CAREER: Explaining the Distribution and Dominance of Lianas and Tree Species - A Test of the Dry Season Advantage Hypothesis

University Of Wisconsin-Milwaukee, Milwaukee WI

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). What mechanisms allow some species to attain and maintain high relative abundance in tropical forests, while other species remain at low population densities? This is a key question in ecology. Although there are a number of theoretical explanations, few have been convincingly supported by experimental evidence. The dry season advantage hypothesis is a novel and simple mechanistic explanation for the distribution of plant species along an important environmental gradient: the change in rainfall. The hypothesis states that many plant species attain high abundance in seasonal tropical forests due to the competitive advantage gained from growth during seasonal drought, when solar radiation is high, moisture is limiting, and competing species are dormant. Because most tropical forests are seasonal, the hypothesis has relevance worldwide, and the ideas underlying the hypothesis can be extended to any ecosystem that experiences seasonal fluctuations. The PI will use a combination of long-term physiological and growth measurements on lianas (woody vines) and trees in experimental gardens and in permanent forest plots along a steep rainfall gradient across the Isthmus of Panama. Lianas are of particular importance because they are integral components of tropical forests and are more prevalent in areas that have less rainfall, a pattern that is consistent with the dry season advantage hypothesis. The project will provide one of the first tests of a simple mechanism that may control the abundance and distribution of plant species based on mean annual rainfall, a readily available parameter for sites around the world. Broader impacts of this research include international capacity building, student mentoring, and field-based education. The PI will actively recruit and mentor Latin American students with the goal of providing a model for increasing participation of Latin American scientists in shaping the field of tropical ecology. The project provides the infrastructure for North American graduate and undergraduate student thesis research focusing on fundamental constraints imposed on organisms over environmental gradients. The PI will also integrate the project into his own Tropical Ecology in Panama course (University of Wisconsin?Milwaukee) to teach students to compare and contrast relevant plant and animal adaptations along this important environmental gradient.