Ecological and Demographic Consequences of the Loss of Native Pollinators to Plant Communities

EPA Grant Number: FP916345
Title: Ecological and Demographic Consequences of the Loss of Native Pollinators to Plant Communities
Investigators: Randle, April M.
Institution: University of Pittsburgh
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2004 through December 31, 2007
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems


Habitat fragmentation, use of agricultural pesticides, and the introduction of nonnative pollinator species have all been implicated as potential causes of the global decline of native pollinator species. Failure of native plants to receive pollen from native pollinators can result in decreased fruit production, decreased seed-set, and lower population growth rates. Chronic pollination failure is expected to result in strong selection for autonomous selfing (the ability to self-pollinate in the absence of pollinators) in animal-pollinated plant species. Empirical studies have shown that highly selfing species have lower genetic diversity than outcrossing species. Theoretically, the transition of a population from an outcrossing mating system to a selfing one is considered an evolutionary deadend that will result in extinction. The loss of diversity and abundance of pollinators also has been linked to crop failure in economically important plant species around the world. Thus, the current decline in pollinator species has strong implications for both the ecology and evolution of wild plant species and for the viability of many important economic crop species. The main objectives of this project are to: (1) quantify the abundance and diversity of pollinator species in a native spring annual plant community; (2) quantify the effects of pollinator abundance and diversity on the vital rates of a subset of focal annual species that differ in their dependence on animal pollinators; (3) use the data from the above experiments to parameterize a demographic matrix model to predict which species will predominate in communities if pollinators become rare or absent; and (4) test the robustness of the model by quantifying changes in local community structure in experimentally controlled pollinator environments.


The proposed fieldwork will be conducted over a 3-year period (April-July) in a guild of spring annual plants in western Pennsylvania. Yearly surveys of pollinator diversity and abundance will be made. A series of life table response experiments will be conducted to examine the effects of pollinator diversity and abundance on the vital rates of annual plant species that differ in their dependence on animal pollinators. These experiments provide a powerful tool for quantifying changes in vital rates that determine population growth rates in response to environmental perturbations, such as the loss of pollinators. Pollinator exclosures will be used in the field to manipulate both the diversity and abundance of pollinators. These data will be used to parameterize a demographic matrix model to predict which plants are more susceptible to population declines in the absence of pollinators. Finally, to examine the community level effects of changes in pollinator diversity and abundance, I will quantify the relative abundance of all focal plant species in control and experimental plots over a 3-year period.

This study will quantify the direct effects of pollinator diversity and abundance on the demographic parameters that structure annual plant communities. These results will provide evidence that support or refute the following predictions:

(1) Highly specialized animal pollinated plants are more susceptible to extinction when pollinators become rare or absent.

(2) Loss of pollinators has significant consequences for plant community structure.

Supplemental Keywords:

fellowship, pollinator decline, pollinator diversity, pollinator abundance, self-compatibility, pollen limitation, plant demography, native pollinators, life table response experiments,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Habitat, Environmental Monitoring, Ecology and Ecosystems, Ecological Indicators, habitat dynamics, pollinator species, demographic factors, plant diversity, complex habitats, plant community structure, indicator plants, pollination, ecological consequences, habitat fragmentation, plant development and tolerance traits, agricultural pesticides, invasive species, plant pollen, plant demographic matrix model, indicator species, effects of fragmentation, adaptation

Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 251KB, about PDF)

Progress and Final Reports:

  • 2004
  • 2005
  • 2006
  • Final