington University, U.S.A., and Department of Botany, Smithsonian Institution, U.S.A. "From Generalization to Specialization â€¦ and Back Again in the Coevolutionary Mosaic of a Heliconia-Hummingbird Pollination System in the Eastern Caribbean"
2:45 p.m. Scott Hodges, University of California Santa Barbara, U.S.A. "Understanding Speciation and Adaptation to Pollinators: From Field to Genomic Studies of Aquilegia"
3:30 p.m. Coffee Break, Upper Level of the Museum Rotunda
4:00 p.m. Ted Schultz, Department of Entomology, Smithsonian Institution, U.S.A. "The Evolution of Agriculture in Ants: 50 Million Years of Symbiosis between Ants, Fungi, and Bacteria"
4:45 p.m. John N. Thompson, University of California Santa Cruz, U.S.A. "Coevolving Networks of Species"
NMNH Rotunda and Coevolution Hall
5:45 p.m. Reception, "Partners in Evolution — Butterflies + Plants" Exhibition
7:00 p.m. Symposium Dinner, Museum Rotunda
Mutualism, Diversity, and Diversification
Mutualisms (reciprocally beneficial interactions between pairs of species) appear to have played a central role in evolutionary processes of diversification on earth. In particular, the evolution of several critical symbiotic interactions appear to have spurred adaptive radiations in many taxa, plants prominent among them. At an ecological time scale, mutualisms generate and help maintain species diversity within communities and ecosystems. At the same time, however, species diversity is threatened by anthropogenic disruptions and dissolution of mutualisms, as well as by the extinction of critical mutualists. In this talk I will review ecological and evolutionary processes inherent to mutualism that both generate and deplete diversity. Conservation of mutualisms, I will argue, is a critical goal in a changing world.
What Can We Learn from the Fossil Record of Plant-Insect Associations?
The fossil record of insect-mediated damage on plant organs provides insight into the diversity, intricacy and timing of insect associations on past floras. The earliest instances of modern plant-insect associations occur during the Paleogene Period, 23 to 65.5 million years ago (Ma). The end-Cretaceous event, at 65.5 Ma, reset the clock for then-existing host-specialized associations that fully recovered during the early Eocene, approximately 10 million years later. This rebound began during the global rise in global temperatures and atmospheric CO2 levels during a 106 year-long interval, the Paleocene-Eocene Thermal Maximum, at 56 Ma.
There are two, major, Mesozoic insect-herbivore radiations. The more recent event, 105 to 90 Ma, coincides with the angiosperm radiation and consisted of external feeders, piercer-and-suckers, leaf miners, gallers and ovipositing insects on basal dicots, including Magnoliales, Chloranthaceae, Laurales, Illiciales, Platanaceae and Cercidiphyllaceae. These associations frequently are attributable to extant insect clades, particularly coleopteran "Phytophaga," monotrysian Lepidoptera and symphytan Hymenoptera. An earlier and more extensive Late Triassic event occurred from 228 to 222 Ma by a diverse array of plant-insect associations that colonized a regional Gondwanan flora in South Africaâ€™s Karoo Basin. This event is represented by 78 distinctive types of insect mediated damage on the foliage and fructifications of peltasperm, corystosperm and ginkgoopsid seed ferns, cycads, voltzialean conifers, ferns, bennettitaleans, and horsetails. The earliest leaf mines originate from this event, attributable to coleopteran and probably lepidopteran lineages.
The oldest, major herbivore diversification event occurs in coal-swamp floras during the late Paleozoic, at 303 Ma. Spectacularly preserved, three-dimensional, anatomical preservation of plant organs occur on marattialean tree ferns and medullosan seed ferns and on subdominant taxa such as herbaceous ferns, sigillarian lycopods and cordaite conifers. Insect culprits responsible for this plant damage include large paleodictyopteroids bearing stylate mouthparts, mandibulate orthopteroid groups, and endophytic, holometabolous larvae.
