From Plant Press, Vol. 9, No. 3 from July 2006.
By Gary Krupnick
On 21-22 April, more than 125 participants gathered at the National Museum of Natural History to attend the Sixth Annual Smithsonian Botanical Symposium, “Island Archipelagos: Cauldrons of Evolution.” The Symposium explored the role that island archipelagos have played in our understanding of ecological and evolutionary processes as well as the future conservation of these unique ecosystems. Six invited speakers presented talks that described different island systems, each containing unique biotas that experience selective pressures different from those that dominate mainland ecosystems.
An opening reception at the United StatesBotanic Garden, a co-sponsor of the symposium, kicked-off the conference on the evening of 21 April. Gathering in the Garden’s atrium, an enthusiastic crowd enjoyed food, conversation, and tours of the amazing collection of plants. The latest Garden exhibit featured plant species that were collected during the U.S. Exploring Expedition (1838-1842).
W. John Kress, symposium convener, welcomed the audience at the morning session on 22 April. Kress described the “what” and “where” of archipelagos, and explained how archipelagos make wonderful systems that can provide to us unique insights about ecology and evolution. He also gave a brief history of how islands have shaped the study of evolution, natural selection, and biogeography.
The morning session began with the awarding of the sixth José Cuatrecasas Medal for Excellence in Tropical Botany, which was awarded to Sherwin Carlquist (see related article, page 8). A leader in the study of phylogeny, biogeography, and anatomy of island plants, Carlquist was highly appreciative of the award and spoke about how the award will encourage him to continue to do better work. “The award is not closure, but a vote of confidence,” he said. Carlquist received accolades throughout the day as each of the speakers began their talks by paying tribute to their highly respected colleague.
The first invited speaker was Warren Wagner, Curator of Pacific Botany in the Department of Botany at the Smithsonian Institution, who presented “Out of Hawaii: A Remote Archipelago as a Source Area.” Oceanic islands, explained Wagner, are natural laboratories for examining evolutionary diversification. He described (1) what plant diversity exists in the Hawaiian Islands; (2) how independently derived groups exhibit similar patterns of colonization and diversification; (3) which groups radiated more than others; and (4) if colonization to isolated archipelagos was one-way. Using diverse images of the Hawaiian flora, Wagner gave a brief tour of the most species-rich lineages: Campanulaceae, Gesneriaceae, Lamiaceae, Rutaceae, Caryophyllaceae, Asteraceae, Arecaceae, Rubiaceae, and Myrsinaceae. He demonstrated that the Hawaiian Islands are not only a place where divergent species arose in many adaptive radiations, but that the islands are a source area for colonization to other oceanic islands leading to new adaptive radiations.
Bruce G. Baldwin, Professor of Integrative Biology and Curator of the Jepson Herbarium at the University of California, Berkeley, next spoke on “Pacific Dispersals and Radiations of Western North American Origin: An Emergent Pattern.” In describing the adaptive radiations from the west coast of North America to Hawaii, Baldwin presented case studies from the Hawaiian silversword alliance (Asteraceae), Hawaiian sanicles (Sanicula: Apiaceae), Hawaiian violets (Viola), Hawaiian mints (Haplostachys), and Hawaiian Schiedea (Caryophyllaceae). He described how five western North American lineages account for more than 12 percent of Hawaiian angiosperms. Baldwin also described how shrubby tarweeds from the islands off the coast of California paralleled the adaptive radiation of the Hawaiian silversword alliance.
