BackgroundThe effect of low nutrient availability on plant-consumer interactions during early succession is poorly understood. The low productivity and complexity of primary successional communities are expected to limit diversity and abundance of arthropods, but few studies have examined arthropod responses to enhanced nutrient supply in this context. We investigated the effects of nitrogen (N) and phosphorus (P) addition on plant productivity and arthropod abundance on 24-yr-old soils at Mount St. Helens volcano.Methodology/Principal FindingsWe measured the relative abundance of eight arthropod orders and five families in plots that received N, P, or no nutrients for 3–5 years. We also measured plant % cover, leaf %N, and plant diversity. Vegetation responded rapidly to N addition but showed a lagged response to P that, combined with evidence of increased N fixation, suggested P-limitation to N availability. After 3 yrs of fertilization, orthopterans (primarily Anabrus simplex (Tettigoniidae) and Melanoplus spp (Acrididae)) showed a striking attraction to P addition plots, while no other taxa responded to fertilization. After 5 yrs of fertilization, orthopteran density in the same plots increased 80%–130% with P addition and 40% with N. Using structural equation modeling, we show that in year 3 orthopteran abundance was associated with a P-mediated increase in plant cover (or correlated increases in resource quality), whereas in year 5 orthopteran density was not related to cover, diversity or plant %N, but rather to unmeasured effects of P, such as its influence on other aspects of resource quality.Conclusions/SignificanceThe marked surprising response to P by orthopterans, combined with a previous observation of P-limitation in lepidopteran herbivores at these sites, suggests that P-mediated effects of food quantity or quality are critical to insect herbivores in this N-P co-limited primary successional system. Our results also support a previous suggestion that the availability of N in these soils is P-limited.

Populations of at-risk butterfly species are declining at an alarming rate. Conservation strategies emphasize a mix of restoration of butterfly habitat, captive propagation, and reintroduction of butterflies to repopulate sites at which populations have gone extinct and to augment declining populations. We review the use of these strategies to conserve butterflies for 25 British species with Species Action Plans and 25 American species listed as Endangered, Threatened, or Candidate under the US Endangered Species Act and found in the continental US. Based on a broad review of published and unpublished literature and 47 interviews with agency staff, we find that the majority of species require active restoration (n = 47 of 50) and that most species receive restoration enhancements (n = 45), but only for a few species are ecological responses to this management monitored (n = 15). In addition, we find that most conservation strategies recommend reintroduction (n = 34) and it has been attempted for 21 British species but for only 5 American ones. Captive propagation is recommended for 12 of 25 American species and has been attempted for 8. Documentation of both reintroduction and captive propagation is limited, with the number of founders known for just over half of the species. We conclude that advancing butterfly conservation will require systematic recording and communication of activities in readily accessible venues, improved experimental design and monitoring, enhanced use of ecological modeling, and improved knowledge of species-specific biology. Project designs that connect on-the-ground efforts to ecological responses of at-risk butterfly species would have tremendous impacts on our ability to use scarce resources to recover these species.

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