Coevolution and Obligate Mutualism: What We Are Learning from Yuccas and Yucca Moths
Obligate mutualisms between seed-parasitic pollinators and their hosts are excellent models for understanding coevolutionary processes. Among the best understood at this time is arguably the interaction between yuccas and yucca moths. In recent years, a combination of ecological and evolutionary studies addressing all partners of the association have unveiled much higher species and life history diversity among the pollinators than previously known and a broader range of outcomes of plant-pollinator interactions. Phylogenetic analyses now provide robust species-level phylogenetic frameworks for both plants and moths, permitting analyses to determine the role of codiversification, life history evolution, and coevolution in this interaction. By the time you read this, they will have been completed so that you can receive them hot off the press. I can't wait.
From Generalization to Specializationâ€¦and Back Again in the Coevolutionary Mosaic of a Heliconia-Hummingbird Pollination System in the Eastern Caribbean
The degree of specialization and inter-dependence between mutualistic species varies in space and time. As stressed by John Thompson in his "Geographic Mosaic Theory of Coevolution" species interactions are neither ecologically nor evolutionarily static, but can change from place to place throughout the distribution of the interaction and from generation to generation of the evolving mutualists. The relationship between the tropical plant genus Heliconia and its hummingbird pollinators in the eastern arc of Caribbean islands is a striking example of this mosaic. Our investigations of this system using a geographic approach reveal the transition in a plant species from pollinator generalization to extreme specialization as well as the floral traits and pollinator characteristics that are associated with this shift from generalization to specialization across an island archipelago.
Understanding Speciation and Adaptation to Pollinators: From Field to Genomic Studies of Aquilegia
The flowering plant genus Aquilegia has undergone a very recent adaptive radiation, producing species adapted to specific pollinators and habitats. For an understanding of the process of adaptation to different pollinators, and whether this process promotes speciation, we have conducted an array of studies including field observations and experiments, analysis of mating patterns in hybrid zones, phylogenetic reconstruction and genetic analysis of floral traits. Manipulative studies have shown that single floral traits can have very strong impacts on pollinator visitation or pollen transfer. In hybrid zones, these same traits contribute to reproductive isolation by causing assortative mating. Genetic studies indicate that some of these traits are likely controlled by one or only a few genes. Taken together, these studies suggest that simple genetic changes can result in major changes in pollinators and promote speciation. Ultimately, our goal is to identify the genes and mutations underlying these traits. Currently we are developing genomic resources for Aquilegia such as an EST database, physical maps, and whole-genome sequencing. These resources will allow detailed genetic studies of the approximately 70 species of the genus and likely many close relatives.
The evolution of agriculture in ants: 50 million years of symbiosis between ants, fungi, and bacteria
Agriculture is a specialized form of symbiosis that is known to have evolved in only four animal groups: humans, bark beetles, termites, and ants. Fungus-growing ants (tribe Attini, subfamily Myrmicinae) are perhaps the most well-studied of the non-human agriculturalists, achieving their evolutionary apex in the leaf-cutting ants of the genera Acromyrmex and Atta, which are the dominant herbivores of the New World tropics. Attine ant agriculture is the product of a 50-million-year-old, quadripartite, symbiotic relationship between three mutualists and one parasite. The mutualists include the attine ants, their fungal cultivars (Leucocoprineae and Pterulaceae), and filamentous bacteria in the genus Pseudonocardia (Actinomycetes) that grow on the integuments of the ants. The parasite, a fungus in the genus Escovopsis (Ascomycetes) known only from attine fungus gardens, infects those gardens as a "crop disease" and is controlled, at least in part, by an antibiotic produced by the Pseudonocardia bacterial symbiont. Intensive study of the attine symbiosis during the past two decades, including phylogenetic analyses of all four symbionts, has revealed that attine agriculture can be divided into five distinct agricultural subsystems, each involving a phylogenetically distinct subset of associated symbionts.
Summary and Perspective
Coevolving Networks of Species
Life has diversified not only into millions of species but also into hundreds of millions of interactions among species. In fact, no complex organism is able to survive and reproduce without interacting with other species. Each species is the center of a web of at least several, and sometimes dozens, of other species on which it depends. As a result, much of evolution is driven directly by the coevolution of interacting species. This exuberance of interconnected life is what Darwin called the entangled bank. Interactions among species are continually evolving in different ways in different ecosystems, creating a geographic mosaic of coevolution that fuels the diversification of life. This talk will discuss what we have learned in recent years about coevolution as one of the major processes driving the adaptation and diversification of species. It will also discuss how human alteration of environments is affecting the coevolutionary process.
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