Moving from the Pacific Ocean to the Atlantic Ocean, Javier Francisco-Ortega, Head of the Plant Molecular Systematics and Conservation Biology Laboratory jointly operated by Florida International University and Fairchild Tropical Botanic Garden, ushered in the afternoon session with his presentation of “New and Old Paradigms for the Macaronesian Flora: Molecular Phylogenetic Perspectives.” Francisco-Ortega began his talk with a description of the unique biogeography of Macaronesia. He then presented arguments against two major paradigms for the Macaronesian flora. The first paradigm says that many Macaronesian taxa are sister to taxa restricted to remote regions of Eastern and Southern Africa, Arabia, and Asia. He argues that most lineages instead have links with the Mediterranean region. The second paradigm states that taxa that are endemic to the palaeo-islands of Tenerife form early branching lineages, which is evidence for old speciation events. Francisco-Ortega explained that there are only a few examples that support that claim. He then presented a new paradigm based on molecular phylogenetics: phylogenies for only 27 percent of endemic species are robust enough to make clear conclusions about continental affinities.
The next speaker presented an ornithological viewpoint. Robert E. Ricklefs, Curators’ Professor of Biology at the University of Missouri St. Louis, spoke about “Avian Perspectives on Evolution and Diversification in Archipelagoes.” Using the West Indies as a case study, Ricklefs described biogeographic patterns and processes of the avian fauna. He explained that the basic pattern of island biography is the species-area relationship; but area is often confounded by environmental heterogeneity. Distance from the site colonization, recolonization, and local extinctions also are important factors on species richness.
Following Ricklefs was Ole Hamann, Director of the Botanical Garden & Museum, Natural History Museum of Denmark, University of Copenhagen, who presented “The Galápagos Islands – Aspects of Vegetation Dynamics and Conservation.” Using three case studies (Opuntia, Bursera, and Scalesia), Hamann described how the Galápagos flora has regenerated time and again after severe disturbances, such as El Niño events and invasive species like goats. He argued that arid and humid zone woody plants display different patterns of mortality and survival and thus have different life expectancies. These species react differently to El Niño events. Whereas Opuntia and Bursera can survive during these long-term disturbances, many species of Scalesia can not and thus deserve high conservation priority.
The final invited talk was “Extinction and Restoration: Oceanic Islands as Testing Grounds for Conservation Biology” presented by Mike Maunder, Executive Director of Fairchild Tropical Botanic Garden in Coral Gables, Miami, and Chair of the World Conservation Union–Species Survival Plant Conservation Committee. In describing the essence of his talk, Maunder said that his presentation will be a “first aid course when you have the last four or five individuals of a species.” Maunder emphasized why islands are important and provided a list of threats to island species. His “islands of the living dead” included Rodgrigues, Mauritius, and St. Helena. After presenting images of extinct and near-extinct plant species, Maunder offered some hope. He described how recovery is possible, and outlined three stages of restoration: salvage, siege, and restore.
Robert Fleischer, Head of the Genetics Program at the Smithsonian Institution, concluded the afternoon session with a “Summary and Perspective.” Fleischer was able to discern four general conclusions: (1) molecular data have greatly clarified our understanding of timing of colonization, region of origin, speciation, and coevolution; (2) plants, like birds, can really move around (sometimes in or on birds); (3) communities are usually not in equilibrium, and only roughly match expectations of theory; and (4) many unexpected phylogenetic relationships and geographic origins have been discovered, which have challenged existing paradigms for many biotas. In addition, island floras and faunas seem to be particularly susceptible to invasion from introduced species, which have devastating impacts on island organisms. Development of effective conservation strategies are usually difficult, and often involve both in situ and ex situ solutions.
In his discussion, Fleischer provided a list of suggested future directions: (1) increase the use of DNA marker methods to document patterns of colonization, geographic origins of biotas, colonization times and rates of evolution; (2) refine studies of island biogeography using temporal scales and information from the fossil record; (3) analyze genes involved in development to better understand adaptation and speciation; (4) consider multiple factors and their interactions in conservation management; and (5) conduct better outreach to the public and government agencies about drastic conservation problems facing island biotas.
To conclude the day of presentations, Kress invited John Burns from Smithsonian’s Department of Entomology to deliver a poem that Burns had written 30 years ago about Drosophila evolution and island biogeography.
Next year, the Smithsonian Botanical Symposium will consider plant classification and conservation in the light of Linnaeus’ 200 birthday celebration. All are invited to attend.
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