Dimensions: Collaborative Research: Biotic and abiotic drivers of Neotropical plant speciation

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Plants are the foundation for terrestrial biodiversity, and the forests of Central and South America are home to more types of plants than anywhere else in the world. Over very long time periods, this diversity of plants is produced by speciation, the complicated process whereby one species becomes two. This project will test ideas about how speciation happens in tropical forests. It will also greatly increase basic knowledge of how plants cope with different environments and how they interact with insects that pollinate their flowers and eat their leaves. Many undergraduate and graduate students, especially those from underrepresented groups in science, will participate in the project, gaining research experience and career training. The team will work to increase international capacity in biodiversity science by helping with field courses in Latin America, involving local research assistants at each tropical field site, and organizing an international research symposium in Costa Rica. Finally, investigators will broadly communicate their experiences and scientific findings to the general public. Results will help guide conservation and management of tropical forests, which are rapidly changing due to human influences.Two evolutionary hypotheses for high tropical speciation rates have been proposed. First, because tropical climates are relatively stable year-round, organisms may not evolve the ability to tolerate a wide range of climates and therefore may not disperse widely. Local populations will then become isolated from their relatives and gradually become new species. Alternatively, interactions between plants and other organisms, such as pollinators and herbivores, may vary from place to place, such that a population adapted to one biological community will grow and reproduce poorly when it spreads to another community. In this way, there may be natural selection for plants in different locations to become different species. This research uses spiral gingers in the monocot genus Costus in Costa Rica and Panama to test these hypotheses about tropical speciation. Spiral gingers occupy a wide range of habitats, extending from lowlands to montane forests and from dense understory to forest edges, with different temperature, water, and soil conditions. They interact with many different orchid bee and hummingbird pollinators, highly specialized beetles that feed on young leaves, and ants that provide protection from herbivores in exchange for nectar. This work integrates phylogenetic studies, broad scale observational approaches, focused field experiments (reciprocal transplants and direct manipulations of interacting organisms and abiotic factors), and genetic mapping. It will determine how plants interact with and adapt to pollinators, herbivores, ant protectors, and climatic conditions across their geographic ranges. It will evaluate whether speciation is caused by traits and genes that have positive effects in one environment and negative effects in other environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.