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Exploring how rapidly changing environments influence natural selection
Many species of plants and animals can be threatened by rapid environmental change, such as an increase in frequency or severity of drought. At the Rocky Mountain Biological Laboratory in Gothic Colorado, we are testing experimentally how snowmelt date and summer precipitation influence natural selection on vegetative traits and floral traits of Ipomopsis aggregata. We are measuring a suite of floral traits including corolla shape, petal color, nectar production, and emission of volatile organic compounds (e.g. alpha-pinene and indole) to determine how selective pressures change in response to water availability and how changes in pollination interact with the physical environment to influence adaptation of plant populations.
Linking Pollinator Behavior to Plant Reproductive Function
Plant reproduction—a critical ecosystem service and function—is sensitive to how “faithful” pollinators are to particular plant species. Given the functional significance of pollinator resource use, it is important to understand the factors driving pollinator behavior. This work focuses on understanding how pollinator foraging behavior is influenced by the composition of the pollinator community, how such changes in behavior relate to pollinator species’ traits, and how such context-dependent behavior ultimately impacts plant reproductive function. By directly and explicitly studying context-dependence as an ecological driver of pollinator behavior, this work demonstrates that the functional contributions of pollinator species in a community depend heavily on the interplay between their traits and their biotic context.
The Feedback between Pollinator Behavior and the Evolution of Plant Traits
For most animal pollinated plants, reproductive success is tied to a pollinator’s ability to move pollen between conspecifics. Therefore, both the frequency and pattern of pollinator visits generates selection on plants. Despite extensive research indicating that pollinators shape floral evolution, we know little about what is driving the pollinator foraging behaviors themselves. For example, why do some pollinators prefer to go to purple flowers over red flowers? Do they have an innate preference for one color over another or are they learning something about floral rewards during foraging? A better understanding of what drives pollinator foraging behaviors will help us understand how plant traits evolve to recruit effective pollination
Interspecific competition drives floral fidelity - We show that a reduction in interspecific competition within a community (through targeted removals of the most abundant bee species) leads to a reduction in floral fidelity of the remaining bee pollinators and ultimately a reduction in plant reproductive output, even when other effective pollinators remain in the system. Furthermore, we find the structure of the plant-pollinator (non-bumblebee) network changes after species removals.
Traits and community context impact pollinator behavior - We explore how traits—specifically pollinator tongue length, —influence behavioral plasticity and drive dynamic interspecific interactions. We show that bee species vary in floral fidelity, and that tongue length explains a large part of this variation. Additionally, we find that the tongue length of the most abundant bee species, a site-level attribute, explains much of the site-to-site variation in pollinator foraging behavior. In particular, we found that as the tongue length of the most abundant bee in the site increases, the site level foraging fidelity decreases.
Heterospecific Pollen Transfer in the Field - Most pollinators are generalists and therefore are likely to transfer heterospecific pollen among co-flowering plants but know very little about the reproductive effects of heterospecific pollen in field settings. We take a comparative field approach to explore how patterns of naturally deposited heterospecific pollen (HP) relate to the reproductive output in alpine plant species. This gives us information about how pollinators are moving pollen in native plant communities which can have important implications for the evolution of plant mating systems.
Dissecting the neuroanatomical roots of pollinator foraging behavior - bees often vary in several important attributes of foraging behavior; including the number and identity of plant species they tend to visit, as well as how they visit them. The extent to which bees vary in these traits consistently and strongly differs between closely-related species. We are exploring the cognitive and neuroanatomical basis of variation in pollinator behavior and determine the degree to which individuals, populations, and species vary in these features. (figure modified from Riveros and Gronenberg, 2010)
Flexibility in Foraging Behavior: We are exploring how variation in floral color impacts flexibility in pollinator foraging behavior in the field. We find that different pollinator species within the same community display distinct patterns of context-dependent behavior, which has important implications for how floral traits might respond to pollinator-mediated selection.
Innate and Learned Foraging Behavior: We are working to understand how flower color influence both innate and learned foraging behavior of the pipevine swallowtail butterfly (Battus philenor) .
Watch this exciting video about our work from Science in Real Life.