California Pollination Networks
In the past decade, network analysis methods originally used in the social sciences have become an integral part of the study of pollination. A pollination network is essentially a map to the plant-pollinator interactions occurring in a community. Solid shapes represent plants or pollinators and lines between these shapes indicate that a given pollinator species pollinates, or at least visits, the plants it connects to. The thickness of lines between plants and pollinators, or "weight" of the relationship can be an indicator of how frequently a pollinator visits a plant, or in the case of the network shown at right, it can represent how frequently a plant species was found in fecal samples from hummingbirds (see network at right). As part of the UCR Macrosystems project, I am travelling to coastal and Sierra Nevada habitats collecting data on plant-pollinator interactions. We will use this information to construct plant-pollinator visitation networks and analyze the impacts of the annual pollinator migrations in California habitats on pollination network structure. Pollination network structure can teach researchers about the resiliency of pollination services under changing conditions, for example those caused by climate change, inform conservation efforts by identifying species important to network stability, and provide insights into the ecology and evolution of pollination and community composition. NOVEL METHODS! This study incorporates DNA barcoding to determine plant-pollinator networks. Plant DNA is extracted from hummingbird fecal samples and bee gut samples from each of our study sites, and the plant barcoding gene rbcl is sequenced and compared to a library of known sequences to identify which plants the pollinator has visited. Traditional observation methods are used to round out the networks. Barcoding methods can vastly increase the quantity and scale of plant-pollinator data that can be collected in a short amount of time, as traditional techniques involve many hours of field observation. Additional data is being collected by citizen scientist volunteers using the iNaturalist app. I have conducted several trainings at field sites to teach volunteers how to use iNaturalist to record plant-pollinator interactions. Citizen science can also help expand the capacity of researchers to collect data on plant-pollinator interactions outside of traditional methods (Photos coming soon!). Nectar RobbingPollination is a complicated dance between plants and pollinators that is moderated by the behavior of pollinators and the physiological responses of plants. Understanding how interactions with other animals may indirectly impact plant-pollinator mutualisms can teach us a great deal about the mechanisms that sustain it.
Nectar robbing refers to the extraction of nectar from a flower without pollination, and has been reported globally in a diversity of species ranging from birds to insects. Generally, nectar robbers achieve this by creating an incision in the side of a flower, generally tubular in shape, that they otherwise would not be able to reach the nectar in. Nectar robbing has a wide array of effects on plants and pollinators, but it can change the nectar properties of robbed flowers in ways that discourage pollinators or change the species of pollinators that visit a flower, with implications for plant reproduction. I study nectar robbing in the Andean tree Oroecallis grandiflora (Hazlehurst et al. 2016) by Diglossa flower-piercers, and how this impacts the behavior of the primary pollinator of Oreocallis, the hummingbird Aglaeactis cupripennis (Hazlehurst & Karubian 2016). My research has revealed a complex cascade of effects from nectar robbing in O. grandiflora. |
A Costa's Hummingbird (Calypte costae) at Sedgewick Reserve in Santa Barbara County, California.
A plant-pollinator visitation network compiled with barcoding data.
Nectar robbing has complex cascading effects on plant reproduction in Oreocallis grandiflora (Hazlehurst & Karubian 2016).
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Hummingbird telemetry tags
RFID sensor antenna on a flower
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Hummingbird Spatial Ecology
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