The tropical regions of the world house a disproportionately high amount of the world's biodiversity. Though the reasons for this are not well understood, a number of hypotheses have sought to explain these high rates of speciation; most focusing on the well-studied biota of the Neotropics. The goal of this research project is to better understand biotic diversification in the tropics by focusing on Madagascar, a natural laboratory for such work. Due to its isolation, Madagascar is well suited to explore how organisms diverge and persist in fragmented habitats without the confounding influence of migration to or from adjacent areas. The researchers will study speciation of ants, which as a group, are younger than the island itself. Thus all 700+ species known from Madagascar are derived from transoceanic colonists, whose speciation and diversification on the island has left a genetic signature of these processes in their descendants. By employing molecular data and genomic methods the scientists will explore the history and the factors influencing the diversification of Malagasy ants.

This high diversity in Madagascar, the comprehensive sampling of the endemic ants, and the availability of newly developed, low-cost DNA sequencing technologies will allow this study to test recent advances in methods of ecological niche modeling, delimiting species, and inferring relationships. These data also will allow rigorous testing of existing hypotheses of biotic diversification and examination of whether temporal and ecological commonalities exist in patterns observed among taxa. This will be one of the broadest assessments of tropical diversification to date and will greatly enhance understanding of 1) the biological history of Madagascar, 2) the role of landscape features and environmental change on biological diversification, and 3) the extent to which modeling methods can contribute to the delimitation of distinct species. The project will train graduate and undergraduate students.

Project Report

Since the early days of evolutionary research the mechanisms responsible for the disproportionate distribution of global diversity has been a subject of immense interest. Processes driving the distribution of life on this planet are inherently interesting as evolutionary phenomena, but are also of great importance as we research a sustainable future for human society and for life in general. In this project, we explored diversification of ants in the southwest Indian Ocean and the relative role of mechanisms driving this process. The southwest Indian Ocean (SWIO) islands of Madagascar, Comoros, Europa, Juan de Nova, the Mascarenes (including Mauritius, Réunion, and Rodrigues), and the Seychelles contain one of the highest concentrations of endemic and threatened organisms on earth. Isolation, geographic placement, varied geological histories, and environmental heterogeneity have all contributed to the diversity of endemic species. With a greater age range than most other island systems, the SWIO island bioregion offers a unique opportunity to explore mechanisms driving the accumulation of restricted-range species at regional and local levels. The southwest Indian Ocean islands are composed of a set of recently-emerged coralline islands: the Aldabra group, Farquhars, and Amirantes, aged 15,000 years to 0.125 Ma; relatively young volcanic islands (the Mascarenes and the Comoros) that range in age from 0.13–15 Ma; and the Seychelles and Madagascar, granitic remnants of the Gondwanan continental block that became isolated around 75–130 Ma. To unravel the history and diversity of ants in the SWIO, inventories were conducted across the island systems by BLF and members of the Malagasy Arthropod team based at the Madagascar Biodiversity Center in Madagascar. The first phase of the research to describe the radiations of the big-headed ants (genus Pheidole) is underway. Pheidole is a priority for taxonomic study because of its local diversity and the threat of introduced species in the region. Small SWIO islands such as the Seychelles are under threat from invasive species such as Pheidole megacephala, deforestation, and urban growth but have not received the same attention from biologists. The second phase of the research will be using molecular data to undercover the process and mechanisms of these radiations and then to use this data to protect the habitats that are home to the unique radiations.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Simon Malcomber
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California Academy of Sciences
San Francisco
United States
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