The resource concentration hypothesis predicts that herbivorous insect density scales positively with plant density because insects are better able to identify, and remain longer in, patches with denser plant resources. While some studies support this hypothesis, others do not. Different explanations have been proposed for this discrepancy, including variation in insect dispersal ability and diet breadth. We test the resource concentration hypothesis using the Karner blue butterfly (Lycaeides melissa samuelis), a specialist that relies on wild blue lupine (Lupinus perennis) as its sole host plant. We extended this hypothesis to test whether Karner blue density also scales positively with nectar plant resources. Our findings did not support the resource concentration hypothesis and demonstrate that the spatial segregation of nectar and host plant resources relative to each other can influence the location and abundance of Karner blues on the landscape. This is because the location of resources relative to each other influences the energy and time butterflies expend for flight activity, and thereby influences resource acquisition. During early summer when first brood Karner blues emerge, nectar and host plants were spatially segregated, and Karner blue density peaked at intermediate densities of nectar and host plants occurring at ratios approximately equal to 1:1. During late summer, we found no significant relationships between second brood Karner blues and nectar plants or host plants when there was no correlation between nectar and host plants. Conservation practitioners of specialist insects with low vagility can strategically manage the distribution of plant resources to minimize insect time and energy expenditure and promote resource acquisition for all of an insect’s life stages.

中文翻译：

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精细空间尺度的资源隔离解释了卡纳蓝蝴蝶（Lycaeides melissa samuelis）的分布

资源集中假说预测，食草昆虫的密度与植物密度成正比，因为昆虫能够更好地识别植物资源更密集的斑块，并在其中停留更长时间。虽然一些研究支持这一假设，但其他研究则不支持。对这种差异提出了不同的解释，包括昆虫传播能力和饮食宽度的变化。我们使用 Karner 蓝蝴蝶 (Lycaeides melissa samuelis) 测试资源集中假设，这是一种依赖野生蓝羽扇豆 (Lupinus perennis) 作为其唯一寄主植物的专家。我们扩展了这个假设来测试卡纳蓝密度是否也与花蜜植物资源成正比。我们的研究结果不支持资源集中假说，并证明花蜜和寄主植物资源相对于彼此的空间隔离会影响卡纳蓝调在景观中的位置和丰度。这是因为资源相对于彼此的位置会影响蝴蝶用于飞行活动的能量和时间，从而影响资源获取。在初夏，当第一窝卡纳蓝出现时，花蜜和寄主植物在空间上是分离的，卡纳蓝密度在花蜜和寄主植物的中间密度达到峰值，比例约为 1:1。在夏末，当花蜜和寄主植物之间没有相关性时，我们发现二代卡纳蓝调与花蜜植物或寄主植物之间没有显着关系。