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Submitted to: Rangelands
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/23/2014 Publication Date: 6/2/2014 Citation: Dimitri, L.A., Tonkel, K.C., Longland, W.S., Rector, B.G. 2014. The insect microcosm of western juniper berries. Rangelands. 36(3):8-11. Interpretive Summary: Expansion of western juniper forests has been a major concern of ranchers and managers working on rangelands within the areas occupied by this tree, which include northern California, Oregon, and western Idaho. Juniper does not sprout from roots of established trees, so this expansion is due exclusively to the establishment of new seedlings. Yet, despite the fact that insects and mites associated with juniper berries often have major impacts on the number of viable juniper seeds produced, little detail is known about how these species affect seeds. We have been investigating insects and mites found inside juniper berries at two western juniper sites in northeastern California. To date, 36 species of insects and one mite species have been found, ranging from species that eat berries or seeds, to “parasitoids” (insects that develop from eggs laid inside other insects, ultimately killing their host), to “hyperparasitoids” (which parasitize other parasitoids). Several insect species have been identified that consume western juniper seeds and, when abundant, may reduce the number of viable seeds considerably. Technical Abstract: Expansion of western juniper (Juniperus occidentalis) has been a major concern of ranchers and managers working on rangelands within the geographical distribution of this tree. Establishment of new seedlings is the basis for juniper expansion. Yet, despite the fact that insects and mites associated with juniper berries often have major impacts on juniper seed production, little is known about arthropods inhabiting western juniper or their effects on seeds. As part of a USDA-ARS study of seed dispersal and seedling establishment of western juniper trees, we have been investigating insects and other arthropods found inside juniper berries at two western juniper sites in northeastern California. To date, 36 species of insects and one mite species have been found, ranging from frugivores and granivores (animals that eat berries or seeds, respectively) to parasitoids (insects that develop from eggs laid inside other insects, ultimately killing their host) to hyperparasitoids (which parasitize other parasitoids). Several granivores have been identified that consume western juniper seeds and, when abundant, may reduce the production of viable seeds considerably. |
