ATBC 2008 - Plenary Abstracts 9 June

Plenary Speakers - Abstract - Monday 9 June

Vicki A Funk (Botany, Smithsonian Institution)

Using biodiversity and systematics to understand evolution on the Guiana Shield

The Guiana Shield region sits on some of the oldest rocks in South America and has long held a fascination for biologists because of its unique habitats, i.e., tabletop mountains, tropical savannas, and broad expanses of rainforest. These areas are home to many endemic taxa, as well as to unique ecosystems such as the Greenheart forests and montane savannas. Using the plant data from recent publications and ongoing research we can look more broadly at the biota of this interesting area. The plant checklist includes 256 families 2,070 genera, and ca.13,357 species. Approximately 6,788 of those species are listed from Amazonas, 6,668 from Bolívar, 1,651 from Delta Amacuro, 7,117 from Guyana, 4,995 from Surinam, and 5,433 from French Guiana. There is a 45% species overlap between the Venezuelan part of the shield and the three Guianas. The top 15 families have a total of 7,080 species which represents over half of the species in the Guiana Shield area. The vast majority of families have no more than 50 species; 41 families are represented by only one species. The largest family on the Shield is the Leguminoseae with 1034 species. We now know enough about the phylogeny of the larger families to begin to ask questions that combine biodiversity and systematics. For instance, we are exploring patterns of species radiation on the Guiana Shield among members of two of the three largest families of flowering plants; the Compositae (Asteraceae) and the Leguminosae (Fabaceae). Both of these families are well represented in South America and have groups of species that are endemic to this region. For instance, the Smithsonian Institution’s Biological Diversity of the Guiana Shield Program (BDG) has an extensive database containing over 22,000 records of plant collections of these two families and both families have current generic phylogenies based on morphological and/or molecular characters. Although there are holes in the data and more information needs to be obtained we have gained insight into these questions as we continue to gather data. As an example, one hypothesis is that these groups were the early inhabitants of this area and went on to colonize other continents. Another hypothesis is that they radiated in from other continents, manly Africa, and went on to colonize South America. Preliminary data suggest that members of the Compositae tribe Mutisieae s.l. may contain examples of the first hypothesis while those of Leguminosae subfamily Caesalpinioideae Tribe Detarieae may represent the second. With the exceptions of the populated localities, the agricultural coastal areas, and the broad savannas, the environment of the Guiana Shield has benefited from limited access and low population densities. Estimates vary, but much of the vegetation is still relatively undisturbed by human activities. Recently, however, the pace of disturbance has greatly increased; current threats to the environment include large scale logging by Asian and local companies, large and small scale gold and diamond mining, oil prospecting, bauxite mining, hydroelectric dams, wildlife trade, and population related pressures such as burning, grazing, agriculture, and the expansion of Amerindian villages. Taken together, these impacts have begun to take their toll, with vast areas vulnerable to increasing disturbance. The Guiana Shield encompasses part or all of five countries with five different governments, five main languages and many more indigenous languages. Cooperation is sometimes hampered by border disputes and illegal cross border transportation of gold and wildlife. The implementation of conservation practices is further complicated by many issues concerning the indigenous peoples of the region. All of these challenges will have to be overcome on the way to designing and maintaining a viable reserve system for the Guiana Shield.

Christopher Dick (EEB and Herbarium, University of Michigan, USA)

Molecular perspectives on Amazon tree diversity - from Wallace to the age of genomics

Molecular biologists find themselves at the cusp of understanding some of the main evolutionary factors that underlie tropical tree diversity. This talk provides a molecular perspective on hypotheses about the origin of tropical rainforest tree diversity. Advances in population genetics open a window into the micro-evolutionary differences between tropical and extra-tropical trees. Fossil-calibrated phylogenies, on the other hand, shed light on the age and geographic origin of major tropical rainforest tree lineages and of the tropical rainforest biome itself. These studies show that South American plant diversity derives from a broader context of migration of lineages from other continents via land bridges and oceanic dispersal. Major pulses of speciation coincide with mountain uplifts, climate change and landscape heterogeneity. A firm understanding of this history provides context to the anthropogenic challenges facing tropical forest today.