Investigations into the Spatial Growth Patterns of Kincaid's Lupine
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Large patches (20-40 meters wide) of threatened Kincaid’s Lupine, Lupinus oreganus Heller, (host plant to endangered Fender’s Blue butterfly Icaricia icarioides fenderi Macy) exhibit a striking ring-like pattern of density suggestive of central die-back, in which there is a less dense outer zone, a denser middle zone, and a less dense center zone. To determine what might be causing this pattern, different zones were tested for seed germination, and the plants were analyzed for pathogen and herbivore damage, carbon and nitrogen content, and reproduction. Total germination and growth of the germinants did not significantly vary across zones or with plant density. Herbivory types and nitrogen levels were greater in the less dense outer zones of the patches. Flowering stems per leaf were more abundant in the denser middle zone. Kincaid’s lupine displays spatially explicit stoichiometric and herbivory patterns similar to those seen in other lupines, in which leaves in the less dense outer zone (margin) are more nutrient rich and receive greater herbivore damage. However, the less dense center zone had less damage from herbivory, implying that herbivory is not strictly density dependent, but instead depends on zone.